R34gtt Boosting

[R34GTX]

Hi guys.

Quick review. Stock as a rock 2001 R34GTT Tiptronic Sedan. Only engine mods CES 3" Turbo Back exhaust with Split Dump HPC coated, hiflow cat and Twin tip muffler. Also has a K&N Panel Filter.

Before zorst upgrade, car ran stock boost, about 7psi. After zorst upgrade, car runs 12psi. Car seem to run perfectly fine. No spikes in boost or loss of boost, irrespective of my driving style.

Okay, now for the problem. Had the car in for a 80K service. (reputable company I shall leave unnamed for now) He said the timing was out by almost 10deg. So he adjusted appropriately. Driving home, boosted a few times, then the car dropped boost and ended up running 7psi. Restart the car, back to 12psi, then boosted a few times and bam back to 7psi.

Have been back to the mechanics a few times, but they are struggling to find the fault. No ECU faults showing, however they are getting an ABS/TCS computer fault showing up. Error code 58 from memory. He seems to think it is something to do with throttle/valve control?? However even after clearing this error code, the problem still reoccured but this time without the error code.

My personal thoughts are that the boost is running too high for stock ECU and thus causing the car to go into a type of limp mode.

My question is, how the hell do I wind back boost when the stock boost after zorst upgrade is sitting at 12psi?? I want to get back to around 10psi. I have tried turbosmart boost controller, but all that did was take the solenoid out of the equation and still left the boost at 12psi.

Any suggestion or thoughts are very much appreciated. Sorry about the epic story!!

[nuffsaid]

Mine was basically doing the same thing after my split dump, hi flow cat and cat back exhaust modification. I have a Apexi panel filter also. Thats it.

It would boost to 12psi, at near redline acceleration would drop off a bit due to rich and retard I think.

Anyways, I was not a big fan of the muffler, so I changed it to my Nismo muffler (which unfortunately is 2.5"). So My exhaust is pretty much 3" all the way except near the muffler where its 2.5".

This brought boost back down to around 9-10psi depending on how cool it is. No drop off in acceleration so its pretty smooth throughout the rev range.

Sticking with my 2.5" muffler for now as its more quieter.

I also thought about getting a controller of some sort to limit the boost when I had the cannon exhaust on, but I dont think its possible. Any controller can only limit boost to what your stock car (upgraded exhaust) pulls.

[Links]

You could look at getting one of the bleed valves from the forum for about $30 delivered..

That should help you with the boost atleast.. as for the errors.. not srue..

[R34GTX]

Mine was basically doing the same thing after my split dump, hi flow cat and cat back exhaust modification. I have a Apexi panel filter also. Thats it.

It would boost to 12psi, at near redline acceleration would drop off a bit due to rich and retard I think.

Anyways, I was not a big fan of the muffler, so I changed it to my Nismo muffler (which unfortunately is 2.5"). So My exhaust is pretty much 3" all the way except near the muffler where its 2.5".

This brought boost back down to around 9-10psi depending on how cool it is. No drop off in acceleration so its pretty smooth throughout the rev range.

Sticking with my 2.5" muffler for now as its more quieter.

I also thought about getting a controller of some sort to limit the boost when I had the cannon exhaust on, but I dont think its possible. Any controller can only limit boost to what your stock car (upgraded exhaust) pulls.

My muffler is already a twin tip Magnaflow, but it is still 3" straight through. I am not keen on changing mufflers as it cost me a mint.

I have heard people saying that maybe I could change the spring tension in the wastegate??

Any ideas??

Links = I already tried the $30 boost controller. The problem did go away, however, I think the only reason it did go away was due to the boost controller bypassing the duty boost solenoid. I have been told this is only a bandaid fix, and it may infact cause the car more damage as the car cannot impliment it's safeguards.

[nuffsaid]

Oh I am definately not implying that you change your muffler, I kind of regret it a bit coz I know its not flowing as good because the boost isnt going as high.

However I get smooth acceleration, no R&R and a quieter cabin. I am looking for a better flowing 3" muffler thats quiet.

You can change the spring in the wastegate, just got to find the right spring. I think thats tough because all of them are slightly different and will probably lead to different boost readings between turbos. Its a tough one, best bet would be to get a PFC to make use of the extra boost.

[TTT]

a boost controller is not a band aid fix.

all bost controllers by pass the factory solenoid.

they either have their own or as a bleed valve, bleed the air off.

if it fixed the problem of overboosting, then leave it on there.

if you want 12psi, go back to mechanic and get them to put the timing back to where they found it before they "FIXED" it.

[Links]

The current boost solenoid will never prevent your car from overboosting.. if you free up enough back pressue your turbo is going to run a higher boost pressure..

the solenoid does not know how much boost you are running, it is purely an on/off device, >4500 rpm it opens, letting less air hit the wastegate spring therefore requiring higher boost before it starts opening the wastegate..

using a boost controller is a damned good fix as it allows you to set within ~1psi of your desired boost level.. you just can't do that with the stock solenoid.

Your only protection against overboost really is R&R by the ECU when it detects too much airflow (overboosting)... but if you run say an Aftermarket ECU - you lose this..

Your choice..

I wouldn't recommend changing the wastegate spring, most people would probably recommend putting a bleed valve in or an aftermarket boost controller..

Also - limp mode locks the car to <2,000rpm.. you'll never be able to rev above it if I am correct..

currently the only thing setting your boost level is the restriction created by the hose running to the solenoid/wastegate.. add more restriction or free up the backpressure on a turbo and it's going to run higher boost/or more efficiently..

not sure why it is spiking to 12psi.. what does it go to when you go over 4,500rpm - does it go from 7psi to - 9/10psi?

Edited March 15, 2006 by Links

[666DAN]

Still no good Pete? That's pretty annoying...I've got my thinking cap on trying to figure what's going down. It's crazy considering we've got similar setups but your car doesn't seem to like boost, whereas my car never twitched when the boost went above 1 Bar (pre-ROM)???? You'll have to let me get my hands on the car sometime, we'll spend an arvo gunning around your neighbourhood

[rob82]

You could try putting a restrictor between the boost control solenoid and where it T's into the wastegate/boost signal point. THis way it will limit the amount of air the solenoid is able to bleed off.

[nuffsaid]

The current boost solenoid will never prevent your car from overboosting.. if you free up enough back pressue your turbo is going to run a higher boost pressure..

the solenoid does not know how much boost you are running, it is purely an on/off device, >4500 rpm it opens, letting less air hit the wastegate spring therefore requiring higher boost before it starts opening the wastegate..

using a boost controller is a damned good fix as it allows you to set within ~1psi of your desired boost level.. you just can't do that with the stock solenoid.

Your only protection against overboost really is R&R by the ECU when it detects too much airflow (overboosting)... but if you run say an Aftermarket ECU - you lose this..

Your choice..

I wouldn't recommend changing the wastegate spring, most people would probably recommend putting a bleed valve in or an aftermarket boost controller..

Also - limp mode locks the car to <2,000rpm.. you'll never be able to rev above it if I am correct..

currently the only thing setting your boost level is the restriction created by the hose running to the solenoid/wastegate.. add more restriction or free up the backpressure on a turbo and it's going to run higher boost/or more efficiently..

not sure why it is spiking to 12psi.. what does it go to when you go over 4,500rpm - does it go from 7psi to - 9/10psi?

But a boost controller wont stop him from getting to 12 psi right? It will only stop him from going OVER 12psi? I am interested to in case I get a good muffler that increases boost again.

Mine used to boost to about 10psi at 5000rpm, then creep up a little more to 12psi with the free flowing exhaust. Got kinda scared because I didnt want to blow the turbo up as I dont have a FMIC either. However, a restrictive muffler dropped everything down by a couple psi. Strange how just a 2.5" muffler can make such a difference to flow. I always thought that the dump and front pipe were more important than just a muffler!

I think it varies on car to car when R&R kicks in. SydneyKid said he had a R34 GTT R&R when boosted to 9psi only.

[Links]

You could try running a hose with a wider diameter so it lets more air through and opens the wastegate earlier??

It does also depend on what is causing the issue.. is it the solenoid?? try a bleed valve and have it screwed out completely and see what boost it runs..

Edited March 15, 2006 by Links

[Sydneykid]

My 20 cents.

Get an SAFC, tune the A/F ratios and enjoy the power increase and improved fuel economy.

cheers

[choyda]

My 20 cents.

Get an SAFC, tune the A/F ratios and enjoy the power increase and improved fuel economy.

cheers

Hi, will the SAFC be sufficient for mods he may have down the track such as FMIC and possibly a turbo change? I know R34GTX has been told that SAFC's arent worth it by this mechanic but just wanted to hear your opinion.

Damien

[Links]

Your mechanic seems to tell you alot of things aren't worth it.. but doesn't seem to be able to fix your problem..

Maybe look at an SAFC or a power fc if it's a manual.. get a SMIC, and try and find a way to keep the boost ~10psi (preserve the stock turbo)..

[paulr33]

yes the safc is a cheap piggyback solution that will give you 80% of the gains with only a fraction of the cost. there is a lot more than needs to go on the car before you can change the turbo, so face that hurdle when you cross it, you can always sell the safc.

a fmic wont add any more power so it doesnt really need to be "tuned" around it. its only when you increase boost pressure after doing the fmic

[Abo Bob]

Instead of an SAFC you could try the new fuel cut defender 3 from Turbosmart.

Cheaper.

http://www.turbosmart.com.au/index.php?s=fuel-cut-defenders

[R31Nismoid]

Hi, will the SAFC be sufficient for mods he may have down the track such as FMIC and possibly a turbo change? I know R34GTX has been told that SAFC's arent worth it by this mechanic but just wanted to hear your opinion.

Damien

First thing to do then... change mechanic.

second thing, get the SAF-C, being auto and stuff it just makes it all easier.

Still doesnt answer why its hitting 12psi.

I would question the actuator side of things.

Is it modded?

I dont think the GT-T should be running 12psi outta the blocks with an exhaust unless something else has been changed.

Findibng that comes back to the First thing... change mechanic

[nuffsaid]

First thing to do then... change mechanic.

second thing, get the SAF-C, being auto and stuff it just makes it all easier.

Still doesnt answer why its hitting 12psi.

I would question the actuator side of things.

Is it modded?

I dont think the GT-T should be running 12psi outta the blocks with an exhaust unless something else has been changed.

Findibng that comes back to the First thing... change mechanic

I wouldnt have thought boost would rise too, but it did for me. Perhaps the factory boost gauge is not as reliable as it is.

[R34GTX]

Thanks for the huge response guys. You would not believe just how frustrating and depressing it is when your car is not running well.

Just to clear up and clarify a few points.

1. Car used to run sweet at 12psi after zorst upgrade, but this was before timing was adjusted. (NO SPIKING) Just a solid 12psi. Car was 100% stock when imported. One owner with log books.

2. The car appears to go into a type of "limp mode" where boost is dropped to 7psi, but I still have the full use of the rev range. Is this what is referred to as R&R???

3. If my problem is R&R, how do I go about dropping my boost safely? Is hose restricting a safe and permanent method?

4. Was mentioned SAFC. This will still keep my boost at 12psi. How will this effect reliability with upcoming track days? Possible turbo blow up??

5. Would dropping my boost down to 10psi (method yet to be determined) stop this phenomenon from occuring?

6. Will an EBC get my boost down?

Thanks for being so helpful guys. Heaps of really good info here!!!!!

[Sydneykid]

Based on my experience with our R34GTT and couple more, yours is no different to any other.

Buy a decent boost gauge, the factory one is not to be relied on.

The 12 psi is most likely really 10 psi, which is OK for track days.

That's what our R34GTT went to with similar mods.

Get the SAFC and tune the A/F ratios

The R34GTT ECU is pretty smart, it goes R&R mapping at around 8 psi. And gets quite savage at 10 psi. This is not actually due to the boost level, it is a result of the AFM seeing the increased airflow that comes from increasing the boost. The SAFC reduces the AFM voltage that the ECU sees, hence leaning out the A/F ratios and at the same time avoiding the R&R mapping

cheers