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Old 10-18-2009, 04:03 AM   #1
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Default hard boost cut-off

doesn't matter what gear, when boost hits around 7-7.5 psi, it automatically cuts off down to about 2psi, and then can carry on back up to 7-7.5 psi.

Faulty WG?

setup: AVO turbo (Garrett T28, BBB; 7psi internal wastegate), AVO FMIC, RC550s, TEC3.

Last edited by mcsinc; 10-18-2009 at 04:16 AM.
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Old 10-18-2009, 04:12 AM   #2
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Much more info needed on setup.
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Old 01-22-2010, 07:17 PM   #3
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okay, back to problem solving this.

I just wanted to confirm how a wastegate works. Please jump in if this is wrong: vacuum line from turbo outlet to WG can starts to see boost -> pushes on diaphragm of WG -> pushes WG arm to open flapper on turbine -> exhaust gases bypass turbine -> less turbine spin = less boost (ie: keeps boost at pre-set spring level)

If this is correct, and it's not an intercooler piping issue, is the WG failing somehow? (this part doesn't make sense) It almost seems like the flapper door on the turbine side doesn't just slowly open but goes wide open and I lose almost all boost pressure suddenly.

Anyone else with ideas?
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Old 01-22-2010, 07:20 PM   #4
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Are you using MegaSquirt?
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Old 01-22-2010, 08:04 PM   #5
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no, TEC3. (see setup in post #1)

I'm thinking it's not software related; I haven't changed anything in that regard. Is there something I should look for ? I may try re-gapping plugs as well, but weather up here is **** so it may be awhile before I get to it. Just collecting some ideas/theories at this point.
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Old 01-22-2010, 08:14 PM   #6
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Boost cutoff? Spark blowout? Weak ignition? Lack of fuel?
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Old 01-22-2010, 08:50 PM   #7
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don't think it's lack of fuel. I've run this system for about 5 years now. This just started happening.

I've changed my plugs, (same plugs as before NGK BKR7E IIRC), gapped to .035". Perhaps need smaller, but I thought I was running .04 before (?)

ignition -- TEC3 coils, unchanged, perhaps some sort of grounding issue, or one or more coils is shot? How do you test if it's a weak ignition?

The boost cutoff happens at any rpm range (eg: 4000 rpm going up hill, or 6500 rpm on the flats). Whenever the engine is loaded and it's building boost, it will totally cut out right at 7psi. I could be boosting at 6.8psi all day (well, you know what I mean), but as soon as it hits that 7 mark, the boost cuts hard.
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Old 01-22-2010, 09:50 PM   #8
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Quote:
Originally Posted by mcsinc View Post
no, TEC3. (see setup in post #1)

I'm thinking it's not software related; I haven't changed anything in that regard. Is there something I should look for ? I may try re-gapping plugs as well, but weather up here is **** so it may be awhile before I get to it. Just collecting some ideas/theories at this point.
Oh...way back there behind injectors, didn't know what that was.


Soooouuunnnddss like overboost protection, which has been known to reset itself sometimes after loading maps or whatnot. I'm not sure if that's true with TEC3 as well...but worth checking.

On the MS you usually have to set it a few psi over your target boost, since it will jump in before-hand.
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Old 01-22-2010, 09:54 PM   #9
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won't overboost protection just drop it down to ____ psi?

good thought though, I'll check it. thanks
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Old 01-22-2010, 09:57 PM   #10
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Dunno...mine was like hitting a brick wall.

Default setting for MS is at 1.5psi though, really frustrating to diagnose when you think it's just a problem going into boost period.

Good luck otherwise, I'd check spark plug gap as well. Not sure what the TEC3 coils are like...but I had to run .023 to get anywhere on my stock crap. COPS are a godsend.
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Old 01-22-2010, 10:18 PM   #11
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Dunno about yours, but when I blew coils recently the engine started to cut out based on load. It's probably not the problem but something worth checking.
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Old 03-12-2010, 04:31 PM   #12
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Default runnin a little rough?

i just put a walbro 190 fuel pump in and i have the emanage blue system in the ecu hasnt been hooked up to the laptop to tune it all up i just manual turned up the settings. im running around 7psi and it seems like its not getting enough fuel but it could be a few things. it will sputter and it wont take off like it should.

spark plug gap?
emanage?
what do you think
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