Quick Question Regarding Boost Spike

[Nskylinerb-25]

Well I have a 240sx hatch w/ an RB20DET all stock exept for a custom intake manifold. The car is not my daily driver I might just use it once or twice a month but this past weekend when I went for a drive it started to get boost spike, the boost needle would go crazy once I hit peak boost and started to blow a bunch of black smoke . My peak boost it's 7 pounds so I don't think that's the problem. I haven't mess w/ the car so I don't know what could be causing the problem. Could it be that it's my MBC it's an Turbo XS brand I believe or could it be my cheap Faze Boost gauge? I also have a couple of boost leaks around the exhaust manifold could that be causing the problem? Let me know what you guys think I'm still a noob so if there's anything else I should check for let me know thanx.

[002-M-P]

I can't really answer your boost spike question, but....I used to have one of those Faze boost gauges and boy do they suck. You could put a little stress on the back of it with your finger and get the needle to move. So, see if a friend has a nice boost gauge that you can just plug up, to see an accurate reading of what is going on.

[matafied]

I would check first the quality of the hose on your mbc, if its dry rotted or cracked it would cause boost spike. That is of course if your boost controller is functioning properly. I’ve had that happen to me in the past a couple of times

[Nskylinerb-25]

I just replace on of them the other one seem to look alittle bit cracked I'll change that out.

[rustbucket]

An exhuast leak between the engine and turbo will definately keep you from having steady boost. Your wastegate is going to be going nuts.

Mbcs are notorious for boost spikes even without leaks.

[Nskylinerb-25]

So I got a new Autometer Boost gauge and change all my vaccum lines and it seems like it fixed the problem but this whole time I had been running at 9psi. So thanx for all the help.