Potential Power - Relative to many things, but is there something to go by?

[Kagetsu]

Just considering for example, a method of working out potential power output of an engine.

has there been anybody else out there that has worked out for example, the average power output per L vs number of Cylinders?

for example, lets say that a 4 cylinder NA 2000cc has approximately 150kw's (not at all impossible numbers) with a relatively square bore.

Each Cylinder is then 500cc capacity, with 37.5kw's. We then break it down further, Each CC is then 0.075kw's.

Taking that number, lets say (for arguements sake) we take a 1GZ, and calculate the possibility of power from it. At approximately 4996cc with a nearly square bore, could we then go onto say the engine then has a possible outcome of 4996 x 0.075kw Giving a result of 374.7kw's? (of course disregarding loading on the crank and other external factors etc).

Just looking for relative power output too, valve seating etc will have an effect on this concept as well.

[DigitalPho3nix]

It is really hard to generalise between engines. Most engines have different design factors that are critical in determining how much power and torque the engine makes and at which point in the rpm range these peaks are reached.

Can you compare a Honda F20C to a Toyota 3SGE? Both have a two litre capacity, but there is a vast difference in design, rpms, fuel management and delivery, engine control. Type of fuel used will have an effect too. The list is almost limitless.

[Billzilla]

Yeah, not too hard.
Work on about 100nm per litre, then use the maximum piston speed of about 4,000ft/min average to get max revs, take about 90% of that max torque per litre at those revs and you can work out roughly a good power output.
That output will vary depending on how hard you rev the engine though, of course.
E.g 4,000 ft/min on a 4AG with its 77mm stroke is 7700rpm.
1.6 litre at 90nm/litre = 144nm at 7700rpm = 156hp.

So that's a generalisation, better cylinder filling (up to 135nm/litre is possible) and more revs also give more HP.
Also read this text to see the relationship between torque and horsepower.
And here for mean piston speed calculations.

[oldcorollas]

/\/\/\ what he said.. and then when you add boost, you start with a similar VE to NA, but then as you add more boost (like... 2 bar for example) the relative VE goes down...

ie.. NA = 90% VE =90Nm/L
1 bar boost = 85% VE = 190Nm/L and so on with dimishing returns (but much more variable depending on turbo and in/out and cooler eff etc)

[Mr Ed]

More valves per L will also give you an advantage over a 16v 2000cc engine.

[Vios-GT_07]

hm.. i've just gotten some figures from here (i'm on holiday in case you didn't know)

the top three highest HP output.. in order are as follows

Evo 3 - 4G63 (owned by the Mitsubishi dealer's son) -
KE70 - 3S-GTE (owned by a small private motorshop) - over 700hp..
Nissun - SR20 DET.. privately owned..

not sure what this would mean but these are highly maxed out motors.. the KE70 has a massive wastegate and exhaust straight from turbo out the side of the car..

[6BOOST]

Some of the big things to keep in mind when thinking of hp are capacity, volumetric efficiency, and rpm of peak power/torque. Without getting as technical as Billzilla, lets say identicle engines have the same capacity and make power at the same rpms, but 1 has more head work and better cams etc, this will give it a higher VE, and hence make more power. Anything you can do to increase VE will net more hp, as this is airflow in and out. Turbo's are a form of increasing VE far past 100%. Bigger turbo's have less restriction in the exhaust manifold, hence even better VE. Cams with increased lift and duration will generally increase VE, and increasing capacity or compression will usually increase power also.

There is no way(or simple way) of back to bvack comparing engines across the board, determining what their VE is and how efficient they are would be impossible without engine dyno figures and some educated guessing.

6BOOST

[jfallen]

http://www.savefile.com/files/286632

This is a spreedsheet I've been working on. I've locked out all the calculations at the moment for puplic viewing. However it is still fully functional.

Yellow is the input colour. and if your looking for NA calculations on the constants page change the BSFC number from 0.55 to 0.45. I'm working on a readme file at the moment which should be done in a few days.

any questions on it send me a PM and I'll answer them. If there are any faults let me know also. The only current error (that I'm aware of) is that the torque figures seem about 50% of what they should be.

Be realistic in your numbers
Jordan

[Marc205]

http://www.savefile.com/files/286632

This is a spreedsheet I've been working on. I've locked out all the calculations at the moment for puplic viewing. However it is still fully functional.

That looks pretty useful. I've been toying Engine Analyser and Pro, but this looks nice and easy. +rep

[jfallen]

Very useful, but expencive. Deffinetly worth the $$ if your in the trade. If there are any functions people would like added to my sheet let me know and I'll do my best to add them in.

Jordan