I've already ran this by all of my 300ZX forums, and nobody seems to have anymore suggestions... here's the details:

Stock 85 Nissan 300ZX Turbo.. installed B&S MBC, cheapie.. ran it, set it to 10PSI, no problems. Ran a buddy of mine in a few friendly races, then did some donuts in the gravel. Came back, and the boost won't go over 7 PSI no matter what I set it to. Stock POV removed, plugged with 1/4 NPT fitting... aftermarket boost guage... the clutch roasted, got it replaced, now still sitting with the 7PSI problem... if you guys have any suggestions, I'd appreciate it. Thanks.

 

Try a different boost controller, or do a quick blast with the line open. (I mean quick.) Is it taking longer to hit 7 psi than it did before?

 

smirk...get a Honda

 

Your problem is that the MBC is stuck open. 7psi is your stock setting, right?

I've had nothing but problems with MBCs. Mine got stuck closed, which is a much bigger problem then you have!

 

if i'm not mistaken, those cars have a feature called a "pop off valve" to prevent creeping or boost spiking. It probably only allows 7psi. Try a search on that

 

I've heard of that on CART champ cars, but never on a street car, I think emissions people would have a fit over that, but I duno maybe it's there?

 

Stuck MBC: Ok, I'll take a look at the MBC and see about that.

Popoff Valve: Yes, it HAD a POV. In the original posting I explained what I did with it.. Thanks for the suggestion though.

Thanks for the replies, and if anyone else thinks of anything, please let me know.