The Real Way of Comparing Engine power

[Trex101]

The answer is to calculate the engine

Edited November 7, 2010 by Trex101

[Prostcode]

Does this mean the higher the bar the better? So in your example of car engines, MINI has the best engine power?

[Trex101]

Does this mean the higher the bar the better? So in your example of car engines, MINI has the best engine power?

 

Yes, it's a way of telling how develop the engine is from the cc, rpm and hp generated. From BMEP, Honda Type R NA engine at 11.9 bar is the highest among all NA engine develop.

[Watwheels]

Your links states "The Real Way of Comparing Engine Designs" not engine power leh.

 

Extract from the link:

BMEP refers to the average pressure that acts on the piston during the engine

[Trex101]

Your links states "The Real Way of Comparing Engine Designs" not engine power leh.

 

Extract from the link:

BMEP refers to the average pressure that acts on the piston during the engine

[Jenggowenggo]

ask a bit ah.

 

Y is the horsepower for a 1.4 liter fiat punto only 77 bhp

as compared to another 1.4 let say Nissan march is 97bhp or kia rio 1.4 94bhp.

All these 3 are auto by the way. All are 1.4cc by right shld be close together rite the horsepower ?? Or Is it because for continental cars they measure the bhp

at the flywheel or whatever they call it ? and for jap cars they measure it differently ?

 

Pardon me for my ignorance.

[Crazecow]

I am not sure how much meaning is there in comparing BMEP........

 

Take the Toyota 3.5L 2GR-FSE for eg. 228KW @ 6400RPM.

 

228KW x 1200 / 3.5 x 6400 = 12.21

 

Btw, my old MR2 engine beats the Mini.

 

165KW x 1200 / 2 x 6000 = 16.5!!! 20yr old engine technology....... (this is stock boost....)

 

The BMW N54B30 even higher

 

243KW x 1200 / 3 x 5800 = 16.75!! Wow!!

 

This will just amplify the scores for TC/SC engines cause high boost means higher HP.

 

Btw, if the article thinks Honda VTEC engines are great, wait till they see BMW... the S54B32 engine on the E46 M3 CSL.

 

265KW x 1200 / 3.2 x 7900 = 12.57....... Not many NA engines can match that.....

 

 

[Crazecow]

Hahahaha... yah, my mistake. Should be "The Real Way of Comparing Engine Designs". Honda type R engine is really a gem

 

The article is old. The K20A has even higher figures.

 

180 x 1200 / 2 x 8400 = 12.85

[Coupecabriolet]

this formula is better for SC / TC cars?

 

Scirocco 1.4TSI gives 17.44 from 118 x 1200 / 1.4 x 5800

E200 CGI gives 17.14 from 135 x 1200 / 1.8 x 5250

Tiguan 2.0TSI gives 17.29 from 147 x 1200 / 2.0 x 5100

Edited November 8, 2010 by Coupecabriolet

[Karnaugh]

The article is old. The K20A has even higher figures.

 

180 x 1200 / 2 x 8400 = 12.85

 

How did you derive at 180 KW? The highest output by a stock K20A now is 222 bhp which translate to about 165.5 KW.

 

You should look at Honda's F20C rated at 13.29 bar.

Edited November 8, 2010 by Karnaugh

[Karnaugh]

This formula can be used for any type of engine. Just that the FI ones are more efficient thus producing higher figures.

[Crazecow]

How did you derive at 180 KW? The highest output by a stock K20A now is 222 bhp which translate to about 165.5 KW.

 

You should look at Honda's F20C rated at 13.29 bar.

 

I got the figure from Wiki one. There is a version of K20A producing 240HP.

 

Oh the F20C.... Its a sad thing for Honda that people dont like the engine because its too noisy and lack of low end torque....

 

Btw, there is one NA gem from Toyota the Formula Atlantic 4AGE 240HP @ 8500RPM.

 

179KW x 1200 / 1.6 x 8500 = 15.79....wow thats even higher than some FI engines!

 

Of course, its a race engine and using extremely aggressive cams and probably idle at 3-4KRPM...... So driveability is almost ZERO.....

 

Thus as I have mentioned before I don't know if it make much sense to compare BMEP. The article mentioned already it does talking about torque range etc, just the peak. You can have an engine with very high peak HP (Honda VTEC and the RA 4AGE). But these engines produces very little torque esp. at low RPM.

 

Even for Turbo engines, there is Turbo lag. A big turbo running at high boost will produce very high BMEP but the lag is going to kill. Image you have to rev till 4K before getting some usuable boost...... Eg. I saw a Dyno graph for a WRX producing over 700HP and 75KG of Torque @ ~7.5K RPM!! Thats 41.76!!!!. Power increase sharply from 5K RPM onwards, anything below is literally dead... Other than for drag race, I don't see how its good for daily driving.

 

Those big CC engines may be low on peak HP (hence low on BMEP), but they produces lots of torque at low RPM which makes accelerating effortless and thats why people wants. Thus BMEP may not accurate show the real performance of the engine.

[Crazecow]

This formula can be used for any type of engine. Just that the FI ones are more efficient thus producing higher figures.

 

I do question the accuracy of such an equation for comparison. IMHO, its quite useless because it does not take into account the design of the engine. Not all engines are designed for high peak power. In fact, most are designed for just moderate peak power but a good spread of torque esp. at low RPM. This means intake and exhaust manifold are designed differently. The port angle etc will be different as well.

 

Engines with good low end torque tends to use low profile cams (maybe just 220-230 degrees) and low lift as well. This becomes a restriction at high RPM and restricts power. Same thing for intake and exhaust manifold and ports. Smaller head ports are better for low RPM because it increases air velocity but becomes a restriction at high RPM. Longer and narrow manfiold good for low RPM. Exhaust manifold 4-2-1 design good for mid range but 4-1 good for high end. And so on.......

 

With these designs affect peak power and hence lower BMEP, does it mean its a bad and inefficienct engine? NO........ ITs designed for different purpose in mind.

[Elfenstar]

I do question the accuracy of such an equation for comparison. IMHO, its quite useless because it does not take into account the design of the engine. Not all engines are designed for high peak power. In fact, most are designed for just moderate peak power but a good spread of torque esp. at low RPM. This means intake and exhaust manifold are designed differently. The port angle etc will be different as well.

 

Engines with good low end torque tends to use low profile cams (maybe just 220-230 degrees) and low lift as well. This becomes a restriction at high RPM and restricts power. Same thing for intake and exhaust manifold and ports. Smaller head ports are better for low RPM because it increases air velocity but becomes a restriction at high RPM. Longer and narrow manfiold good for low RPM. Exhaust manifold 4-2-1 design good for mid range but 4-1 good for high end. And so on.......

 

With these designs affect peak power and hence lower BMEP, does it mean its a bad and inefficienct engine? NO........ ITs designed for different purpose in mind.

 

Autospeed is about performace, so taking it in context, I guess thats what they're looking at (as per normal) rather than drivability, etc.

 

P.S. Yes this article is backdated (in terms of engines used). Its a re-published article from 2006. Says so in a blue box above the body

Edited November 9, 2010 by Elfenstar

[Trex101]

Autospeed is about performace, so taking it in context, I guess thats what they're looking at (as per normal) rather than drivability, etc.

 

P.S. Yes this article is backdated (in terms of engines used). Its a re-published article from 2006. Says so in a blue box above the body

 

Depends on what you after? I would prefer torque at low rpm then peak hp because most of the time my driving rpm range is between 1500-2500rpm.

[Elfenstar]

Depends on what you after? I would prefer torque at low rpm then peak hp because most of the time my driving rpm range is between 1500-2500rpm.

 

I know, but autospeed is generally about performace

 

[Trex101]

I know, but autospeed is generally about performace

 

Autospeed is pretty good, i like reading all their DIY performance mod. did you read the one about the real 12v electrical supercharger? sound very interesting

[Crazecow]

Depends on what you after? I would prefer torque at low rpm then peak hp because most of the time my driving rpm range is between 1500-2500rpm.

 

If thats that case, then your engine would most likely have a rather low BMEP score unless its TC or SC. NA will have rather low figures unless its DI and high compression (eg. BMW or Toyota DI engines with 12:1 compression).