kllrvet

iTrader: (4)

I installed an STS system on my 05 GTO a couple of weeks ago. Had a base tune made last Tuesday. The car seems to run strong, but no where near the 500+ RWHP I was hoping for.

I had it dyno'd today (Sunday) and found it only made 418 RWHP (it made 348 with a cat back and NO tune)I also found it would only make 4 lbs of boost on the dyno, and peak power was at like 4000rpm . I have a .60 bar spring in the wastegate, so it should make around 7lbs at the throttle body. On the street, it will spike to mid 5's for boost, but fall off quickly.

We checked for leaks, but did not find anything worth mentioning. I did find that the blow off is not working at all though

Any ideas? For reference, this the is the intercooled system with .67 turbo, it has 1.85 rocker arms, a bigger walbro fuel pump, a Kenne Bell BAP, 60 lb injectors, and no cats. We are getting zero knock, and the A/F looked good as well.

Something else..the car has so much crankcase vacuum at idle, is whistles if I have the oil cap tight. Is this normal? I mean it really sucks hard.

Thanks in advance,

EPP

iTrader: (22)

I installed an STS system on my 05 GTO a couple of weeks ago. Had a base tune made last Tuesday.

I hope you were not going wide open throttle prior to having the car tuned? Bob

socalstreetracer

iTrader: (4)

so I take it you dont have a boost controller right? I know after I did my intercooler I also made 4psi with the my boost controller set at 0. I was told I had to change the boost reference and that raised my base boost back up to 5psi.

Slowhawk

iTrader: (12)

I'm willing to bet the PCV/vacuum lines are wrong but can't tell without pictures.Also the vacuum reference for the Turbo has to come off the intake manifold-not the Turbo.

ddnspider

iTrader: (26)

If your peaking at 4k then that would bring valve float to mind,are the stock springs still in it?And Slowhawk is probably right about the PCV setup as well.check on both of those.

Slowhawk

iTrader: (12)

Good call,I missed that. Every car I dyno's with 1.85 rockers and the springs they came with float the valves when boosting the motor.

ddnspider

iTrader: (26)

i got it covered just seemed odd to me,lol

RealQuick

iTrader: (14)

Actually, 8.7psi to be exact....(14.5psi = 1 bar, multiplied by .6)

ddnspider

iTrader: (26)

that makes it even worse

kllrvet

iTrader: (4)

Right, but others have seen about 7psi at the throttle body with the .6 bar spring.
I figured it was loss due to plumbing, intercooler etc.

Tony

kllrvet

iTrader: (4)

I am not using the stock springs. I have a new set of Comp 918 springs installed. Do you think I'd see valve float with 918 springs?

I have the boost reference line going from the turbo, to the wastegate.
Tony

bboyferal

iTrader: (9)

No way, there has to be something else going on.

ddnspider

iTrader: (26)

actually people have floated with 918's....swapped to doubles and it went away.But i agree that something else is going on.Id reference the wastegate at the back of the intake

dynedta

iTrader: (4)

i would also agree its the reference

Zombie

iTrader: (2)

Another vote for the waste gate reference. I had issues holding boost until I ran a line from the intake to the wastegate.

HydroStream6

iTrader: (16)

My wastegate on my STS is referenced at the compressor, through a boost controller, with no problems.

With a GT67, there's no reason power should peak @ 4k... something else is going on.

MTBDOC

iTrader: (1)

Sorry to hear you are having issues. Mine didn't make but 5.5psi on the dyno [on low boost] making ~450-460 rwhp. I get a solid 7 psi on the road. What is even more weird is that I added 5psi on the dyno [via the 0-5psi controller] and promptly made 15psi!!! That was a tad scary, but no damage was done.

I still don't like the idea of boost reference lines running the length of the car [despite some folks finding it works well]. Boost psi is not really as significant as we want to think, but is simply another 'measure' at the engine. Having the wastegate open based on what happens at the turbo outlet is fine...we simply are going to see some losses in the intake manifold.

Not much to add to the discussion, however!

TeeKay

Boost at the TB is the boost the engine sees, slice it however you want. If you want to "lead the bird", go for it. I believe having a reliable ENGINE boost reference (i.e. at the intake manifold) is best. I think you will too. Try it and see. HTH

fenix99

iTrader: (1)

another vote for boost reference to the manifold....no reason for it not to be making more boost and/or power with everything mentioned above... anyways good luck and hope u find whats holding u back man