So, I'm having one hell of a boost problem, and I'm hoping one of you yahoos can help me figure out what it is.

Yesterday, I installed a MBC and started tuning the car. Accidentally took it to 210ish kpa. But ever since then, I've been unable to build boost.

Ever since then, I haven't been able to get it above 130kpa. Today, I tightened the ---- out of all of my t-bolt clamps, and it managed to make it to a peak of almost 140ish kpa. I'm pretty confident the boost leak is not from any of my couplers at this point.

I'll be building a DIY boost leak tester tomorrow, and picking up some hairspray too, but I'm looking for any other avenues I could check and/or potentially find a way to hunt down the problem and fix it tonight.

 

wga operating correctly?

 

....Embarassingly, I completely forgot to check this. Going out to check it right now, thank you 18psi.

 

Pulling off the actuator, the wastegate flapper moves easily. The actuator holds it shut tightly.

I'm not even gonna try to force that actuator open this late, but I don't think the wastegate is necessarily a concern due to that - I mean, if it was wastegate related, it would overboost right?

 

Blown out gaskets? what kind of MBC?

 

Brand new exhaust manifold gasket (< 100 miles), no turbo gaskets with brand new surfaces, fleabay ball and spring MBC. I can remove the MBC if needed no problem to test.

 

overtightened t-bolt clamp sliced a silicon hose somewhere?

 

instead of just moving the flapper i would suggest hooking it up to a pressured air source/gauge and verifying that actually moves at whatever your wg spring pressure is..

 

Answer, for future searching:

I am using an eBay BOV. When I took it to 16.5psi, it somehow bent the internal shaft in the BOV, and it no longer operates correctly.

That's where the problems stem from. The BOV is acting as a giant boost leak.

Now, time to start a BOV thread.

 

get non-knockoff valve
profit

 

What's the cheapest non-knockoff valve available atm 18psi?

 

a used one

 

https://www.miataturbo.net/miata-parts-sale-trade-5/fs-hks-ssqv-ver-2-a-66001/

 

Checked that, I'm not Socal Cpolly.

 

depending what flange your using, cheapest to use would be dsm let off valve from a 1g talon
can pick them up for 10-30 bucks, good for 20-25psi, and make a pretty loud whoosh when releasing. just note, it will open in vacuum

 

x2 for a DSM bov. Hit a junkyard and it'll be $10. Definitely a little noisy in vac if it's vented (vibrating/wheeze sound) but stock holds great to about 15psi, with the "Dodge Garage" mod good for 25+. I've got one on my Miata. Can also be made to fit a Greddy flange if you drill a couple extra holes in it.

 

1g DSM BOV purchased and hopefully will be in the mail tomorrow.

Just dropped a ton of props for being generally awesome.