K04 Boost & MAF

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Feb 22, 2004 | 12:24 PM

one8t

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K04 Boost & MAF

My current boost readings are in the .85-1 bar range from 3,000 to redline in 3rd gear WOT runs. No codes or other problems, I just periodically check vagcom data. In August and September I was seeing consistent 1.3-1.5 bar. The requested boost now is judt slightly lower throughout the RPM range than during the warmer months, the actual is just much lower. For some reason, this programming always gave me actual boost between .2-.3 bar higher than requested without fluctuating. The interesting thing is even at the lower boost levels, my MAF readings are in the 170's-180's, same or slightly better than summer/fall. Timing is great, fuel trims are fine and N75 duty cycles are in the 50-60% range at WOT. If I had a boost leak, I'd think the duty cycles would be higher trying to generate more boost.

Any thoughts or similar experiences? I'm guessing it might have something to do with the load/torque based programming and I'm hitting the target output so that's all the boost it's making.

Feb 23, 2004 | 04:44 AM

Stratocaster1422

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where do you live?

Colder ambient air is denser, so you can get the same/better mass air flow under less boost.

Boost is phat...
But airflow's where it's at.

Feb 23, 2004 | 04:15 PM

one8t

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Joined: May 2003

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Ohio

Spoke to GIAC today and they said it is part of the programming to limit boost with colder ambient temps - a form of safety device to prevent overboost and/or lean. I understand what you're saying about the air mass, I just didn't think it made that much of a difference. I had found some calculators that adjusted for flow/temp/humidity, but I guess the MAF doesn't lie and those readings are still fine. Sort of a shame really that the boost gets cut back because I think I have enough fuel to cover more flow. I guess it doesn't get in the 30's very often in GIACland!