Collective Thoughts on AJP Power
Discussion
Right lets say that someone had a large capacity AJP which made its peak power at 6700 rpm....
How could you go about making that engine rev to 7500rpm and create more power at these revs?? Obviously i will be talking to the engine builder but i wanted to see if anyone on here had any ideas?
What is it that restricts revs/power..
Mike
How could you go about making that engine rev to 7500rpm and create more power at these revs?? Obviously i will be talking to the engine builder but i wanted to see if anyone on here had any ideas?
What is it that restricts revs/power..
Mike
itsallyellow said:
Right lets say that someone had a large capacity AJP which made its peak power at 6700 rpm....
How could you go about making that engine rev to 7500rpm and create more power at these revs?? Obviously i will be talking to the engine builder but i wanted to see if anyone on here had any ideas?
What is it that restricts revs/power..
Mike
I an under the impression that its many things...How could you go about making that engine rev to 7500rpm and create more power at these revs?? Obviously i will be talking to the engine builder but i wanted to see if anyone on here had any ideas?
What is it that restricts revs/power..
Mike
The relationship between the bore and stroke...materials...piston weight...bearing strength and type...don't you get valve bounce at higher revs?
Not sure what can be acheived by modifying an existing design...?
Sure there will be more technical information from others!
Sounds interesting...how bigs the cheque!
Lighter pistons - assuming same bore/stroke
Billet crank - lighter for the same strength/stronger to enable higher revs
Tuned induction - shorter to move the torque peak up and help the engine breathe better at higher revs
Tuned exhaust - again for more top end
Head work - to cope with the higher flow rates required to get enough gas in and out at the new rpm range
However by going for more top end, you'll naturally lose out in the mid range.
Billet crank - lighter for the same strength/stronger to enable higher revs
Tuned induction - shorter to move the torque peak up and help the engine breathe better at higher revs
Tuned exhaust - again for more top end
Head work - to cope with the higher flow rates required to get enough gas in and out at the new rpm range
However by going for more top end, you'll naturally lose out in the mid range.
Cylinder head design ie port size, valve size and the time the valves are open hence cam lift (x rocker ratio if applicable eg rover but not AJP) and cam duration are the main things.
Basically an engine will not rev producing usefull power if the cylinders cannot get full enough charge of air....fuel is the easy part at approx 1:13 ratio especially with injection.
Basically an engine will not rev producing usefull power if the cylinders cannot get full enough charge of air....fuel is the easy part at approx 1:13 ratio especially with injection.
What will limit your RPM (ignoring valve float) is basically when then engines HP production is equal to the frictional losses inside the engine (piston/rings, bearings, camshaft, all have friction and take power to turn). The more RPM, the more force on the frictional surfaces and thus the greater the frictional loss. Also as RPM rise your camshaft, heads, and intake will reach an absolute limit of how much air they will flow relative to the vacuum the pistons can produce. So as RPM climbs, power production will plane off, frictional losses will rise, until net HP produced will reach zero and the engine is basically using all it's power just to spin itself.
Then you've got to consider fuel burn velocity, accerational loads on main bearings, lubrication, cooling etc...
Then you've got to consider fuel burn velocity, accerational loads on main bearings, lubrication, cooling etc...
Shifting the air is the key, so you've got to work out what's stopping the cylinders filling at higher rpm as said above. Until you start playing with the engine you would only be guessing but the obvious cheap and relatively simple starting point would be to shorten the induction even further as stevet suggested and flow the inlets. After that (as you already have your exhaust and engine built) it gets expensive.
brogenville said:
What will limit your RPM (ignoring valve float) is basically when then engines HP production is equal to the frictional losses inside the engine (piston/rings, bearings, camshaft, all have friction and take power to turn). The more RPM, the more force on the frictional surfaces and thus the greater the frictional loss. Also as RPM rise your camshaft, heads, and intake will reach an absolute limit of how much air they will flow relative to the vacuum the pistons can produce. So as RPM climbs, power production will plane off, frictional losses will rise, until net HP produced will reach zero and the engine is basically using all it's power just to spin itself.
Then you've got to consider fuel burn velocity, accerational loads on main bearings, lubrication, cooling etc...
That's a good reply and possibly why some engines use a low dynamic c/r in order to rev. Thus reducing pumping losses.Then you've got to consider fuel burn velocity, accerational loads on main bearings, lubrication, cooling etc...
This looks like a good game, can I join in?
What will limit your revs is the ability of your engine to pump air. Everything else is secondary. An engine is an airpump. Just that the fuel keeps it pumping.
Increase the airflow and you increase the pump performance.
Strangely if you want to go faster revs in an engine, I don't think you can do better than look at a jet engine. Exactly the same stages in combustion cycle, and exactly the same technique to use in getting the air in. I think the weight of the internals is secondary. If one of them breaks you know they werent strong enough. but unless they are significantly heavy away from the centre line of your crankshaft I'm not sure they are the limiting factor. but they are expensive
.
Out of interest have you ever thought of setting up a MAP gauge on your car. See what revs and how fast you lose manifold pressure. The shape of that graph might give you a clue to whats limiting the airpump at those revs?
Ideally a throttle angle, MAP setup datalogged cos I don't think you should be taking your eye off the road at the spped you travel.
Few sensors, and easily programmed pic chip could be done for shoestring money.
What will limit your revs is the ability of your engine to pump air. Everything else is secondary. An engine is an airpump. Just that the fuel keeps it pumping.
Increase the airflow and you increase the pump performance.
Strangely if you want to go faster revs in an engine, I don't think you can do better than look at a jet engine. Exactly the same stages in combustion cycle, and exactly the same technique to use in getting the air in. I think the weight of the internals is secondary. If one of them breaks you know they werent strong enough. but unless they are significantly heavy away from the centre line of your crankshaft I'm not sure they are the limiting factor. but they are expensive
.Out of interest have you ever thought of setting up a MAP gauge on your car. See what revs and how fast you lose manifold pressure. The shape of that graph might give you a clue to whats limiting the airpump at those revs?
Ideally a throttle angle, MAP setup datalogged cos I don't think you should be taking your eye off the road at the spped you travel.
Few sensors, and easily programmed pic chip could be done for shoestring money.
Not too much of a worry on an engine which will be refreshed every year. Agreed that it would need to be reliable though!!
Intresting posts so far...
Julian64 you have lost me! Too much electronic talk!!
Boosted: stop trying to make me blow it!!!!!!!
im too easily lead for that kind of talk!
Intresting posts so far...
Julian64 you have lost me! Too much electronic talk!!
Boosted: stop trying to make me blow it!!!!!!!
im too easily lead for that kind of talk!I'm no expert on engine tuning, but I've just bought a Saab 9000 2.3 - a lot of car for the money - obviously it's a Turbo engine, and develops 175bhp. I've just bought a new ECU for it that cost £110.00 I swapped it put with the old one, plugged it in, a simple 20 minute job and I now have 270hp. I can't quite get my head round how that works but it does - it was a simple 'plug and play'. The guy I bought the ECU from, has the same engine in his car, with an HPT Turbo and custom exhaust, and he has 396bhp and with the torque 'limited' to 400lb. No internal changes to the engine at all - How ??
On a more serious note, Honda hate Turbo's - it's a 'dishonourable' way to increase power, and they get ridiculous figures from there natutally aspirated engines, give them a ring and ask nicely and see if they can fit a couple of 16 valve Vtec head's to your car. that's the way to go
On a more serious note, Honda hate Turbo's - it's a 'dishonourable' way to increase power, and they get ridiculous figures from there natutally aspirated engines, give them a ring and ask nicely and see if they can fit a couple of 16 valve Vtec head's to your car. that's the way to go
itsallyellow said:
Not too much of a worry on an engine which will be refreshed every year. Agreed that it would need to be reliable though!!
Intresting posts so far...
Julian64 you have lost me! Too much electronic talk!!
Boosted: stop trying to make me blow it!!!!!!! im too easily lead for that kind of talk!
everyone is giving you an opinion. Some like mine are pretty useless because they use theory rather than practice. Some are valuable because that person has a lot of trial and error experience at doing what you're doing.Intresting posts so far...
Julian64 you have lost me! Too much electronic talk!!
Boosted: stop trying to make me blow it!!!!!!!
im too easily lead for that kind of talk!If you are like me and you need to bypass experience then you tackle things from the theory point of view. Boosted knows a sure fire method of increasing the airflow to your pump. Jools and Andy have probably done it so many times they dream it.
On the other hand from my point of view at tickover there is a very high vaccum pressure and low flow. When you car is hitting its rev limit there will be a high flow and low differential pressure in your inlet. Increasing this pressure when its at its weakest will power your engine to higher and higher revs. Hence boosted switches on his compressor at this point.
In a perfect engine the crossover will dictate your maximum revs, and you will be hard pressed to beat this unless you increase your engine (pump) size.
BUT and this is the bit you want to look for. If there is a limitation in your engine which is not the size of your pump. Hoses compressing, standing wave, non laminar flow, endless rubbish, you see this on a graph of load vs airflow. Instead of a slow linear crossover the graph will be modified by the limiting factor, and the shape of that limiting factor might tell you what it is.
There are a few ways of plotting load vs airflow, but I would suggest revs/throttle position can be got from the original MBE ecu quite easily, but you will need a pressure sensor or airflow meter in the inlet of your car somewhere as close to the butterfly as possible.
This could interrogate a few hundred times a second by a small embedded processor chip called a picchip from microchip.com ( just one of many possible examples of an embedded chip. And you could then plot a graph while you are driving of load and airflow.
I bet this has already been done many times and there is cheap kit out there that will plot this for you automatically.
In theory you wouldn't need to do too much.
You could do it with a well version of t you current lump with a few tweaks.
Short Intake, about 3-4 inches above the throttles.
A nice small volume airbox.
Shorter equal length exhaust primaries.
A new grind on the cams to sort the intake and exhaust timing.
A fully balanced bottom end.
Dry sumped.
Provided you can make the same torque at the higher engine revs then you have more power.
You could do it with a well version of t you current lump with a few tweaks.
Short Intake, about 3-4 inches above the throttles.
A nice small volume airbox.
Shorter equal length exhaust primaries.
A new grind on the cams to sort the intake and exhaust timing.
A fully balanced bottom end.
Dry sumped.
Provided you can make the same torque at the higher engine revs then you have more power.
ridds said:
In theory you wouldn't need to do too much.
You could do it with a well version of t you current lump with a few tweaks.
Short Intake, about 3-4 inches above the throttles.
A nice small volume airbox.
Shorter equal length exhaust primaries.
A new grind on the cams to sort the intake and exhaust timing.
A fully balanced bottom end.
Dry sumped.
Provided you can make the same torque at the higher engine revs then you have more power.
Yes but apart from the smaller air box it has all of this. I could maybee go even shorter on the intakes?You could do it with a well version of t you current lump with a few tweaks.
Short Intake, about 3-4 inches above the throttles.
A nice small volume airbox.
Shorter equal length exhaust primaries.
A new grind on the cams to sort the intake and exhaust timing.
A fully balanced bottom end.
Dry sumped.
Provided you can make the same torque at the higher engine revs then you have more power.
Mike
julian64 said:
itsallyellow said:
Not too much of a worry on an engine which will be refreshed every year. Agreed that it would need to be reliable though!!
Intresting posts so far...
Julian64 you have lost me! Too much electronic talk!!
Boosted: stop trying to make me blow it!!!!!!! im too easily lead for that kind of talk!
everyone is giving you an opinion. Some like mine are pretty useless because they use theory rather than practice. Some are valuable because that person has a lot of trial and error experience at doing what you're doing.Intresting posts so far...
Julian64 you have lost me! Too much electronic talk!!
Boosted: stop trying to make me blow it!!!!!!!
im too easily lead for that kind of talk!If you are like me and you need to bypass experience then you tackle things from the theory point of view. Boosted knows a sure fire method of increasing the airflow to your pump. Jools and Andy have probably done it so many times they dream it.
On the other hand from my point of view at tickover there is a very high vaccum pressure and low flow. When you car is hitting its rev limit there will be a high flow and low differential pressure in your inlet. Increasing this pressure when its at its weakest will power your engine to higher and higher revs. Hence boosted switches on his compressor at this point.
In a perfect engine the crossover will dictate your maximum revs, and you will be hard pressed to beat this unless you increase your engine (pump) size.
BUT and this is the bit you want to look for. If there is a limitation in your engine which is not the size of your pump. Hoses compressing, standing wave, non laminar flow, endless rubbish, you see this on a graph of load vs airflow. Instead of a slow linear crossover the graph will be modified by the limiting factor, and the shape of that limiting factor might tell you what it is.
There are a few ways of plotting load vs airflow, but I would suggest revs/throttle position can be got from the original MBE ecu quite easily, but you will need a pressure sensor or airflow meter in the inlet of your car somewhere as close to the butterfly as possible.
This could interrogate a few hundred times a second by a small embedded processor chip called a picchip from microchip.com ( just one of many possible examples of an embedded chip. And you could then plot a graph while you are driving of load and airflow.
I bet this has already been done many times and there is cheap kit out there that will plot this for you automatically.
Regarding more power though, I'd ask the engine builder if he feels he can get any more out of it without forced induction. I suspect not that much, but perhaps a new ram air, throttle body - short pipe/bonnet intake system tuned for acoustic ramming effect at high revs could be designed. Intake and exhaust resonant tuning can have a pretty profound effect on peak power. Although from experience, theories generally predict peak torque rather than peak power so the bhp tuning is more like guess work...
You could test it on a dyno with varying length primary pipes though and find the optimum pretty easily?
For even more power, what about looking into a serious ECU such a MOTEC or GEMS? With these you can squeeze a bit more power out using more accurate maps, and could also look into the possibility of individual cylinder trimming to extract optimum performance from each cylinder separately. Then what about fuel? Do you have to run on pump fuel or can you up the octane?
Edited by 450Nick on Tuesday 12th May 17:03
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