weird boosting

[green_GST]

car- 97 GST 5 speed
stock everything except gauge

I have the factory boost control solenoid bypassed just going from the WG to the turbo nipple. The boost will flash to 11 psi then as my rpms rise the boost will drop to 8 psi. All the couplers seem to be tight and on all the way and the vacuum hoses look to be in good shape. I also don't hear any sucking noises such as a leak. The boost gauge I'm using is an autometer, and I've had friends watch it while I drive.

Any ideas?

 

[1gDSM4g63]

It's probably a boost leak. Best to use a boost tester to be certain.

 

[Gstclipse69]

Do a boost leak test and tell us the results
http://vfaq.com/mods/ICtester.html

 

[green_GST]

cool, i've actually seen that boost leak tester in my friends garage, but didn't know what it was.

Will do soon to listen for leaks and such. Thanks!

 

[r6speed]

I have been following this also because I am having the same problem...I did the test and found no leaks what so ever...I don't know what to do next

 

[Mr Peepers]

The stock t25 will have trouble holding boost to redline. Upgrading the exhaust may help, but you'll still be limited.

BTW, boost will be higher with the BCS hooked up correctly. A line directly between the pressure source and WGA is the lowest boost possible.

EDIT: Does it spike to 11 psi then immediately settle to 8? T25's are known to spike, and it may get confused with boost dropping off. See if hooking up your stock BCS helps it hold boost at higher rpms or get a MBC. Stop at 15psi.

 

[green_GST]

The stock t25 will have trouble holding boost to redline. Upgrading the exhaust may help, but you'll still be limited.

BTW, boost will be higher with the BCS hooked up correctly. A line directly between the pressure source and WGA is the lowest boost possible.

EDIT: Does it spike to 11 psi then immediately settle to 8? T25's are known to spike, and it may get confused with boost dropping off. See if hooking up your stock BCS helps it hold boost at higher rpms or get a MBC. Stop at 15psi.

It goes to 11 psi then drops off to about 7-8 psi at about 5k rpms.

I checked all the couplers/clamps and everything was tight. Pretty much I need to get a MBC and set it to 15 psi and I'll be straight?

 

[Mr Peepers]

You would do a boost leak test by pressurizing the intake then listening/checking for leaks and seeing how long the pressure stays, not just by checking the couplers.

Yes, a MBC should help. It may still drop off a little bit by redline, and in theory exhaust should help it hold psi a little better.

With a n/t muffler(had an exhaust ticket ) fitted to the end of my 3" turboback I could barely hold 10 psi by redline, but this was with a 14b. With the normal setup it would hold 15 psi easily to redline. This does NOT mean just go out and buy a muffler though, in my case it was the bottleneck with a full 3" exhaust.

 

[green_GST]

You would do a boost leak test by pressurizing the intake then listening/checking for leaks and seeing how long the pressure stays, not just by checking the couplers.

Yes, a MBC should help. It may still drop off a little bit by redline, and in theory exhaust should help it hold psi a little better.

With a n/t muffler(had an exhaust ticket ) fitted to the end of my 3" turboback I could barely hold 10 psi by redline, but this was with a 14b. With the normal setup it would hold 15 psi easily to redline. This does NOT mean just go out and buy a muffler though, in my case it was the bottleneck with a full 3" exhaust.

I did forget to mention I'm just running my 02 housing and downpipe, nothing more than that. Since we have no emissions and the cops don't bother me, I have no reason not to, sounds bad a** too.

Yeah, my buddy and I are both boost leak testing our cars tomorrow or friday via the home-made leak tester.