Overboosting Problem

[Pal]

hey guys,

picked up a highflow for a decent price so chucked it on around november last year. had it freshened up with new seals and new compressor wheel as old one was eroded . took it for a tune and set the bleed valve to 12 psi and it was boost creeping to 17 psi at 7000 rpm. was running a 2 1/2 inch split pulse dump pipe into a nismo 3" font pipe, had read on forum that the split pulse dumps caused boost creep so modded my split dump and changed it to a bell mouth. chucked it back on dyno and still going to 17psi. pulled off turbo again and machined out waste gate from 24mm to 28mm (exhaust wheel hole size off 52mm) this was a 36% increase in surface area. putt the turbo back on and still went to 17 psi. i have finally taken off the 2 1/2 " dump and front and fitted a 3" front dump pipe hoping to drop the pressure in the exhaust and get better flow but alas it is still doing it. cant think of anything else that can cause the problem. got in contact with the guy who had it before and he had it running on 14psi ok. any ideas anyone!!!!!!!!

modds as follows

safc2

stock injectors

nismo fuel reg

walbro fuel pump

full 3" exhaust

FMIC

thanks

Eric

Edited January 6, 2009 by Pal

[Ultimategtr]

Hey bud, was it doing this before you put the turbo on?

I had a similar issue with my stock turbo, i had a turbotech boost tap and it would creep up to around 15psi. I finally pulled it off and put the stock solenoid on and it holds boost fine..

Where have you tee'd off the tap? tried a differend tap? u using the same diameter hoses??

[Bakes]

What if you fit a electronic Boost Controller? Would that help?

[Pattygtst]

what wastegate actuator are you using?

[Pal]

i had no problems with the stock turbo, i had it set to 12 and would drop back to 10, i am using a GFB bleed valve, i removed the bleed valve and run a straight through hose so it would go to wastegate pressure of 7 psi but is still going to 17 only a bit slower. not sure if a EBC will make a difference. using standard tapping point

Edited January 7, 2009 by Pal

[Ultimategtr]

When it starts to creep, do you actually FEEL the extra power? or does it go no where, ie no extra pull? Get what i mean?

Just a wild suggestion but have you checked your base timing? i had a very similar thing where my timing was retarded by 3 degrees.. set it to 15 and it helped with the creep issue ALOT.

does your car have a stock solenoid?? if so try running through there and see if it creeps??

[Pal]

my tuner has detuned it due to the boost creep, its only on 230 rwhp at the moment. will try the stock solenoid.

[Bennett]

Do you have a cat? After i took my cat out the boost went from holding perfectly at 12psi to creaping over 14 and thats with one of the best boost controllers you can get. But after playing round with the gain setting its all good again. So my advice is to get a good model EBC and set it up right.

[blind_elk]

i had no problems with the stock turbo, i had it set to 12 and would drop back to 10, i am using a GFB bleed valve, i removed the bleed valve and run a straight through hose so it would go to wastegate pressure of 7 psi but is still going to 17 only a bit slower. not sure if a EBC will make a difference. using standard tapping point

I reckon you have a split in one of the hoses, acting like a bleed valve. Check them all for splits / holes.

[Pal]

have a xforce high flow cat. will have a look at the pipes. you are talking about the pipes for the bleed valve and watsegate?

[bubba]

The "race" cat? or just the "hiflow"?

I had bad experiences with my Xforce "hiflow"

+1 for checking your base timing.

Edited January 7, 2009 by bubba

[Pal]

highflow, still all there. what problems did u have Bubba.

i'll have a talk to my tuner about base timing and see what he says.

[Pal]

checked all lines between actuator and wastegate and all in very good condition. is too much flow through the exhaust a problem. only have a cat, resonator and cannon.

[lachlanw]

make sure your waste gate flapper valve isnt hitting on anything inside your dump pipe . eg pull the actuator off and make sure you can flap the little arm all the way round

[Pal]

done that, had it on the dyno and eyeballed made sure it was fully opening. also checked when dump pipe went on

[Pattygtst]

again what size actuator, maybe it has a 1 bar garrett or something on it?

[blind_elk]

"Eyeballing" isn't checking. Does the valve end up perpendicular to the "closed" position when you have full boost?

[Pal]

yes, opened it up with wategate disconnected when fitted dump pipe

Edited January 9, 2009 by Pal

[toffy]

I had(have) the same problem with my std turbo, i had a big long post written but my computer failed on me , so ill keep this one a lil shorter . i put a op6 housing onto my r33 s2 turbo after having massive trouble with boost spike. as i dissasembled the turbo to fit tho new rear housing i noticed that the actator shaft fouls heavily on the side of the diaphram and has a fair bit of sideways pressure on the wastegate flap. Im in the process of modifying it atm , ill let you know if it does anything

NOTE: The turbo was/is assembed correctly , if i moved the housing any further around the inlet would foul on the exh manifold.

Edited January 9, 2009 by toffy

[Pal]

yeah, i noticed that the diaphragm arm needs to be forced a little to get in onto the waste gate. let me know how you went.