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Dyno Reading.

Rav

By Rav,
in Engines & Forced Induction

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Klymax Contributor

Klymax

Posted
Posted

I don't know anything about the GTR driveline but I can imagine the front wheels smoking the hell out of the tune shop lol overheard someone saying you can pull a relay out or something for rear wheel drive only but I dunno about how truthful that is, seems a little silly to me but as above I've no idea if the front an rears can seperate 100% to stop it launching out the front door :D

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Klymax Contributor

Klymax

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P.S. Rav i apologise for my sarcastic post :D my imagination just got the better of me ;) I would assume they would be very comparable as the output of the motor will be the same just depends how well the driveline holds up running 4 or 2 wheels. I wouldnt imagine too much difference

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Rav Proficient

Rav

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Just asking because i made 297kw on a rw drive Dyno, And some guy was giving me Sh*t saying there no way i made that power with stock AFM's and if i put it on a 4wd Dyno it be way lower out put.

So i thought i would post up and ask if this is true.

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SLAPS Rising Star

SLAPS

Posted
Posted (edited)

Power has nothing to do with AFM's.

If you max the afm you can still tune for peak power. Just means there's a point when its ramping up on to boost where its a little rich and missing a little ignition timing as that 'load point' is tuned expecting more airflow which requires more fuel and less ignition.

Edited by TheRogue
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R31Nismoid Grand Master

R31Nismoid

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Just asking because i made 297kw on a rw drive Dyno, And some guy was giving me Sh*t saying there no way i made that power with stock AFM's and if i put it on a 4wd Dyno it be way lower out put.

So i thought i would post up and ask if this is true.

Well he clearly doesn't know what he's talking about

So don't listen to him :D

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Rav Proficient

Rav

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Thanks guys for the info, It was pretty funny because i only meet this person for few mins and we fighting over how much the stock AFM's can handle and my tuner dyno is so happy.(I know thats not true so many people get a lower rideing on it then any other dyno).

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WYTSKY Veteran

WYTSKY

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Thanks guys for the info, It was pretty funny because i only meet this person for few mins and we fighting over how much the stock AFM's can handle and my tuner dyno is so happy.(I know thats not true so many people get a lower rideing on it then any other dyno).

Man i hate those guys... think they know it all and u dont even know them from a bar of soap, yet they are apparently the fountain of knowledge about YOUR car... I just laugh at them these days like these guys don't know crap... normally makes them madder and you win :)

I have a GTS4 and I always thought it was about 20-30kw less on a 4wd dyno?

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MRGTR911 Experienced

MRGTR911

Posted
Posted (edited)
You cant just pull the fuse out in a R34 GTR to go to RWD like with the R32s

I think in a R34 there is ~10% difference. Ie: 300AWKW is 330RWKW

Anyone done both in an R34??

You can pull a fuse out in a 34 , i have , its just highly unrecommended ... I done a test .

Power On RWD 17PSI = 335 REAR WHEEL KWS

Power On 4WD 17PSI = 310 REAR WHEEL KWS

Not much of a difference , Seems to be right .

Edited by MRGTR911
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Brockas Proficient

Brockas

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Don't pull the fuse on the R33/R34, the clutch packs there is a pre-load on the transfer case, see the above post...

Its fine to do it in an R32 because they don't use this pre-load...

I've read this, but is the pre-load applied electronically or mechanically?

I have an R32 gearbox/transfer case in an R33 GT-R.

Does this mean that the transfer case still has a pre-load applied to it by the ATTESSA computer, or is there no pre-load because its an R32 transfer case?

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**RB2530** Proficient

**RB2530**

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There will be a difference between 2WD and 4WD readings on a dyno...

Its simple physics..In 4WD mode you have an extra driveline (minus g/box) running the front wheels. The transfer case, prop shaft, front diff and front drive shafts all exhibit frictional loss and therefore when they are moving, consume power. When they are not moving (2WD mode) they are not consuming power. There is also a fair amount of power loss between the tyres and the dyno rollers...So an extra pair of tyres spinning an extra two rollers...you guessed it more friction.

So there WILL be a difference between 2WD and 4WD mode on a Dyno...I would guess around 10-15%...

On the road however it is a completely different story... the front driveline is either being rotated by the transfer case (when torque is being directed to the front) or in 2WD mode, by the road itself turning the front wheels. Irrespective of what is turning what, the front driveline is rotating so it is still consuming power.

So in my mind looking at GTR dyno figures in 2WD mode and comparing to RWD figures is not a useful comparison because it is not considering 100% of the driveline loss. Even with a RWD on a dyno you are neglecting to measure the loss from the front wheels and bearings as well.

It all gets down to what do you really want to find out...If you want to know how quick your car really is take it to the strip..If you like seeing big (slightly exaggerated) HP numbers on a screen, put it in 2WD mode and take it to the dyno... If you are looking for a simple correlation between the 2, stop looking because it is not as simple as that. (PS I know you weren't asking this but I know it will come up...)

cheers

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STATUS Grand Master

STATUS

Posted
Posted (edited)
bugger all because a GTR isnt fulltime 4WD, nor is it a 50/50 split like a WRX/EVO

The guy (he is THE GTR tuner) who does your dynoing does the same we do and simulate the small extra load, . That way they pull the same whether it be 4wd or 2wd.

Edited by URAS
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