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patkeefe patkeefe is offline
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Join Date: Apr 2004
Location: Ringwood, NJ
Posts: 2,850
Brian:
IA modded the fuel head, exactly how I don't know. I asked what could they do, and they said we can get the AFR reduced by about a point. So, last year, on the old stock fuel head, I couldn't get enrichment below 13:1. So, they did come through as advertised.

Also, I went with a Brian Leask modded 930 WUR, which is a Bosch PN 0 438 140 153. It is fully adjustable WRT cold control pressure, warm control pressure, and boost enrichment pressure. Brian set the enrichment pressure to 2.3 bar at 5 PSI boost. I think if I fiddle with the enrichment pressure, I may be able to shift the AFR curve, and perhaps moderate the lean condition when boost pressure exceeds 6 PSI (using 12.5:1 as a nominal "safe" value).

Referencing the HP/AFR curves, I also think that the lean condition (on the 7.5 PSI graph; at 5 PSI the AFR stays below 12.5) may be affected by limitations of the SC fuel system to deliver enough fuel to support that boost. I have 72 PSI fuel pressure on my CIS test gauges. My options are at this point to deliver higher pressure to the fuel head (possible), deliver more fuel to the head (possible), shift the enrichment pressure curve (possible), lower my warm control pressure (possible), or add an extra injector and Hobbs switch to activate it. Some of the above options will simply enrich AFR across the board; I think further WUR enrichment pressure adjustment and addition of an extra injector are the best options.

The car runs fine at 5 PSI, but I still believe I can run 8 PSI. I also need to think about recurving the distributor, as soon as I can figure out what would be the optimum ignition timing. I am open to suggestion on the timing issues.

Pat
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Patrick E. Keefe
78 SC
01 Boxster
Old 09-06-2007, 11:56 AM
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