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patkeefe patkeefe is offline
one of the great unwashed
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Join Date: Apr 2004
Location: Ringwood, NJ
Posts: 2,851
Thanks to all. This is all very good informaton and food for thought. I did notice the self regulating feature 911st describes when I played around with the fuel system pressures.

I can recap: I deliver too much fuel in mid-range. It is just brutal to drive at the track in this condition; I just can't get out of the corners.

My original fuel head is from my 78 SC. My car is an SC with an old BAE kit, T04B, "V" trim. It did not flow enough fuel at the high end, but was pig rich at low and mid range. I did have the Leask WUR on it at the time, but I was running with BL's suggested settings. This was the AFR on the dyno, boost was rifgt around 5.5 PSI . I also had some air leaks, which account somewhat for the spike in power:

I put in a Leask RPM solenoid switch to flatten out the valley, and adjusted out the WUR (countless times). Even by holding off boost enrichment until 4800 RPM, I just can't get the valley to go away, and it is really noticable on the track.

Now, I have the IA head removed, and have put in a fuel head from a later SC, which had some extra port and line, line going to some sort of solenoid switch...maybe the Lambda stuff? I plugged this port with an 8x1.0 short bolt and gasket.

I just got the car running, adjusted up the plate screw to get the thing to idle, and I have 4 bar warm control pressure. AFR at idle is around 12.3, and at 3000 it is mid to high 13's. Tomorrow, I'll drop the control pressure back down, and see if I can get things to settle out a bit. I also have brand new injectors, which I put in a few weeks back, so I will check the squirt pattern and volume on those also.

I have to believe with this configuration, I should be able to get a bit leaner across the board, and get some adjustability back. I can probably live with the 13+ AFR at top end, but the mid range is a killer.

Also, the air metering assembly is the original 78 SC. I have the other assembly from the later SC...I know some of the venturis are shaped differently through the years and models, so I can check that also.

BTW, I did not notice the individual injector adjustment screws painted any special color
Patrick E. Keefe
78 SC
01 Boxster
Old 06-16-2008, 06:35 PM
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