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q: parallel MBC -- boost lag & tuning strategy

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Old 03-28-2005, 10:51 AM
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Definitely not. MBC in no way shape or form slows down boost ramp up.
Old 03-28-2005, 10:53 AM
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ok then i retract my statement
Old 03-28-2005, 11:20 AM
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hmmm. still with MAF codes. try a run with no MAF; that max charge pressure code is worrysome
Old 03-28-2005, 01:07 PM
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run with no MAF? hmm, what will that prove?
Old 03-28-2005, 01:20 PM
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Default He means MAF sensor. If it ran better unplugged, that woudl prove the sensor is failing/dead

Hitachi MAF sensors are known to read unusually high when dying/dead, but before doing that I'd check for boost leaks. That would explain the charge pressure and MAF too high codes.
Old 03-28-2005, 01:24 PM
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which means check the normal places: throttle body boot, divertor valves
Old 03-28-2005, 01:31 PM
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Default hehe. well i got the MAF part, but i figured it'd go into limp mode if it can't detect air flow

i'm not too familiar with motronic management, but usualy the initial fuel mixture amount is guessed based on MAF, then corrected via O2. if it has no MAF data, wouldn't it run rather crappy?

time to STFA.
Old 03-28-2005, 01:32 PM
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Default What if the ball in your MBC doesn't seat perfectly, but allowed a steady leak? --->

That might counteract the N75's efforts to bleed pressure while the boost rises.
Old 03-28-2005, 01:33 PM
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id still like to see what the MAF is at during idle, should be in the 2.x range
Old 03-28-2005, 01:37 PM
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Default With no MAF sensor, it'll run in speed density mode. You may be a little richer, but shouldn't be

too bad. I have never tried it myself, though.


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