Jump to content
SAU Community

Recommended Posts

R34 GTT Auto High Revs 'Mystery Noise'

Hello experts,

I'm experiencing a very strange problem with my R34 GTT (Auto Tiptronic) at high-revs as I change between gears, usually between 3 & 4 but can't say for sure (I've not driven it for quite some time as the water pump has gone and I'm waiting on parts as it'll be a full 100k service anyway so I cant say for sure).

Basically, If i plant it, I hear a unique "BRRRRRRT" sound between some gear changes and sounds like its coming from underneath the car (the A/T?) and is usually followed a puff of black smoke out the back of the exhaust, like its delayed that fraction of a second and the exhaust gases have backed up. I know she's running a bit rich, it's mostly stock but this is something that I really noticed after I had most the stock exhaust system replaced (X-Force 3.5 Catback, Venom 5" Cat - yet to fit a dump to complete the system).

My gears change just fine under normal load/cruisey driving, I dont have any issues or lag between changes, and I dont often flog it as its a daily driver (only every now and then to clear out the crap and whenever there is some p-plater pleb in a commy at the lights trying to get a rise out of me).

As I'm at 197,000k's (and just done a water pump), I'm conducting half the 100k service myself for the minor things such as oil & fluids, filters, radiator flush and my local mechanic will do the water pump, timing belt, seals etc - would it be worthwhile having it booked in to have the A/T serviced or is this issue cause by opening up the exhaust a bit.

Any light anyone could shed would be fantastic - it's not overly problematic, but it can be quite embarrassing really.

Cheers!

Mike

2 hours ago, GTSBoy said:

This is usually an exhaust heat shield.

There was one on the stock cat, but nothing on the Venom now - do you recommend having a shop custom make one for my cat (or an area of the exhaust as you say?).

Also, from your recommendation and putting down to an exhaust heat shield, whats happening down there to make it cause that noise?

It's usually that one is loose in some way and buzzes when the harmonics are right.  Low revs, mid revs, high revs, whatever it takes to get it buzzing.  If you don't have any heat shields down on the exhaust, then it won't be one of them.  It might be one on the manifold or turbo.  Or it could be the exhaust touching something, like at the mount on the gearbox crossmember.

Or it might not be the exhaust.  It could be the tranny.  In which case........manual conversion time.  It's the only way to be sure.

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...