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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Learned Master:

When the stock fuel pumps are not performing to spec, I do not believe it is control pressure that adjusts to compensate.

I think it is the Fuel Distributor's ability to maintain the differential pressures between the upper and lower chambers that allows it to compensate and maintain AFR's.

However, reduced fuel pump performance might show up as lower system pressure. The FD's pressure differential will work to maintain AFR's probably up to the point where system pressure is reached then the AFR's will lean out.



There was one one very skilled engineer / C2 Turbo owner here that seems to find that by going to a 044 pump he did not go lean any longer.

In an effort to get more fuel up top he did the normal thing and tried to shim his system pressure and found no change in the upper rpm range. This was with a K27-7200 turbo maxed out on boost. Say a bit over 400 whp w the stock fuel dist but with lowered control pressure visa ve his custom fueler. The higher spec pump seems to cure his lean issue.

I think it is here:ELECTRONIC CIS fueling & BOOST control


Thus, if it was me I would look for a genuine 044 fuel pump. There are copies out there I hear.

Last edited by 911st; 10-13-2010 at 05:59 PM..
Old 10-13-2010, 05:53 PM
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