R33 Gtst - Problem Getting A Constant Boost Level, Causing R&r

[Sparky206]

Hey guys,

The problem I am having is that i can not get my car to hold a consistent boost level. Boost will jump around between 10-14 PSI which is causing me major issues with what i assume is the ECU going into R&R mode from what I've gathered reading around here.

The previous owner has installed a 3 inch turbo back exhaust along with a FMIC, after which he said the boost level rose to 12 psi, which in reality can be anywhere from 10-14 psi.

This is how it is currently set up. Ignore the T-piece $30 boost controller, It was originally running straight hose in its place and it has had no effect on boost levels since adding it

The problem that this is causing is a major flat spot in the rev range between 3.5-5000 RPM. It basically kicks in boost hard at 2500RPM, feels like I'm only on 3/4 throttle for 3.5-5000RPM then kicks hard again to redline. From what I've read this seems like the engine is going into R&R mode as I'm maxing out the airflow meter at 14psi. I think i confirmed this when i reset the ECU, the car felt like it was on 3/4 throttle for the first 5 minutes, then after that I'm assuming as the ECU learned A/f ratios again it leaned out most of the rev range and the car felt the same again.

From reading around here, it has been suggested that the 3 inch exhaust is not causing enough back pressure for the waste-gate to function correctly because air is flowing too freely through the turbo and there is not enough pressure for the air to need to flow through the waste gate. The fix for this would be fitting a 2.5 inch muffler only to increase pressure throughout the rest of the system. Quoted at $380 but seems weird as most people would be running 3 inch exhausts and mufflers here.

Any ideas on whats causing the boost to jump around so much? This isnt spiking either, it'll jump to about 14psi and stay there.

Plugs are brand new coppers, the NGK ones with the recessed tip, gapped to 0.8. Coils have been siliconed to eliminate them but they looked alright and i couldnt see any arcing at night before i did them so im pretty sure they were ok. Cars only done 65,000km, Series 2

I'm only looking to run 10psi so i can avoid R&R issues.

Cheers

Edited October 16, 2009 by Sparky206

[boostn0199]

that exhust story is rubbish , you have a stock ecu i was getting the same thing it was hitting R and R it has nothing to do with the exhuast turning your boost controller all the way down should run it at 10 if it doesnt it could be a faulty controller or you have a intercooler leak somewhere so the boost is all over the place, is your turbo stock

[Sparky206]

The boost controller has no effect, when i got the car, it didn't even have a controller, that blue line was just T-peiced onto the black line and connected straight to the waste gate. Turbo is stock

Edited October 16, 2009 by Sparky206

[femno]

Connect a hose from the metal pipe coming from the plenum straight to the actuator to eliminate and faulty controllers or solonoids and it should be fine. If not there is a problem elsewhere.

[Sparky206]

I've tried that, That is how it was when i first purchased it. To expand a bit, it does seem to be rev related, that it will hold 10psi, then creep up to 14 the harder it revs

[Yeedogga]

If you just have a vac hose running from the plenum/intake manifold directly to the wastegate actuator, and you block the hose that runs from the stock boost solenoid to the intake pipe the boost should be steady. If not, the wastegate actuator may be at fault. Pull it off (easy 2 bolts and a circlip) and use a bike pump with a gauge to test it.

[JonnoHR31]

pull the actuator rod off the wastegate and go for a drive, see what it does.

[Sparky206]

Pulled the actuator rod off and as expected car would not build any boost at all

[femno]

Nah it wont be that...it will most likely be the actuator...its the only other thing.

Chuck another on or check that the rod is not seized and that the diaphram holds vacuum.

[Sparky206]

Well i had another go at it today with great results. Made up a restrictor plate with a 2 1/2 in hole in it and put it in where the muffler bolts up, plumbed boost lines straight into the waste-gate actuator and took it for a drive.

Boost sat solid at 7psi, previously setup like this it would be hitting 14 psi. Plumbed in the boost controller set to 10 psi, started at 10 psi, crept to 11 then dropped off to 9.5 towards the top of the rev range.

Very happy with results and i guess ill stick on a 2.5" muffler as a permanent fix

[gotRICE?]

Well i had another go at it today with great results. Made up a restrictor plate with a 2 1/2 in hole in it and put it in where the muffler bolts up, plumbed boost lines straight into the waste-gate actuator and took it for a drive.

Boost sat solid at 7psi, previously setup like this it would be hitting 14 psi. Plumbed in the boost controller set to 10 psi, started at 10 psi, crept to 11 then dropped off to 9.5 towards the top of the rev range.

Very happy with results and i guess ill stick on a 2.5" muffler as a permanent fix

What you should do now, is take the plate out and try again.

Changing two thing isnt the best idea, its better to do one at a time.

But glad to hear its fixed! I would def try removing the plate 1st and leave everything how it is.

I have a 3" turbo back, the dump pipe is custom and is massive. No cat, and HKS cat back. There would be sweet FA backpressure there. I use an R32 10psi actuator and dont have problems. So i would guess that your exhaust isnt actually the issue.

[Sparky206]

Yeah i did one thing at a time, wouldnt go past 11 psi with the boost controller in at first and was dropping slightly at higher revs like most cars instead of going up like it was. Was a bit hard to tell if it was just the hot day here or the plate keeping the boost levels down so i removed the controller and just used wastegate to hold boost and it sat rock solid on 7, when in the same configuration it didnt before.

It was this thread that basically led me to trying the restrictor, and he had already replaced the wastegate

http://www.skylinesaustralia.com/forums/R3....html&st=60

It may just be a certain stage of mods that make this happen, combined with a certain dump pipe. Looking around i noticed it was common on supra's to need a restrictor plate aswell

[rob82]

I bet you have a split diaphram causing it not to open fully - usually becomes an issue at peak turbo efficency as the wastegate port needs to open the most at this point to maintain actuator pressure.

The idea of blocking the exh to fix another issue is just stupid.

[Sparky206]

could you expand a little more on the symptoms of a split diaphragm and a replacement part?

[rob82]

could you expand a little more on the symptoms of a split diaphragm and a replacement part?

You most likely have a split diaphram within the actuator. Meaning that some air maybe bleeding away causing the wastegate not to open as much as it should. Get an upgrade actuator or one that isn't split you can test them by putting 20psi into them and listening for leaking air.

You do realise that with a 3" exh on a std R33 ECU running more than 10-11psi you will actually start loosing power - thats if the AFM is still in good condition.

[Sparky206]

Yes i realise that i'll start loosing power, im happy enough to run 10psi, not looking for anymore.

As for testing the accuator, what would i use to build up 20psi on it?

[rob82]

Yes i realise that i'll start loosing power, im happy enough to run 10psi, not looking for anymore.

As for testing the accuator, what would i use to build up 20psi on it?

Tee you boost gauge in so you can watch the pressure than add a bike pump or air compressor with a blower nozzle if you have one and listen for leaks. If you dont hear any leaks by 20psi than its fine.

[Stealthynsa]

i put a rb25det in my non turbo r33, i dont have the gold thing with the vacuum tubes running to it.

can someone tell me what it is and what its on the car for?

Edited November 1, 2009 by Stealthynsa

[gotRICE?]

Its a boost solenoid.

It switches from 5psi to 7psi after a set RPM, think its 4500.