Hey guys, I am having what I suspect to be a boost leak issue. At idle and under load, my boost gauge will read vacuum pressure from 20 to 0 when revving the motor. At idle and under load, my boost gauge will never read above 0, so I am not making any boost. (I know I won't make any boost at idle).

I have tried disconnecting my boost reference line from the compressor housing to the internal wastegate itself and running it under load like that, still nothing over 0. I also tried disconnecting the previous line^ as well as my BOV vac reference line and still nothing over 0 under load.

This almost makes me think that the wastegate could be the issue. It functions properly, though, because I connected my air compressor to it and it opened up at 7 PSI. Maybe the flapper door isn't seated all the way?? Could a slight exhaust leak where the exhaust housing sits on the manifold be the issue?

Any insight on the situation would be greatly appreciated. Here is a video for some visual reference to the situation...
'90 1.6 miata with DIYPNP, Greddy TD04H turbo, Kinugawa wastegate (7.35 psi spring), Greddy RS style BOV, Glowshift boost gauge, Hallman Pro manual boost controller (disconnected at the moment), RX7 460cc red top injectors, NGK 4644 spark plugs, Innovate MTX-L wideband

 

Assuming there's not a hole in your charge piping big enough to sick your fist in, there's another issue going on beyond a boost leak. "Boost leak" issues usually mean slower spool, you're getting nothing. Even with a 100% open wastegate you should still make a couple PSI so it's not the wastegate either.

I've never had a journal bearing turbo, but I think your turbo is the issue. When I shut my car off I can hear my turbo spinning down from idling for ~20 seconds. It looks like yours isn't even spinning at idle which seems very wrong to me, I feel like there should be enough exhaust passing it that it's spinning anytime the car is on. I wouldn't be surprised to see some serious shaftplay on your turbo and/or some good sized chunks missing from your exhaust wheel.

Also, you have to tune your VE map to tell the car how much fuel to squirt at any given MAP & RPM. The AFR Target table is what your car adjusts to when your tuning or in closed loop.

 

Ah, alright. I'll look into that then... I really hope that the turbo itself is not damaged. There's virtually no shaft play and I know it's getting oil. But I'll look into it

 

Silicone intakes makes leak testers you could purchase and try. Here is a link to them.

 

I've had a journal bearing Garrett, and a BB EFR. Both would spin very fast at idle. You turbo STOPS?! That isn't right at all. Hell even when I killed the thrust bearing in the GT3271 from running it at choke flow, it still spun fine at idle.

OP- You got something going on with your turbo, start there.

Also do a boost leak check. And check all your hoses. Use a clamp or zip tie on every hose so they can't leak or pop off.

 

Turbo should be spinning at idle, IMO. You have a big exhaust leak (unless you're running open downpipe, which is going to wreak havoc with your wideband readings at idle), and I think looking at the flapper door is a great place to start.

Rule out your IC pipes from turbo to throttle body by capping the air filter and the coupler at the TB, drill a hole in one of the PVC caps, hook up a Schrader valve, and pressurize the entire system to ~10psi (don't go higher or you'll blow a cap out).

I had a similar issue years and years ago, ended up wiring the WG "shut", but the flapper was caught on the downpipe and wasn't actually shut.

 

Oil restrictor used?
Melted cat?

 

I took everything off and put it all back on today. Boosts safely up to 8 psi now!!

 

apparently you don't poverty turbo often.

 

Oh, FWIW, if anyone cares... It does spin very freely at idle now!

 

Great news. Any idea what the problem was or did you just take it apart and put it back together and it's fixed?

 

I'm not entirely sure but I'm fairly certain that I just didn't have the exhaust housing mated to the manifold tight enough... I bought some good locking nuts and those seemed to do the trick. I also made sure that my waste gate arm was holding the flapper door shut really tightly. Rookie mistakes... But there's a first time for everything I suppose.

 

My last $75 turbo wouldn't spin at all for about... the first 45 seconds of driving. Once it got a little heat in there it would break free and i'd get the spinny whistle noises.

Pretty awesome.

 

If you have a journal bearing turbo and are not using an oil restrictor in the oil supply line, then that is actually normal-ish. It's called hydro-locking and it's fairly common when you don't run an oil restrictor in the line with journal bearing turbochargers.

But the spinny whistle noises are all that matter, right?

 

Replace "often" with "ever"