D15Bastard

Ive looked and looked through all of the threads but havent come across any answers yet. Ok I have a d15b vtec with a ihi vj11 turbo, intercooled, 450's, dsm bov, yada yada.... I was running 2 1/2 dp through a cat, back to a stock muffler. With that set up and a mbc, i was running a steady 11 psi. I redid my whole exhaust 2 1/2 dp into a long resinator. thats it.

Now cant keep the boost down around 11 psi. It wants to climb.

Now with the mbc fully closed shouldnt the turbo only spool to what the stock actuator is set at? its at 8 psi. Well it dosent. I let off the the gas at 16 psi. With the mbc closed. Wastegate must not be opening so that makes me think the mbc might be faulty. Or wastegate getting stuck shut?

88dx

No mbc all the way closed pretty much='s no WG back the mbc off some or take it all the way off and just run a vac line to the WG if you only want 8psi and thats what your wg spring is.

D15Bastard

the thing is I want more than 8 lbs. Ive tryed backing the mbc off a 1/2 turn at a time. maybe I should make smaller adjustments to the mbc

Minor Threat

Isn't MBC all the way closed, not bleeding any air?

D15Bastard

with the mbc closed, it should be just like running a line from wastegate to turbo nipple , right?

NCHATCH

can also depend on the length of hose, remember that hose must fill up before the wastegate will see pressure.

and if it is a small turbo sometimes it spools up too fast and the wastegate cant catch it

D15Bastard

"and if it is a small turbo sometimes it spools up too fast and the wastegate cant catch it" NCHATCH

Good point, I do have a damn small turbo that spools hella quick. I guess I can try shortning the lines again. I did that before and wierd things would happen. like boosting all the way to maybe 5500 and then boost would just quit. But Ill try again. nothin to loss.

StanB

I noticed you did not list the maker fo the MBC you are using. However, I had a Turbo XS MBC (the cheap one for $75.00) and the same thing happened to me. I had a Garrett turbo with A/R .60/.48. No matter the adjustment made with the screw or the lenght of the hose the boost would rise to 15 psi. It would hold the 15 psi until redline. I threw mine away and bought an adjustable internal wastegate. If you are using the same brand/model, good luck fixing the problem.

nonvtec

Run 16 psi Maybe I missed this but did you take your MBC off and see what it runs?

D15Bastard

found the problem! bad mbc. The old one was a Norgren. I had never heard of it before , but it was the only one I had lying around at the time. A new mbc was made just to see if it was the problem, and sure enough it was. So now time to buy a good mbc. Any suggestions?