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Originally Posted by sperry
That's because a MBC *can't* respond. It's a spring. And by your log, it looks like it's hooked up incorrectly, because you're still tapering boost at high RPMs. Do you have both the MBC and the EBC hooked up?
Here's what MBC's usually do:
1000 2
1500 3
2000 4
2500 8
3000 14
3500 16
4000 16
4500 16
5000 16
5500 16
6000 16
6500 16
7000 16
And it's that 5500 to 7000 16psi that ends up killing the motor... since that turbo can't put out that sort of boost efficiently at that rate of flow, you end up running really hot.
Also, what are your EGT's running around with a MBC, specifically at partial throttle closed loop 16psi. Your data is from an open loop WOT pull, no? Aren't you concerned about running an MBC w/o changes to your closed loop programming, since it's now possible to hit full boost w/o running with open loop fuel levels?
Call me a stick in the mud, but switching to a MBC is a step backwards IMO. Reeks of the MBC/UniChip days.
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Just because it uses a spring doesn't mean it can't respond. It's just a much more simple system. The stock solenoid is completely disconected from all vaccum lines and I will probably just remove it completely as Ed suggested. The MBC is connected properly.
Perhaps you have used an MBC that doesn't taper, but this one does.
Full boost, partial throttle EGT's are slightly higher. Under load on the freeway on a cool morning its gone as high as 1525*F whereas before it would only go to 1500*. However its rare I see EGT's above 1400 and I've been watching the gauge like a hawk. Ed says these temps are perfectly fine.
Yes, that data is from a WOT 3rd gear pull.
Apparently once you remove the programming on the stock map that is designed to save on emissions, you program the ECU to compensate AFR's for full boost at partial throttle.
Counter-intutive? Yes. But the results speak for themselves.