hey guys, i just got my turbo in and im having boost problems. my car boosts to 7lbs at around 3-4k rpm up untill around 4.5k the boost will slowly start dropping all the way till redline. at 8k im at about 2psi. i've checked all my vacuume lines, replaced my intake manifold gasket, throttle body gasket, checked all my charge pipe connections, opened up my wastegate and made sure the diaphram was ok inside, made sure the turbo and wastegate is tight to the manifold and manifold tight to the head. the only thing i havent checked in my FMIC, which is brand new, but ill pressure test it tomorrow anyways. my wastegate vacuum line (on the side of the wastegate) is "T"ed to my brake booster hose.does anyone know why im losing boost when i get into the high rpms?
i have a 96 b18c1 with a garret t3 .42A/R and tial sport wastegate (7lbs spring)

Thanks,
Jon

 

Make sure you have the steel valve seat installed on the bottom of the tial.
without it, it will do what you are describing.

 

yea its in there. when i put it in, the seal stuck up from the surface a little bit, i dont know if thats normal or not. is it supposed to sit flush?

 

yes the ring gets crushed in as you tighten it. helps it seal better i guess.

If your air filter or intake is restrictive you will get the exact symptoms you described. try it with no filter to see if that's it.

 

The side of the wg is tee'd into the brake booster line? That's it? If the prblem were the wg, you need some pressure on the top of the wg to keep the valve closed. If it's not the wg, my best bet is there is a leak somewhere, that's why you're getting an initial spike then dropping.

 

i was told the side nipple goes into a vacuum source, and the top one is if you want to use an electronic boost controller.

 

The bottom port on the wastegate should never see any vaccum, boost only from the compressor outlet.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xtremeazian &raquo;</TD></TR><TR><TD CLASS="quote">i was told the side nipple goes into a vacuum source, and the top one is if you want to use an electronic boost controller.</TD></TR></TABLE>

exactly right.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by pngfolife &raquo;</TD></TR><TR><TD CLASS="quote">The bottom port on the wastegate should never see any vaccum, boost only from the compressor outlet.</TD></TR></TABLE>

not exactly right. Any source of boost is going to be vac when your not boosting. You would only want to use the compressor vac/boost port if you wanted the lowest possible boost from your WG. Otherwise it is a better idea to use a port from the IM (like the brake booster) so the WG signal is what the engie is seeing. This will account for any pressure loss between the compressor housing and the intake valves like the piping or intercooler.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bailhatch &raquo;</TD></TR><TR><TD CLASS="quote">
not exactly right. Any source of boost is going to be vac when your not boosting. You would only want to use the compressor vac/boost port if you wanted the lowest possible boost from your WG. Otherwise it is a better idea to use a port from the IM (like the brake booster) so the WG signal is what the engie is seeing. This will account for any pressure loss between the compressor housing and the intake valves like the piping or intercooler.</TD></TR></TABLE>

What about the port on the compressor housing? There would be no vaccum in the compressor housing. This is afterall, why compressor housings have ports on them, as a boost only source.