Noob Turbo questions...

[shift2drift38]

Hey all, I'll come out and say it, I have no knowledge with fixing a factory turbo setup. I picked up a 90 GST and the t-25, manifold, some air hoses and the filter were all in the back seat. The guy said it needed seals done due to the oil leaks up front, but it ran a when I went to look at it, he didn't rev it up because he said it would overboost from the wastegate or bov? I know they ACT the same, and i know what each thing does.... but the sad part is I dont know where it's at, would it be the thing next to the air filter (bottom left corner looking under the hood?) Would that cause over boost and would an aftermarket replacement work for it? From what I've seen, the wastegate and bov i have from an old t3/t4 kit that was given with an old project car, and some photos of cars on here, the wastegate bolts up near the exhaust manifold... The confusing part is I was led to believe the factory bov's were big black plastic things, so now I'm thinking that piece next to the air filter is the wastegate...because it looks like the big hose attached to it runs down under the upper radiator hose and bolts to the top of the turbo housing (charger on the right, rusty looking thing to the left, not sure of the term for it, and the flange pipe that runs from the right side of the turbo itself attachs to the exhaust pipe/downpipe if you will) I know this is long but i'm giving the most info I can about it. Thanks to anyone with insight on it.

 

[blkgst97]

Virtual Tour of the DSM Engine Bay - Quadrant map

 

[JuGs]

can I ask why does it have a T25? stock it shoud have the 14b or 13c if its a auto. and that link should help you.

 

[thatblondechik]

It's difficult to understand what exactly it is that you're asking.

I'm assuming you're asking where the wastegate and BOV are located.

BOV- Is going to be on top of the UICP. Black, plastic, and about the diameter of a tennis ball.

Wastegate- Is going to be on the exhaust housing of your turbo.

Now what I'd like to know is how the guy started the car with the turbo sitting in the backseat. Also, a faulty BOV and stuck wastegate do not have the same symptoms. A wastegate that's stuck closed will cause the "overboost" that you were referring to, a BOV can either not hold enough pressure, or too much. Not enough and your BOV will open too early, letting the charge pipe vent without pressurizing the cylinders. If it's holding too much, you'll hear a very lovely and unique sound called "compressor surge". Sounds cool...but it'll eventually kill your engine.

 

[werx]

If you have a 90 gst you shouldn't have anything black and plastic when dealing with the BOV. The Plastic BOV were on the 2G (95-99) cars and it's a mild meager upgrade to go to the greenish metal BOV on the 1G (90-94) cars. I hope you have a 14G on that 90 (stock on the 1G) instead of the T-25(P.O.S. stock on the 2G cars. The 1G motor and turbo set up was for the most part a better set up than what came stock on the 2G's. If u don't have one I would recommend getting a repair manual like haynes. I call it the mechanics for dummies handbook. I would also use all the resources (forums, pics, and how to's) on dsmtuners before,during,and after you get the car straightened out . It will save you a world of headache in the end.

 

[thatblondechik]

My mistake. I was looking at his profile and didn't read correctly.

As far as the 2g BOV being an upgrade...yea, no. Just crushing a 1g BOV makes it ten-fold better than the stock 2g plastic POS.

 

[shift2drift38]

Wow that cleared ALOT up for me everyone thanks. The turbo was still bolted up btw when he started it, he took it out for me so i could access everything better, would've been smarter if i had taken it all out i guess but i wanted it seperate in case i needed to post pics before putting it back in. That visual link helped a ton! Now, will any aftermarket wastegate work for that?, and yes it is a 14b, i was thinking 2g for some reason.... i have one of those too. Also, how do I adjust the boost so I dont "overboost" it when I fire it up? Anyway to test stiffness of the sort before putting some throttle into it?