Shamrock1054

Hey guys,

Will a pop-off valve control over boost with a stock wastegate on an "87 TII, or does the waste gate still need to be opened up. This is with an upgraded turbo compressor and unrestricted exaust.

Thanx, Gregg

SaabGuy

I hear is it extremely bad for the turbo. It will make your turbo spin so fast that the impellers may fly off. The wastegate is the way to control the turbo's speed... BUT....

I am going to use a pop-up valve to control accidental boost creep. Even though I may blow the turbo it will be better than blowing a seal. I dought I'll hit 12psi anyways on a stock exhaust with gutted cats and maybe a slight w/g port, but I am going to use a pop-up valve for protection (really not an ideal way to go).

Shamrock1054

Hey SaabGuy,

Thanx. Yeah, that makes sense. Guess I'll be pulling the turbo and porting the wastegate. Pop-off valve protects your motor at the expense of the turbo, right?

Thanx, Gregg

Shamrock1054

Oh, one more thing,

Will the stock wastegate, ported, be adequate with a turbo with a TO4 compressor, or must you go with an external wastegate setup?( big bucks)

Thanx, Gregg

Shamrock1054

Uh, sorry,

Did more reading, there's no way I have a TO4 compressor.

Thanx, Gregg

Shamrock1054

Sorry Guys, more dumb questions,

Looked by the turbo inlet, has A/R .60 and M12 on it, can't make out the serial #. What compressor is this?

Gregg

CosmicButtHairs

whoa whoa whoa wait a sec
So the pop off valve could kill your turbo??? What if you have both a pop off valve and blow off valve setup?
Doesn't the blow off valve release vaccum pressure so it won't kill the turbo??
Also, could you control the boost limit with a pop off valve? Or do you need a crazy plumbing job with the wastegate to do this?

SaabGuy

You can set up a one way adjustable check valve to release your stock BOV at a tuned PSI, this would be less expensive than a pop up valve.

It kills the turbo because pressure would be greatly reduced, IE - No backpressure from the engine. its sort of like beating on your car, and then mashing the clutch - engine revs due to less resistance.

I guess if you are going to rely on a pop up valve the best thing you can do is run synthetic or create a seperate oil system to run synthetic through the turbo so the bearings dont sieze but im no expert.



The BOV relieves boost pressure from the engine, same thing with a pop up valve, the only difference is when the BOV opens, usually you are off the throttle - no exhaust - and the wastegate is open so the turbo begins to slow down.

Scott 89t2

the pop off vavle is like a fuse. it's a safty item and it's not ment to be used on a normal basis. you set it to higher then what your boost is. so if some how your boost contoller or wastegate fail. then the pop off vavle goes off. when it goes off you pretty much loose all boost and it jerks. it's not somthing you want to have happen while you drive. and when it lets if off you turbo will spin up way faster which will cause wear.

so no, you can't control boost with a pop off vavle.