nofrills

Hi guys, I've just bought an sa22 with some serious fruit on it, which also has a no boosting problem..

It's a 12a, no idea if it was an original turbo model, but it is now, has aftermarket injection run off a microtech mt-4, big garret turbo, external wastegate etc. Someone spent a fortune on this thing. The guy I bought it off only had it for a few months and didn't seem to know too much about it, and sold it as he was moving overseas. He said it used to run great, then the last time he took it out, he found it wasn't boosting anymore.

Bearing in mind I have no idea if he is telling the truth about whether it ever ran properly, I took it for a drive but couldn't get more than maybe half a pound of boost out of it. It was noisy (no interior), but there wasn't any obvious sounds indicating a huge boost leak. The car also idles pretty steadily.

It doesn't have an electronic boost controller (which is a bit odd given the other stuff it has) but rather a bleed valve, but I can't think of any vacuum issues that would result in the gate staying *open*. The gate has a single vacuum line from the lower part of it, to the piping just off the turbo. Seems about right to me, the vacuum and spring keeps the gate shut, and at the correct pressure, the diaphragm moves and opens the gate. I pulled the screamer pipe off it and felt inside, I could feel the valve is in the shut position, and I couldnt move it or pull it open by hand (if it had a broken spring or something). So.. I don't *think* it's the wastegate. The port from the intercooler piping is at 90 degrees as it should be, so it's not like it's getting ram air pushing on the diaphragm either....

What else should I be looking at? I'm actually wondering if the microtech has a valet mode or something that's preventing it from boosting, although you'd think it would do that via an EBC... I'm also pretty sure it's a fuel only computer so probably can't retard the timing to prevent boosting. I'm still trying to get my head around this car.

What else could it be? The wastegate valve working normally, but leaking? A massive crack in the exhaust? (couldn't see one, didn't sound like it had one).. the car pulls fine up to where you'd expect it to start spooling, then it just sort of tapers off into nothing.. oh and I checked the turbo, it's not frozen or anything (although my workmate joked that the turbine might have fallen off!)

FCinWV

iTrader: (8)

Although I am sure you already have, but I would check all over that IC piping around the couplers. Id also really inspect the intercooler itself for a rotted out hole or smashed spot.

I had a cheap coupler on my FD and it had split on the bottom side and was doing the same EXACT thing. Could not for the life of me figure out what was going on until I pulled it all apart and by chance saw that big *** rip in the coupler.

bumpstart

take aircleaner and air intake pipe off and tests again ,, but expect the normal culprit is collapsed muffler

Vicoor

Just because the turbo spins by hand doesn't mean it doesn't lock up under pressure. Check for excessive radial and axial play in the shaft.
If that's ok take the exhaust loose at the back of the down pipe. Then see if it will build boost

arghx

iTrader: (3)

Boost leak pressure test. You can search, it's been discussed.