300bhp, 350lbs feet torque 944 3 litre turbo
Discussion
Anyone that's considered a 3.0 conversion up to now has needed deep pockets and a 2.7 head, I know people on Rennlist talk about welding the turbo head to fit on a 2.7 or 3.0 block but I don't know if it's been tried here, I've been looking for a 2.7 head for ages, only seen 2 for sale in the last year or so, both of them unknown condition and hours away from me.
hartech said:
We are considering manufacturing replacement liners to enable any 2.5 to 3 litre block to be repaired and if so any block could be fitted with 4 liners to suit 104mm pistons for changing a 2.5 to a 2.7 (with a 2.5 crank or 3 litre with the S2 or 968 crank). You also need bigger injectors and a re-mapped ECU.
Baz
Ahhh yes poor observation sorry! What are the approximate costs of this? Have you got anywhere near figures for producing the blocks yet? I would imagine it would be many a 944 owners dream to have 'off the shelf' replacement engines available for exchange (similar to your wishbone service - which is excellent). Since most internal engine troubles suffered with 944 internals are simply from scored bores and very rarely anything mechanical most blocks would be perfectly suitable for exchange.Baz
I'm very confident that not only would such an arrangement meet a surprisingly large market but I believe the availability of such a service might jump start a market for the 944 in a similar way to other classics such as the Toyota A86 as a track car.
Extreme high end custom build options such as Jon Mitchels 3.2 engines and some of those now available from america will always have a place. But are not going to be of interest to 95% of owners who could never justify spending that kind of money on what is realistically a sub £10k car. Even if its final value is raised to £10-15k once completed, you could never hope to recover anywhere near the money you put into it.
If a 'quick exchange' option in the region of £5k was available using longer lasting 2.5 liners and with the options of 2.7 or 3.0 variations at an extra over for the parts needed. Well.. do you have shares?
diver944 said:
Barry, I've taken the liberty of copying your graphs from the 968 UK forum. Hope you don't mind but it does clearly show the very noticeable gains you have made. What sort of boost pressure are those figures made at?
What a bizarre power curve! What happened above 5000 rpm? Even more, what about above 6000rpm? The car's producing way less power there than non-turbo cars. Is this down to a small turbo that can't maintain boost at those rpms or another serious restriction (intercooler?) in the intake system?Mid range torque is all very well, but at the expense of a massive percentage of top end like this it isn't. This car would need a massively long diff to reach its v-max as the engine would need to be running at no more than 5000 rpm. Even then, if you dropped a gear you'd slow down as there'd be less power!!
A lot (lot) more development work required here I think! (Until someone tells me I'm totally wrong and shoots me down in flames).
Ian
Edited by Ian_UK1 on Friday 6th November 14:21
Edited by Ian_UK1 on Friday 6th November 14:22
I think you get a better understanding if you think of torque as the rate of change of power with respect to engine speed (revs), so if you see a nice steep power curve you know there's going to be loads of torque there. Agree that well placed torque is what's needed.
hartech said:
It is not only quick but flexible and manageable - a very nice road car to drive.
On the 968.uk register - over the years - there have been many lengthy arguments about the merits of power and torque (and probably some on here) and - which is more important. Much of this has continued on that web site but I didn't realise that it was not easy to access that site if you have not joined.
Basically - to put it very very simply - it is the torque at the rear wheel that accelerates a car. Torque mutiplied by revs creates the bhp reading. If you have a lot of torque at low revs - from the engine - this will result in a lot of torque at low revs in any gear. If you can change the ratios and the diff ratio then you can alter the torque at the rear wheel - so a high revving engine with lower torque - when the torque is aplied through a greater speed reduction may have higher rear wheel torque - but if you cannot change those ratios - then just revving an engine higher to create more bhp may not make it faster since the gear ratios are the same and the relative torque at any revs must be higher to increase acceleration - and you usually reduce the power band as well.
The higher it revs the less time there is for the intake to receive the quantity of air that results in the compression pressures needed to create torque - so although it is easy to raise revs and bhp - this may lower torque.
With a fixed 5 speed gearbox (in the 944 turbo) with high final drive ratio - increasing the torque in mid range - in my view - should create a quicker car and as tuning a 2.5 with more boost usually results in a harsh power curve and difficulty controlling rear wheel spin - I thought that this creation might result in a nice quick car to drive that is also very manageable - and that seems to be the case.
Baz
On the 968.uk register - over the years - there have been many lengthy arguments about the merits of power and torque (and probably some on here) and - which is more important. Much of this has continued on that web site but I didn't realise that it was not easy to access that site if you have not joined.
Basically - to put it very very simply - it is the torque at the rear wheel that accelerates a car. Torque mutiplied by revs creates the bhp reading. If you have a lot of torque at low revs - from the engine - this will result in a lot of torque at low revs in any gear. If you can change the ratios and the diff ratio then you can alter the torque at the rear wheel - so a high revving engine with lower torque - when the torque is aplied through a greater speed reduction may have higher rear wheel torque - but if you cannot change those ratios - then just revving an engine higher to create more bhp may not make it faster since the gear ratios are the same and the relative torque at any revs must be higher to increase acceleration - and you usually reduce the power band as well.
The higher it revs the less time there is for the intake to receive the quantity of air that results in the compression pressures needed to create torque - so although it is easy to raise revs and bhp - this may lower torque.
With a fixed 5 speed gearbox (in the 944 turbo) with high final drive ratio - increasing the torque in mid range - in my view - should create a quicker car and as tuning a 2.5 with more boost usually results in a harsh power curve and difficulty controlling rear wheel spin - I thought that this creation might result in a nice quick car to drive that is also very manageable - and that seems to be the case.
Baz
I too really hope Hartech make those liners. Parts for classics cars get harder to obtain by the day. Specialists like Hartech are doing more to keep the older Porsche cars on the road than the factory themselves.
I have a chipped 944 Turbos S Silver Rose. The goal of a 944 with as much torque as a 5.4 928 GTS whilst maintaining its reliability is amazing.
Stephen
944 Turbo S
928 GTS
I have a chipped 944 Turbos S Silver Rose. The goal of a 944 with as much torque as a 5.4 928 GTS whilst maintaining its reliability is amazing.
Stephen
944 Turbo S
928 GTS
Ian_UK1 said:
What a bizarre power curve! What happened above 5000 rpm? Even more, what about above 6000rpm? The car's producing way less power there than non-turbo cars. Is this down to a small turbo that can't maintain boost at those rpms or another serious restriction (intercooler?) in the intake system?
I would bet good money that it is the turbo and then to some extent exhaust. Top speed with that curve would probably be about what, 140 mph? My S2 tops out at 159 mph indicated at something just over 6K rpm, probably less then 150 real speed.hi all my 86 turbo makes 280 pf and 241 bhp at 3250 ish rpm it has t/p w gate and a k/n and up ed fuel pressure but has standard chips and runs 12 psi of boost it seems a lot different to the standard I'm not sure what more the promax chips will do to my car maybe a bigger turbo is the way forward can i fit the bigger 250 bhp turbo to my 220 car
Ian_UK1 said:
What a bizarre power curve! What happened above 5000 rpm? Even more, what about above 6000rpm?
I would agree it's all down to the standard exhaust struggling to cope with all that gas from a bigger engine. The actual curve looks very similar in shape to my own 3.2 Litre which is why it is currently having a bigger exhaust fitted. The backpressure is huge and the exhaust gas temperatures creep up. You get a huge dollop of useable power low down and don't have to wait for the turbo to spool up which is what makes the car so driveable.Barry's plan was just to see if a 3 litre could easily be created from existing parts and it looks like it can. It's up to the next owner if they want to take it further
A lot of very bizarre comments recently – all very difficult to deal with without offending people as many of them are not only misleading but completely wrong. I am frankly not sure if a group of people are trying to catch me out and have posted a load of cr*p to test me as their comments either reveal a serious lack of understanding of torque, power and gear ratio graphs or is this just the typical reaction one might expect on here from a small minority - or is it that people really don’t understand simple basic issues – but feel they should never the less post their criticisms as if they were the experts for others to absorb? Sorry if I seem b
hy - but I am rather gob smacked about some of those comments from people I imagined knew better!
For those who don’t know who to believe – it is important that someone explains the real issues properly and as no one else seems to have jumped to correct them – it falls to me to do so. So - for those not sure what to believe - I will patiently try and explain (although for people whose understanding of dynamics is so far out – I doubt it will do any good and probably just provoke more uneducated criticism).
Firstly let us please remember that we set out specifically to construct a relatively simple, relatively inexpensive conversion that we planned to provide more bottom end torque, about 300 bhp top end and reduced turbo lag and we achieved all that.
Anywhere between 3000 and 6000 rpm this engine has anything between much more power or torque than a standard 944 250bhp turbo, S2 or 968 or finally at 6000 rpm about the same.
You have to drive the car from the revs you hit when you change gear to the maximum revs before changing up again.
In this gearbox from 1st to second you drop to 3500 rpm from which you must drive it again all the way to 6000 rpm. Just look at the torque or power graph from 3500 to 6000 rpm. Where is it less than the other engines and is it not plain obvious that it is massively more throughout? It is on average about 50% more!
From 2nd to third you drop to 4100 rpm which is the point of peak torque (and torque provides acceleration through the simple formula that Torque = (Inertial, drag and rolling resistance) * acceleration or put another way acceleration = Torque divided by various forms of resistance (which are the same for all the cars I have compared) and therefore acceleration is proportional to torque.
From 3rd to 4th you drop to 4450 rpm which is almost on peak torque and 100 lbsft more than a standard turbo.
From 4th to 5th you drop to 4750 rpm which is just coming on to peak power that is almost flat to 5500 rpm by which time you are travelling at about 147 mph.
These graphs show a superb match between the ratios available and the power and torque delivered.
Throughout all these gear changes you are constantly driving with much more torque or bhp than the other engines. This means that you will be accelerating to that speed very much quicker and get there very much sooner. 6000 rpm is about 160 mph in 5th and as you drive on to that speed – you are still driving with more power and torque than a standard 944 2.5 turbo but you got there much quicker. It is only at 160mph that the power then – for the first time – is slightly less than a 968 and std turbo (but still more than an S2 until about 6300 rpm or 168mph (where an S2 would have to rev to about 7200 with the same power to match it). It may well be that on a very long straight road – several miles long - a 250bhp turbo or a 968 may eventually reach a couple of mph more in top speed – but would they ever catch you up? – I doubt it.
I don’t know how NJH reckons my curve would only give 140mph – totally beyond my understanding that one! 6000 rpm in a 944 turbo is about 160 mph.
Another reverse lack of understanding is Ajax50’s comment that a steep power curve = loads of torque – as really the opposite is true (although to be fair he did support the advantages of torque – perhaps just got a bit muddled up about the graphs). Since power is proportional to torque * revs, if the torque was say a flat line – then the power would increase in a straight line as the revs rise. Since maximum torque is always achieved before maximum bhp, and the maximum possible is in proportion to the breathing capabilities of the engine – any increase in torque before top revs or peak bhp, will make the line higher at lower revs and therefore the bhp line would not be steeper but flatter. Anything that increases top revs and bhp at high revs more (which is the common tuning result) almost always lowers the torque at lower revs and the result again is always a steeper power curve. So once again the stated criticism is actually arse about face!
Those of you that don’t seem to understand the first thing about these graphs or power and torque really should try and resist the temptation to make firm statements on such a forum because many others simply don’t know what is right and wrong and it will not only mislead them and confuse many but also is very unfair criticism when in most cases it seems to be wrong and even the opposite of what actually happens.
Fortunately many others who have contacted me directly fully appreciate the results and some even can imagine driving the car from viewing the graphs and in one case has done both and found the graphical description and the practical experience the same. For those that quite rightly immediately recognised the achievement and the benefits of such a pair of graphs – can I add that although acceleration is proportional to torque (if resistance is constant or the same between compared cars) there is a phenomenon inside an engine and its transmission that relates to the stored energy between individual power pulses and strain energy lost as a result. It means that in actual fact there is a slight benefit from slightly reduced torque if the number of revs is increased and the strain energy lost is reduced. Put into more simple terms it means that a small increase in bhp at high revs can offer a small improvement in acceleration even if the torque is slightly lower and putting it simply it means that the best torque or power curve for the fastest acceleration, is one in which the torque is dropping off while the power is still increasing between the gear change revs.
However you must qualify that last point by stating that such benefits can only be exploited if you have the freedom to alter gear and final drive ratios. Unless you can alter these (and most of us are limited to the ratios we inherited with our car) for most cases these ratios are far too high to use on a race track or a drag race. Since - as you change up in the gears - the gear ratios gradually reduce the rev drop as you change up to higher gears - it means that most drivers on a track are using the lower gear ratios that require an engine to produce a relatively wide torque or power curve and not a narrow peaky one (even if that produces slightly more bhp to boast about). This is not true of GP racing or non restricted competition – but for most of us it is a fact of life we have to understand and adapt to if we are to get the best out of a road based car or gearbox.
I fully accept that there is more potential from this engine, and if it was easy to change the final drive ratio – there would be a benefit from different internal ratios as well and a different power curve may be better (although sometimes too close a ratio does not suit a turbo due to reduced time to spin it up under full power and heat etc) – but we don’t usually have that luxury and if not and if we are stuck with the gear ratios of our car and want to use it on the track or on the road (who needs more than 160mph on the road?) then looking at the rev band we are forced to work with at the speeds we are likely to encounter in the lower gears we will be using – it all means that a torquey engine like this one may be faster accelerating compared to a peaky one with more bhp but a narrower power band – and what’s more the torquey engine will be easier to drive out of corners on the limit as it will have more power control and therefore should lap quicker. There is a problem with the exhaust capacity - mainly when the back pressure on the valve overlap fights against the incoming charge pressure - but look we just put together a handful of parts to see what would happen and it achieved our objectives perfectly.
So compared to those objectives I don’t think a lot more development work is needed Ian UK1 and you really need to look at graphs showing the engine revs between the gear change points to fully understand that there is a power band you are forced to work with and the average power or torque in that power band is what is important and you also need to work out the speeds you will be reaching at various revs to understand that most road cars are massively over-geared for track use often only using two or three gears 2nd 3rd and 4th.
I am trying to develop a system to superimpose the test results onto a graph tracing the torque and power in each gear as the car accelerates and then to compare the areas under the graphs to see if a general rule of area to acceleration can be determined (I think it can).
Unfortunately all our actual road dyno test results have been carried out in second gear (as they are on public roads and for general safety) so at the moment I only have records for acceleration in second gear to compare between cars. The road dyno takes readings every 1/24th of a second and the results show that our 3 litre turbo in second between 3500 rpm and 6000 rpm is quarter of a second quicker (or 10%) than a standard 944 turbo, 0.6 of a second quicker (or 20%) than a 968 and three quarters of a second quicker (or 25%) than an S2 (and our car is geared slightly higher anyway).
It doesn’t matter if you understand graphs or engine characteristics – this is simply a lot faster in second gear and proves all the theory and who is right or wrong beyond any doubt. At the moment I can only speculate about how much quicker that will be in the higher gears – but all records (including Porsches own printed graphs) show that an S2 takes 28 secs 0 - 120 mph, and a 944 turbo takes 23 secs for the same 0-120 mph.
If you plot a graph of all 944/968 Porsche’s (from the manufacturers figures in the various handbooks) of say 0-120 mph and the time you will find an almost straight line graph for bhp and time and a very slight curve plotting torque against time. In both cases if you plot the torque and bhp of our engine on this graph is predicts a 0-120 mph time of 12 to 13 secs. I am not claiming this but I will test it out - although it feels very similar and when I prove it is similar - I hope it will put to bed the criticism that has recently seemed to imply that somehow this engine is all wrong, is slower than an S2 or somehow is undeserving of any recognition.
To be fair there is more on the 968.uk web site on this subject.
Thanks also for those of you who recognised our achievement with encouraging comments and support.
Baz
hy - but I am rather gob smacked about some of those comments from people I imagined knew better!For those who don’t know who to believe – it is important that someone explains the real issues properly and as no one else seems to have jumped to correct them – it falls to me to do so. So - for those not sure what to believe - I will patiently try and explain (although for people whose understanding of dynamics is so far out – I doubt it will do any good and probably just provoke more uneducated criticism).
Firstly let us please remember that we set out specifically to construct a relatively simple, relatively inexpensive conversion that we planned to provide more bottom end torque, about 300 bhp top end and reduced turbo lag and we achieved all that.
Anywhere between 3000 and 6000 rpm this engine has anything between much more power or torque than a standard 944 250bhp turbo, S2 or 968 or finally at 6000 rpm about the same.
You have to drive the car from the revs you hit when you change gear to the maximum revs before changing up again.
In this gearbox from 1st to second you drop to 3500 rpm from which you must drive it again all the way to 6000 rpm. Just look at the torque or power graph from 3500 to 6000 rpm. Where is it less than the other engines and is it not plain obvious that it is massively more throughout? It is on average about 50% more!
From 2nd to third you drop to 4100 rpm which is the point of peak torque (and torque provides acceleration through the simple formula that Torque = (Inertial, drag and rolling resistance) * acceleration or put another way acceleration = Torque divided by various forms of resistance (which are the same for all the cars I have compared) and therefore acceleration is proportional to torque.
From 3rd to 4th you drop to 4450 rpm which is almost on peak torque and 100 lbsft more than a standard turbo.
From 4th to 5th you drop to 4750 rpm which is just coming on to peak power that is almost flat to 5500 rpm by which time you are travelling at about 147 mph.
These graphs show a superb match between the ratios available and the power and torque delivered.
Throughout all these gear changes you are constantly driving with much more torque or bhp than the other engines. This means that you will be accelerating to that speed very much quicker and get there very much sooner. 6000 rpm is about 160 mph in 5th and as you drive on to that speed – you are still driving with more power and torque than a standard 944 2.5 turbo but you got there much quicker. It is only at 160mph that the power then – for the first time – is slightly less than a 968 and std turbo (but still more than an S2 until about 6300 rpm or 168mph (where an S2 would have to rev to about 7200 with the same power to match it). It may well be that on a very long straight road – several miles long - a 250bhp turbo or a 968 may eventually reach a couple of mph more in top speed – but would they ever catch you up? – I doubt it.
I don’t know how NJH reckons my curve would only give 140mph – totally beyond my understanding that one! 6000 rpm in a 944 turbo is about 160 mph.
Another reverse lack of understanding is Ajax50’s comment that a steep power curve = loads of torque – as really the opposite is true (although to be fair he did support the advantages of torque – perhaps just got a bit muddled up about the graphs). Since power is proportional to torque * revs, if the torque was say a flat line – then the power would increase in a straight line as the revs rise. Since maximum torque is always achieved before maximum bhp, and the maximum possible is in proportion to the breathing capabilities of the engine – any increase in torque before top revs or peak bhp, will make the line higher at lower revs and therefore the bhp line would not be steeper but flatter. Anything that increases top revs and bhp at high revs more (which is the common tuning result) almost always lowers the torque at lower revs and the result again is always a steeper power curve. So once again the stated criticism is actually arse about face!
Those of you that don’t seem to understand the first thing about these graphs or power and torque really should try and resist the temptation to make firm statements on such a forum because many others simply don’t know what is right and wrong and it will not only mislead them and confuse many but also is very unfair criticism when in most cases it seems to be wrong and even the opposite of what actually happens.
Fortunately many others who have contacted me directly fully appreciate the results and some even can imagine driving the car from viewing the graphs and in one case has done both and found the graphical description and the practical experience the same. For those that quite rightly immediately recognised the achievement and the benefits of such a pair of graphs – can I add that although acceleration is proportional to torque (if resistance is constant or the same between compared cars) there is a phenomenon inside an engine and its transmission that relates to the stored energy between individual power pulses and strain energy lost as a result. It means that in actual fact there is a slight benefit from slightly reduced torque if the number of revs is increased and the strain energy lost is reduced. Put into more simple terms it means that a small increase in bhp at high revs can offer a small improvement in acceleration even if the torque is slightly lower and putting it simply it means that the best torque or power curve for the fastest acceleration, is one in which the torque is dropping off while the power is still increasing between the gear change revs.
However you must qualify that last point by stating that such benefits can only be exploited if you have the freedom to alter gear and final drive ratios. Unless you can alter these (and most of us are limited to the ratios we inherited with our car) for most cases these ratios are far too high to use on a race track or a drag race. Since - as you change up in the gears - the gear ratios gradually reduce the rev drop as you change up to higher gears - it means that most drivers on a track are using the lower gear ratios that require an engine to produce a relatively wide torque or power curve and not a narrow peaky one (even if that produces slightly more bhp to boast about). This is not true of GP racing or non restricted competition – but for most of us it is a fact of life we have to understand and adapt to if we are to get the best out of a road based car or gearbox.
I fully accept that there is more potential from this engine, and if it was easy to change the final drive ratio – there would be a benefit from different internal ratios as well and a different power curve may be better (although sometimes too close a ratio does not suit a turbo due to reduced time to spin it up under full power and heat etc) – but we don’t usually have that luxury and if not and if we are stuck with the gear ratios of our car and want to use it on the track or on the road (who needs more than 160mph on the road?) then looking at the rev band we are forced to work with at the speeds we are likely to encounter in the lower gears we will be using – it all means that a torquey engine like this one may be faster accelerating compared to a peaky one with more bhp but a narrower power band – and what’s more the torquey engine will be easier to drive out of corners on the limit as it will have more power control and therefore should lap quicker. There is a problem with the exhaust capacity - mainly when the back pressure on the valve overlap fights against the incoming charge pressure - but look we just put together a handful of parts to see what would happen and it achieved our objectives perfectly.
So compared to those objectives I don’t think a lot more development work is needed Ian UK1 and you really need to look at graphs showing the engine revs between the gear change points to fully understand that there is a power band you are forced to work with and the average power or torque in that power band is what is important and you also need to work out the speeds you will be reaching at various revs to understand that most road cars are massively over-geared for track use often only using two or three gears 2nd 3rd and 4th.
I am trying to develop a system to superimpose the test results onto a graph tracing the torque and power in each gear as the car accelerates and then to compare the areas under the graphs to see if a general rule of area to acceleration can be determined (I think it can).
Unfortunately all our actual road dyno test results have been carried out in second gear (as they are on public roads and for general safety) so at the moment I only have records for acceleration in second gear to compare between cars. The road dyno takes readings every 1/24th of a second and the results show that our 3 litre turbo in second between 3500 rpm and 6000 rpm is quarter of a second quicker (or 10%) than a standard 944 turbo, 0.6 of a second quicker (or 20%) than a 968 and three quarters of a second quicker (or 25%) than an S2 (and our car is geared slightly higher anyway).
It doesn’t matter if you understand graphs or engine characteristics – this is simply a lot faster in second gear and proves all the theory and who is right or wrong beyond any doubt. At the moment I can only speculate about how much quicker that will be in the higher gears – but all records (including Porsches own printed graphs) show that an S2 takes 28 secs 0 - 120 mph, and a 944 turbo takes 23 secs for the same 0-120 mph.
If you plot a graph of all 944/968 Porsche’s (from the manufacturers figures in the various handbooks) of say 0-120 mph and the time you will find an almost straight line graph for bhp and time and a very slight curve plotting torque against time. In both cases if you plot the torque and bhp of our engine on this graph is predicts a 0-120 mph time of 12 to 13 secs. I am not claiming this but I will test it out - although it feels very similar and when I prove it is similar - I hope it will put to bed the criticism that has recently seemed to imply that somehow this engine is all wrong, is slower than an S2 or somehow is undeserving of any recognition.
To be fair there is more on the 968.uk web site on this subject.
Thanks also for those of you who recognised our achievement with encouraging comments and support.
Baz
Well done Baz, nice to see you got it running.
Baz's power output is roughly what we would expect to be seen from a 3.0 and otherwise standard setup.
The TDi style power curve which someone mentioned is due to restrictions in standard components.
We have found the following limitations on performance tuning and standard parts on the 944 turbo. Much of this is relevant whatever the engine size, due to flow restrictions.
Standard exhaust (non cat) 350-360 BHP
Standard k26/6 turbocharger (220 cars) 300 BHP (beyond this it becomes a heat pump)
Standard k26/8 turbocharger (250 cars) 320 BHP (beyond this it becomes a heat pump)
standard Cylinder head (2.5) 420 BHP
standard throttle body 420 BHP
Standard fuel pump - 320 BHP
Standard injectors - 320 BHP
Standard breather system - 340 BHP
Intake manifold - 420 BHP
All of these items reflect a 2.5 through to 3.2 944 turbo.
Other items which are poor performers are the camshaft (designed to hold performance back), intercooler (poor flow above 320 BHP), intake port design (designed to hold performance back)
The crankshafts are insanely strong, if you were to compare on to a typical impreza, evo or other well tuned car you can see why it takes abuse.
The early con rods are stronger than the later ones, but for higher performance cars where an engine rebuild is part of the package we use uprated custom made items.
The standard head gasket, if the car is tuned properly (including mapping) is good for up to 380 BHP. In our opinion the widefire item is only marginally better. For our 3.2 engines we don't use a head gasket at all, just rely on seriously precise engineering tolerances and specially designed sealing rings.
The standard clutch has design flaws, the turbo cup clutch is good for up to 400 BHP, but if abused is marginal at that power level. above 400 BHP we tend to recommend a uprated item which increases the friction area and the clamping force of the cover.
Through a lot of mad scientist experiments, we have found that some of the following examples give a good example of expected performance levels.
2.5L 1986 220 944 turbo - 9xx chipset alone - 290 bhp - 310 lbs of torque
2.5L 1989 250 944 turbo - 9xx chipset alone - 300 bhp - 320 lbs of torque
2.5L 1990 250 944 turbo - 9xx chipset, 9xx wastegate, - 320 BHP - 340 lbs of torque
2.5L 1990 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors - 320 BHP - 375 lbs of torque
2.5 1990 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx bb-turbo - 330 BHP - 385 lbs of torque @ 2800 rpm!!!
2.5 1990 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors - 9xx BB-turbo -
2.5L 1992 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx budjet turbo - 342 BHP - 350 lbs of torque.
2.5L 1992 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx BB-turbo, 9xx Maf kit - 360 BHP, 400 lbs of torque
2.5L 1992 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx BB-turbo, 9xx Maf kit, 9xx 3.0 inch exhaust, 417 BHP, 425lbs of torque
Dyno charts for all the above are available on request.
From these figures you can see what holds the cars back and what releases the power, much of this information also translates to the 2.8, 3.0 and 3.2 engines we produce. So may possibly help in developing Baz's car further.
I agree with Baz that reducing lag with the 944 turbo is an important thing to address, we have spent a lot of time fine tuning mapping, wastegates and turbo's to bring the boost point as early as possible, the last car in the list above achieved its peak torque at about 4000 rpm.
Too many people chase peak BHP, torque is king, its nice to see Baz is on the same page.
All in all, I agree with Baz, this 3.0 turbo is producing exactly the power it should and it will, like we found with our experiments in tuning torque in particular, be a much faster car than a car with a higher BHP with a power curve which just ramps up in BHP to the redline yet has less low down and midrange power.. not only this, but torque makes for a much better GT or touring car, a lot less stressful to drive.
Jon Mitchell
JMG Porsche
Baz's power output is roughly what we would expect to be seen from a 3.0 and otherwise standard setup.
The TDi style power curve which someone mentioned is due to restrictions in standard components.
We have found the following limitations on performance tuning and standard parts on the 944 turbo. Much of this is relevant whatever the engine size, due to flow restrictions.
Standard exhaust (non cat) 350-360 BHP
Standard k26/6 turbocharger (220 cars) 300 BHP (beyond this it becomes a heat pump)
Standard k26/8 turbocharger (250 cars) 320 BHP (beyond this it becomes a heat pump)
standard Cylinder head (2.5) 420 BHP
standard throttle body 420 BHP
Standard fuel pump - 320 BHP
Standard injectors - 320 BHP
Standard breather system - 340 BHP
Intake manifold - 420 BHP
All of these items reflect a 2.5 through to 3.2 944 turbo.
Other items which are poor performers are the camshaft (designed to hold performance back), intercooler (poor flow above 320 BHP), intake port design (designed to hold performance back)
The crankshafts are insanely strong, if you were to compare on to a typical impreza, evo or other well tuned car you can see why it takes abuse.
The early con rods are stronger than the later ones, but for higher performance cars where an engine rebuild is part of the package we use uprated custom made items.
The standard head gasket, if the car is tuned properly (including mapping) is good for up to 380 BHP. In our opinion the widefire item is only marginally better. For our 3.2 engines we don't use a head gasket at all, just rely on seriously precise engineering tolerances and specially designed sealing rings.
The standard clutch has design flaws, the turbo cup clutch is good for up to 400 BHP, but if abused is marginal at that power level. above 400 BHP we tend to recommend a uprated item which increases the friction area and the clamping force of the cover.
Through a lot of mad scientist experiments, we have found that some of the following examples give a good example of expected performance levels.
2.5L 1986 220 944 turbo - 9xx chipset alone - 290 bhp - 310 lbs of torque
2.5L 1989 250 944 turbo - 9xx chipset alone - 300 bhp - 320 lbs of torque
2.5L 1990 250 944 turbo - 9xx chipset, 9xx wastegate, - 320 BHP - 340 lbs of torque
2.5L 1990 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors - 320 BHP - 375 lbs of torque
2.5 1990 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx bb-turbo - 330 BHP - 385 lbs of torque @ 2800 rpm!!!
2.5 1990 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors - 9xx BB-turbo -
2.5L 1992 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx budjet turbo - 342 BHP - 350 lbs of torque.
2.5L 1992 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx BB-turbo, 9xx Maf kit - 360 BHP, 400 lbs of torque
2.5L 1992 250 944 turbo - 9xx chipset, 9xx wastegate, 9xx injectors, 9xx BB-turbo, 9xx Maf kit, 9xx 3.0 inch exhaust, 417 BHP, 425lbs of torque
Dyno charts for all the above are available on request.
From these figures you can see what holds the cars back and what releases the power, much of this information also translates to the 2.8, 3.0 and 3.2 engines we produce. So may possibly help in developing Baz's car further.
I agree with Baz that reducing lag with the 944 turbo is an important thing to address, we have spent a lot of time fine tuning mapping, wastegates and turbo's to bring the boost point as early as possible, the last car in the list above achieved its peak torque at about 4000 rpm.
Too many people chase peak BHP, torque is king, its nice to see Baz is on the same page.
All in all, I agree with Baz, this 3.0 turbo is producing exactly the power it should and it will, like we found with our experiments in tuning torque in particular, be a much faster car than a car with a higher BHP with a power curve which just ramps up in BHP to the redline yet has less low down and midrange power.. not only this, but torque makes for a much better GT or touring car, a lot less stressful to drive.
Jon Mitchell
JMG Porsche
Edited by jonmitchell on Saturday 7th November 13:19
NJH said:
Ian_UK1 said:
What a bizarre power curve! What happened above 5000 rpm? Even more, what about above 6000rpm? The car's producing way less power there than non-turbo cars. Is this down to a small turbo that can't maintain boost at those rpms or another serious restriction (intercooler?) in the intake system?
I would bet good money that it is the turbo and then to some extent exhaust. Top speed with that curve would probably be about what, 140 mph? My S2 tops out at 159 mph indicated at something just over 6K rpm, probably less then 150 real speed.I don't want to get involved in an argument about opinions but it is a fact that torque is the rate of change of power with respect to revs. I guess as an engineer you understand differential calculus, if you take your equation of power being proportional to torque times reves and differentiate with respect to revs, you can see that the rate of change of power (p) with repect to revs (r) (ie dp/dr) is then the torque.
hartech said:
A lot of very bizarre comments recently – all very difficult to deal with without offending people as many of them are not only misleading but completely wrong. I am frankly not sure if a group of people are trying to catch me out and have posted a load of cr*p to test me as their comments either reveal a serious lack of understanding of torque, power and gear ratio graphs or is this just the typical reaction one might expect on here from a small minority - or is it that people really don’t understand simple basic issues – but feel they should never the less post their criticisms as if they were the experts for others to absorb? Sorry if I seem bhy - but I am rather gob smacked about some of those comments from people I imagined knew better!
For those who don’t know who to believe – it is important that someone explains the real issues properly and as no one else seems to have jumped to correct them – it falls to me to do so. So - for those not sure what to believe - I will patiently try and explain (although for people whose understanding of dynamics is so far out – I doubt it will do any good and probably just provoke more uneducated criticism).
Firstly let us please remember that we set out specifically to construct a relatively simple, relatively inexpensive conversion that we planned to provide more bottom end torque, about 300 bhp top end and reduced turbo lag and we achieved all that.
Anywhere between 3000 and 6000 rpm this engine has anything between much more power or torque than a standard 944 250bhp turbo, S2 or 968 or finally at 6000 rpm about the same.
You have to drive the car from the revs you hit when you change gear to the maximum revs before changing up again.
In this gearbox from 1st to second you drop to 3500 rpm from which you must drive it again all the way to 6000 rpm. Just look at the torque or power graph from 3500 to 6000 rpm. Where is it less than the other engines and is it not plain obvious that it is massively more throughout? It is on average about 50% more!
From 2nd to third you drop to 4100 rpm which is the point of peak torque (and torque provides acceleration through the simple formula that Torque = (Inertial, drag and rolling resistance) * acceleration or put another way acceleration = Torque divided by various forms of resistance (which are the same for all the cars I have compared) and therefore acceleration is proportional to torque.
From 3rd to 4th you drop to 4450 rpm which is almost on peak torque and 100 lbsft more than a standard turbo.
From 4th to 5th you drop to 4750 rpm which is just coming on to peak power that is almost flat to 5500 rpm by which time you are travelling at about 147 mph.
These graphs show a superb match between the ratios available and the power and torque delivered.
Throughout all these gear changes you are constantly driving with much more torque or bhp than the other engines. This means that you will be accelerating to that speed very much quicker and get there very much sooner. 6000 rpm is about 160 mph in 5th and as you drive on to that speed – you are still driving with more power and torque than a standard 944 2.5 turbo but you got there much quicker. It is only at 160mph that the power then – for the first time – is slightly less than a 968 and std turbo (but still more than an S2 until about 6300 rpm or 168mph (where an S2 would have to rev to about 7200 with the same power to match it). It may well be that on a very long straight road – several miles long - a 250bhp turbo or a 968 may eventually reach a couple of mph more in top speed – but would they ever catch you up? – I doubt it.
I don’t know how NJH reckons my curve would only give 140mph – totally beyond my understanding that one! 6000 rpm in a 944 turbo is about 160 mph.
Another reverse lack of understanding is Ajax50’s comment that a steep power curve = loads of torque – as really the opposite is true (although to be fair he did support the advantages of torque – perhaps just got a bit muddled up about the graphs). Since power is proportional to torque * revs, if the torque was say a flat line – then the power would increase in a straight line as the revs rise. Since maximum torque is always achieved before maximum bhp, and the maximum possible is in proportion to the breathing capabilities of the engine – any increase in torque before top revs or peak bhp, will make the line higher at lower revs and therefore the bhp line would not be steeper but flatter. Anything that increases top revs and bhp at high revs more (which is the common tuning result) almost always lowers the torque at lower revs and the result again is always a steeper power curve. So once again the stated criticism is actually arse about face!
Those of you that don’t seem to understand the first thing about these graphs or power and torque really should try and resist the temptation to make firm statements on such a forum because many others simply don’t know what is right and wrong and it will not only mislead them and confuse many but also is very unfair criticism when in most cases it seems to be wrong and even the opposite of what actually happens.
Fortunately many others who have contacted me directly fully appreciate the results and some even can imagine driving the car from viewing the graphs and in one case has done both and found the graphical description and the practical experience the same. For those that quite rightly immediately recognised the achievement and the benefits of such a pair of graphs – can I add that although acceleration is proportional to torque (if resistance is constant or the same between compared cars) there is a phenomenon inside an engine and its transmission that relates to the stored energy between individual power pulses and strain energy lost as a result. It means that in actual fact there is a slight benefit from slightly reduced torque if the number of revs is increased and the strain energy lost is reduced. Put into more simple terms it means that a small increase in bhp at high revs can offer a small improvement in acceleration even if the torque is slightly lower and putting it simply it means that the best torque or power curve for the fastest acceleration, is one in which the torque is dropping off while the power is still increasing between the gear change revs.
However you must qualify that last point by stating that such benefits can only be exploited if you have the freedom to alter gear and final drive ratios. Unless you can alter these (and most of us are limited to the ratios we inherited with our car) for most cases these ratios are far too high to use on a race track or a drag race. Since - as you change up in the gears - the gear ratios gradually reduce the rev drop as you change up to higher gears - it means that most drivers on a track are using the lower gear ratios that require an engine to produce a relatively wide torque or power curve and not a narrow peaky one (even if that produces slightly more bhp to boast about). This is not true of GP racing or non restricted competition – but for most of us it is a fact of life we have to understand and adapt to if we are to get the best out of a road based car or gearbox.
I fully accept that there is more potential from this engine, and if it was easy to change the final drive ratio – there would be a benefit from different internal ratios as well and a different power curve may be better (although sometimes too close a ratio does not suit a turbo due to reduced time to spin it up under full power and heat etc) – but we don’t usually have that luxury and if not and if we are stuck with the gear ratios of our car and want to use it on the track or on the road (who needs more than 160mph on the road?) then looking at the rev band we are forced to work with at the speeds we are likely to encounter in the lower gears we will be using – it all means that a torquey engine like this one may be faster accelerating compared to a peaky one with more bhp but a narrower power band – and what’s more the torquey engine will be easier to drive out of corners on the limit as it will have more power control and therefore should lap quicker. There is a problem with the exhaust capacity - mainly when the back pressure on the valve overlap fights against the incoming charge pressure - but look we just put together a handful of parts to see what would happen and it achieved our objectives perfectly.
So compared to those objectives I don’t think a lot more development work is needed Ian UK1 and you really need to look at graphs showing the engine revs between the gear change points to fully understand that there is a power band you are forced to work with and the average power or torque in that power band is what is important and you also need to work out the speeds you will be reaching at various revs to understand that most road cars are massively over-geared for track use often only using two or three gears 2nd 3rd and 4th.
I am trying to develop a system to superimpose the test results onto a graph tracing the torque and power in each gear as the car accelerates and then to compare the areas under the graphs to see if a general rule of area to acceleration can be determined (I think it can).
Unfortunately all our actual road dyno test results have been carried out in second gear (as they are on public roads and for general safety) so at the moment I only have records for acceleration in second gear to compare between cars. The road dyno takes readings every 1/24th of a second and the results show that our 3 litre turbo in second between 3500 rpm and 6000 rpm is quarter of a second quicker (or 10%) than a standard 944 turbo, 0.6 of a second quicker (or 20%) than a 968 and three quarters of a second quicker (or 25%) than an S2 (and our car is geared slightly higher anyway).
It doesn’t matter if you understand graphs or engine characteristics – this is simply a lot faster in second gear and proves all the theory and who is right or wrong beyond any doubt. At the moment I can only speculate about how much quicker that will be in the higher gears – but all records (including Porsches own printed graphs) show that an S2 takes 28 secs 0 - 120 mph, and a 944 turbo takes 23 secs for the same 0-120 mph.
If you plot a graph of all 944/968 Porsche’s (from the manufacturers figures in the various handbooks) of say 0-120 mph and the time you will find an almost straight line graph for bhp and time and a very slight curve plotting torque against time. In both cases if you plot the torque and bhp of our engine on this graph is predicts a 0-120 mph time of 12 to 13 secs. I am not claiming this but I will test it out - although it feels very similar and when I prove it is similar - I hope it will put to bed the criticism that has recently seemed to imply that somehow this engine is all wrong, is slower than an S2 or somehow is undeserving of any recognition.
To be fair there is more on the 968.uk web site on this subject.
Thanks also for those of you who recognised our achievement with encouraging comments and support.
Baz
hy - but I am rather gob smacked about some of those comments from people I imagined knew better!For those who don’t know who to believe – it is important that someone explains the real issues properly and as no one else seems to have jumped to correct them – it falls to me to do so. So - for those not sure what to believe - I will patiently try and explain (although for people whose understanding of dynamics is so far out – I doubt it will do any good and probably just provoke more uneducated criticism).
Firstly let us please remember that we set out specifically to construct a relatively simple, relatively inexpensive conversion that we planned to provide more bottom end torque, about 300 bhp top end and reduced turbo lag and we achieved all that.
Anywhere between 3000 and 6000 rpm this engine has anything between much more power or torque than a standard 944 250bhp turbo, S2 or 968 or finally at 6000 rpm about the same.
You have to drive the car from the revs you hit when you change gear to the maximum revs before changing up again.
In this gearbox from 1st to second you drop to 3500 rpm from which you must drive it again all the way to 6000 rpm. Just look at the torque or power graph from 3500 to 6000 rpm. Where is it less than the other engines and is it not plain obvious that it is massively more throughout? It is on average about 50% more!
From 2nd to third you drop to 4100 rpm which is the point of peak torque (and torque provides acceleration through the simple formula that Torque = (Inertial, drag and rolling resistance) * acceleration or put another way acceleration = Torque divided by various forms of resistance (which are the same for all the cars I have compared) and therefore acceleration is proportional to torque.
From 3rd to 4th you drop to 4450 rpm which is almost on peak torque and 100 lbsft more than a standard turbo.
From 4th to 5th you drop to 4750 rpm which is just coming on to peak power that is almost flat to 5500 rpm by which time you are travelling at about 147 mph.
These graphs show a superb match between the ratios available and the power and torque delivered.
Throughout all these gear changes you are constantly driving with much more torque or bhp than the other engines. This means that you will be accelerating to that speed very much quicker and get there very much sooner. 6000 rpm is about 160 mph in 5th and as you drive on to that speed – you are still driving with more power and torque than a standard 944 2.5 turbo but you got there much quicker. It is only at 160mph that the power then – for the first time – is slightly less than a 968 and std turbo (but still more than an S2 until about 6300 rpm or 168mph (where an S2 would have to rev to about 7200 with the same power to match it). It may well be that on a very long straight road – several miles long - a 250bhp turbo or a 968 may eventually reach a couple of mph more in top speed – but would they ever catch you up? – I doubt it.
I don’t know how NJH reckons my curve would only give 140mph – totally beyond my understanding that one! 6000 rpm in a 944 turbo is about 160 mph.
Another reverse lack of understanding is Ajax50’s comment that a steep power curve = loads of torque – as really the opposite is true (although to be fair he did support the advantages of torque – perhaps just got a bit muddled up about the graphs). Since power is proportional to torque * revs, if the torque was say a flat line – then the power would increase in a straight line as the revs rise. Since maximum torque is always achieved before maximum bhp, and the maximum possible is in proportion to the breathing capabilities of the engine – any increase in torque before top revs or peak bhp, will make the line higher at lower revs and therefore the bhp line would not be steeper but flatter. Anything that increases top revs and bhp at high revs more (which is the common tuning result) almost always lowers the torque at lower revs and the result again is always a steeper power curve. So once again the stated criticism is actually arse about face!
Those of you that don’t seem to understand the first thing about these graphs or power and torque really should try and resist the temptation to make firm statements on such a forum because many others simply don’t know what is right and wrong and it will not only mislead them and confuse many but also is very unfair criticism when in most cases it seems to be wrong and even the opposite of what actually happens.
Fortunately many others who have contacted me directly fully appreciate the results and some even can imagine driving the car from viewing the graphs and in one case has done both and found the graphical description and the practical experience the same. For those that quite rightly immediately recognised the achievement and the benefits of such a pair of graphs – can I add that although acceleration is proportional to torque (if resistance is constant or the same between compared cars) there is a phenomenon inside an engine and its transmission that relates to the stored energy between individual power pulses and strain energy lost as a result. It means that in actual fact there is a slight benefit from slightly reduced torque if the number of revs is increased and the strain energy lost is reduced. Put into more simple terms it means that a small increase in bhp at high revs can offer a small improvement in acceleration even if the torque is slightly lower and putting it simply it means that the best torque or power curve for the fastest acceleration, is one in which the torque is dropping off while the power is still increasing between the gear change revs.
However you must qualify that last point by stating that such benefits can only be exploited if you have the freedom to alter gear and final drive ratios. Unless you can alter these (and most of us are limited to the ratios we inherited with our car) for most cases these ratios are far too high to use on a race track or a drag race. Since - as you change up in the gears - the gear ratios gradually reduce the rev drop as you change up to higher gears - it means that most drivers on a track are using the lower gear ratios that require an engine to produce a relatively wide torque or power curve and not a narrow peaky one (even if that produces slightly more bhp to boast about). This is not true of GP racing or non restricted competition – but for most of us it is a fact of life we have to understand and adapt to if we are to get the best out of a road based car or gearbox.
I fully accept that there is more potential from this engine, and if it was easy to change the final drive ratio – there would be a benefit from different internal ratios as well and a different power curve may be better (although sometimes too close a ratio does not suit a turbo due to reduced time to spin it up under full power and heat etc) – but we don’t usually have that luxury and if not and if we are stuck with the gear ratios of our car and want to use it on the track or on the road (who needs more than 160mph on the road?) then looking at the rev band we are forced to work with at the speeds we are likely to encounter in the lower gears we will be using – it all means that a torquey engine like this one may be faster accelerating compared to a peaky one with more bhp but a narrower power band – and what’s more the torquey engine will be easier to drive out of corners on the limit as it will have more power control and therefore should lap quicker. There is a problem with the exhaust capacity - mainly when the back pressure on the valve overlap fights against the incoming charge pressure - but look we just put together a handful of parts to see what would happen and it achieved our objectives perfectly.
So compared to those objectives I don’t think a lot more development work is needed Ian UK1 and you really need to look at graphs showing the engine revs between the gear change points to fully understand that there is a power band you are forced to work with and the average power or torque in that power band is what is important and you also need to work out the speeds you will be reaching at various revs to understand that most road cars are massively over-geared for track use often only using two or three gears 2nd 3rd and 4th.
I am trying to develop a system to superimpose the test results onto a graph tracing the torque and power in each gear as the car accelerates and then to compare the areas under the graphs to see if a general rule of area to acceleration can be determined (I think it can).
Unfortunately all our actual road dyno test results have been carried out in second gear (as they are on public roads and for general safety) so at the moment I only have records for acceleration in second gear to compare between cars. The road dyno takes readings every 1/24th of a second and the results show that our 3 litre turbo in second between 3500 rpm and 6000 rpm is quarter of a second quicker (or 10%) than a standard 944 turbo, 0.6 of a second quicker (or 20%) than a 968 and three quarters of a second quicker (or 25%) than an S2 (and our car is geared slightly higher anyway).
It doesn’t matter if you understand graphs or engine characteristics – this is simply a lot faster in second gear and proves all the theory and who is right or wrong beyond any doubt. At the moment I can only speculate about how much quicker that will be in the higher gears – but all records (including Porsches own printed graphs) show that an S2 takes 28 secs 0 - 120 mph, and a 944 turbo takes 23 secs for the same 0-120 mph.
If you plot a graph of all 944/968 Porsche’s (from the manufacturers figures in the various handbooks) of say 0-120 mph and the time you will find an almost straight line graph for bhp and time and a very slight curve plotting torque against time. In both cases if you plot the torque and bhp of our engine on this graph is predicts a 0-120 mph time of 12 to 13 secs. I am not claiming this but I will test it out - although it feels very similar and when I prove it is similar - I hope it will put to bed the criticism that has recently seemed to imply that somehow this engine is all wrong, is slower than an S2 or somehow is undeserving of any recognition.
To be fair there is more on the 968.uk web site on this subject.
Thanks also for those of you who recognised our achievement with encouraging comments and support.
Baz
Debates about the science are not the point. Baz has succeeded with what he set out to do and for me this is very important because he has shown that without special parts one can make a very big improvement in both how the car drives and its performance potential. Just looking at those graphs its clear that when you change gear the amount of power available in the next gear is greatly increased, by more then a 1/3. OK it would be great if it was much higher at 6k rpm but I think we all accept that isn't going to be possible without non stock turbo or exhaust etc. Baz said all along the point was to see what could be done with stock Porsche parts not what could be done to build the ultimate 3 litre turbo. I would certainly enjoy driving that car and I am sure everyone else on here would as well. Well done Baz because believe it or not but there are a good few of us around that have wondered what the result would be if a 2.7 head, S2/968 bottom end with lowered CR and turbo everything else was bolted together into a frankenmotor and now we know. Thank you.
AJAX50 said:
I don't want to get involved in an argument about opinions but it is a fact that torque is the rate of change of power with respect to revs. I guess as an engineer you understand differential calculus, if you take your equation of power being proportional to torque times reves and differentiate with respect to revs, you can see that the rate of change of power (p) with repect to revs (r) (ie dp/dr) is then the torque.
hartech said:
A lot of very bizarre comments recently – all very difficult to deal with without offending people as many of them are not only misleading but completely wrong. I am frankly not sure if a group of people are trying to catch me out and have posted a load of cr*p to test me as their comments either reveal a serious lack of understanding of torque, power and gear ratio graphs or is this just the typical reaction one might expect on here from a small minority - or is it that people really don’t understand simple basic issues – but feel they should never the less post their criticisms as if they were the experts for others to absorb? Sorry if I seem bhy - but I am rather gob smacked about some of those comments from people I imagined knew better!
For those who don’t know who to believe – it is important that someone explains the real issues properly and as no one else seems to have jumped to correct them – it falls to me to do so. So - for those not sure what to believe - I will patiently try and explain (although for people whose understanding of dynamics is so far out – I doubt it will do any good and probably just provoke more uneducated criticism).
Firstly let us please remember that we set out specifically to construct a relatively simple, relatively inexpensive conversion that we planned to provide more bottom end torque, about 300 bhp top end and reduced turbo lag and we achieved all that.
Anywhere between 3000 and 6000 rpm this engine has anything between much more power or torque than a standard 944 250bhp turbo, S2 or 968 or finally at 6000 rpm about the same.
You have to drive the car from the revs you hit when you change gear to the maximum revs before changing up again.
In this gearbox from 1st to second you drop to 3500 rpm from which you must drive it again all the way to 6000 rpm. Just look at the torque or power graph from 3500 to 6000 rpm. Where is it less than the other engines and is it not plain obvious that it is massively more throughout? It is on average about 50% more!
From 2nd to third you drop to 4100 rpm which is the point of peak torque (and torque provides acceleration through the simple formula that Torque = (Inertial, drag and rolling resistance) * acceleration or put another way acceleration = Torque divided by various forms of resistance (which are the same for all the cars I have compared) and therefore acceleration is proportional to torque.
From 3rd to 4th you drop to 4450 rpm which is almost on peak torque and 100 lbsft more than a standard turbo.
From 4th to 5th you drop to 4750 rpm which is just coming on to peak power that is almost flat to 5500 rpm by which time you are travelling at about 147 mph.
These graphs show a superb match between the ratios available and the power and torque delivered.
Throughout all these gear changes you are constantly driving with much more torque or bhp than the other engines. This means that you will be accelerating to that speed very much quicker and get there very much sooner. 6000 rpm is about 160 mph in 5th and as you drive on to that speed – you are still driving with more power and torque than a standard 944 2.5 turbo but you got there much quicker. It is only at 160mph that the power then – for the first time – is slightly less than a 968 and std turbo (but still more than an S2 until about 6300 rpm or 168mph (where an S2 would have to rev to about 7200 with the same power to match it). It may well be that on a very long straight road – several miles long - a 250bhp turbo or a 968 may eventually reach a couple of mph more in top speed – but would they ever catch you up? – I doubt it.
I don’t know how NJH reckons my curve would only give 140mph – totally beyond my understanding that one! 6000 rpm in a 944 turbo is about 160 mph.
Another reverse lack of understanding is Ajax50’s comment that a steep power curve = loads of torque – as really the opposite is true (although to be fair he did support the advantages of torque – perhaps just got a bit muddled up about the graphs). Since power is proportional to torque * revs, if the torque was say a flat line – then the power would increase in a straight line as the revs rise. Since maximum torque is always achieved before maximum bhp, and the maximum possible is in proportion to the breathing capabilities of the engine – any increase in torque before top revs or peak bhp, will make the line higher at lower revs and therefore the bhp line would not be steeper but flatter. Anything that increases top revs and bhp at high revs more (which is the common tuning result) almost always lowers the torque at lower revs and the result again is always a steeper power curve. So once again the stated criticism is actually arse about face!
Those of you that don’t seem to understand the first thing about these graphs or power and torque really should try and resist the temptation to make firm statements on such a forum because many others simply don’t know what is right and wrong and it will not only mislead them and confuse many but also is very unfair criticism when in most cases it seems to be wrong and even the opposite of what actually happens.
Fortunately many others who have contacted me directly fully appreciate the results and some even can imagine driving the car from viewing the graphs and in one case has done both and found the graphical description and the practical experience the same. For those that quite rightly immediately recognised the achievement and the benefits of such a pair of graphs – can I add that although acceleration is proportional to torque (if resistance is constant or the same between compared cars) there is a phenomenon inside an engine and its transmission that relates to the stored energy between individual power pulses and strain energy lost as a result. It means that in actual fact there is a slight benefit from slightly reduced torque if the number of revs is increased and the strain energy lost is reduced. Put into more simple terms it means that a small increase in bhp at high revs can offer a small improvement in acceleration even if the torque is slightly lower and putting it simply it means that the best torque or power curve for the fastest acceleration, is one in which the torque is dropping off while the power is still increasing between the gear change revs.
However you must qualify that last point by stating that such benefits can only be exploited if you have the freedom to alter gear and final drive ratios. Unless you can alter these (and most of us are limited to the ratios we inherited with our car) for most cases these ratios are far too high to use on a race track or a drag race. Since - as you change up in the gears - the gear ratios gradually reduce the rev drop as you change up to higher gears - it means that most drivers on a track are using the lower gear ratios that require an engine to produce a relatively wide torque or power curve and not a narrow peaky one (even if that produces slightly more bhp to boast about). This is not true of GP racing or non restricted competition – but for most of us it is a fact of life we have to understand and adapt to if we are to get the best out of a road based car or gearbox.
I fully accept that there is more potential from this engine, and if it was easy to change the final drive ratio – there would be a benefit from different internal ratios as well and a different power curve may be better (although sometimes too close a ratio does not suit a turbo due to reduced time to spin it up under full power and heat etc) – but we don’t usually have that luxury and if not and if we are stuck with the gear ratios of our car and want to use it on the track or on the road (who needs more than 160mph on the road?) then looking at the rev band we are forced to work with at the speeds we are likely to encounter in the lower gears we will be using – it all means that a torquey engine like this one may be faster accelerating compared to a peaky one with more bhp but a narrower power band – and what’s more the torquey engine will be easier to drive out of corners on the limit as it will have more power control and therefore should lap quicker. There is a problem with the exhaust capacity - mainly when the back pressure on the valve overlap fights against the incoming charge pressure - but look we just put together a handful of parts to see what would happen and it achieved our objectives perfectly.
So compared to those objectives I don’t think a lot more development work is needed Ian UK1 and you really need to look at graphs showing the engine revs between the gear change points to fully understand that there is a power band you are forced to work with and the average power or torque in that power band is what is important and you also need to work out the speeds you will be reaching at various revs to understand that most road cars are massively over-geared for track use often only using two or three gears 2nd 3rd and 4th.
I am trying to develop a system to superimpose the test results onto a graph tracing the torque and power in each gear as the car accelerates and then to compare the areas under the graphs to see if a general rule of area to acceleration can be determined (I think it can).
Unfortunately all our actual road dyno test results have been carried out in second gear (as they are on public roads and for general safety) so at the moment I only have records for acceleration in second gear to compare between cars. The road dyno takes readings every 1/24th of a second and the results show that our 3 litre turbo in second between 3500 rpm and 6000 rpm is quarter of a second quicker (or 10%) than a standard 944 turbo, 0.6 of a second quicker (or 20%) than a 968 and three quarters of a second quicker (or 25%) than an S2 (and our car is geared slightly higher anyway).
It doesn’t matter if you understand graphs or engine characteristics – this is simply a lot faster in second gear and proves all the theory and who is right or wrong beyond any doubt. At the moment I can only speculate about how much quicker that will be in the higher gears – but all records (including Porsches own printed graphs) show that an S2 takes 28 secs 0 - 120 mph, and a 944 turbo takes 23 secs for the same 0-120 mph.
If you plot a graph of all 944/968 Porsche’s (from the manufacturers figures in the various handbooks) of say 0-120 mph and the time you will find an almost straight line graph for bhp and time and a very slight curve plotting torque against time. In both cases if you plot the torque and bhp of our engine on this graph is predicts a 0-120 mph time of 12 to 13 secs. I am not claiming this but I will test it out - although it feels very similar and when I prove it is similar - I hope it will put to bed the criticism that has recently seemed to imply that somehow this engine is all wrong, is slower than an S2 or somehow is undeserving of any recognition.
To be fair there is more on the 968.uk web site on this subject.
Thanks also for those of you who recognised our achievement with encouraging comments and support.
Baz
hy - but I am rather gob smacked about some of those comments from people I imagined knew better!For those who don’t know who to believe – it is important that someone explains the real issues properly and as no one else seems to have jumped to correct them – it falls to me to do so. So - for those not sure what to believe - I will patiently try and explain (although for people whose understanding of dynamics is so far out – I doubt it will do any good and probably just provoke more uneducated criticism).
Firstly let us please remember that we set out specifically to construct a relatively simple, relatively inexpensive conversion that we planned to provide more bottom end torque, about 300 bhp top end and reduced turbo lag and we achieved all that.
Anywhere between 3000 and 6000 rpm this engine has anything between much more power or torque than a standard 944 250bhp turbo, S2 or 968 or finally at 6000 rpm about the same.
You have to drive the car from the revs you hit when you change gear to the maximum revs before changing up again.
In this gearbox from 1st to second you drop to 3500 rpm from which you must drive it again all the way to 6000 rpm. Just look at the torque or power graph from 3500 to 6000 rpm. Where is it less than the other engines and is it not plain obvious that it is massively more throughout? It is on average about 50% more!
From 2nd to third you drop to 4100 rpm which is the point of peak torque (and torque provides acceleration through the simple formula that Torque = (Inertial, drag and rolling resistance) * acceleration or put another way acceleration = Torque divided by various forms of resistance (which are the same for all the cars I have compared) and therefore acceleration is proportional to torque.
From 3rd to 4th you drop to 4450 rpm which is almost on peak torque and 100 lbsft more than a standard turbo.
From 4th to 5th you drop to 4750 rpm which is just coming on to peak power that is almost flat to 5500 rpm by which time you are travelling at about 147 mph.
These graphs show a superb match between the ratios available and the power and torque delivered.
Throughout all these gear changes you are constantly driving with much more torque or bhp than the other engines. This means that you will be accelerating to that speed very much quicker and get there very much sooner. 6000 rpm is about 160 mph in 5th and as you drive on to that speed – you are still driving with more power and torque than a standard 944 2.5 turbo but you got there much quicker. It is only at 160mph that the power then – for the first time – is slightly less than a 968 and std turbo (but still more than an S2 until about 6300 rpm or 168mph (where an S2 would have to rev to about 7200 with the same power to match it). It may well be that on a very long straight road – several miles long - a 250bhp turbo or a 968 may eventually reach a couple of mph more in top speed – but would they ever catch you up? – I doubt it.
I don’t know how NJH reckons my curve would only give 140mph – totally beyond my understanding that one! 6000 rpm in a 944 turbo is about 160 mph.
Another reverse lack of understanding is Ajax50’s comment that a steep power curve = loads of torque – as really the opposite is true (although to be fair he did support the advantages of torque – perhaps just got a bit muddled up about the graphs). Since power is proportional to torque * revs, if the torque was say a flat line – then the power would increase in a straight line as the revs rise. Since maximum torque is always achieved before maximum bhp, and the maximum possible is in proportion to the breathing capabilities of the engine – any increase in torque before top revs or peak bhp, will make the line higher at lower revs and therefore the bhp line would not be steeper but flatter. Anything that increases top revs and bhp at high revs more (which is the common tuning result) almost always lowers the torque at lower revs and the result again is always a steeper power curve. So once again the stated criticism is actually arse about face!
Those of you that don’t seem to understand the first thing about these graphs or power and torque really should try and resist the temptation to make firm statements on such a forum because many others simply don’t know what is right and wrong and it will not only mislead them and confuse many but also is very unfair criticism when in most cases it seems to be wrong and even the opposite of what actually happens.
Fortunately many others who have contacted me directly fully appreciate the results and some even can imagine driving the car from viewing the graphs and in one case has done both and found the graphical description and the practical experience the same. For those that quite rightly immediately recognised the achievement and the benefits of such a pair of graphs – can I add that although acceleration is proportional to torque (if resistance is constant or the same between compared cars) there is a phenomenon inside an engine and its transmission that relates to the stored energy between individual power pulses and strain energy lost as a result. It means that in actual fact there is a slight benefit from slightly reduced torque if the number of revs is increased and the strain energy lost is reduced. Put into more simple terms it means that a small increase in bhp at high revs can offer a small improvement in acceleration even if the torque is slightly lower and putting it simply it means that the best torque or power curve for the fastest acceleration, is one in which the torque is dropping off while the power is still increasing between the gear change revs.
However you must qualify that last point by stating that such benefits can only be exploited if you have the freedom to alter gear and final drive ratios. Unless you can alter these (and most of us are limited to the ratios we inherited with our car) for most cases these ratios are far too high to use on a race track or a drag race. Since - as you change up in the gears - the gear ratios gradually reduce the rev drop as you change up to higher gears - it means that most drivers on a track are using the lower gear ratios that require an engine to produce a relatively wide torque or power curve and not a narrow peaky one (even if that produces slightly more bhp to boast about). This is not true of GP racing or non restricted competition – but for most of us it is a fact of life we have to understand and adapt to if we are to get the best out of a road based car or gearbox.
I fully accept that there is more potential from this engine, and if it was easy to change the final drive ratio – there would be a benefit from different internal ratios as well and a different power curve may be better (although sometimes too close a ratio does not suit a turbo due to reduced time to spin it up under full power and heat etc) – but we don’t usually have that luxury and if not and if we are stuck with the gear ratios of our car and want to use it on the track or on the road (who needs more than 160mph on the road?) then looking at the rev band we are forced to work with at the speeds we are likely to encounter in the lower gears we will be using – it all means that a torquey engine like this one may be faster accelerating compared to a peaky one with more bhp but a narrower power band – and what’s more the torquey engine will be easier to drive out of corners on the limit as it will have more power control and therefore should lap quicker. There is a problem with the exhaust capacity - mainly when the back pressure on the valve overlap fights against the incoming charge pressure - but look we just put together a handful of parts to see what would happen and it achieved our objectives perfectly.
So compared to those objectives I don’t think a lot more development work is needed Ian UK1 and you really need to look at graphs showing the engine revs between the gear change points to fully understand that there is a power band you are forced to work with and the average power or torque in that power band is what is important and you also need to work out the speeds you will be reaching at various revs to understand that most road cars are massively over-geared for track use often only using two or three gears 2nd 3rd and 4th.
I am trying to develop a system to superimpose the test results onto a graph tracing the torque and power in each gear as the car accelerates and then to compare the areas under the graphs to see if a general rule of area to acceleration can be determined (I think it can).
Unfortunately all our actual road dyno test results have been carried out in second gear (as they are on public roads and for general safety) so at the moment I only have records for acceleration in second gear to compare between cars. The road dyno takes readings every 1/24th of a second and the results show that our 3 litre turbo in second between 3500 rpm and 6000 rpm is quarter of a second quicker (or 10%) than a standard 944 turbo, 0.6 of a second quicker (or 20%) than a 968 and three quarters of a second quicker (or 25%) than an S2 (and our car is geared slightly higher anyway).
It doesn’t matter if you understand graphs or engine characteristics – this is simply a lot faster in second gear and proves all the theory and who is right or wrong beyond any doubt. At the moment I can only speculate about how much quicker that will be in the higher gears – but all records (including Porsches own printed graphs) show that an S2 takes 28 secs 0 - 120 mph, and a 944 turbo takes 23 secs for the same 0-120 mph.
If you plot a graph of all 944/968 Porsche’s (from the manufacturers figures in the various handbooks) of say 0-120 mph and the time you will find an almost straight line graph for bhp and time and a very slight curve plotting torque against time. In both cases if you plot the torque and bhp of our engine on this graph is predicts a 0-120 mph time of 12 to 13 secs. I am not claiming this but I will test it out - although it feels very similar and when I prove it is similar - I hope it will put to bed the criticism that has recently seemed to imply that somehow this engine is all wrong, is slower than an S2 or somehow is undeserving of any recognition.
To be fair there is more on the 968.uk web site on this subject.
Thanks also for those of you who recognised our achievement with encouraging comments and support.
Baz
Just curious about a couple of things here Baz. Is this with a stock turbo? If so, K26/8?
Not sure that I'd use stock 3L pistons as they're cast not forged. Not expensive to get a set of custom pistons anyway.
What sort of liners are you talking about? Wet or dry? Having gone down the path of the MID installation out of Darton USA, I would be interested to see if this is the path your are contemplating. Of course Darton make dry sleeves. This is what I have wound up with in my 3L motor.
I think judging by your tq curve your car would be very driveable. Do you run with an LSD? Also we have changed our Crown Wheel and Pinions to that of the S2 which shortens the long stock 951 ratio by about 15%. Great for town and track. Oh, this is with our 2.5L motors though. With the 3L motor I will go back to a stock 951 tranny. Drive the car on torque, not revs.
Patrick.
Not sure that I'd use stock 3L pistons as they're cast not forged. Not expensive to get a set of custom pistons anyway.
What sort of liners are you talking about? Wet or dry? Having gone down the path of the MID installation out of Darton USA, I would be interested to see if this is the path your are contemplating. Of course Darton make dry sleeves. This is what I have wound up with in my 3L motor.
I think judging by your tq curve your car would be very driveable. Do you run with an LSD? Also we have changed our Crown Wheel and Pinions to that of the S2 which shortens the long stock 951 ratio by about 15%. Great for town and track. Oh, this is with our 2.5L motors though. With the 3L motor I will go back to a stock 951 tranny. Drive the car on torque, not revs.
Patrick.
Edited by 333pg333 on Monday 9th November 07:30
Hi Patrick, I didn't realise you were on Pistonheads too 
The only thing that Barry has done is change the engine and the mapping, everything else is a standard 250bhp Turbo. It wasn't an exercise to build a max modded turbo, but simply to prove that a 3 litre could be easily built using existing Porsche parts. I'll let you know just how driveable it is, as he's kindly letting me test it on track on Wednesday
If he allows it I'll fix my bullet cam to the inside and get some good video to share
The only thing that Barry has done is change the engine and the mapping, everything else is a standard 250bhp Turbo. It wasn't an exercise to build a max modded turbo, but simply to prove that a 3 litre could be easily built using existing Porsche parts. I'll let you know just how driveable it is, as he's kindly letting me test it on track on Wednesday
If he allows it I'll fix my bullet cam to the inside and get some good video to share
I think for a prototype engine on a budget where further tuning isnt on the cards, the pistons should be ok as long as the mapping is good.
What Baz has done is a good down to earth investigation into whats possible where the customer wants a big torque increase, on a budget especially where for example the engine has expired anyway.
Paul, if you can strap on a webcam that will be excellent, mostly because the more videos on youtube of these cars modified will open a lot of eyes to the possibilities with the 944 turbo to the general public.
What Baz has done is a good down to earth investigation into whats possible where the customer wants a big torque increase, on a budget especially where for example the engine has expired anyway.
Paul, if you can strap on a webcam that will be excellent, mostly because the more videos on youtube of these cars modified will open a lot of eyes to the possibilities with the 944 turbo to the general public.
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