Profec B Boost Overboosting?

[CAT_SPEW]

I just installed a Greddy Profec B spec II onyo my RB25 and it is still boosting past what I have set it at.. I have an custom plenum which is pretty large and I'm just wondering if that could be part of the problem? Being too large and not giving a good vacuum source???

any help would be much appreciated..

Cheers

[LTHLRB]

drop your start boost? and set your limiter a little lower.

[CAT_SPEW]

By start boost do you mean the lower boost level I have set?

[LTHLRB]

no go thru ur setting if its the spec 2. And it would be start boost as in when it starts comming onto boost, drop it to around 7psi.

or just drop it to 15% gain or a lil less if its the old profec b.

[CAT_SPEW]

Ok I will give that a go in the morning. currently high boost is set to 15Psi and it's going to around 17-18Psi..

I think the gain is set at about 18% and it's the spec II controller.

If this doesn't work do you have any other suggestions? Would the large plenum have any affect on this?

[WogsRus]

I have a problem with my Gizzmo, i have some issues as the new exhaust is so free and the stock wastgate is so restrictive i get creep. There are many solutions, porting the gate, lower gain but higher response settings, you will have to just work on it. i have spent two weeks on my Gizzmo, and it's getting better all the time.

[skylinecouple]

Hi cat spew.

Start by telling me what combination you have.IE:turbo, intercooler.I have the spec II and it controls boost perfectly.Unfortunately even the people who sell them dont know how to set them up.(some any way).

Edited December 12, 2006 by skylinecouple

[LTHLRB]

skylinecouple, i had to figure out how to tune mine, 13psi perfectly and sits there like a dream. After 3 days of thrashing and getting it right.

[CAT_SPEW]

I've got an RX7 turbo which has been highflowed, small front mount, large custom forward facing plenum, blitz bov, haltech e6k ecu, no afm, 3" exhaust, 740cc injecters, larger fuel pump

I will soon be upgrading to a GT35/40 bu until then I need the cotrol the boost with the current setup..

[skylinecouple]

I started by turning my set gain to zero and gain to 10. Then ended up at 16 on the gain before boost started to spike past the 15lbs I was aiming for.So I turned the gain back to 15 and held boost perfectly.Then I turned the set gain to 4lbs less than my boost(15lbs) so set gain is 110.But you might find a little difference due to your setup but very little.Try 80 as a set gain.