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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
My understanding is both the Vac-Sensing 3.0 and the Boost-Sensing 3.3 Turbo WUR's are all or nothing. There is not really a progressive nature to either when triggered. (However I am sure someone could engineer a progressive system which would have benifit.)

With CIS the AFR's are not really liner. They are more of a curve.

We basically have a Cruse-AFR curve. And,

We have an Acceleration-AFR Curve.

Then there is a quick 'transition between the two fuel curves.

I do not believe that if you could plot the two curves they would have a consistent delta between them. The control pressure can determine the slope of each curve. The the metering cone determines the rate of change of the curve at different air flow rates.

The typical 3.3T boost-trigered enrichment CIS goes lean with first accel then stabilized pulls back to near 14.5/1 untill enrichment is effected depending on one's CO setting.

My thought is we should be able to set up with a vaccum-trigered WUR where we are at around 14.7 at idle and get an instant 13/1 AFR with acceleration just off ideal which is where a 911 motor makes its most normaly asperated torque.

If we continued to accelerate we could set up the fuel curve so it would continue to become richer until it is gets into the low 11's at Torque Peak (apx 5krpm)which is where we are most sensitive to detonation. After that it might start to lean some depending on how much fuel and air one can flow.

The other place we are concerned about our AFR will be on curse. If cruse is under 3000rpm we should be able to stay at above 14/1 with out much issue and at still meet our other goals.

Here is a crude drawing of what we might be working toward.

Old 10-19-2009, 10:39 AM
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