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it occurs to me that measuring AWD power and AWD drivetrain loss is nothing more than an academic exercise on a GT-R. The car is, for all intents and purposes, RWD, and the front wheels only engage a fraction of the time, and only as a traction control system that does not reduce total power delivered to the ground (unlike ignition-cut systems or systems that engage individual brakes to the spinning tire).

AWD dyno measurements measure total power minus the full drivetrain loss, when the power split is 50/50 - a situation that occurs extremely rarely and only in, say, an ice storm, and is hence more or less pointless in maximum power measurement.

Discuss, debate, flame :)
 

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yup!

ideally shouldnt take full awd drivetrain losses into consideration when dynoing
 

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so my question then is this: how does a Hub dyno manage the GTR's AWD system? Under load, does it ever see "wheelspin" and engage the front diff? Or does the car run in RWD mode fully?? I would imagine this would be more of a common occurance on a rolling road setup.

Anyone watched a GTR power run on a Dyanpack? I assume these display power @ each hub during the run...
 

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They drive all four - why would it be any different to running it on a rolling road dyno? The car doesn't know if there are wheels sitting on rollers attached to the hubs, or if the hubs are bolted directly to packs...
 

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They drive all four - why would it be any different to running it on a rolling road dyno? The car doesn't know if there are wheels sitting on rollers attached to the hubs, or if the hubs are bolted directly to packs...
But it sends out different amount of power to front/rear wheels constantly, no?

It would work if you have a skylab/similar controller set at either RWD or 50/50 torque split.
 

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Agree with bkvj...there would be zero slip on a hub dyno so why7 would it need to send any power to the front?

Interesting question!!

Anyone with dynapack experience fill us in?
 

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There IS going to be slip as far as ATTESA is concerned, the rear wheels will start driving and the fronts won't as obviously the car doesn't start rolling - so it will transfer torque to the front.

Yeah it won't necessarily be 50:50 but thats the way it works, I don't know why people would be hung up on it as the dyno is just a tuning tool - so long as the dyno configuration and car stays the same, the results will be consistant with themselves... if you are really hung up on engine power then the only way of working that out for sure is getting the engine on an engine dyno.
 

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There IS going to be slip as far as ATTESA is concerned, the rear wheels will start driving and the fronts won't as obviously the car doesn't start rolling - so it will transfer torque to the front.

Yeah it won't necessarily be 50:50 but thats the way it works, I don't know why people would be hung up on it as the dyno is just a tuning tool - so long as the dyno configuration and car stays the same, the results will be consistant with themselves... if you are really hung up on engine power then the only way of working that out for sure is getting the engine on an engine dyno.
Exactly....I can't work out why people need to display "Engine Power"

....If it's not at all 4 wheels, It doesn't count!!:chairshot
 

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I did not take into acount that ATTESA would care that the front wheels were not moving...good point, which does make sense.
 

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Discussion Starter #12
Exactly....I can't work out why people need to display "Engine Power"

....If it's not at all 4 wheels, It doesn't count!!:chairshot
yes and no. wheel horsepower is the only real figure that is quantifiable and pertinent. However, since the Skyline rarely puts down power on all four, REAR wheel horsepower is the one standard figure that should be cited for the Skyline GT-R. Front torque is so rare as to be meaningless in an all-out maximum power measurement. Think not? Unless you're using a torque split controller to lock in a torque split and override the ATTESA, just watch the torque split gauge and see how often it moves. Might also pull up that YouTube video of paint drying while you're at it.

The ATTESA works, and works wonders. It just comes in about as often as stability control does on a BMW. It does, but for seconds only, and only at the extreme limits.

It's no wonder that ATTESA clutckpack rebuilds are so rare, even on 20 year old R32s - they never see much use.
 

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How about the periods of time where there would be tyre slip? I've driven an R32 GTR making around 400wkw in RWD vs 4WD, in RWD if you gave the thing a bootful of throttle the tyres would let go in 1st, 2nd and 3rd rolling and if it was damp 4th gear was dangerous... I'd go so far as to say if you are running a typical upgraded twins setup, an AWD dyno run would be more realistic for the real world unless you only ever give it beans in 4th gear.
 

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my torque gauge flicks up to 10 or so whenever I bootit, car is an r32, is the attessa buggered?
 

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it occurs to me that measuring AWD power and AWD drivetrain loss is nothing more than an academic exercise on a GT-R. The car is, for all intents and purposes, RWD, and the front wheels only engage a fraction of the time, and only as a traction control system that does not reduce total power delivered to the ground (unlike ignition-cut systems or systems that engage individual brakes to the spinning tire).

AWD dyno measurements measure total power minus the full drivetrain loss, when the power split is 50/50 - a situation that occurs extremely rarely and only in, say, an ice storm, and is hence more or less pointless in maximum power measurement.

Discuss, debate, flame :)
Problem is, an AWD drivetrain has to be driven by either the road or the engine. (There is only one AWD design where this does not apply, and it is not used by the GTR)

Either way it is a parasitic power loss.

The idea that a GTR has as much drivetrain power loss as a RWD car, because it runs in RWD mode mostly................is nonsense.

The transfer case, front drive shafts, front diff, front prop shaft are always spinning, and that takes power.

Obviously the faster the road speed, the more the power drain.

Unfortunately there is no such thing as a free lunch, or should that be launch??? :chuckle:
 

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my torque gauge flicks up to 10 or so whenever I bootit, car is an r32, is the attessa buggered?
Something's amiss, have you checked your tyre pressures and tread depths? You may find your rears are substantially more warn than your fronts, thus giving a smaller rolling-radius and fooling the ATTESSA in to thinking you're experiencing wheelspin.
 

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This may help in determining what should happen; if I boot it I get torque fed to the front, and I reckon I should. :D

Clicky
 

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Something's amiss, have you checked your tyre pressures and tread depths? You may find your rears are substantially more warn than your fronts, thus giving a smaller rolling-radius and fooling the ATTESSA in to thinking you're experiencing wheelspin.
Its always done it, even when I had 4 new tyres put on as the importer gave me the car with unroadworthy ones! Also does it if one of the fronts goes over a noticable bump in the road too
 

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Roy,

So does my old man's.

Don't forget you have amodified R32, so would spin up the rears hence the torque transfer.

Cheers,
 

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The rears aren't spinning when this happens mate - its whenever I floor it, its almost as if the attessa is linked to the TPS instead of the wheel speed sensors lol
 
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