Tech Time: Drivetrain Power Loss

[[PIMPIN]]

What you guys reckon the drive train losses of a GTR should be? Basically, the % variance between power at the engine and at the wheels?

I've been reading and some reckon 20-30% which is considered 'about right' for 4wd cars and is consistent with Evos and Subarus. However true that may be, I believe the number to be much lower, under 20% in fact.

My view is that on a dyno, a GTR is not experiencing any loss of traction whatsoever therefore most of the power, for arguments sake let's say 90% through the rear wheels. This means that there is no 4wd levels of drive train loss to speak off simply because its a RWD.

What are your thoughts on the matter? I believe there is no real figure nor is there any possible way of calculating or estimating the diffence with any form of accuracy but nevertheless it's interesting to see what people think.

 

[gobiz]

Most people quote 20-25%.

Some people say the R35 GT-R has a lot less.

It's actually easy to find out but difficult to actually do:

1. You need an engine dyno and a hub dyno.
2. Dyno the engine out of the car on the engine dyno.
3. Then put the engine in the car, and then dyno the car at the hubs.

To complicate things, we all know dynos vary depending on so many variables ie. elevation, temperature, slip, dyno brand, etc etc.....

For definitive power, I would believe engine dynos rather than wheel/hub dynos.

 

[Liner]

From my observation, i tend to think 32 and 33 gtr's have more drivetrain loss, as the power they make from the engine, after minusing out 30% is about right.While for 34gtr's, i would say around 25%, as, if you put 30% to it, the hp amount on engine seems abit too high.

 

[gobiz]

From my observation, i tend to think 32 and 33 gtr's have more drivetrain loss, as the power they make from the engine, after minusing out 30% is about right.While for 34gtr's, i would say around 25%, as, if you put 30% to it, the hp amount on engine seems abit too high.

Interesting, I heard that the R34 GTR has higher output anyway...so that could explain it.

Otherwise, the R34's Getrag 6-speed might be a better gearbox?:hmmmm:

 

[iexit]

I use to agree about the percentage calculation on the power lost at the drivetrain, but I was thinking about it and it make sense that the power lost is static vs. % which is not static but active. Think about it the power lost should not correlate with the increase of power on the engine.

A 400bhp and 600bhp engine will still suffer the same amount of drivetrain lost if the vehicle is the same; it’s about drag & resistance. So the power lost should be e.g. 50bhp (estimated for RWD) and that should hold true as the engine develops more power at the later stages. My 2 cents only open to interpretation and correction :-)