mmurray75

I just installed a vf34 on a 2002 WRX this weekend. When we were out tuning I found that anything over 14psi before ~2800rpm would produce very bad compressor surge. Has anyone had this problem, or heard of this problem? For now I have limited the boost to 14psi until 2800rpm then have it go to 17psi after 3000rpm. I would like to take advantage of the quick spool and higher pressure achievable in the low rpm band. This is probably not fixable and I will just have to live with it and map around it. But if someone has any suggestions on how to use the boost that is available i'll take it.
Thanks
Mark

sg72

I have VF 34 fitted to my car, running 20 psi.

What dump v/v are you using?

mmurray75

This is not my car I am just setting it up.
The dump valve is a TurboXS Type H-RFL full vent to atmosphere. The dump valve is working properly, venting when the throttle is closed quickly. The surge happens at wide open throttle. It seem like the turbo makes to much boost at to low an rpm.
Also before I put the turbo in I had heard that this turbo will boost creep. So I ported the wastegate, at the same time I polished the hot side inlet. Could this be why I am getting the surge?

sg72

I certainly had a problem with overboost at one point.

But this was due to the solenoid?turbo hose spliting due to rubbing on back of manifold .
However this is on an STI 5 and should not be a problem with the 7.

Are your restrictors in pipes OK?(IE Right way about?)

mmurray75

I have complete control of the boost With the UTEC. When I run wastgate settings on the UTEC I get ~.5 bar. I Have the boost going to 1 bar@~2000rpm then at 3250rpm I have the boost set to 1.24 bar to redline. The only problem That I am having with the car is I can not run anything over 1 bar in the lowwer rpm range or it will surge. Is this normal?
Thanks for the help
Mark

[Edited by mmurray75 - 9/15/2003 9:52:47 PM]

[Edited by mmurray75 - 9/15/2003 9:54:04 PM]

Bob Rawle

Yes its pretty much par for the course, to make a bar at 2000 is pretty good going (in general terms) . I would have thought you could let it go from about 3000 onwards though. We would probably try and run 1.35 from 3500 to 5500 then taper it from there to 1.2 at the redline. By then charge temps are going to be well up.

cheers

bob

mmurray75

I thought that was going to be the case. Just have to live with it and map around it I guess. To bad it would be nice to be able to use the boost down there. The car needs a good fuel map made EGT's are 750C max. It was my first time tuning one of these turbo's and I did not want to push it to far so I settled with 1.2bar for a daily driven map. When we go to the 1/4 mile track I will set up the car for a tolulene coctail high boost map and see what this thing can do.
Is the one bar limit hold true for all of the turbos that can make it that low?
Thanks for the info
Mark

Bob Rawle

If the turbo is small enough then no its more than possible, a TD04 for example, but it won't make boost at high rpm's, least not more than 1 bar. And it heats the charge up doing it. Mappable though with resonable results given its limitations. There aresome TD04 based hybrids around which help this but not to any great extent.

bob