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patkeefe patkeefe is offline
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Join Date: Apr 2004
Location: Ringwood, NJ
Posts: 2,794
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Last question of the year...
I had to perform a few mods recently to the SC 3.0 BAE convert: new stainless steel airbox to replace the plastic one which exploded, and had BL fix my toasted 930 WUR. I put the WUR back in tonight, and took the car for a spin..not too hard, as it's a bit icy out. The car runs fine, til I hammer it at 2500 or so; when I get to 3500, which is my full 5 PSI boost, it gets (what I think is) real rich, like 10 or below on AFR (according to my AFR gauge), and bogs like crazy. If I feather it up to that RPM range, it's still there, but not as pronounced. As I have the BL RPM solenoid, set to 4600 RPM, I have taken boost enichment threshold out of the picture at the range where this problem exists. Up to, and when on boost, the car runs fine.

I will put the gauges on it tomorrow, but am left to wonder. The SS airbox is the type with the 2.7L runner diameters, so I had to get 2.7 rubber boots and stretch them over my early SC intake runners. Could I be inducing this enrichment a bit because of the restricted airfox flow capacity (which I don't think is much)? But, if I'm flowing less air, I'm also not moving the airflow plate as much, hence delivering less fuel. Or, does this sound like a control pressure adjustment issue?

I fabbed a different popoff plate from the one pictured, as I thought that may have been the problem. New plate is 3/8 6061 T6, with different springs, such that the 5 psi won't open it, but a backfire will. Also ditched the AAV in the photo; I determined I didn't need it.

TIA, and Happy New Year!
Pat

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Patrick E. Keefe
78 SC
92 968 Cab
01 Boxster
RIP, Early_S_Man & RoninLB
Old 12-31-2007, 05:47 PM
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