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!!
), 4 cyl, 62hp = 195
Major Fallout said:
114 for the speedster :-( But it's developing twice as much power as stock haha
I'm happy with that, I will need to change the head for over head valves to get over 120 in the speedster really. To double the power again I would have to spend about 6-7k. Something to do later on in life.
Well that puts paid to my theory about low PI engines being cheap to get more power from! I'm happy with that, I will need to change the head for over head valves to get over 120 in the speedster really. To double the power again I would have to spend about 6-7k. Something to do later on in life.
havoc said:
Interesting article. Maths follows the logic, but I'd want to check your constants more closely.
FD2-R engine, as standard (86x86 I-4), 774PI - and the factory redline is REALLY close to your theoretical max-rpm of 8,700+
NA1 NSX, as standard (oversquare 90x76 V6), 577PI - but a theoretical 9,700rpm!
Yes, that's correct. 76mm vs 86mm stroke, big difference in piston speeds with the V6s shorter stroke allowing much higher speeds.FD2-R engine, as standard (86x86 I-4), 774PI - and the factory redline is REALLY close to your theoretical max-rpm of 8,700+
NA1 NSX, as standard (oversquare 90x76 V6), 577PI - but a theoretical 9,700rpm!
AW111 said:
Interestingly, the old RAC (taxable) horsepower was calculated in a similar manner -
RAC hp = bore^2 x cyl / 2.5, with bore in inches.
= bore(mm) ^ 2 / 1612.9
RAC hp = bore^2 x 0.62 x 10^-3
Kozy max hp = bore^2 x 9.694 x 10^-3
So in 1910, the RAC assumed a PI of 64, if my maths is correct
Interesting... What was this calculation used for? RAC hp = bore^2 x cyl / 2.5, with bore in inches.
= bore(mm) ^ 2 / 1612.9
RAC hp = bore^2 x 0.62 x 10^-3
Kozy max hp = bore^2 x 9.694 x 10^-3
So in 1910, the RAC assumed a PI of 64, if my maths is correct
Edited by AW111 on Sunday 13th October 14:55
havoc said:
Oh - one thing - the DC2s limiter (c.8,700) is about bang-on what the OP's calcs say is possible reliably (8,621). And the engine can clearly do it for >>100k miles without any trouble!
The early B18s are known for piston speeds exceeding F1 levels at redline. AFAIK the later ones were lowered to an 8400rpm though? The B16B was 8600 with a theoretical limit of 9600, and they are proven to be a longer lasting engine than the B18C, most of which will burning at least a bit of oil and could do with a refresh by now.williredale said:
Tax.
The amount of road tax / VED you paid depended on the RAC horsepower rating.
This was all prewar. I can't remember when they changed it but it was affecting engine designs
I see, so it didn't matter what the engine actually put out, only what it should have put out according to the bore size?The amount of road tax / VED you paid depended on the RAC horsepower rating.
This was all prewar. I can't remember when they changed it but it was affecting engine designs
Edited by williredale on Sunday 13th October 18:13
As fair as any other tax I guess..
No problem!
Looked up the LSx engines...
LS1 - 99mm - 345bhp = 454
LS2 - 101.6mm - 412bhp = 515
LS3 - 103.1mm - 430bhp = 522
LS7 - 104.8mm - 505bhp = 593 (good for 842bhp NASP!
)
One thing I am interested in is the costs of tuning various engines. If anyone posting here has actually tuned their engine, an interesting one to know would be the before and after PI score and the cost to upgrade!
Obviously, this will be a bit sketchy as we all know rolling roads can be dubious, but I'd still be interested to hear about it, I image there is probably a strong trend in cost per point as the scores go up...
The website is only a few months old and doesn't have much on it at the moment. So I should mention the obligatory 'follow on facebook' if you like the gist of the article, as I'll be doing a lot more.
Looked up the LSx engines...
LS1 - 99mm - 345bhp = 454
LS2 - 101.6mm - 412bhp = 515
LS3 - 103.1mm - 430bhp = 522
LS7 - 104.8mm - 505bhp = 593 (good for 842bhp NASP!
)One thing I am interested in is the costs of tuning various engines. If anyone posting here has actually tuned their engine, an interesting one to know would be the before and after PI score and the cost to upgrade!
Obviously, this will be a bit sketchy as we all know rolling roads can be dubious, but I'd still be interested to hear about it, I image there is probably a strong trend in cost per point as the scores go up...
The website is only a few months old and doesn't have much on it at the moment. So I should mention the obligatory 'follow on facebook' if you like the gist of the article, as I'll be doing a lot more.
Edited by Kozy on Sunday 13th October 22:51
stevesingo said:
2467cc BMW S14 238hp as standard PI=680
Pistons £750
Head work £1000
Cams £800
Airbox £1200
Exhaust £600
EMS I spent £3000, but you can get away with £1500
TOTAL £5850
Result is 280 hp on the Dyno PI=800
800-680=120
5850/120=
£48.75 per PI
Ouch
Excellent start thanks for that. Going to collect as much info as I can and put together some of graph to see how much of a trend there is in the cost of tuning across a wide variety of engines.Pistons £750
Head work £1000
Cams £800
Airbox £1200
Exhaust £600
EMS I spent £3000, but you can get away with £1500
TOTAL £5850
Result is 280 hp on the Dyno PI=800
800-680=120
5850/120=
£48.75 per PI
Ouch
Scuffers said:
no (only the speed of the HG failing is super-charged!)
Wow, pretty impressive indeed! But not quite as impressive as:motor mad said:
The Mugen tuned K20 that went in the limitied run Ariel Atom must be pretty good. 270bhp from 2 litres makes it a bit special.
941! Edited by Kozy on Monday 14th October 10:20
SonicShadow said:
Am I missing something here? The 'start' button doesn't seem to do anything, and I've tried it on 3 different browsers.
EDIT: Nevermind. Got it now.
It can be a bit finickity about where you click it for some reason! Changing any of the cyan values and hitting enter will do the same thing.EDIT: Nevermind. Got it now.
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