Gtr - 4wd ??

[8thSIN]

Hi

this question has been bugging me for a while.. on a R33 GTR V-spec, I have been told that it's strictly rwd car until the rear wheels loose traction, only then the ecu switches on the front whees and it sorta becomes 4wd mode??

then I watch mpegs of GTR's on 4wd dyno's and all 4 wheels are driving the car

lastly, I don't know if this is a factory option or aftermarket mod, but heard that there is a switch in the cabin which allows the driver to simply switch from rwd to 4wd mode?

can someone pls clarify this.. thanks

[Jay95R33]

Hi

this question has been bugging me for a while.. on a R33 GTR V-spec, I have been told that it's strictly rwd car until the rear wheels loose traction, only then the ecu switches on the front whees and it sorta becomes 4wd mode??  

then I watch mpegs of GTR's on 4wd dyno's and all 4 wheels are driving the car

lastly, I don't know if this is a factory option or aftermarket mod, but heard that there is a switch in the cabin which allows the driver to simply switch from rwd to 4wd mode?  

can someone pls clarify this.. thanks

Yepp, that is correct regarding how the 4wd works. It's called ATTESA. Although on the R33 GTR's there is always a small amount of torque going to the front wheels - hence seeing them on a 4wd dyno. R32's are slightly different, still ATTESA but can be made rwd only by pulling a fuse. With the R33 GTR's they usually remove the front drive shaft to totally disable the torque to the front wheels.

And to the last question, nope, there's isn't a factory switch in the cabin to disable/ switch to 4wd and rwd.

There are after market controlers which can do that (eg. the HKS drag controller), or, so people with R32's wire up a switch/relay to cut the fuse to the ATTESA which put's it into rwd only mode, but again, it's not factory.

Cheers

J

[N I B]

33s and 34s don't need the shafts removed but the tricks private info.

[Jay95R33]

33s and 34s don't need the shafts removed but the tricks private info.

I heard that draining the transfer case does the same thing if that's what the 'private info' is !

[Laurence]

In answer to the first question, on a dyno the car is standing still with its wheels moving. If that isn't wheelspin then nothing is... The V-Spec has ATTESA E-TS PRO which can redirect up to 50% of the torque to the front wheels within 1/1000th of a second so that doesn't give you much time to see the wheels not spinning~

R33 non-V-spec is simply a matter of two fuses instead of 1

There is an interesting article on the R32 here

http://autospeed.com/cms/A_0060/article.html

[Scotsman]

I thought this forum was to help people understand their cars??? Private info is just your way of being tight.

[Merli]

33s and 34s don't need the shafts removed but the tricks private info.

HAHAHAHA you wanker

[Laurence]

Ummm more like being full of shit

[Merli]

Okay, Jay explained it quite nicely, but I'll add a little more info.

The ECU doesn't control the ATESSA. Rather, it has it's own computer that detects when the rear wheels spin. Depending on the amount of spinning, the ATESSA computer pushes, what is effectively another multiplate clutch system together, which engages the front wheels. Simple, but so effective.

To answer your dyno question, it's pretty straight forward if you think about it. The person driving the car puts it in first gear, gives it some revs and lets out the clutch like he's taking off normally. At this stage, the rear wheels are the only driving wheels. IMMEDIATELY, the ATESSA computer detects that the rear wheels are the only ones spinning!!! It thinks it's wheelspinning, so it does what it's supposed to do, and it activates the front transfer case and engages the front wheels! Pretty simple right? It all happens so quickly, to the casual observer it seems like all four wheels spin immediately, but next time, have a closer look, and you'll see the rear wheels start turning first, and then a few milliseconds later, the front wheels start turning too

Hope that helps,

Andrew.

[sammus]

Very well explained gojira

and you too merli...

[Scotsman]

So does anyone want to post the 'how to' on R33 / R34 RWD only? (without damaging your clutch packs)

[blind_elk]

You don't necessarily require wheel slip for the ATTESSA system to engage 4WD. There are also lateral and longitudinal G-sensors, that detect how hard you are accellerating or cornering, and tell the ATTESSA ECU to engage 4WD accordingly.

[Merli]

You don't necessarily require wheel slip for the ATTESSA system to engage 4WD. There are also lateral and longitudinal G-sensors, that detect how hard you are accellerating or cornering, and tell the ATTESSA ECU to engage 4WD accordingly.

Absolutely...

To elaborate, by theory, the ATESSA computer also has two G-sensors to measure, as blind_elk said: lateral and longitudinal forces. That is, to see how the car is moving. Longitudinal is pretty straight forward. It uses the lateral sensor to monitor cornering g-forces and to try and "predict" when the car is going to oversteer whilst cornering, before it actually starts to oversteer. Reason being it wants to feed torque to the front wheels so when you do eventually break rear traction and oversteer, your front wheels are already there pulling the car out of the oversteer.

My friend Yang and I, both with R33 GTR VSpecs, have tried this out at Wakefield Park, and we noticed that the ATESSA is a little slow to activate the front wheels... In fact, not only does it not feed torque to the front before oversteer, it waits until about half a second-ish AFTER you've already started to oversteer before the front wheels start pulling. By that stage you've already got the rear end out quite a bit, and washing off speed, instead of blasting out of the corners...

This is with standard suspension, so bodyroll was extremely evident... I'll give it another try shortly, after I get some proper suspension put in... Perhaps it will be able to monitor g-forces more accurately because bodyroll won't be absorbing some of the g-forces measured in-cabin.

Anyone else have some track experiences with their GTRs/GTS-4s they can share?

[Warpspeed]

The thing to realise with the Nissan ATESSA system is there is no centre diff. Most other 4WD cars have full time 4WD where a fixed proportion of torque is split front/rear.

The ATESSA system has the gearbox output shaft continuously driving the rear diff through the tail-shaft, and it is fixed 100% solid drive, just like a normal RWD car.

Also on the gearbox output shaft is a multi-plate wet clutch that drives a front "tailshaft" via a chain in the transfer case.

Now normally, this clutch is fully disengaged so the rear wheels only are driven. The ATESSA computer can apply hydraulic oil pressure to the clutch and feed torque to the front wheels. The clutch can go smoothly from open, to fully locked, or any degree of slip in between.

As said above, the ATESSA computer is pretty smart. It looks at front and rear wheel speeds, and has lateral and longitudinal accelerometers. It may also look at throttle position, but I am not absolutely sure about that. The computer in the R32 GTR reacts more slowly than the similar computer in the R33 GTR. So the R32 is a bit notorious for being slower to respond.

The R33 GTR V spec also has a similar electronic clutch in the rear diff, whereas normal GTRs have a conventional LSD.

To disable the 4WD you can remove a fuse which supplies power to the hydraulic pump that operates the clutch pack. I do not know which fuse, but the hydraulic pump is located behind the right hand rear wheel.

With the FWD clutch disabled the car becomes 100% RWD.

[Scotsman]

I have now had a chance to add to this topic. Due to a recent skidpan day.

With a R33 GTR (non V-Spec) you can simply pull the fuse in the boot located second from the middle in the small fuse box to give yourself 100% RWD power.

However on a GTR V-Spec as mine is. Pulling the fuse labeled 4WD/LSD also causes the LSD to become inactive because of the hydraulic pump supplying pressure to both the 4WD transfer clutch and LSD clutch.

Therefore making it useless for dirft and skidpan days.

So i'm still searching for the solution without removing front shaft or spending $$ on HKS splitter crap.

Any comments ??

[GTRman1992]

There is a really good article in ZOOM number 56 on the ATTESSA system.

The R32's update at 4 times a second, R33's 100 times a second and the V-Specs at 500 times a second. They reckon this is only for passenger perception and has no effect on the handling. That late coming in of the system is how it is designed.

I'm building a 4WD controller that modifies the accelerometer signal similar to others. With mine you will be able to download a curve you draw yourself and it will have data logging / real time display output to a laptop. I'm going to have it have about 4 different curves to select as you drive and 6 different settings for each curve.

Also it will have two different pre-setups so, say for a track that has a few hairpins then a sweeper you could have optimised two curves and quick-select between them as you drive.

Anyway, I was building it for myself, but if anyone is interested in the results or more details let me know.

The Trick:

The trick to disengage the 4WD system (works on 32, not sure 33, 34) is to be rolling forward and flick the ignition switch off and on quickly, the warning light on the dash will come on and it will be RWD until you become stationary again.

[MINES_DATSUN]

hey ,

i just checked on my 96 GTR and the fuse box in the rear boot hasnt got ROWS as you said. it has columns . the second COLUMN is Green fuses.. it has 2 fuses , does this mean its the second green one ? because they are differnt..

[R31Nismoid]

So i'm still searching for the solution without removing front shaft or spending $$ on HKS splitter crap.

Any comments ??

How about another useful one like this one?

33s and 34s don't need the shafts removed but the tricks private info.

PFFT... i agree with Gojira on that point.

What is the use of even having a forum if there is going to be people un-willing to share information.

If you dont wanna share it then kindly dont post IMO.

[Pva_Glue]

Steve is pulling all of your legs...

I am pretty sure EVL R33 http://www.skylinesaustralia.com/forums/sh...19&page=1&pp=25 already told you guys, how to do it.

as far as I can see

you can do it either

taking out the transfer case

or

Draining the fluids

of course on R33 GTR that is.

also you can try to SEARCH on this topic

or also try here http://www.skylinesdownunder.com

[JimX]

What is the use of even having a forum if there is going to be people un-willing to share information.

If you dont wanna share it then kindly dont post IMO.

I agree. And the same goes for people that say "I can get part X for $Y". If you can't get that price for everyone else or at least point people in the right direction, why bother wanking on about it? Who cares how cheap you can get stuff if you're not willing to share the cheap prices?