Wastegate problem, please help

[Colton]

I'm using an ebay 40mm HKS style wastegate. The spring they gave me was junk so I went ahead and ordered a true HKS spring rated at 9 psi.

The wastegate holds 8-10 psi under light load (1st and 2nd gear), but when the engine starts to rev past 5000-5500 rpm the boost will creep to 12 psi.

When I shift into third or fourth and do a few highway pulls the wastegate will hover at ten psi until 5000-5500 rpms then it pulls to 12 psi and doesn't seem to want to stop!!

I don't want this type of boost right now. The car is scary fast at 9psi. Please help. My mods are below.

Precision turbo SC-61HKS step 2 264 intake and exhaust camsHKS cam gearsHKS valve springsHKS 2.0mm head gasketGreddy style intake manifold (ported)Greddy front mount intercoolerCustom 3 inch downpipeApexi N1 cat back (with test pipe)Equal length tubular top mount manifoldPorted and Polished headUnorthodox racing pulleyand other misc. stuff

I have 740cc injectors, but currently I'm using the 370's. I want to make sure everything works at low boost with my stock computer before I go modifying everything else (I'm using an apexi safc 2 to add fuel where it's needed, but honestly the stock fuel system maxes out at 11psi (completely maxed out)

Please help!!

[Colton]

Guys I know some of you out there must be running a similar setup, help me out.

[Turb0wned]

sorry way off topic but where did u get ur cover thing over by the overflow tank?

[bruinbear714]

Is there any restriction in your wastegate dump tube? If there are, it may allow some boost creep. IE, tube diameter not big enough, or goes into your downpipe at 90 degrees instead of at an angle.

Also, where are you getting your wastegate vacuum from?

[SillyRB]

Where are you getting your vacuum from ?Yeah with that turbo your car shold not pull super fast @ 9psi, because the turbo is way ouut of its effieciency @ that lower of boost. Do not get me wrong, its not gonna be slow but you know what i'm saying. The stock 370's are good for a max for about 280~ RWHP. @ about 85-90 % .

[Colton]

The cover is custom made. Fast is a relative term, but I'd say it's pretty amazing to have 280-300 whp at 9psi. The turbo is very efficient, check out it's specs on Precision Turbo's site; also cams, cam gears, springs, ported manifold, and head make for serious power gains regardless.

I believe I remedied the problem, thank you guys.

[Turb0wned]

wow thats nice where can i get one of those made? and what would i ask for? and how much was it

[Colton]

I can make you one for $75 shipped if you would like. My phone number is 612-760-1435 if you would like to contact me. I can have it professionally painted any color you would like. Ask for Colton

[codyace]

A SC61 may be 'efficient' in it's own right, however it is certainly not most effecient or in good efficiency range at 9psi....Granted it's not monster, but it's regarded as being a 'big turbo' for smaller engines...

Try 1 bar+ for that bad boy and you'll be better suited for the turbo...

I thnk the problem still lays in the fact that your wastegate is hks 'style' and not true HKS (much like I said on altimas.net)...

I also believe your car would be more fun with more boost, or more fun with a smaller turbo at that boost level :]

[Colton]

If you want to find out the problem and reason I was running low boost check out the KAT forums, but to recap I wanted to make sure everything was working properly before I put the 740cc injectors and boosted to 18 pounds.

The problem lies in the design of manifold, not the actual wastegate itself, I also had a small leak in the line that runs from the compressor housing to the wastegate nipple (fixed), but still small amount of boost creep (manifold design).

I appreciate your guys help.