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patkeefe patkeefe is offline
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Join Date: Apr 2004
Location: Ringwood, NJ
Posts: 2,843
CIS AFR Questions

I recently replaced the plastic, blown up CIS airbox with a Webb stainless steel unit. The ss unit has the 2.7L runner sizes, and my SC had the larger intake runners. I finally got to take it for a ride today. I had it pretty well dialed in with the Leask WUR and RPM Solenoid switch prior to the airbox destruction. I checked the control pressures yesterday, and they were where I had set them, which were 2.2 bar cold, and 2.8 bar warm.

Anyway, the car ran well, except for the hideous mid range bog down. My springs on the blowoff valve in the airbox may need to be a bit stronger (I have to calculate the spring rates and order some new ones this week), but with a high 4th-gear-bring-on-the-boost, it was bad. Part of that is the airbox blowoff valve opening a bit, maybe. And, I was still under the 4600 RPM switch opening on the rpm switch, so I wasn't sending the boost signal to the WUR.

I am wondering if the restriction in the airbox ports to the intake runners is causing this relative enrichment issue. After all, I have basically choked the airflow a bit. I imagine the airflow plate should indicate this lack of airflow via the control plunger. Regardless, I'll reset the warm control pressure up a bit, and revisit the boost threshold setting on the WUR.

I am open for opinions.

TIA
Pat
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Patrick E. Keefe
78 SC
01 Boxster
Old 12-09-2007, 12:54 PM
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