new turbo questions

[john84]

Hi all, i've just put together a 7mgte with a 57trim ct.

My first question is to do with the stock BOV. i seem to be getting a chirping noise from the turbo when i lift off, and i'm sure this is a bad thing.

How can i check the stock BOV and should i get an aftermarket one? if so which is best for protecting the turbo?

My other question is to do with how much lag to expect from a 57 trim. the boost is standard at the mo as i want to sort out all the issues with the car before i turn up the boost.

i don't see any real pressure until above about 3200rpm, peak is about 6.5 - 7 psi, very little pressure is made in first gear, maybe about 5psi. At about 5500rpm the engine is out off puff, this is more obvious in first and second.

I do still have the stock downpipe on the car.

Any thoughts on this would be great, Many thanks.

 

[jetjock]

I'll answer your first question and leave the others to, well, others.

The stock Compressor Bypass Valve (what you're calling a BOV) is closed when the small control port is at atmospheric pressure and above. Looked at another way the valve is open whenever your boost gage is below zero and closed at zero and above.

When removed from the engine you should not be able to blow through it because under those conditions it's at atmospheric pressure. If you put a little vacuum on the control port you should then be able to blow through it. If you're able to blow through it with no vacuum applied to the control port it's bad. Since the stock CBV has a high failure rate don't be surprised to find it's dead...

 

[black91turbo]

If you get a aftermarket DP you will see a huge difference in spool time on that 57 trim. I would definately make that one of my next purchases. CT's will fall off in the top end like you said....that is pretty typical from what i have seen.