Still no boost...

[kwnate]

Your car won't build boost when there is no load, the turbo will still spin. This probably why you don't hear the noise with the downpipe disconnected. Its possible that your car is boosting and the gauge or sender is bad.

Inspect all your vacuum lines and Intercooler piping and let us know what you find. I might be able to take a look at it sometime next weekend.

[Supra2NR]

Maybe that's why you think your not boostin, bcuz your not boostin
You been revving it at nuetral or park
That's why there's no no boost
If the gauge reads at -4 but not moving at all
Its a bad sending unit
If its broken the boost gauge will be at 0 constantly
The hissing sound can be a bov problem
Have you tried blowing on the bov
If you can blow on it freely, that's most likely where you're problem lies

[drmmr15]

Well, I forgot to mention there was no power when I drove the car. The turbo wasnt spooling before. Now that the exhaust is disconnected, I can hear the turbo spool, but get no boost read from the guage. I dont wanna drive it with the exhaust disconnected, so Im going to take my car to an exhaust shop and have him fix the terrible job the previous owner did on the custom exhaust. He welded everything in, and I think the cat is clogged, Imma get a new cat and have the shop do some rewelding on the downpipe. I would get an aftermarket exhaust, but I will eventually sell this car (another story). I just wanna get it running right. Plus Ive never driven anything with more than 120HP, so I want boost So i think the backpressure from the bad exhaust system was causing the boost to only reach 1psi max. When the exhaust is unhooked, I can hear the turbo spool nicely, but that guage reads -4psi. So my problem is the exhaust, I think. Im not sure, so thats why it'd be nice to have someone come look at it. Thanks kwnate. Im pretty sure you would know a helluva lot more than I do, so we should try to set up a meeting. Next weekend Im pretty swamped. But maybe next Sunday afternoon? PM me. Thanks everyone for their replies.

Edit - Ill try blowing through the BOV tomorrow. Thanks.

[Kuban]

Keep in mind, in neutral or in park (wether u have auto or 5spd) you wont boost, the engine will pop the wastegate at a very low psi to keep it from overspooling. And the backpressure from the exhaust would indefinately hold your spool abit.

[drmmr15]

That helps a lot. Sounds like its the exhaust system. Im getting a Cat off an '89 turbo that had 90,000 miles for $20 and taking it to an exhaust shop to fix things. lets hope this works out. Thanks.

[drmmr15]

HELL YES!!!!! Well, today, I fixed the timing of the car, and i revved the car up a bit (exhaust still unhooked from the O2 housing back) and I heard the turbo spool up and the once i let off i heard the BOV. It sounded sweet, but the boost guage still sat at -4psi. I said screw it, and decided to drive the car around the block with the exhaust off to see if it worked. HOLY S***!!! The turbo kicked in hard and broke the tires loose in 2nd. I had no idea how amazing boosting was. SO i know there is no boost leak, and my turbo guage is bad. I am going to hook the exhaust back up and see if it works fine. If not, Ill keep going to forward with what I had planned, and that is to have an exhaust shop do some rewelding on the downpipe, and put in a new cat. Thanks you all for your advice, and am happy to be part of the boost addiction......FINALLY!!!

[drmmr15]

Also. Im such a genius that i forgot to put a heat shield back on the exhaust manifold right under the turbo. My question is, can i leave it off, or will it melt things if I dont? The reason i dont wanna do it, is i would have to take the whole turbo assembly back off to get it on there...and that sux...
Thanks.

[OmeGa]

I dont have mine on, it gets in the way of things IMO. Also the stock boost gauge is garbage, mine reads -4 when im around 5 lbs then it jumps to +8 instantaniously.