Jump to content
SAU Community

Recommended Posts

OK, I had a bunch of work done on my R33 GTR before xmas - incluing transfer case rebuilt and pan baffle. I'm sure they had to pull a bunch of the front suspension and cross member as they did the pan baffle with the motor in the car.

Now, my problem is really bad understeer. In the wet the car will understeer out of a round about if I accelerate out from normal speed. In fact at speed limit speeds, if I just aggresively turn the wheel the fronts slide and slip.

The car also kicks in the diff lock really agressively as even turning at 5 kph out of my driveway it will lock up the rear diff and make the car surge a bit as it turns.

I've only ever driven the car in 2wd mode as the transfer was stuffed when I bought it. But it never understeered this badly. In fact I think it drove better before becasue at least it oversteered when I put the power on.

I'm thinking I need to bring it in for an alignment check up as the first place to start. If that isn't the prob then I guess back to the shop for more check up (but I'm not really feeling confident as the shop has really taken me for a expensive ride so far).

Link to comment
https://www.sau.com.au/forums/topic/256972-gtr-understeering-badly/
Share on other sites

Ok, it's got greddy S-Tune all the way around. I lighted up the front adjustment all the way to hope to give it some more grab on the front.

Lowered 1" with whiteline camber bushes and aftermarket sway bars front and rear. The sway bars aren't adjustable so they aren't whitelines, but I don't know which brand.

Adjustable upper camber arms in rear.

Camber at front 1.5-2 negative and rears @ 1 negative degree.

In the wet this is what happens. The understeer happens entry, mid and exit. So entry if I just turn the wheel a bit too much will just slide. Mid if I accelerate will just slide. And exit will slide if I accelerate.

I don't drive that hard in the dry so I cannot comment too much aside from you can still feel the understeer a lot, it just takes a bit more speed and harder acceleration so I'm sure it will be the same as on the wet.

I just feels so wrong and really compromises my confidence.

Have you got a 4WD alignment done recently? Its worth a try and may improve things quite a bit....

I only had serious understeer issues when the transfer case was dying, the GTR does still understeer but not that easily.

The diff does lockup as you described depending on how cold it is.

It's a pity you cant soften the front bar that would be a good start after checking tyre pressures, How low is the front end, top of the guard inside to the deck? What are the spring rates? In the end it looks like a few things and I guess the diff isn't helping. I'd talk with the guys in the NSW section to get a referral to a good suspension shop...Heasmans or similar.

This is why I get my tuner to go the mechanical and a specialist suspension shop to do the suspension

Tyre pressures are 32 PSI all around. I've got Toyo Transas 275 35 18's all around with plenty of tread so those aren't the prob either.

It could be that the car didn't have the prob before as the diff (and 4wd) wasn't working before so it would spin a back tyre before breaking the fronts loose. I just can't belive how easily the fronts break loose now.

May have to investigate a better front roll bar.

Thanks for the input fellas.

Get a 4 wheel alignment done first. That way you know the wheels are pointing straight. Secondly, what oil are you using for the diff and transfer case? Maybe wrong type of oil used? The diff should not lock up in the driveway. Just some suggestions.

If you have redline light weight shock proof in the rear diff then that can make it lock up at low speeds. Its probably not ideal for a street car if you just want it to be quiet, damn good oil though and makes the diff tighter which is great for track days/spirited driving...

Ok, it's got greddy S-Tune all the way around. I lighted up the front adjustment all the way to hope to give it some more grab on the front.

Lowered 1" with whiteline camber bushes and aftermarket sway bars front and rear. The sway bars aren't adjustable so they aren't whitelines, but I don't know which brand.

Adjustable upper camber arms in rear.

Camber at front 1.5-2 negative and rears @ 1 negative degree.

In the wet this is what happens. The understeer happens entry, mid and exit. So entry if I just turn the wheel a bit too much will just slide. Mid if I accelerate will just slide. And exit will slide if I accelerate.

I don't drive that hard in the dry so I cannot comment too much aside from you can still feel the understeer a lot, it just takes a bit more speed and harder acceleration so I'm sure it will be the same as on the wet.

I just feels so wrong and really compromises my confidence.

Rake angle (or front to rear balance) plays a huge part in how the GT-R corners. Lowering overall by 1" as you say is OK, but you must make sure you keep the front (as measured from the centre of the wheel to the arch) is around 10mm higher than the rear. If you have a neutral (or worse rear elevated) rake the car will understeer like a bitch.

You don't mention if you have a subframe alignment kit (aka "pineapples") installed. If you do, make sure the setting is neutral rather than "traction" or "squat".

Gav

  • 3 weeks later...

Thanks all. Had the 4 wheel alignment done and they said there was a ton of toe in at the front causing my issue. Must have gotten out of alignment with the work that was done.

Driving today in the rain and all seems good so far.

Glad it was just an alignment issue.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • It would be well worth deciding where you want to go and what you care about. Reliability of everything in a 34 drops MASSIVELY above the 300kw mark. Keeping everything going great at beyond that value will cost ten times the $. Clutches become shit, gearboxes (and engines/bottom ends) become consumable, traction becomes crap. The good news is looking legalish/actually being legal is slighly under the 300kw mark. I would make the assumption you want to ditch the stock plenum too and want to go a front facing unit of some description due to the cross flow. Do the bends on a return flow hurt? Not really. A couple of bends do make a difference but not nearly as much in a forced induction situation. Add 1psi of boost to overcome it. Nobody has ever gone and done a track session monitoring IAT then done a different session on a different intercooler and monitored IAT to see the difference here. All of the benefits here are likely in the "My engine is a forged consumable that I drive once a year because it needs a rebuild every year which takes 9 months of the year to complete" territory. It would be well worth deciding where you want to go and what you care about with this car.
    • By "reverse flow", do you mean "return flow"? Being the IC having a return pipe back behind the bumper reo, or similar? If so... I am currently making ~250 rwkW on a Neo at ~17-18 psi. With a return flow. There's nothing to indicate that it is costing me a lot of power at this level, and I would be surprised if I could not push it harder. True, I have not measured pressure drop across it or IAT changes, but the car does not seem upset about it in any way. I won't be bothering to look into it unless it starts giving trouble or doesn't respond to boost increases when I next put it on the dyno. FWIW, it was tuned with the boost controller off, so achieving ~15-16 psi on the wastegate spring alone, and it is noticeably quicker with the boost controller on and yielding a couple of extra pounds. Hence why I think it is doing OK. So, no, I would not arbitrarily say that return flows are restrictive. Yes, they are certainly restrictive if you're aiming for higher power levels. But I also think that the happy place for a street car is <300 rwkW anyway, so I'm not going to be aiming for power levels that would require me to change the inlet pipework. My car looks very stock, even though everything is different. The turbo and inlet pipes all look stock and run in the stock locations, The airbox looks stock (apart from the inlet being opened up). The turbo looks stock, because it's in the stock location, is the stock housings and can't really be seen anyway. It makes enough power to be good to drive, but won't raise eyebrows if I ever f**k up enough for the cops to lift the bonnet.
    • There is a guy who said he can weld me piping without having to cut chassis, maybe I do that ? Or do I just go reverse flow but isn’t reverse flow very limited once again? 
    • I haven’t yet cut the chassis, maybe I switch to a reverse flow. I’ve got the Intercooler mounted as I already had it but not cut yet. Might have to speak to an engineer 
    • Yes that’s another issue, I always have a front mount, plus will be turbo plus intake will big hasstle. I’ve been told if it looks stock they’re fine with it by a couple others who have done it ahahaha.    I know @Kinkstaah said the stock gtt airbox is limiting but I might just have to do that to avoid a defect so it atleast looks legit. Or an enclosed pod so it’s hidden away and feed air from the snorkel and below Intercooler holes like kinstaah mentioned. Hmm what to do 
×
×
  • Create New...