Compressor surge on 50 trim?
 

That is what seems to be happening to me. So heres the details, Turbo was on a 90 GST stock internals ran around 30psi, on a cool winter day it would hit full boost just after 3k rpms ran perfectly fine.

Now I have a 90 AWD talon, has bc 272's, comes on a little later in the rpms, and If you roll on 4th or 5th gear when the boost gets above 25ish the boost gauge starts jumping from 20-30psi, I've done a boost leak test, and while its not super air tight, It doesn't have any huge leaks anymore, and besides more airflow should push me farther away from the surge line anywase... I'm baffled I've never heard of people having issues with 50's surging, Is it possible that the BOV could do this? but why just in 4th or 5th gears? The BOV is a greddy and holds over 35psi so I don't know how it could be that...

Re: Compressor surge on 50 trim?
 

Are you doing the roll on from a low rpm?

Re: Compressor surge on 50 trim?
 

I would investigate the BOV further.

Is this a internal gate?

Re: Compressor surge on 50 trim?
 

It is a internally gated mitsu bolt on PTE 50 trim.
Yeah, I'm talking about a 3k- 4k rpm then rolling on it. I did a wot pull once and kept the rpms higher in 4th and 5th (on a racetrack of course...) and it did not surge...

Re: Compressor surge on 50 trim?
 

A blow off valve works on the premise of a pressure drop. Ideally pressure on both sides of the valve should be the same until the throttle is released. In your case it may not be, and may be caused by a boost leak at the blow of valve's signal pressure, or the signal pressure hose is too small, too long, kinked, or is bulging.

Also it could be a bad signal location, near one cylinder from the intake manifold, signal should be near the throttle as close as possible.

Re: Compressor surge on 50 trim?
 

I'm using the line that was originally used for the stock purge valve, It definatly is related to the slow spool up, cause I tryed letting off soon as it started doing that, then hitting it again and it was fine... Pretty sure its the BOV but why only on slow spool up? cause it will sometimes start doing it below 20psi, and it has held 35+ psi on the car when my boost controller was set a lil too high...

Re: Compressor surge on 50 trim?
 

Welcome to compressor surge. It is hard on the turbo so avoid this low RPM 4th and 5th gear pulls, just down shift.

~John

Re: Compressor surge on 50 trim?
 

huh, Well thats lame, only why on this motor and not the other 6 bolt... thats what bewilders me...

Re: Compressor surge on 50 trim?
 

Did you figure it out?

Re: Compressor surge on 50 trim?
 

+1 Big turbo + lots of time to spool (Low RPM WOT in high gears) = surge. I haven't heard of a lot of surge issues on 50 trims, but it's possible to surge ANY turbo (they all have surge lines).

Re: Compressor surge on 50 trim?
 

nope, only thing I can think of is this motor has BC 272 cams and maybe flows a little less in the 3-4k rpm range? I have a 56 trim which is bigger now and that surges too, but those are known to do that...