For the 'natural aspirators' - How tuned is your engine?
Discussion
One for the PHers with NASP performance engines (four stroke piston engines anyway).
I've written the article (link below) on the performance limitations of NASP engines and derived a simple 'Performance Index' calculation using nothing more than the engine's bore, cylinder count and power output, that reflects the level of tune of the engine. This cropped up on a recent thread titled 'Horsepower per litre'.
The theory is that the bore and number of cylinders is the overriding limit to engine power output, and as far as I can see this is almost universally applicable to all four stroke NASP engines. It doesn't gurantee that you can ever actually achieve the maximum, but as far as I can see it does seem to work as a pretty universal comparison.
Why is this any more useful than specific power and why would anyone care about it? Power/litre can be corrupted by high engine speed, motorbike engines and F1 engines are a prime example of this. BMEP, or specific torque are more useful comparisons of engine performance, but only really relate to torque and we all know how one dimensional that is in terms of performance potential.
The performance index combines the two, it uses the maximum achievable BMEP and also the maximum reliable piston speed to calculate the maximum power an engine could potentially make. It is rated out of 1000 (which is F1 engine levels of tune), with most well tuned factory production engines producing around 650-750, with a few truly exceptional engines breaching the 800 marker.
Interesting to see also, what some highly tuned modified engines manage to make. I've had a couple of people claiming low 900s with well built Honda VTEC engines.
The article and the calculator are here:
http://blackartdynamics.com/EngineLimits/Index.php
You don't have to read the full piece if you have no interest in the theory and maths, you can just check the 'How tuned is your engine' section at the end.
I checked my MX5, an 83mm bore and 128bhp give it a miserable 479.
My ATR with 87mm bore and 209bhp gives an altogether more impressive 713.
Other one's I've checked:
E46 M3 with 84mm bore, 6 cyls and 333bhp gets 811.
The S2000 with an 87mm bore and 240bhp scores a hugely impressive 818.
The Ferrari 458 (current production car record holder for specific torque and specific power) 94mm bore makes 820.
Old Honda BTCC engines 86mm bore, 4 cyl, making around 280bhp score 976.
An F1 engine with a 98mm bore, 8 cylinders and 740bhp scores 994.
So, there's a bit of technical waffle from me, feel free to pick the theory apart, or post some PI numbers for your own engines. Interested to know how a wider range of engines scores outside of the Honda marque!
=ETA=
[b]I also want to have a look at the costs of tuning various engines, so if yours has been upgraded, please post up the before and after PI scores, and the cost of doing so. This would be equally as useful in steps if that is how you did it. I.e an exhaust cost £500 and took PI from 500 to 510, cams cost £600 and went from 510 to 530... etc etc.
If I get enough data together I'll put together some kind of infographic type thing![/b]
(Why do the bold tags not work on PH?)
I've written the article (link below) on the performance limitations of NASP engines and derived a simple 'Performance Index' calculation using nothing more than the engine's bore, cylinder count and power output, that reflects the level of tune of the engine. This cropped up on a recent thread titled 'Horsepower per litre'.
The theory is that the bore and number of cylinders is the overriding limit to engine power output, and as far as I can see this is almost universally applicable to all four stroke NASP engines. It doesn't gurantee that you can ever actually achieve the maximum, but as far as I can see it does seem to work as a pretty universal comparison.
Why is this any more useful than specific power and why would anyone care about it? Power/litre can be corrupted by high engine speed, motorbike engines and F1 engines are a prime example of this. BMEP, or specific torque are more useful comparisons of engine performance, but only really relate to torque and we all know how one dimensional that is in terms of performance potential.
The performance index combines the two, it uses the maximum achievable BMEP and also the maximum reliable piston speed to calculate the maximum power an engine could potentially make. It is rated out of 1000 (which is F1 engine levels of tune), with most well tuned factory production engines producing around 650-750, with a few truly exceptional engines breaching the 800 marker.
Interesting to see also, what some highly tuned modified engines manage to make. I've had a couple of people claiming low 900s with well built Honda VTEC engines.
The article and the calculator are here:
http://blackartdynamics.com/EngineLimits/Index.php
You don't have to read the full piece if you have no interest in the theory and maths, you can just check the 'How tuned is your engine' section at the end.
I checked my MX5, an 83mm bore and 128bhp give it a miserable 479.
My ATR with 87mm bore and 209bhp gives an altogether more impressive 713.
Other one's I've checked:
E46 M3 with 84mm bore, 6 cyls and 333bhp gets 811.
The S2000 with an 87mm bore and 240bhp scores a hugely impressive 818.
The Ferrari 458 (current production car record holder for specific torque and specific power) 94mm bore makes 820.
Old Honda BTCC engines 86mm bore, 4 cyl, making around 280bhp score 976.
An F1 engine with a 98mm bore, 8 cylinders and 740bhp scores 994.
So, there's a bit of technical waffle from me, feel free to pick the theory apart, or post some PI numbers for your own engines. Interested to know how a wider range of engines scores outside of the Honda marque!
=ETA=
[b]I also want to have a look at the costs of tuning various engines, so if yours has been upgraded, please post up the before and after PI scores, and the cost of doing so. This would be equally as useful in steps if that is how you did it. I.e an exhaust cost £500 and took PI from 500 to 510, cams cost £600 and went from 510 to 530... etc etc.
If I get enough data together I'll put together some kind of infographic type thing![/b]
(Why do the bold tags not work on PH?)
Edited by Kozy on Monday 14th October 09:45
Edited by Kozy on Monday 14th October 09:46
C.A.R. said:
Unfortunately for me extortionate rent and other bills have forced me into a dull old diesel, but the old 2ZZ-GE engine in the Celica I used to drive had an 82mm bore and gave 189bhp - scoring an impressive 725 on your calculator.
Those engines appear to be extremely under-rated!Why oh why did they not put that VVTLi system in the GT86!!
williredale said:
Kozy said:
leafspring said:
1960's 2286cc petrol Land Rover...
90.49mm bore, 4 cyl, 77hp = 243
I think we've got a contender for the lowest score ever here! 90.49mm bore, 4 cyl, 77hp = 243
ETA: bolting on a later 'High compression' cylinder head gives you another 11hp (apparently) so that ups the score to a heady 277
Edited by leafspring on Saturday 12th October 23:13
Gassing Station | General Gassing | Top of Page | What's New | My Stuff