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🔧 Technical Boost control troubleshooting: Low boost issue with electric controller

v6buicks

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I started having issues with my turbo Camaro. For a couple years I was running a Precision PW40 wastegate with a Turbonetics MBC. The wastegate had an 8psi spring in it and the MBC pushed boost up to 12psi. I started noticing this year that boost was only making it up to 8psi so I immediately condemned the cheap MBC. I had my AEM Tru-BoostX gauge wired up for years except for the mac valve, so I figured it was time to make the switch. According to AEMs manual, the valve was a direct swap for my MBC in terms of plumbing.
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I made a little bracket, wired and installed the valve, set up the controller, and some very unexpected stuff happened.

Somehow I have even less boost. I'm only making 5-6 psi. How can I be making less than gate pressure? The only explanation would be a leak, right? I'm guessing that If I pull the mac valve out and trying blowing through port 1, I'll have leakage out ports 2 and/or 3. I already know that if I blow through port 2 I get very little air flow out port 3 which is not normal in its deenergized state.

I'm getting a bit ahead of myself with this question because I haven't tried the first test yet. I could also hook the gate up without the mac valve and see if I at least make 8psi again. This will rule out a wastegate problem. Anyway, if I find that the valve is leaking can it be cleaned out or fixed or do I just need to replace it? This is a controller and valve that I bought used, so I don't know what might have happened to it. Maybe there's some teflon tape stuck in there that I can't see.
 

01bluesnake

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I would pull the wastegate off, make sure the valve is sealing, then take it apart and verify the shaft moves freely, with no sticking. Look for obvious signs of damage/galling of the metal that could be causing it to stick under high heat when stuff expands. While your in there, probably wouldn't be a bad time to throw in a new diaphragm too. You can't make less boost then gate, assuming everything elese is trouble free and no leaks.
 
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v6buicks

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I would pull the wastegate off, make sure the valve is sealing, then take it apart and verify the shaft moves freely, with no sticking. Look for obvious signs of damage/galling of the metal that could be causing it to stick under high heat when stuff expands. While your in there, probably wouldn't be a bad time to throw in a new diaphragm too. You can't make less boost then gate, assuming everything elese is trouble free and no leaks.
I'm only more suspect of the mac valve because the gate was working like it was supposed to with the busted MBC. Rather unfortunately Precision discontinued the PW40 Gen1 and now only makes the Gen2 and parts which are supposedly not interchangeable. :rolleyes: If the mac valve tests bad, I'll take the gate off and check everything. If I have to I'll just pony up and buy the Gen2 I guess.
 

v6buicks

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This is odd, and I think NOMIEZVR4 NOMIEZVR4 is on the right track. I still have no smoke. I was able to blow freely through port 2 and out port 3. I could not blow through port 1 unless I energized the solenoid. That's normal.

I took the wastegate apart, and still found nothing out of the ordinary. The diaphragm was in tact, and I could actuate the valve with by sucking on the tit. That was with the spring out of course. I threw it all back together but with a 16 psi spring this time. I just wanted to see if it would make any difference.
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I put new plugs in the car, gapped them to .025", and went for a test drive. Not much changed. The boost only gets up to about 8 psi now as confirmed by the recorded high on the gauge.

It's kind of hard to hear what's actually going on because what sounds like my screamer pipe might just be a gross leak? ?‍♂️ One thing to note is that my boost response used to be really good, and now it just feels like a slightly hopped up NA. I will not reach any boost around town. It sits at 0 vacuum for a long time before going positive, and I need a long open road to achieve that measly 8 psi. This only strengthens the boost or exhaust leak theory. My wideband may be telling me something too. It's idling around 17:1 and cruising around 16-16:1. WOT is 11.5-12 like it should, but idle and cruise was always 14-15:1 before. hmmmm
 

sktchy

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I'm gonna have to think about this one a little bit but it sounds like a vacuum or exhaust problem for sure.

Didn't you have issues with your turbo smoking not long back? Might not hurt to take a look at the turbine blades and make sure it didn't cook the journal bearings and dig into the housing or somethin.
 

Turbocharged400sbc

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I had the same thing with the Turbo regal pull off your filter after it sat overnight and the Turbo is pretty well drained and you'll find that. Anywhere off of exact center you'll drag the turbine against rust.
I didn't have boost for my first drive but it actually started spooling after I "worked it in" as it were... Bye clearancing off the rust using the turbine via the compressor nut gently and carefully.
 
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sktchy

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I had the same thing with the Turbo regal pull off your filter after it sat overnight and the Turbo is pretty well drained and you'll find that. Anywhere off of exact center you'll drag the turbine against rust.
I didn't have boost for my first drive but it actually started spooling after I "worked it in" as it were... Bye clearancing off the rust using the turbine via the compressor nut gently and carefully.
Or hear me out, quit fighting with the damn thing and buy a cheap t04e 67mm that'll support those big power goals easily :s00ls:
 

v6buicks

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I tried a few things but didn't come up with anything conclusive. The O2s randomly get stuck very low, but they're usually fine. The AFR is always super lean unless I stab the throttle.

The narrowbands are on the manifolds and the wideband is on the downpipe which could be suggesting that the issue has to do with a leaking turbo or wastegate. However, I don't think that's it because the exhaust smell is horrible. I've never smelled a lean condition without cats so maybe this is it? It doesn't smell like E85 anymore which is concerning. I'm scared to make a log if it's actually running at 19:1.

I still don't hear or feel anything that resembles a vacuum or exhaust leak. Idle speed is normal and smooth.
 

sktchy

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So, my Buick thinks it's 30% lean with a big vacuum leak and rarely a stumble. My Camaro on the other hand will have an absolute fit if it sees 16s at idle and will start spitting about it. Lean condition kinda smells like a hair dryer if that makes any sense.

Does your smoke tester have some sort of regulated air to back it up to where you could spray things down with soap and bubbles or see that it's holding pressure?
 

sktchy

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Do you have a way to boost test it with compressed air? I use a tire gauge to set the regulator on my little 2 gallon Milwaukee compressor accurately around 15 lbs and have a boot set up with a nipple in the end of it, crude as per my usual but works fantastic. Sometimes you gotta break out some soapy water and look for bubbles but I'm thinking you have a big enough leak that won't be an issue.

Also idk if I asked but how many inches of vac do you have at idle or what's your kpa reading in hptuners. You want at least 20 inches with stock cam or better and 33 or 34 kpa on the map sensor. 18 and 38 and your probably gonna see issues and misfires.
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Have you made any other big changes that would change airflow enough that your tune would be off? I've had injector o rings not get seated well a couple times and then it'll get pissy but smell like fuel when you get into boost.

You said fuel trims are ok for the most part but sometimes swing lean?
 

v6buicks

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I haven't made anything like that yet. I've had great luck with the smoker, but if it doesn't show anything I'll make something to mimic pressure.

I haven't made any changes that would change air flow. The problem seemed to just appear out of nowhere. All I've messed with are the wastegate, boost controller, changing spark plugs, changing injectors, and repairing the wideband harness. There are a lot of opportunities for failure there, but I have 21" at idle.
 

sktchy

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Check those injector o rings would be my first thought, or it's possible the injectors you put in have a slightly different flow rate than what you had and you may have to do some maf flashing. Another thing is probably do is check fuel pressure at key on just for the hell of it. I went through 3 sets of injectors and I still don't know if I'm happy with the fic 80s I have.
 
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