Rb25 Has Me All Confused!

[sparco33]

Hi guys. I have a 33 with 55000km.

mods include:

-fmic

-3inch exhaust turbo back

-bleed valve

-high flow t28 turbo (ball bearing, steel wheeled)

-k&n pod.

Heres my problem. Ever since installing the high flow turbo i bought from a guy on SAU it over boosts and spikes to 16 or 17psi.. which causes fuel cut because the afm is maxing out. A tuner told me that there is too much flow from my exhaust and need to put back my standard dump pipe. Another ive noticed also is my waste-gate (the valve that opens) is stuck open about 3mm when the car isnt even running!.. its meant to be tight shut.. (im thinking the centre of my turbo is different to that of a stock 33 one and i am using an actuator from a 33.. thus causing the constant opening).

so my question is.. why's it over boosting pretty much..any thoughts guys. Please?

[allthewaytotheskyline]

do you have any photo's of your turbo and the way the wastegate is showing with the gap?

if so post it up as it may help.

[sparco33]

do you have any photo's of your turbo and the way the wastegate is showing with the gap?

if so post it up as it may help.

hey dude.. nah i dont man.. its just being held open by the actuator arm.. where its supposed to be held in tight shut... any ideas?

[blind_elk]

You can never have too flow away from the turbo.

If the wastegate is partially open, that should reduce the max boost, because some of the exhaust gas is by-passing the turbine wheel (which is how the controller limits boost). You could have the wrong wastegate controller - actuator arm too long.

Do you have an aftermarket boost controller? Where does the wastegate controller get its boost signal from?

[paulr33]

a highflow of a t28? are you sure?

a t28 is typically a tiny turbocharger, the GTR twin turbos are t28s

so if you have a GTR single (from one of the twin) on your GTST, even hiflowed its tiny

do you have pics of the housing?

[FordyR31]

A couple of things to maybe look for.

If the wastegate is open just a tiny little bit, the turbo could still make boost but it may take a lot longer to build up... If the gate doesn't open at all from the 3mm e.g it is fused for whatever reason in that spot, could that cause the overboost as the turbine is copping a lot more vented exhaust gas than needed?

Is the diaphram in the actuator still in tact or is it damaged? I had a damaged actuator on one turbo that was supposed to run 10psi and spiked up to 14. Maybe get ur hands on another actuator and test that?

I have also heard of lesser quality high flow turbo's not being able to vent the exhaust gas through the wastegate (coz it's too small) enough even when it is working properly also causing overboost. Not entirely sure how correct that could be but I have heard. I have read when running higher boost through a high flowed stock turbo sometimes it doesnt hurt to enlarge the gate and flap over it.

If u have an adjustable actuator rod, try adjusting that also to see if it makes any difference.

Just a couple of things to try out, start at the cheapest and work ur way up lol.

[britz1]

mate make shure your auctuator is bolted on corectly and that if you loosen the 2 bolts that support the auctuator try and move it that little bit that it needs to close......

and turn down your boost controller.. or bypass it

[sparco33]

I thought turbos on series 2 r33's are t28s? well its a standard 33 thats high flowed bought from a guy on here ans receipts showed it cost 1500 bucks done by mcg in melb. About the "never have too much flow'.. i think ur actuator works on sum sort of back pressure so u always need sum. Anyway, one guy said the wastegate is bonded to the housing.. no, just stuck open a bit but able to move from that point. i think the right thing to do would be try out another actuator or shorten it some how. I worked out the arm is about 2-3mm too long .. the boost controller is aftermarket one from ebay.. it was one that sau guys loved but only 30 bucks.. turbosmart or sumthing like that...

thanx heaps guys

[sparco33]

I thought turbos on series 2 r33's are t28s? well its a standard 33 thats high flowed bought from a guy on here ans receipts showed it cost 1500 bucks done by mcg in melb. About the "never have too much flow'.. i think ur actuator works on sum sort of back pressure so u always need sum. Anyway, one guy said the wastegate is bonded to the housing.. no, just stuck open a bit but able to move from that point. i think the right thing to do would be try out another actuator or shorten it some how. I worked out the arm is about 2-3mm too long .. the boost controller is aftermarket one from ebay.. it was one that sau guys loved but only 30 bucks.. turbosmart or sumthing like that...

thanx heaps guys.. got sum fotos below. ps the high flowed one is obviously on the right

Edited July 6, 2009 by sparco33

[Pal]

had the same problem with my BB high flow on my 33. tried to set it to 12 psi and wanted to go to 17 psi no matter what i did. had split dump so go a 3" single dump, still did it. took it off and opened up the waste gate from 24mm to 28 mm to get better flow, still did it. cryed myself to sleep until my tuner said that sometimes the 2j's need a reducing plate in the exhaust to control boost spikes. so tried it . put a plate just before the cat (on the flange between two gaskets)with a 2 1/2" hole in it and it worked, boost only went to 11psi at top end. i put it down to not enough back pressure and the gasses were finding it easier to go out the exhaust wheel instead of the waste gate flap. another problem can the car is running to rich, this will also cause the same problem

[JonnoHR31]

try removing the boost controller completely and hook the actuator up directly to manifold pressure and see how it goes

[sick_skidz]

had the same problem with my BB high flow on my 33. tried to set it to 12 psi and wanted to go to 17 psi no matter what i did. had split dump so go a 3" single dump, still did it. took it off and opened up the waste gate from 24mm to 28 mm to get better flow, still did it. cryed myself to sleep until my tuner said that sometimes the 2j's need a reducing plate in the exhaust to control boost spikes. so tried it . put a plate just before the cat (on the flange between two gaskets)with a 2 1/2" hole in it and it worked, boost only went to 11psi at top end. i put it down to not enough back pressure and the gasses were finding it easier to go out the exhaust wheel instead of the waste gate flap. another problem can the car is running to rich, this will also cause the same problem

got it in 1 this is what will happen when u pump up perssure in a hight flow you either put in a reducer plate or weld up wastegate and mount one externaly its simple air flow dynamicy stuff (uhh hu) the air will go the easiest path and your wastegate cant flow that much check that they machined out the wastegate port and fiteed a lager flap. i hate high flows tsk tsk you can get a plain bearing garrett for not much more and they can be low mounted to i got a 3576 bb unit running same boost as a mates "fully sick hi flo" and i leave him behind while layin marks cost a bit more but i know what i would rather

Edited July 7, 2009 by sick_skidz

[Pal]

yeh, wouldn't put one in now without the supporting mods. i run it on stock injectors for about 5 months but now have the bigger injectors and PFC. was 307rwhp with stock injectors and now 355rwhp @15psi with skids too

[simpletool]

Sparco33. You can always bend the actuator arm to effectively shorten it. A bit ghetto, but it should work. Putting in an exhaust restrictor may indeed work, but it's treating a symptom that the small exhaust housing combined with small wastegate can't flow enough efficiently.