Greddy Profec B Spec II Questions (EBC)

[Fubar231]

My boost keeps falling off in the high rpms. No matter what i do with the gain or setgain it still falls off. When i floor it it spikes up to about 15psi then slowly goes down to 11-12. Any ideas? If i run like 40% on the boost, 5% gain, and 0 set gain it climbs to 14-15 smoothly and nice then falls off. If i set the gain to like 15% itll hit 13-14psi then flutter for a second then stable out, and same with the setgain. I dont get it.

Mods: 57 trim ct-26 built by dm, 550's, lex afm, turboxs bov (recirc'd), walbro 255, Spearco Replica (Ebay), ic hardpipes, apexi intake, 3" turbo back, HKS MHG, arp headstuds and i think thats the most of it everything else is gauges/piggybacks etc.

Any ideas though?

---------- Post added at 09:39 PM ---------- Previous post was at 09:25 PM ----------

http://www.greddy.com/upload/file/PRofec_Bspec2.pdf

Says raise the gain if boost falls off or climbs in higher RPMs. Ill have to make some pulls adjusting 1-2% at a time.

If this doesn't help/work ill come back. Sorry for making a pointless thread SM! Maybe if someone else has this prob someday theyll use the search function and all their info will be answered!

Will report back to let you know if this is a go or no go.

 

[Nick M]

My first thought is the CT26 exhaust housing. Do you have a big downpipe? I didn't see it in the list. I say that because what you are describing is not uncommon on the CT26.

 

[Fubar231]

3" TMS downpipe to a Blitz Nur Spec exhaust with no cat
Its the DP that mattes to the back of the turbo, not one that connects to the stock turbo elbow.

---------- Post added at 12:05 PM ---------- Previous post was at 12:01 PM ----------

Also had a thought that maybe the exhaust housing wheel/wastegate was too small on the ct-26 because i didnt get a exhaust housing clip or anything, but that would just cause boost to keep climbing on the high rpms right?

 

[Nick M]

Then again, 15 to 12 isn't a huge drop. And the engine is moving a lot of air at 5500 rpm.

 

[Fubar231]

Went and played with it a little till i ran outta gas lol, but couldnt get it to stabilize. In GReddy's manual it says on some cars charistics the boost just might not stabilize.