Fox No Boost And Stumped

a91what

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Simple way to figure that out.

Put a timing light to it and rev the engine the timing should advance properly. If it doesn't there is an issue, however retarded timing is how we setup "antilag" tunes. It causes the exhaust gasses to be much hotter. I can retard the timing in a tune file and send that to you, I really doubt it will make any difference.

You could try removing the charge pipe from the throttle body, put one of those caps in the coupler with a fitting to attach a pressure gauge to. hook your boost gauge to it and see if you can create boost against a sealed environment. If it does not make significant pressure you have turbo issues.
 
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FastDriver

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I think you need to connect those wastegates. They're vacuum operated. I had the same system in my car years ago.
turbo023.jpg


But if you know they're closing and they're blowing your hand off of the intercooler housing, then something's wrong with your sensor, not your turbos. Mine didn't even have a BOV and you could here a ch ch ch ch sound when the TB slammed shut. Are you hearing that?

These days, I run 2 sensors. One is in the inlet pipe, and the other is tapped into my intake. Helps me diagnose a sensor issue or leak before it causes a tuning problem.

Finally, on my 302, I was building boost by 2700 RPM and maxed, depending on gear, in the low 3000 rpm range. Your 347 should built boost even faster.
 
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TWEECD

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Fastdriver... the gates are closed by the internal springs normally. It takes boost to open them which is why you need to run the vac lines to them. Without a vac source, they will remain closed and you will see boost all day long. But I am not which is the issue.

As for my sensor - it and my Autometer boost gauge are tied into the same source and are showing zero boost. That said, I can try moving it and see if the source is somehow clogged - worth a shot although I'm skeptical as they register just fine when I blip the throttle.
 

TWEECD

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Steve - It definitely advances when I rev it, I've seen that before. I'm not convinced there's a disty problem, but wondering if someone saw some freak thing like that before tied to boost... yeah, I'm digging because I'm so lost here.

I can try capping the turbo outlet. I have a cap with a nipple on it already that I use for boost leak checks. I suspect I'll blow the cap off without much effort, but at least then we'll know.
 

FastDriver

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Fastdriver... the gates are closed by the internal springs normally. It takes boost to open them which is why you need to run the vac lines to them. Without a vac source, they will remain closed and you will see boost all day long. But I am not which is the issue.

As for my sensor - it and my Autometer boost gauge are tied into the same source and are showing zero boost. That said, I can try moving it and see if the source is somehow clogged - worth a shot although I'm skeptical as they register just fine when I blip the throttle.

That's only gonna work if it's the source location and not the sensor itself. Without a source to the wastegates, aren't you worried about overboosting?
 

TWEECD

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Point I was making about the sensor is that there's a MAP sensor (inside the megasquirt) and a mechanical boost gauge (Autometer). They both say the same thing so I'm not questioning the MAP sensor being bad.
 
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bird_dog0347

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I still recommend disconnecting the MSD as they have caused crazy issues for many people in the past. It's easy to do and worth a shot. You have a problem either with Air, Fuel, or Spark... that's all that's needed for it to run and since it's running I'm gonna guess air and fuel are ok (assuming you always have good fuel pressure) so I'd look at ignition first.
 

a91what

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Hmm... spark is the only thing I can't see on the output side of the tune. I can see the MS command what I set in the tune from my side but I cannot see what is happening on your side. According to the datalog however you never even achieve barometric pressure, so no matter how much air your blowing in it's not even reaching atmosphere.....
 
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TWEECD

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I have yet to verify this, but I think I just figured out the problem with not building boost!! Or should I say not seeing boost on the gauges. I was messing with the vac lines to trace the boost gauge/MAP sensor source and then leaned a bit further to get a look at the back of the intake manifold and noted that the vac line feeding the vac tree (from intake manifold) has a check valve in it!!!!!!

In my infinite wisdom and foresight, I recall installing a check valve in order to prevent boosting all the accessories that come off the intake, but completely forgot about it when I connected both the boost gauge/MAP sensor and FP regulator. So, essentially they never see boost although I'm undoubtedly making it. I plan to verify it on Thursday when I get some time, but I'm pretty sure this is it... makes perfect sense since the gauge never goes above atmospheric and that's exactly what a check valve will do! I knew it had to be something stupid!
 

TWEECD

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The sensors were working fine but since they're fed with the tree and the tree is sourced by the manifold with a check valve in the way they had no hope in seeing boost. I always thought the car felt like it was getting some boost but never understood why I wasn't seeing any. With two gauges matching each other that tends to fall to the back of your mind as the culprit. But the true find was when I laid over the engine to really see back behind the manifold and there she was. I'm gonna drink a nice beer on Thursday when I finally see the boost gauge swing past zero. Thanks for getting me thinking in that direction, it was the nudge I needed to look further down that path. :cheers:
 

TWEECD

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Yeah, that was the selling point for me, plus I always liked the idea of a factory like setup with the turbos down low and tucked in... downside are the plugs. #6 is horrible to get to. I'm an old school centrifugal supercharger guy, but over the years and a number of turbo cars brought me to the dark side you might say. Nothing like low end torque + top end power.
 

FastDriver

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Yep. After I did blow up my combo trying to shade-tree tune it, I went to a single with plenty of room around all the plugs and will never look back.
 

a91what

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Maybe now the datalog s you send will make sense.:confused:

Real progress can now be made, still need to schedule that live tune session so I can get the closed loop idle sorted out for you. :nice:
 

TWEECD

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Looking forward to it. It all adds up when you think about it.... FPR was not seeing boost so not increasing FP and ECU was thinking it was down in low load area of the map so not adding fuel or pulling timing like it should have had it known the engine was getting boost
 

General karthief

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Looking forward to it. It all adds up when you think about it.... FPR was not seeing boost so not increasing FP and ECU was thinking it was down in low load area of the map so not adding fuel or pulling timing like it should have had it known the engine was getting boost
Jeez, sounds like what I go through just get'n up in the morning!
 
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