Quick question, what is the HP at the wheels for a UK spec pre'01 Impreza Turbo?
Its purely for knowledge purposes, Id like to gauge some idea on the efficiency of the drivetrain, and am doing some comparisons.
Thanks
Gray

 

On my car the rolling road printout shows 204.5bhp, 130bhp at the wheels.

 

have a look at

 

Thanks vmuch both, but it does seem that the car loses a hell of a lot between flywheel and wheel, is this a factor of being 4wd?
Should a FWD car show a lot less of a loss between the two?

Okay, it obvuously is, because the power has to be delivered to two places, as opposed to one, Duh, sorry for the stupid question.
A typical dyno btwn a FWD and 4WD car should be approx twice the loss for the 4wd, right?
Edit, not so stupid a question, thanks for asking it too Robertio

[This message has been edited by IntegraR (edited 26 January 2001).]

 

Yep, it is a feature of 4WD, don't ask me to explain why, but it is, if you want lots of power at the wheels FWD is a lot better. If there is somebody who knows the reason why, would it follow that a 1WD car would have a very small loss?

 

A one wheeled car...try a motorbike

Nito

 

I had noticed that, but a motorbike only has 2 wheels, I said 1WD, there are still 4 wheels, however only one of them is driven

Coat is at the dorr waiting for me to leave

 

Anywhere that one component moves against another, there is friction and friction requires power (could be work, but you know what I mean! ) to overcome it.

There are more bearings, differentials, etc. in an AWD transmission, and they all sap power from the engine on its way to the wheels.

 

I wouldnt fancy cornering in the wet in a 1WD car.

A bike looses about 10% through the drive train - i guess a scooby does that through each wheel!

J

 

A theory - what do you think?

A big percentage of the power losses in 4WD cars(as measured by a chassis dyno anyway) comes from the fact that the measured transmission drag includes the rolling resistance of four driven tyres rather than two. The rollers can't distinguish between transmission drag and energy losses due to sidewall distortion during the coast down test.

each sidewall is distored at two points by being supported on two rollers, rather than once as on the road. The extra energy converted into heat in the tyre wall has often caused tyres to subsequently fail where Motorbikes are tested on Chassis dynos, so we are talking about large amounts of energy!. These inflated losses increase the estimated flywheel HP because the dyno overestimate transmission drag during the coast down.

I'd like to compare a run at standard pressures with one at 45psi in the tyres to see the effect.

Cheers,

Alex


[This message has been edited by AlexM (edited 26 January 2001).]