Got Over 400kw Atw?

[Beer Baron]

The rear wheels are not in a slip event if the dyno allows the front wheels to match speed... Even for a split second

there are a few other factors that govern GTR all wheel drive though. not just wheel speed difference between front and rear. but consider that the wheels are driving the dyno not the other way round so yes as you start the car rolling teh rears are moving but the fronts aren't, the ecu then tells the transfer case to pressurise and torque is transferred to the front. anyway, most awd dynos can give you a reading for the front and rear.

[SimonR32]

there are a few other factors that govern GTR all wheel drive though. not just wheel speed difference between front and rear. but consider that the wheels are driving the dyno not the other way round so yes as you start the car rolling teh rears are moving but the fronts aren't, the ecu then tells the transfer case to pressurise and torque is transferred to the front. anyway, most awd dynos can give you a reading for the front and rear.

Yeah it's not the end of the world either way!

R32's are good because you can flick the switch

[GTRPowa]

Yeah it's not the end of the world either way!

R32's are good because you can flick the switch

Yeah but if you truly lose <10kw why would you do it?

skidz?

Only time I've pulled fuse was driving home with a broken front drive shaft. (Mounts) - Mind you, it DID take me a few months to fix it..

Edited February 7, 2011 by GTRPowa

[Marko R1]

when i had my gtr tuned @ 405awkw - my tuner told me that is approx 450rwkw (he would know his own dyno lol)

[mico]

there are a few other factors that govern GTR all wheel drive though. not just wheel speed difference between front and rear. but consider that the wheels are driving the dyno not the other way round so yes as you start the car rolling teh rears are moving but the fronts aren't, the ecu then tells the transfer case to pressurise and torque is transferred to the front. anyway, most awd dynos can give you a reading for the front and rear.

is it possible that the computer takes power out when its running in rwd ? then puts bak in when awd ?

[mico]

if u run the car in awd then rwd on the same dyno and the result is the same, that means the dyno is equalling it out bcos it knows whats happening ? where as if u ran the car on an awd dyno then went around the corner to somewhere else and ran it in rwd it would be totally different ? and yes i know different dynos show differently.

[Rolls]

Bloody hell don't start the fixed vs percentage debate again. There like a 10 page thread on it.

Percentage loss is a good way to work out factory approximate drivetrain losses. When you start making 3, 4 or even 5 times the factory power levels, those percentages are not logical any more. There was a big thing on it here, once again, a lot of people agreeing to disagree.

My arguement is you can't say that a drag car making 3000hp at the wheels is still going to have a 20% drivetrain loss coz that's BS

The most accurate models I've seen based on lots of data use a percentage loss + a fixed component, but even then it is only accurate for a certain range because as you said, you cant be making 3000hp and expect 20% drivetrain loss.

Like a lot of models they are only accurate in a small range.

Edited February 7, 2011 by Rolls

[GT-R32]

nah it's no where near that much. 400rwkw is about 375-380awkw or so. if you've got 301awkw you would be about 320-325rwkw on most dynos. there is not much difference between AWKW and RWKW on dyno dynamics dynos. certainly not 15%. and it's not a fixxed percentage anywway. the gap does widen a little bit the higher the power level but it's not linear. like it might be 20kw difference at 200kw and only 25kw at 400kw. there is no fixed answer. regardless of that even just different dynos vary a bit even when all reading RWKW or AWKW.

I got 294awkw and 307rwkw (R32 GTR). So, pretty close!

[Nee-san]

Yeah, fairly sure swiper ran his back to back and got a minuscule variance, people drastically overestimate the power losses in drive trains.

[NickR33]

all depends the condition of the transfer case... but on standard transfer cases its 10kw difference max... a modded transfer case can increase the awkw > rwkw difference... but on some older 32's with worn cases there is zero difference

anything more than 10-20kw is an exaggeration IMHO

[Beer Baron]

Yeah it's not the end of the world either way!

R32's are good because you can flick the switch

agree on both points. yes it's not the end of the world, and yes flipping the AWD/2WD switch is fun.

is it possible that the computer takes power out when its running in rwd ? then puts bak in when awd ?

no it the ecu doesn't 'remove' power when you put the system into RWD. it just sends all the power the engine makes to the rear wheels. the reason you get a little less power when the car is in AWD is that there is a parasitic power loss in the transfer case, front shaft and front diff. it's not much though and certainly not 50kw on a car making 400kw.

if u run the car in awd then rwd on the same dyno and the result is the same, that means the dyno is equalling it out bcos it knows whats happening ? where as if u ran the car on an awd dyno then went around the corner to somewhere else and ran it in rwd it would be totally different ? and yes i know different dynos show differently.

no it makes no difference. an AWD dyno dynamics dynamometer is basically 2 "2WD" units together. so you can run it in awd using both sets of rollers, and then simply run it in RWD using only the rear set (with the car in RWD mode). The dyno doesn't "know" what you're doing. it's exactly the same as "going around the corner to a RWD dyno". they operate exactly the same way.

I got 294awkw and 307rwkw (R32 GTR). So, pretty close!

yeah that's more like it. very typical result for a GTR at that power level for AWD vs RWD. god if it were 50kw as some people claim imagine how fast the car would feel when you switched to 2WD mode! you'd suddenly be free of the 50kw drivetrain power loss and your car would be a rocket ship. that's the easiest way to tell. any GTR I've run on the road between AWD and RWD you can tell it accelerates (when rolling) a little better in RWD (providing you have traction at that power level), just enough that you can notice something, but not a huge difference. which again backs up the evidence that's it's a handful of kw's at most 'normal' power levels.

[Marko R1]

if i could judge the difference between rwd & awd that would be good - rwd mode is stupid though, 3rd gear has no traction what so ever

[The Dan]

if i could judge the difference between rwd & awd that would be good - rwd mode is stupid though, 3rd gear has no traction what so ever

Is it an RB20? I heard they do that at 5700rpm

[Marko R1]

Is it an RB20? I heard they do that at 5700rpm

haha very funny

mine does that off idle

[Mosullivan]

haha very funny

mine does that off idle

That is the dream.

Who knows when you're going to need to rip a burn out and when that time comes, do you really want to be wasting precious smoky seconds with things like 'spooling the engine up' and 'clutch dumping'

Didn't think so.

[Deano 1]

Is it an RB20? I heard they do that at 5700rpm

hahaha he hasnt returned after the burn thread either hahahahaha

[Piggaz]

I'll throw up my little 2 cents with this 4WD vs RWD garbage.

On unigroups dyno a few years ago I made 370 RWKW.

One week later I made 361 AWKW on Rigoli's dyno at a Dyno day.

I realise they are different dynos's and stuff but they are my results.

[Beer Baron]

if i could judge the difference between rwd & awd that would be good - rwd mode is stupid though, 3rd gear has no traction what so ever

yeah I know that's a problem when you have 400kw! try getting on it hard in 4th gear it should have plenty traction in RWD at those speeds, then try in AWD. you will find it feels a bit quicker in RWD but it's not a huge amount. if it were really 50kw I would say find some stickier rear tyres, cut off the transfer case and enjoy the cheapest 50kw we will ever make!

[T04GTR]

WELL WHEN MINE WAS TUNED IT WAS 375AWKW. dyno comp did 376rwkw.. so f**k all. bear in mind that the skyline has a locked center when on a dyno.. if the transfer was slipping i would expect to see a differance.. not a viscous coupling sapping power.

[iplen]

Further reading on trash forums, I found a bright spark with a convincing way of saying the drive train losses are fixed, what with all the articles/forum threads around talking about percentage losses.

Eg: You might make 200kw at the engine, and 140kw at the wheels. Then if you make 400kw at the engine, you'll make around 340kw at the wheels. Excuse the fact some of you probably know this, but I'd assume lots of people (myself included) think about fixed percentages.

And if that's the case, then the AWD mode on GTR's would used a fixed amount, instead of a percentage too. The pieces come together!

Edit: Excuse the fact if it's posted somewhere here, but I haven't seen it, and in fact, I've never read it this way until today... And I read forums a bit too..

So a 100kw car makes -60awkw???