scott(pittsburgh)

ok, with the screw all the way out on the wastegate, i'm seeing 9-10 psi but at around 5k rpms, the boost starts creep to 14-15 psi.. this is with the side port hooked to a vac source and the top port vented to atmoshpere.. i hooked up a boost source to the side port and when i gave it about 20-25 psi, i could hear the w/g open(click) i could also hear a small amount of air bleeding off somewhere in the w/g. normal?

i even use borrowed my budys wastegate, and same thing.. whats gives?

what do you guys think?

scott(pittsburgh)

bump

scott(pittsburgh)

anyone??

Silver7

what manifold are you using? Do you have any pics of your setup?

RICE RACING

It is normal to hear a little bit of bleed but it should be real small, do not confuse it with a leak from the pressure source.

As far as the WG creeping, when you hear the WG click open, you need to pay attention to what pressure it is opening at, you said you applied 20 to 25 psi, try applying 15 to 17psi and see if you hear it click open. If not and there is no "bad" leaks then the WG spring is quite stiff ! As you wind down on the adjuster the WG pressure required to open shoud go up from there.

It is common for alot of the Japanesse WG's to come with 1 bar or greater springs which means they will not open before around 15psi.

Once you sort this out, the only other thing can be a misdesign in the exhaust manifold, the easy way to check this is take the spring out of the WG and take the car for a drive, and see what boost you pull. It should be minimal depending on the design of the WG pipes.

scott(pittsburgh)

i have the greddy ss manifold..
the spring in there now is a .8 bar springs, with the screw all the way out, it holds boost till like 5krpms or so, then it'll start to creep up from there

the thing thats gets me is: is workrd fine for about 2k miles, then i hooked up my profec b and the boost would spike a little, so i went back to just the wastegate, and bam, won't hold boost..

i did try to open it with about 10 psi, and nothing
dunno what i'm gonna do/..

rx7tt95

What is the stock spring rate that comes in the GReddy kits? I have a T78 kit which uses the middle-of-the-line wastegate. I can't get significant boost until 5K+ rpm. At say 3-4K I'm getting 1-2psi.

The way I thought it was supposed to be hooked up was pressure to the side port and the top left open. I'm using an Apexi AVC-R so my setup goes like this:
AVC-R "NO" fitting to positive pressure (just after the compressor discharge)
AVC-R "COM" fitting to the top of the GReddy wastegate
Wastegate side port to positive pressure (just after the compressor, teed into the same AVCR "NO" line leading to the same nipple.

I was told that running positive pressure to the top port and leaving the side open would provide quicker spool up. I guess the side port would route to the "COM" on the AVCR.

Regardless, I'm not getting much boost. The wastegate screw is all the way out. Theoretically, if there was a 7psi spring in there, the AVC-R would ultimately determine boost above 7psi, no? Do I simply need to screw the adjuster on the wastegate in a bit more?
Michel

scott(pittsburgh)

it opens at 10 psi with the screw all the way out, but boost still creeps after 5k rpm's.. an di do hear a small amount of air leaking when i applied the 10 psi to the wasegate..

can it be the wastegate? why would it work one day, and then not the next?

scott(pittsburgh)

ok, i seem to have fixed the prob.
i put the silencer back in my apexi n1 exhaust, and it fixed it!
tho i drove the car for 2k miles with it out, and all worked fine..
now, why does back pressure fix the prob?

rx7tt95

Is your wastegate routed back into the downpipe? Backpressure restricts flow down to a level that apparently, the wastegate can handle. Which turbo kit are you using? Is it the T78? I know they make several wastegates. The T78 kit comes with the middle of the road version, not the full race, not the base WG. Maybe your external wg is too small for your turbo?
Michel

scott(pittsburgh)

the w/g is vented to the atmosphere, and yes, i got the T-78 with the middle size wastgate..

rx7tt95

Hrm..interesting...I'll think about it a bit more :-)
Michel