Power lost from engine to wheels

[skylineakt]

Hi guys

Just a quick question, does anyone know how much approximately power loss is there from the engine to the rear-wheels in a Skyline??

I got told it is about 80% but is this general for all rwdrive cars??

It seems that alot of the guys here have their car dyno and just wondering what was the reading for the engine output compare to the rw output.

The reason I ask is that i went for a spin in my car (R33 GTST) with a G-tech meter and got a pretty low hp reading. It was only like 170 hp at the rear wheels which in kilowatts is about 120 if my calculation is right.

That's in a car with me and one passnger, runing 11psi with catback exhaust.

Any input??

Cheers

[skylineakt]

Also i we only entered the stock weight of the car (1350) without passengers. Not sure if we had to entered our body weight as well. Maybe that would of made a different.

[DanS15]

170hp is 126.8kw.

Is that really low for your car with 11psi and catback exhaust. Considering catback wouldnt be doing a whole lot from standard.

[EVOIV]

With those G-Techs it's important to get the weight and other factors correct. But even so, they aren't that accurate. A dyno is the only sure way, but even still...different dynos on different days will give different results.

I have heard that the power lost from the engine to wheels is about 15% on a RWD car. On an AWD it's a bit more, like 20% or even more. There has always been a lot of debate about this. Whether it's a certain %, and if so what %? Or is it a fixed amount of power and not a %? I don't really know if anyone really knows?

[hippy]

i think you're being a bit optimistic there evo boy ... its more powerloss than that .. someone care to give us real figures??

[skylineakt]

The reason I say it is low Dan is because if (my theory haha) a stock GTST has 185kw at the engine and if there is a 80% power lost through drivetrain etc. There should be still 148 rwkw right?!?! 185X.80=148 or am I mean to minus the 148 to 185?? That's mean it is only 37kw@rw!!

That's is why I think it is abit low I was hoping that my car would have maybe close to 190 kw at the engine hehe

Cheers

[EVOIV]

But how many skylines actually have that amount of power? Brand new, yeah. But after a few years, things don't work as well, rotating parts don't spin as fast and make as much power...etc.

Hiep: Nah, I'm pretty sure that a RWD loses no more than 15%. Some people say AWD lose more like 25%.

Damn I want a chaser!! How much are they? $50k? Too much!!!

[skylineakt]

Yeah true that an old skyline would be less in power.

I know 4wd loss more than RWD but I also think that it is more than 15%?!? Anyone here have had their car dyno and got a reading for engine output and RWkws??

[EVOIV]

Well when I first had my EVO4 dynoed on an AWD dyno, it only put 123kW@wheels on 11psi. Then on 16psi is pumped out 155kW@wheels. Seeing that a standard EVO4 is supposed to have 206kW@engine, which I'm pretty sure mine didn't...it's still a huge power loss. For RWD cars, I'm not sure. But again it depends on temperature as well, cos at the time it was at the beginning of the year and the weather was still pretty hot. I'm sure a few more kW could be had on cooler weather.

[hippy]

what about when it was 224kw@all 4?? did they measure the engine power??

[blind_elk]

The 'rule-of-thumb' is around 30%.

EVOIV, the G-Tech is supposed to be remarkably accurate. But it has to be set up properly.

I had a run up on AVO's DTS dyno. This dyno is supposedly capable of calculating fwkw from rwkw.

My R32 GTS4 (RB20DET 4WD) ran:

115 4wkw

145 rwkw

175 fwkw (calculated from rwkw)

Do the calculations of loss yourselves.

[DanS15]

Yeah I would have said 20% to 30% for rwd depending on the type of car. Not all are going to be the same.

[EVOIV]

I still think 20% to 30% is a little too big.

Hiep: At one stage my car had 206kW@4wheels, but that power was recorded on a dyno (at the wheels). To record power at the engine, you would need to take the engine out I believe?

If I account for a 30% loss, that makes it around 290kW@engine. Almost 400hp.

[Ronin 09]

In a recent motor mag:

Dyno Dynamics Dyno:

*Ford Falcon XR8 5.4 V8:

260kW @ fly, 193rwkW, 24.6% power loss

*Holden Monaro CV8 5.7 Gen 3 V8:

235kW @ fly, 189rwkW, 19.6% power loss

*HSV GTS Coupe, Gen 3 V8:

300kW @ fly, 222rwkW, 26% power loss

*HSV Clubsport Gen 3 V8:

260kW @ fly, 196rwkW, 24.6% power loss

*FPV Falcon GT 5.4 V8:

290kW @ fly, 225rwkW, 22.4% power loss

*Ford Falcon XR6 4.0 inline six turbo:

240kW @ fly, 185rwkW, 25% power loss.

Consider a RWD car loss between 20 - 25%.

[EVOIV]

Hmm...interesting figures there.

It's kinda weird cos one time I saw a figure of an R34GTR that was dynoed as RWD and AWD and the readouts were the same!??? I don't know...

[DanS15]

EVOIV - those 206kw figures are a fantasy... Most jap cars with that figure are always more.

Im sure if you would calculate as 20% - 25% you would come to a better figure.

[Ronin 09]

Quote:

Hmm...interesting figures there.

It's kinda weird cos one time I saw a figure of an R34GTR that was dynoed as RWD and AWD and the readouts were the same!???

This should be true, as i understand. GTRs are basically RWD until they detect rear slip (on a dyno there shouldn't be any), at which point a power is apportioned to the front wheels. So the difference should be negligible between RWD and AWD for a GTR.

[Jay95R33]

As said before, around 30% for rwd cars - in particular the R33's.

Some 4wd cars can have losses as high as 48% !!!!

Makes you wonder why hay....

[DanS15]

Hey Skylineakt - did you get any 0 - 100kmh or 1/4 mile figures from the G-Tech. Would be interesting to know what they are cos it will give a good idea of whether your car is performing ok.

I believe you have to wiegh your car before using the G-Tech. Don't just use the factory wieght figures. You have to consider driver and a passenger if any and the amount of fuel should be similar when u wiegh it and test it on the G-Tech.

[predator]

25-30% .. that is why when you work out the power/weight ratio of say a modified skyline to any of these "top" aussie cars, the skyline still comes out on top.. on the street its pretty much the same I've found. Its all about the weight, and the aussie cars just keep getting heavier and heavier.

Ronin: interesting figures.. thanx for those.. so much heresay.. unless its all measured in a proper testing environment (e.g. same dyno) its hard to compare apples with apples.

Skylineakt: There is talk of a dyno day in melbourne with the VIC SAU crew. Al said he'd try bringing some vehicle scales so we can do some interesting calculations as well as receive dyno figures. Get along and find out for sure - it should be within the next couple of weeks.