Advanced engine performance question....
Discussion
What would one need to do, to slide the peak power curve down to mid range revs?
Am I right in believing that an engine that produces 400bhp in the 3000-4000 rev range will result in a "faster" car than one that produced 400bhp in the 6000-7000 rev range?
And what effect would having a peak power output in mid-range revs have on max attainable speed?
This has been bugging me for a while, cant seem to get my head round it.... can anyone enlighten me?
Am I right in believing that an engine that produces 400bhp in the 3000-4000 rev range will result in a "faster" car than one that produced 400bhp in the 6000-7000 rev range?
And what effect would having a peak power output in mid-range revs have on max attainable speed?
This has been bugging me for a while, cant seem to get my head round it.... can anyone enlighten me?
SXS,
If the engine revved to 6-7000 rpm, and produced max power at 4000, it would be a very odd power curve. RPM is part of the HP equation and so if everthing else in the engine can cope on the breathing and fueling fronts, then more revs normally equates to more power for a given cc.
Torque is what I think you would be wanting to prodeuce lower down the rev range normally.
........retires awaiting to be shot down in flames.
If the engine revved to 6-7000 rpm, and produced max power at 4000, it would be a very odd power curve. RPM is part of the HP equation and so if everthing else in the engine can cope on the breathing and fueling fronts, then more revs normally equates to more power for a given cc.
Torque is what I think you would be wanting to prodeuce lower down the rev range normally.
........retires awaiting to be shot down in flames.
I pulled this one off another forum... would this be true...
"The 'best' way to increase low end response on the road is to install numerically higher rear end gears. Stock is 4.10:1, may are going to 4.40:1, 4.57:1, even 4.8:1. This doesn't actually increase engine power, but it increases the torque to the road at any speed."
"The 'best' way to increase low end response on the road is to install numerically higher rear end gears. Stock is 4.10:1, may are going to 4.40:1, 4.57:1, even 4.8:1. This doesn't actually increase engine power, but it increases the torque to the road at any speed."
Mmmm, ok now I'm getting round this, but I was wandering, how come near the top end of the rev range, you see a drop in torque and bhp on a dyno chart?
Oh and a golden question, could in theory something similar to a stroker-crankshaft be used on the flat plane model of an AJPV8? or am I barking up the wrong tree....
Oh and a golden question, could in theory something similar to a stroker-crankshaft be used on the flat plane model of an AJPV8? or am I barking up the wrong tree....
[quote=SXS ]What would one need to do, to slide the peak power curve down to mid range revs?
[/quote]
Something really bad I would think....
But, you can move the torque peak around by playing with induction and exhaust systems, cams etc.
There was an article in "Sprint" last year explaining the induction systems on the 4.2 and 4.5 Cerbera. In short the 4.5 has a longer induction tract which produces maximum torque, (maximun amount of air per induction cycle), at 4500rpm. Whereas with the 4.2 with shorter induction tracts produced maximum torque at 6500rpm or so. That's why the 4.2's develop pretty much the same power as the 4.5's but the 4.5's are quicker, they have more torque and from lower in the rev range.
what you really want is lots of torque with as flat a curve as possible over the rev range.
>> Edited by VYT on Friday 28th May 13:20
>> Edited by VYT on Friday 28th May 13:21
[/quote]
Something really bad I would think....
But, you can move the torque peak around by playing with induction and exhaust systems, cams etc.
There was an article in "Sprint" last year explaining the induction systems on the 4.2 and 4.5 Cerbera. In short the 4.5 has a longer induction tract which produces maximum torque, (maximun amount of air per induction cycle), at 4500rpm. Whereas with the 4.2 with shorter induction tracts produced maximum torque at 6500rpm or so. That's why the 4.2's develop pretty much the same power as the 4.5's but the 4.5's are quicker, they have more torque and from lower in the rev range.
what you really want is lots of torque with as flat a curve as possible over the rev range.
>> Edited by VYT on Friday 28th May 13:20
>> Edited by VYT on Friday 28th May 13:21
[quote=SXS ]Mmmm, ok now I'm getting round this, but I was wandering, how come near the top end of the rev range, you see a drop in torque and bhp on a dyno chart?
Oh and a golden question, could in theory something similar to a stroker-crankshaft be used on the flat plane model of an AJPV8? or am I barking up the wrong tree....[/quote]
YHM not regarding this thread tho'
Oh and a golden question, could in theory something similar to a stroker-crankshaft be used on the flat plane model of an AJPV8? or am I barking up the wrong tree....
[/quote] YHM not regarding this thread tho'
The only reason I am asking these simple questions is because I was a firm believer in certain principles but of late, I've noticed thre are sooo many different views on this subject from a number of technical forums, especially the american forums.
Effectively, I always believed that delivery of high torque at the low end and delivery of high bhp at the top end and meet somewhere in the middle would be the perfect balance....
But I've come across some theories that suggest increasing the frequency between the torque and bhp overall distance gap to bring the peak to the mid range....
Now theres a number of ways you can do this, but I was just wandering if this is something that someone has looked into before, just a research thing really.
Mainly doing a lot of reading up on the LS1 engines and the various upgrades routes, and wandering if these upgrade routes would be easily achievable on an AJP series engine too....
Effectively, I always believed that delivery of high torque at the low end and delivery of high bhp at the top end and meet somewhere in the middle would be the perfect balance....
But I've come across some theories that suggest increasing the frequency between the torque and bhp overall distance gap to bring the peak to the mid range....
Now theres a number of ways you can do this, but I was just wandering if this is something that someone has looked into before, just a research thing really.
Mainly doing a lot of reading up on the LS1 engines and the various upgrades routes, and wandering if these upgrade routes would be easily achievable on an AJP series engine too....
swilly said:
Power is torque times revs, so the power curve is dictated by the torque curve.
Isn't Power = Torque x revs/5250 ????
What I mean is the power is directly proportional to torque times revs. If you use BHP and lbft then:
power(BHP) = torque(lbft) x revs / 5252
The ideal torque "curve" is flat or even rising slightly. With a flat torque curve, the power plot will be a straight line rising with revs.
Fellas the calculations are one thing, but I was more interested in the mechanics 
I think my questions have misled some of you, to even have caused confusion (cerber450 ), let me write what I'm after in a more literal form...
Ok when it comes to modifying a car there's invariably little thought given to 'the big picture'. Most people are content to fit a high-flow exhaust and intake, bump up the boost (on aspirated beasts) and deal with whatever clutch and gearbox consequences that result. But there is a much more driveline friendly approach – the quest for a constant torque output within gearbox limits and overall a greater power increase... and I'm wandering how this would be achieved in a realistic manner of speaking, in say a normally aspirated car....
>> Edited by SXS on Friday 28th May 14:41
I think my questions have misled some of you, to even have caused confusion (cerber450
), let me write what I'm after in a more literal form... Ok when it comes to modifying a car there's invariably little thought given to 'the big picture'. Most people are content to fit a high-flow exhaust and intake, bump up the boost (on aspirated beasts) and deal with whatever clutch and gearbox consequences that result. But there is a much more driveline friendly approach – the quest for a constant torque output within gearbox limits and overall a greater power increase... and I'm wandering how this would be achieved in a realistic manner of speaking, in say a normally aspirated car....
>> Edited by SXS on Friday 28th May 14:41
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