14 Feb 2004, 05:27 pm
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Cool Cruiser
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Join Date: Jul 2003
Location: .
Posts: 347
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Quote:
quote:Originally posted by Dalite
Quote:
quote:Originally posted by Steve03GT
Quote:
quote:Originally posted by 3BarBoost
...and at wide open throttle the engine map doesn't adapt fuelling for more or less air like it would at part throttle with the O2 sensor. Spark also is mapped out based on the intake manifold pressure, so you could potentially develop something that passes a lot more air at the same manifold pressure and lean out and knock...
So if you have a setup that breathes better for the same manifold pressure, the wastegate adaption will try to maintain the same boost (for a given throttle and engine speed) and therefore will try to close the wastegate to deliver more air. Conversely, something that doesn't breathe as well will make more boost (dead-heading the compressor to some extent) and the wastegate algorithm will open the wastegate more to bring boost back down to goal.
Simple, right? 
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I pretty much follow your comments; however, does this mean an open element, hi-flo air filter, e.g., K&N doesn't improve performance at WOT???
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Also, at lower speed, when the PCM is in control, extra air volume (over the PCM's anticipated flow rate) is merely vented; thereby taking taking valuable processing time from the PCM.
If anything, higher flow could be seen as an "out-of-tune" condition by the PCM, and performance derated until the parameters fall back into line at the PCM's input sensors for turbo intake pressure and volume.
So, we now are looking at a system that doesn't care about barometric pressure, ambient air temp or higher volume intake pressures.
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This isn't entirely true. The surge valve does not ever vent when the throttle is opened. However, since the power consumed by the compressor is a function of the pressure ratio across it - the wastegate will open up more if you have a decent CAI due to the higher pressure in front of the turbo. Wastegate more open means less backpressure, and therefore a little more power. However, same total volume of air going through the engine.
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