I have been boosted for a few months and just now got it running almost good. I got a question for anyone who could help. Why is it that i am spooling around 4000-4500 rpm and i have a super 16G with FMIC, sfmu, custom 2.5 downpipe to the converter. Also since i spool up late i get only 5psi in first and in the rest of the gears i get normal 6-7 psi which is what i set my manual boost controller at. I have no exhaust leaks and i am not losing air in any couplers b/c then it would not hold 6-7 psi in 2,3,4th gears and it holds fine. Please anyone help. Thanks

If you have your cat on, check it out it may be melted and restricting flow. that's what happened to me. it limited my boost to 5 psi when i normally am boosting 12 psi.

lates
james

I am planning on buying a test pipe within the next week, so hopefully that is it and i can boost b/c this makes me mad when i only get 5 and 7psi when i am close to redline only, when i spool up it goes up but i dont get full boost until redline which makes no sense. Thanks for the suggestion.

check the actuator arm going from the wastegate to the turbo housing. i bet it came off

what BOV do you use? make sure it isnt leaking.

1999 Black C5
1997 Silver RS
Wiseco 8.8:1 Pistons(back to low compression!)
Eagle Rods
T3/T4 Turbo
Custom FMIC
Greddy Exhaust
390's
Most current 1/8th mile time: 8.3@90mph 2.015 60'(Nitto Drag radials, i suck)

I am using the turbo xs rfl bov, i installed it just like it came, i have not changed anything on it. I am pretty sure there is no leak. I may be wrong so i will check it this weekend. I checked my actuator arm and i it still does the same, i took the wastegate actuator off and reinstalled it to make sure it was on right and no change. I have no leaks as far as the downpipe and manifold. Keep suggestions b/c i know it will get fixed soon and it would be b/c of you guys helping me out.

why do you need a mbc on your setup? what is the wastegate spring set for?

I bet youhave a boost leak. You didn't check, you just assume there isn't one. That's not the right way to look at a problem.

Build an IC pipe tester, it's real easy and costs $5 in home depot parts. Search, it's been covered a few times.

Originally posted by siueclipse
check the actuator arm going from the wastegate to the turbo housing. i bet it came off

If that were the case he would be building too much boost seeing as how the wastegate actuator opens the normaly closed wastegate.

Like Dino said, you have a boost leak sir.

Originally posted by etx

Originally posted by siueclipse check the actuator arm going from the wastegate to the turbo housing. i bet it came off

If that were the case he would be building too much boost seeing as how the wastegate actuator opens the normaly closed wastegate. Like Dino said, you have a boost leak sir.

youre wrong dude. it doesn't create boost unless you are at very high rpms and flooring it.

when my actuator arm came off.. i would floor the car and very slowly my boost would come up and would never hit the set limit.

if you have never experienced it, don't post who is right or wrong.

The wastegate arm controls the flapper which will open when the actuator tells it to. Thats why when you set your MBC to 15psi it will open the flapper at 15psi and release. If your arm came off then the flapper would not open and would not release. Therefore the boost would keep rising. If the flapper door were stuck open then you might have a problem with no boost. Look at the arm and see if it is stuck all the way open sometimes this happens. I have seen more than one person have this problem. I had this problem on my AWD.

Originally posted by Mattchew
The wastegate arm controls the flapper which will open when the actuator tells it to. Thats why when you set your MBC to 15psi it will open the flapper at 15psi and release. If your arm came off then the flapper would not open and would not release. Therefore the boost would keep rising. If the flapper door were stuck open then you might have a problem with no boost. Look at the arm and see if it is stuck all the way open sometimes this happens. I have seen more than one person have this problem. I had this problem on my AWD.

With an internal wastgate, if the actuator rod comes off the flapper, you will build little to NO boost. I have had this happen before, and freaked me out! What happens, is when that arm comes off the flapper, it keeps the flapper completly OPEN becuase nothing is there to keep the flapper closed. Exhaust gases force the flappper open, hence not spooling the turbo enough to build boost pressure.If you ever take off your wastegate actuator, or the arm, you can easily move the flapper back and forth. Its completly loose, with no tension on it. When that flapper is all the way open, that means most of the exhaust gases are being bypassed from the exhaust turbine..

OK but see this is what I don't understand. On my 4G we had the arm stick all the way open once on us and once we unstuck it the boost went back to normal before that we could build no boost. I see what your saying but do you see what I mean?

Also couldn't carbon buildup on the flapper cause a leak too?

Nevermind I see what your saying. If the flapper arm is not hooked up then there is no resistance to keep it closed... totally different than the scenario I'm talking about. D'oh

Originally posted by Mattchew
Nevermind I see what your saying. If the flapper arm is not hooked up then there is no resistance to keep it closed... totally different than the scenario I'm talking about. D'oh

Yep :) I really dont have much experience with ohter turbo's than the S16G/S20G, but I know for a fact this is what happens when the wastgate arm comes off of these..its pretty stupid that one tiny little pin can cause the issue...bad engineering IMO..