boost questions????

[scarface8087]

i still have a problem, only getting 2-3 psi boost...correct if im wrong, but my understanding of an 87 tr's boost system is, when eng loaded in gear, wastgate is normally closed & should build boost; wastegate is controlled by wastegate sol by bleeding off boost ,so it dosn't exceed 12-14 psi(or whatever the stock spec is)..so if the wastegate sol vaccum line is removed & plugged, wastgate fully closed, turbo should build boost like crazy when driven; if there still isn't a change(2-3 max psi) & turbo dosn't sound like its going to blow up, id assume that the problem would have to be w/ boost being bled off before it got a chance to reach the thrttle body(ie: ic hses,air duct); i just replaced the ic hses & made sure air ducts not leaking,most of the vaccum lines replaced, & still no change...now im assuming the only thing else ,would be exh leak that i can't hear, or not enough exh backpressure???
correct if im wrong w/ anything..if any body has any input please help me out...also ,has anybody had a problem w/ not enough backpressure or small exh leaks that couldn't be heard, but caused a problem like this??? :banghead:also, what is the exh backpressure spec when loading & trying to build boost?can i get an accurate reading @ o2s bung?

[Keller]

The problem may be that your wastegate is not fully sealed to begin with.

Another problem could be that your turbo is shot and not spinning freely.


You are correct that with the control host disconnected, the boost should rise very rapidly.

[scarface8087]

no idea on exh backpress spec when trying to build boost & most accurate place to get reading? also, i removed turbine housing to ck waistgate -looks ok, & turbo blades appear to be spining; you can hear turbo spool up slightly when boost registers on gauge; you can also feel the 2-3 psi ,even though its not much.........whats the best way to verify that the waistgate is sealing all the way? theres no roughness or binding when i inspected surfaces;& i dont see how all of a sudden the waistgate would not seal correctly........i do have a slight problem w/ oil getting into the ic from the turbo......

[Keller]

To check the sealing, one good way is to remove the whole thing and shine a light up the exhaust inlet path. Look in the exhaust exit path and see if any light is getting past the flapper valve. With the elbow off you should see patterns if exhaust is frequently leaking past it while closed, too.

I would suspect a control or gauge problem faster than a sealing problem. But anything is possible.

I suppose pre-turbo pressure could be measured at the O2 sensor location. After the turbo...not sure how best to so it without hacking things up. You wouldn't want to go too far down stream, and don't want to cut into the downpipe.

[scarface8087]

wow! what a relief! :D i found the problem ,& its what i suspected but doubted from day one. the freakin cat was 80% plugged...i decided to cut holes in frnt & back of the cat & feel the exh when reving; nothing would come out behind the cat....i replaced the cat w/ a high flow magnaflow cat; i feel like i bought a new eng today, its faster than when i fisrt bought it....thanks for the advice...
i think its time to upgrade my injectors & turbo now; thinking of going w/ green stripes & ta49. ;)
like we say at work " el gato es no bueno!" :crackup:

[Keller]

thinking of going w/ green stripes & ta49.

Glad you found your problem!

Just make sure those 'green stripes' are 43 lb/hr and not the 30 lb/hr variety. That would not be enough fuel. :nono: