My name is peter Burgess and I am a tuning junky
Discussion
PeterBurgess said:
We have hit 50+ bhp losses at 160 mph, I think one would need a rather special motor to take it up to this speed and power absorption?
Stone age suits me, very repeatable thanks.
Peter
A 100 hp three phase motor can be bought new for a couple of thousand quid, second hand for about a quarter of that.Stone age suits me, very repeatable thanks.
Peter
Enjoy the stone age.
stevieturbo said:
Screw guesstimated figures for transmission. Measure at the wheels.
A coastdown test is a totally unloaded test so really dont get how it can be valid.
Although for a before/after tuning, it shouldnt really matter either way ?
A coastdown test is a totally unloaded test so really dont get how it can be valid.
Although for a before/after tuning, it shouldnt really matter either way ?
Measure at the filler cap, it adds about 70~75% to the figure
I find it fascinating folk seem to just look for the negatives not positives. Stevie, am I right you only work mainly on your one comp car? I use the figures we get to compare and improve many cars and bikes. Tango, I haven't a clue what you do maybe you would enlighten me?
The coastdown losses are for comparison purposes, I think most folk would think it a pretty good idea to get all that lovely power to the wheels rather than lose it in unnecessary friction? It works well for our race stuff.
Was that Performance Bikes mag? I got on well with John R when I met him for an article in the late 80s and I stil get on well with Dave W now running Emerald, I have a lot or respect for them.
Tango, a 100 hp motor and all the time to fit and try and make it work would be both time consuming and expensive, how would it benefit my customers and my research and how much do you think it would cost? Maybe you would like to produce a project we could discuss?
Overall, with the Dynocom rollers we have moved forwards and improved power outputs both at the engine and through transmission testing. There may be various criticisms of the set up as with all dynos whether rollers or engine dyno, that is fair play. However, I would ask those who knock, how do they compare and contrast power outputs and transmission losses? Without reliable, repeatable measuring it can only be guesswork or head in sand or 'it'll be alright on the night'philosophy? When a race car comes in with the driver saying it feels a little soft we do runs to check wheel power and transmission losses to see how the graphs compare to the last time in. This way we have picked up diffs failing, gearboxes failing and even prop joint failure onsets. Without measuring and testing it is guesswork and or seat of the pants. As I said, many race teams use the inertia testing, including coastdowns to optimise power output, must be a reason for that. Over the years I have found folk who don't rate dynos and the uses of dynos, rollers or engine and even pooh pooh the humble static state flow bench don't win much on the track. The other positive I get is a lot of input from many different race drivers and engine builders and head modifiers, I learn from these meetings and we all move forwards. Isolated and we lose the race.
I started the thread to invite dyno operators, engineers, power junkies etc to join in, does no one have positives? Would that be a sad indictment of the attitude of threaders? Or maybe some folk are concerned about posting in case they get attacked?
Peter
The coastdown losses are for comparison purposes, I think most folk would think it a pretty good idea to get all that lovely power to the wheels rather than lose it in unnecessary friction? It works well for our race stuff.
Was that Performance Bikes mag? I got on well with John R when I met him for an article in the late 80s and I stil get on well with Dave W now running Emerald, I have a lot or respect for them.
Tango, a 100 hp motor and all the time to fit and try and make it work would be both time consuming and expensive, how would it benefit my customers and my research and how much do you think it would cost? Maybe you would like to produce a project we could discuss?
Overall, with the Dynocom rollers we have moved forwards and improved power outputs both at the engine and through transmission testing. There may be various criticisms of the set up as with all dynos whether rollers or engine dyno, that is fair play. However, I would ask those who knock, how do they compare and contrast power outputs and transmission losses? Without reliable, repeatable measuring it can only be guesswork or head in sand or 'it'll be alright on the night'philosophy? When a race car comes in with the driver saying it feels a little soft we do runs to check wheel power and transmission losses to see how the graphs compare to the last time in. This way we have picked up diffs failing, gearboxes failing and even prop joint failure onsets. Without measuring and testing it is guesswork and or seat of the pants. As I said, many race teams use the inertia testing, including coastdowns to optimise power output, must be a reason for that. Over the years I have found folk who don't rate dynos and the uses of dynos, rollers or engine and even pooh pooh the humble static state flow bench don't win much on the track. The other positive I get is a lot of input from many different race drivers and engine builders and head modifiers, I learn from these meetings and we all move forwards. Isolated and we lose the race.
I started the thread to invite dyno operators, engineers, power junkies etc to join in, does no one have positives? Would that be a sad indictment of the attitude of threaders? Or maybe some folk are concerned about posting in case they get attacked?
Peter
Part of my ever expanding duties at work have got me in to digital communications/social media, you will see more negative posts earlier on, if we had a like button you would find more likes compared with negative posts.
It is the psychology of some to do this and you need to develope a thick skin when using social media.
We read, we listen, we discuss and react, we really try not to take it personally .
On a blog forum we have like and dislike buttons but this got complicated when you could like/dislike not only the original discussion post but also the individual responses.
This thread is starting to give me an understanding of the technical complexities of a rolling road and the lengths the operator has to go to just to get consistency.
Peter that's a "Like" from me.
It is the psychology of some to do this and you need to develope a thick skin when using social media.
We read, we listen, we discuss and react, we really try not to take it personally .
On a blog forum we have like and dislike buttons but this got complicated when you could like/dislike not only the original discussion post but also the individual responses.
This thread is starting to give me an understanding of the technical complexities of a rolling road and the lengths the operator has to go to just to get consistency.
Peter that's a "Like" from me.
PeterBurgess said:
I find it fascinating folk seem to just look for the negatives not positives. Stevie, am I right you only work mainly on your one comp car? I use the figures we get to compare and improve many cars and bikes.
I work on a small handful of cars, although obviously have no access to a dyno etc.I'd certainly like to own one....but it wouldnt be a viable proposition over here and TBH all the cars I've either built, helped work on, tuned etc etc since the dawn of time....have always been the fastest either in their respective classes or often much further afield too. But also all boosted. I learnt a long time ago that in order to go fast, n/a is largely futile.
Paul, I am very happy to pass on any experience I can, we all have different skills and it is nice to share. I pressed a mental 'like' when I read your post.
It is the same with my engine dyno install. I have slowed down to a crawl but cheered up as I had a phone call about prepping a head for a firm and during the conversation the topic of dynos came up. Low and behold, this was the guy who originally was responsible for buying, installing and running the Lister dyno we bought. He said it was last used in 2004 and gave me loads of info and kindly offered to jump in and help if we need it. Then, yesterday another mate comes in who has dealings with SU and sportdevices dyno software as well as running a comp car prep business. I haven't seen him for a couple of years so showed him our dyno...turns out he worked on it in the early 2000s, small world and yet more kind offers of sleeves rolled up and let's get stuck in
I have often thought, in your specific case Stevie, you are an unusual (in terms of not many folk in your enviable position) yet very lucky man who suffers from a surfeit of power when the rest of us are trying to wring out every last drop of power and grunt juice
Peter
It is the same with my engine dyno install. I have slowed down to a crawl but cheered up as I had a phone call about prepping a head for a firm and during the conversation the topic of dynos came up. Low and behold, this was the guy who originally was responsible for buying, installing and running the Lister dyno we bought. He said it was last used in 2004 and gave me loads of info and kindly offered to jump in and help if we need it. Then, yesterday another mate comes in who has dealings with SU and sportdevices dyno software as well as running a comp car prep business. I haven't seen him for a couple of years so showed him our dyno...turns out he worked on it in the early 2000s, small world and yet more kind offers of sleeves rolled up and let's get stuck in
I have often thought, in your specific case Stevie, you are an unusual (in terms of not many folk in your enviable position) yet very lucky man who suffers from a surfeit of power when the rest of us are trying to wring out every last drop of power and grunt juice
Peter
PeterBurgess said:
I started the thread to invite dyno operators, engineers, power junkies etc to join in, does no one have positives?
I'm in what I suspect is the silent majority who aren't qualified to contribute but are reading and learning and enjoying. I'm not sure whether I qualify even as a power junkie - I'm a DIY tinkerer and my only first hand 'tuning' (using the term loosely) experience is taking my MegaSquirt installation from 'barely starts and runs' to emissions compliant, tractable with reasonable AFRs and no detectable det. It uses two stage injection and getting the handover to work was a pita. This was all on the real road and done by hours of painstaking data logging and incremental adjustments. A rolling road would have been much easier, but this way suited my budget better. I neither know nor care how much losses are in the transmission or what the absolute numbers are - only whether I can make the car a bit more tractable and a bit faster. When somebody down the pub asks me what it makes, I can pluck a number out of the air as well as the next guy. I hope you'll take this as a positive. Hi Peter
Who am I to judge what is positive or not? It is good you have come on and posted about what you have done, I rather think you fall into tuner junky purely on the hours hands on tuning and probably the many, many more hours thinking about it and what if and why not!
We have quite a few customers who do all they can then do a run or three on the rollers to see how close they were and if we can improve it, all part and parcel of 'The Game'
Peter
Who am I to judge what is positive or not? It is good you have come on and posted about what you have done, I rather think you fall into tuner junky purely on the hours hands on tuning and probably the many, many more hours thinking about it and what if and why not!
We have quite a few customers who do all they can then do a run or three on the rollers to see how close they were and if we can improve it, all part and parcel of 'The Game'
Peter
PeterBurgess said:
I have often thought, in your specific case Stevie, you are an unusual (in terms of not many folk in your enviable position) yet very lucky man who suffers from a surfeit of power when the rest of us are trying to wring out every last drop of power and grunt juice
Peter
It's just different goals etc....obviously trying to remain within a specific engine size class, n/a etc etc it will be far far harder to be at the top of that class in terms of performance.Peter
That sort of thing just isnt for me, ultimately it's just restrictive, very expensive and for minimal real gains.
Whilst there are many caveats....in simple terms more power = go faster. So I've always chosen the more power route, and boost does that ! And even if it doesnt make you go faster...it still puts a smile on your face lol
Peter, you are clearly getting useful information from your roll down tests, so obviously it's worth it for you.
A word of warning - coastdown losses are only an indication. Losses vary not just with speed, but with torque at the wheel - as the load increases, the tyre deforms more on the roller. Gearbox and diff losses also go up with transmitted torque.
We did a lot of testing to characterise driveline losses, and at the end of the day flywheel power on a chassis dyno is only an estimate.
For tuning, it's not all that important - as long as the readings are consistant, you know whether you are improving the power/torque, at what revs, and by how much.
The key to consistancy is to tie the car down the same way each time, same strap tension, same tyres and pressures, run in the same gear, etc.
Our test mule we warm up under light load, then do 3 consecutive runs. The power starts dropping off as the engine gets hotter, so runs 2 & 3 are best, a 4th run without letting the car cool will be lower. We warm the car up at around 100 kph - cold gearbox and diff oil robs some power.
Using the same vehicle and test procedure, we get power readings within a few % day in, day out year round. Significant variations tend to be an indication that the test hack needs a bit of tlc.
I'm on the other side of the fence to Peter - I do control systems and software for a dyno manufacturer.
While I am not a tuner, I have tuned a couple of cars and done hundreds of dyno runs.
A word of warning - coastdown losses are only an indication. Losses vary not just with speed, but with torque at the wheel - as the load increases, the tyre deforms more on the roller. Gearbox and diff losses also go up with transmitted torque.
We did a lot of testing to characterise driveline losses, and at the end of the day flywheel power on a chassis dyno is only an estimate.
For tuning, it's not all that important - as long as the readings are consistant, you know whether you are improving the power/torque, at what revs, and by how much.
The key to consistancy is to tie the car down the same way each time, same strap tension, same tyres and pressures, run in the same gear, etc.
Our test mule we warm up under light load, then do 3 consecutive runs. The power starts dropping off as the engine gets hotter, so runs 2 & 3 are best, a 4th run without letting the car cool will be lower. We warm the car up at around 100 kph - cold gearbox and diff oil robs some power.
Using the same vehicle and test procedure, we get power readings within a few % day in, day out year round. Significant variations tend to be an indication that the test hack needs a bit of tlc.
I'm on the other side of the fence to Peter - I do control systems and software for a dyno manufacturer.
While I am not a tuner, I have tuned a couple of cars and done hundreds of dyno runs.
Hi Adrian
You have given me loads of useful info before.
Are you running pau runs to have that quick an effect on power readings?
I presume I get less deflection running inertia rather than full pau controlled runs?
One topic I think folk are a little frightened of talking about is turbo engine testing. I find it damned nigh impossible to keep all temps just so. I prefer testing in the winter time when it is usually cooler. What I do find fascinating is the power graphs vs temp with turbos. It is very near perfect power differences for manifold temps almost like a physics lesson BUT doesn't help tuning!
Peter
You have given me loads of useful info before.
Are you running pau runs to have that quick an effect on power readings?
I presume I get less deflection running inertia rather than full pau controlled runs?
One topic I think folk are a little frightened of talking about is turbo engine testing. I find it damned nigh impossible to keep all temps just so. I prefer testing in the winter time when it is usually cooler. What I do find fascinating is the power graphs vs temp with turbos. It is very near perfect power differences for manifold temps almost like a physics lesson BUT doesn't help tuning!
Peter
Our dynos are all eddy-current retarders, or paus. There is still inertia to be factored in, but it's the retarder applying nearly all the load.
I avoid turbo cars - there are so many more variables, and keeping charge temeratures down is always an issue.
There's a reason our test mule is a 3.8l v6 in standard tune - although the raw power varies with air temperature, it is very predictable, and matches the atmospheric correction well.
By the way, the engine test standard I know best (SAE J1995) is for engine dynos, and sets limits on allowable air temperature and pressure, and total correction factor. Unfortunately, without an airconditioned cell you can't stick to those limits and still run a workshop.
We have customers whose shops can go from 10 degrees C to over 40 during the course of a day, let alone running the same car summer and winter.
I'm not sure what you mean by less deflection? Generally speaking tyre deflection is related to the amount of force transmitted through the tyre - in order to prevent wheelspin, the strapping usually works to pull they tyre down as it tries to climb the front roller under power.
It's only really an issue if running in a low gear, or lots of power. Strapping down 1,000 hp dyno queens I leave to the experts.
We have started building hub dynos, and it will be interesting to compare the same cars back-to-back between hub and chassis. Unfortunately we don't have the luxury of keeping one for r&d, so comparisons will have to wait.
I avoid turbo cars - there are so many more variables, and keeping charge temeratures down is always an issue.
There's a reason our test mule is a 3.8l v6 in standard tune - although the raw power varies with air temperature, it is very predictable, and matches the atmospheric correction well.
By the way, the engine test standard I know best (SAE J1995) is for engine dynos, and sets limits on allowable air temperature and pressure, and total correction factor. Unfortunately, without an airconditioned cell you can't stick to those limits and still run a workshop.
We have customers whose shops can go from 10 degrees C to over 40 during the course of a day, let alone running the same car summer and winter.
I'm not sure what you mean by less deflection? Generally speaking tyre deflection is related to the amount of force transmitted through the tyre - in order to prevent wheelspin, the strapping usually works to pull they tyre down as it tries to climb the front roller under power.
It's only really an issue if running in a low gear, or lots of power. Strapping down 1,000 hp dyno queens I leave to the experts.
We have started building hub dynos, and it will be interesting to compare the same cars back-to-back between hub and chassis. Unfortunately we don't have the luxury of keeping one for r&d, so comparisons will have to wait.
PeterBurgess said:
I find it fascinating folk seem to just look for the negatives not positives. Stevie, am I right you only work mainly on your one comp car? I use the figures we get to compare and improve many cars and bikes. Tango, I haven't a clue what you do maybe you would enlighten me?
The coastdown losses are for comparison purposes, I think most folk would think it a pretty good idea to get all that lovely power to the wheels rather than lose it in unnecessary friction? It works well for our race stuff.
Was that Performance Bikes mag? I got on well with John R when I met him for an article in the late 80s and I stil get on well with Dave W now running Emerald, I have a lot or respect for them.
Tango, a 100 hp motor and all the time to fit and try and make it work would be both time consuming and expensive, how would it benefit my customers and my research and how much do you think it would cost? Maybe you would like to produce a project we could discuss?
Overall, with the Dynocom rollers we have moved forwards and improved power outputs both at the engine and through transmission testing. There may be various criticisms of the set up as with all dynos whether rollers or engine dyno, that is fair play. However, I would ask those who knock, how do they compare and contrast power outputs and transmission losses? Without reliable, repeatable measuring it can only be guesswork or head in sand or 'it'll be alright on the night'philosophy? When a race car comes in with the driver saying it feels a little soft we do runs to check wheel power and transmission losses to see how the graphs compare to the last time in. This way we have picked up diffs failing, gearboxes failing and even prop joint failure onsets. Without measuring and testing it is guesswork and or seat of the pants. As I said, many race teams use the inertia testing, including coastdowns to optimise power output, must be a reason for that. Over the years I have found folk who don't rate dynos and the uses of dynos, rollers or engine and even pooh pooh the humble static state flow bench don't win much on the track. The other positive I get is a lot of input from many different race drivers and engine builders and head modifiers, I learn from these meetings and we all move forwards. Isolated and we lose the race.
I started the thread to invite dyno operators, engineers, power junkies etc to join in, does no one have positives? Would that be a sad indictment of the attitude of threaders? Or maybe some folk are concerned about posting in case they get attacked?
Peter
My profession? I'm a precision engineer, you know them, the people that manufacture and then measure things, then measure again in a different way to confirm or deny the first result, then get someone else to check again.The coastdown losses are for comparison purposes, I think most folk would think it a pretty good idea to get all that lovely power to the wheels rather than lose it in unnecessary friction? It works well for our race stuff.
Was that Performance Bikes mag? I got on well with John R when I met him for an article in the late 80s and I stil get on well with Dave W now running Emerald, I have a lot or respect for them.
Tango, a 100 hp motor and all the time to fit and try and make it work would be both time consuming and expensive, how would it benefit my customers and my research and how much do you think it would cost? Maybe you would like to produce a project we could discuss?
Overall, with the Dynocom rollers we have moved forwards and improved power outputs both at the engine and through transmission testing. There may be various criticisms of the set up as with all dynos whether rollers or engine dyno, that is fair play. However, I would ask those who knock, how do they compare and contrast power outputs and transmission losses? Without reliable, repeatable measuring it can only be guesswork or head in sand or 'it'll be alright on the night'philosophy? When a race car comes in with the driver saying it feels a little soft we do runs to check wheel power and transmission losses to see how the graphs compare to the last time in. This way we have picked up diffs failing, gearboxes failing and even prop joint failure onsets. Without measuring and testing it is guesswork and or seat of the pants. As I said, many race teams use the inertia testing, including coastdowns to optimise power output, must be a reason for that. Over the years I have found folk who don't rate dynos and the uses of dynos, rollers or engine and even pooh pooh the humble static state flow bench don't win much on the track. The other positive I get is a lot of input from many different race drivers and engine builders and head modifiers, I learn from these meetings and we all move forwards. Isolated and we lose the race.
I started the thread to invite dyno operators, engineers, power junkies etc to join in, does no one have positives? Would that be a sad indictment of the attitude of threaders? Or maybe some folk are concerned about posting in case they get attacked?
Peter
You ask what use fitting a 100hp motor to your dyno would be to your research and customers? Well for starters you wouldn't need to estimate transmission losses you could accurately measure them to give accurate flywheel figures.
After all, the variables as AW111 has already posted, are huge in number. Transmission losses vary depending on which gear the car has been run in, tyre deflection, tyre width, how the car has been secured to the dyno, even tyre tread pattern! The fact that you're running twin rollers also means double the rolling resistance on the tyres which throws any calculations out straight away!
Another plus to being able to drive the rollers is the ability to run engines in 'backwards' which is an old engine builders trick, build everything up less the plugs then use the dyno to turn the engine over at speed for the initial 'bedding in'
And if you really want a Brucie bonus you can use your customers cars to generate electricity to offset your overheads...
Pointing out that your method for measuring transmission losses contains far too many unknown variables and is actually little more than a guesstimate isn't being 'negative' it's fair criticism.
Excellent news that you are being positive. What sort of power supply might I need , how do I connect it to my rollers? I imagine a 100 hp motor is pretty hefty volune wise and weight wise? The rollers are fairly small compared to the tyre size so I wonder how we could gear up the motor in some way? Most motors only do about 1500 or 3000rpm? Not my skillset I am afraid, it is why I ask you. Do you fancy coming up and seeing if we have the room for the fitting as you describe it? I suppose one would need some sort of software to manage this? Sounds rather an expensive project to me? Do many rolling roads come equipped with a 100hp motor to power up the car/test transmission?
I found these specs 562kg is hefty and I think 132 amp is a lot for a basic three phase supply? looks like a higher voltage is preffered but I don't know what I am talking about,
TEC Electric Motors 280S Frame 75kW 4 Pole Cast Iron High Efficiency AC Induction Motor for 400V or 690V 3 phase supply. Suitable for use with a Variable Frequency Drive or fixed-frequency mains supply at 50/60Hz.
Power Output: 75kW (100HP) at 50Hz
Speed: 1480RPM at 50Hz
Torque: 484Nm at 50Hz
Full Load Current: 132.7 at 400V, 76.6A at 690V
Power Factor: 0.87 (when mains connected at 50Hz)
Efficiency: 93.8%
Rated: 40°C Ambient.
Size: 550mm Wide x 985mm Long x 680mm High
Shaft: Shaft is 75mm Diameter x 140mm Length with 20mm Key.
Mounting: Mount via 4 x 24mm holes on 457mm x 368mm centres, 190mm back from the shaft shoulder.
Weight: 562kg.
Set terminal box links 'three-a-breast' for 400V 'Delta' connection.
Set terminal box links 'two at one side' for 690V 'Star' connection.
Ventilation space required at rear cooling air intake.
Full part number is - TECC2-280S-4 B3
From Jan 1st 2017, three phase electric induction motors with a rated output of 0.75kW to 375kW and efficiency less than IE3 must be equipped with a variable speed drive (Inverter Drive). For exceptions, see EC Commission Regulation 640/2009.
I look for consistency with my rollers and am content with what I achieve. Have you worked on many rolling roads or been to many test sessions?
Peter
I found these specs 562kg is hefty and I think 132 amp is a lot for a basic three phase supply? looks like a higher voltage is preffered but I don't know what I am talking about,
TEC Electric Motors 280S Frame 75kW 4 Pole Cast Iron High Efficiency AC Induction Motor for 400V or 690V 3 phase supply. Suitable for use with a Variable Frequency Drive or fixed-frequency mains supply at 50/60Hz.
Power Output: 75kW (100HP) at 50Hz
Speed: 1480RPM at 50Hz
Torque: 484Nm at 50Hz
Full Load Current: 132.7 at 400V, 76.6A at 690V
Power Factor: 0.87 (when mains connected at 50Hz)
Efficiency: 93.8%
Rated: 40°C Ambient.
Size: 550mm Wide x 985mm Long x 680mm High
Shaft: Shaft is 75mm Diameter x 140mm Length with 20mm Key.
Mounting: Mount via 4 x 24mm holes on 457mm x 368mm centres, 190mm back from the shaft shoulder.
Weight: 562kg.
Set terminal box links 'three-a-breast' for 400V 'Delta' connection.
Set terminal box links 'two at one side' for 690V 'Star' connection.
Ventilation space required at rear cooling air intake.
Full part number is - TECC2-280S-4 B3
From Jan 1st 2017, three phase electric induction motors with a rated output of 0.75kW to 375kW and efficiency less than IE3 must be equipped with a variable speed drive (Inverter Drive). For exceptions, see EC Commission Regulation 640/2009.
I look for consistency with my rollers and am content with what I achieve. Have you worked on many rolling roads or been to many test sessions?
Peter
Would the proposed electric motor tell you anything you can't already calculate from the roller's speed and torque measurements?
The main missing information seems to be the transmission and tyre losses under load (as opposed to coasting). Have you got some cunning scheme to work that out using the motor?
The main missing information seems to be the transmission and tyre losses under load (as opposed to coasting). Have you got some cunning scheme to work that out using the motor?
Spot on, I suppose it would have to be motored from the other end of the gearbox, then, if it isn't as powerful as the inputting si or ci engine it would not pick up this tyre deflection problem or the %increase in gear losses should they happen with greater power input.
I suppose the nearest one could get is if Adrian builds an engine dyno, uses the same dyno on some rollers then uses the same dyno on his hub dynos, that would give numbers for one car and transmission and could not be extrapolated to other cars even of the same type Hence we do power tests and coastdown tests on all cars, this gives us some numbers which can be used for comparison purposes, over nearly seven years we have retuned many cars and seen how close the figures remain, unless there is a change in the engine/transmission which shows up comparing coastdown and power figures. The system is boring and simple but gives really consistent results. These can only really be appreciated in terms of I have done nearly every run and have seen the figures mount up and build up a picture, especially the transmission coast downs.
Least power losses live back axle (crap for cornering) worst losses old fashioned uj drive shafts and centre (De Dion style) diff on such as TR6s, you can even hear the rubbers on the driveshafts creak! Low tyre pressures, not good. Wide and sticky tyres power sappers. Modern boxes are more efficient than old ones. Slippy diffs sap more power. I know this is common knowledge, but, I have been able to quantify differences as the data mounts up. So we can see types of transmission variation and we can compare like with like to ensure all is well.
I do not do coastdowns on autos. However, looking at the wheel power of old 3speed boxes versus manual boxes, the losses seem pretty high. Modern autos seem pretty good, a lot of v8 specials run the modern auto stuff, power delivery is good and gear changes so slick!
Peter
I suppose the nearest one could get is if Adrian builds an engine dyno, uses the same dyno on some rollers then uses the same dyno on his hub dynos, that would give numbers for one car and transmission and could not be extrapolated to other cars even of the same type
Hence we do power tests and coastdown tests on all cars, this gives us some numbers which can be used for comparison purposes, over nearly seven years we have retuned many cars and seen how close the figures remain, unless there is a change in the engine/transmission which shows up comparing coastdown and power figures. The system is boring and simple but gives really consistent results. These can only really be appreciated in terms of I have done nearly every run and have seen the figures mount up and build up a picture, especially the transmission coast downs.Least power losses live back axle (crap for cornering) worst losses old fashioned uj drive shafts and centre (De Dion style) diff on such as TR6s, you can even hear the rubbers on the driveshafts creak! Low tyre pressures, not good. Wide and sticky tyres power sappers. Modern boxes are more efficient than old ones. Slippy diffs sap more power. I know this is common knowledge, but, I have been able to quantify differences as the data mounts up. So we can see types of transmission variation and we can compare like with like to ensure all is well.
I do not do coastdowns on autos. However, looking at the wheel power of old 3speed boxes versus manual boxes, the losses seem pretty high. Modern autos seem pretty good, a lot of v8 specials run the modern auto stuff, power delivery is good and gear changes so slick!
Peter
PeterBurgess said:
Slippy diffs sap more power.
That's an interesting observation. I wouldn't have predicted that a slippy diff would make any difference in a straight line since the guts of the diff are essentially stationary wrt the crownwheel under those conditions. How much difference does it make? Any idea what mechanism causes it? It depends on the percentage lock. I have seen 4 on a locked (welded!) diff, having said that we got about the same as that when our customer cured a diff leak with gloop syrup!
I have no idea why it absorbs power, not my field I am afraid, hopefully a diff savvy person will explain? Too much camber on one wheel (fwd) grasstracker lost 6 extra! It was very, very cambered though!
The worst we have ever had, not transmission was a grasstrack racer conned into crushing his rear ex pipe as he was told it would help with backpressure etc etc.....wheel power went from 18 to 40 when we used mole grips (other brands are available!) to sort of restore the shape!
Which takes me to another point, on the engine dyno, we built the cell so we can run the full ex system to be used on the car as I have never understood why only headers seem to be used? We can also test ex systems then
Peter
I have no idea why it absorbs power, not my field I am afraid, hopefully a diff savvy person will explain? Too much camber on one wheel (fwd) grasstracker lost 6 extra! It was very, very cambered though!
The worst we have ever had, not transmission was a grasstrack racer conned into crushing his rear ex pipe as he was told it would help with backpressure etc etc.....wheel power went from 18 to 40 when we used mole grips (other brands are available!) to sort of restore the shape!
Which takes me to another point, on the engine dyno, we built the cell so we can run the full ex system to be used on the car as I have never understood why only headers seem to be used? We can also test ex systems then
Peter
Hi Stan
I think they must be the same, a limited slip diff, I note my Cherokee XJ jeeps have these as standard.
How about, tyres not perfectly matched because of wear etc etc, standard diff would cope but limited slip wouldnt?
I know diffs on range rovers can 'wind up' whatever that means? We tend to run permamnent 4wd by using centre diff lock and removing front prop. When the wind up happens the engine about stalls, to cure it I have to reverse the car gently on the rollers until the transmission sorts itself.
Peter
I think they must be the same, a limited slip diff, I note my Cherokee XJ jeeps have these as standard.
How about, tyres not perfectly matched because of wear etc etc, standard diff would cope but limited slip wouldnt?
I know diffs on range rovers can 'wind up' whatever that means? We tend to run permamnent 4wd by using centre diff lock and removing front prop. When the wind up happens the engine about stalls, to cure it I have to reverse the car gently on the rollers until the transmission sorts itself.
Peter
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