Boost Control

[skylinegtr_r34]

Hi, New Member. I have been searching the threads for answers to my problem. However have yet to find someone with the same problem. I have a series 2 GTS 25T auto. Motor is standard with factory turbo. Basic first mods include K&N pod filter with cold air box, intake air temperature sensor, x force 3 inch bell mouthed dump and front pump and G.F.B. bleed valve. The bleed valve was plumbed up in series with the factory boost solenoid to obtain a dual boost of 7 and 9 psi. This worked well with no spiking. Most recent mods include new 600 x 300 x 75 fmic and replacement of remainder of factory exhaust with 3 inch pipe with existing cat and mufflers replaced with 3 inch mufflers (no cat) and terminating at rear with a Bee-R cannon muffler with 4.5 inch tip. The factory 2 stage boost controller has been removed and bleed valved plumbed in between the intercooler piping (hot side) and waste gate actuator. I have also installed an Apexi SAFC but yet to have tuned. My problem is that I cannot control boost even with the bleed valve screwed in (no bleed off). Boost increases to 15 psi at 5000rpm and hits R&R (sometimes). I have tried plumbing straight from piping to actuator without bleed valve also have disconnected actuator arm and wired waste gate fully open and this resulted in huge lag but ultimately boost still peaked at 15psi. I have a separate boost guage (auto guage) and have checked this against a HKS guage with no discrepancies. Surely other members must have experienced this problem as my mods are basic and common. Appears my only option would be to remove the turbo and dye-grind the waste gate to increase the opening. Any suggestions to the contrary would be welcomed. NOTE: I am from Southland, New Zealand and the intake temperature at the time was 6 degrees celcius.

[QWK32]

you said you fitted a new dump pipe? have you checked to see if the wastegate flap isn't hitting on the inside of the new dump pipe. if it is it wont be opening all the way and causing your boost to climb.

[R33GTRKid]

^^^ my first thought exactly

[skylinegtr_r34]

you said you fitted a new dump pipe? have you checked to see if the wastegate flap isn't hitting on the inside of the new dump pipe. if it is it wont be opening all the way and causing your boost to climb.

The dump pipe was my first mod and did not affect boost. The waste gate actuator works fine. I have pressurised it with an air pump and it opens to the full extent. As I mentioned before I have tried disconnecting the actuator arm and wired the gate flap wide open against the heat shield bracket, i.e. fully open well past that of the extent of the actuator arm and still have 15 psi boost at high revs.

[Alex_r33s2gts25t]

U know factory turbo can blow around 14psi right? 11-12 is considered safe...

I have a 33 gtst auto aswell, upgraded to r34 smic, pod and cold air intake, and a 3" dump, 3.5" catback xforce system, and for some reason it boosts at almost 12psi with the breathing mods done... i cant make it go any lower... and you got rid of even more restrictions (like the cat) and your boost is even higher :S.

I cant see a boost controller being much help but id try a couple see if they have any effect... when i put a turbotech manual boost controller in my car went spastic with R&R, nd with the dual stage turbo smart one for some reason it doesnt build boost instantly and my car likes it better lol...

Id try getting the safc tuned and get them to pressure test it... but then again if its still boosting at 15psi youd need to spend more money to retune after you solve the boost prob... so yeah sounds like ur gunna have to either restrict the breathing mods, modify/upgrade wastegate, or highflow/new turbo.... i guess it just depends on how much u wanna spend...