Thread: 3% CO on LM-1
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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Agreed, a fatter CO is more about throttle response.

My heavly modified 3.3 CIS used to lean to above 15/1 on first accel off idle. Setting it up so I went instantly to near 13/1 helped my throtle response.

It is interesting that per the reference above, 3% CO is about 13.3 AFR. I believe a 911 motor makes it's most power at about 13.2 so a 3 to 3.5% CO is near perfect for normally aspirated acceleration on a CIS motor. Not good for cruse MPG, emmissions, or motor life.

If the O2 system can pull things back with a fat CO it might be the best of both worlds.

However, increasing CO has been a traditionally accepted first step toward helping to extend fueling a bit on boost for a mildly modified motor (muffler, ports, inter-cooler, .9 bar boost, stock or K27-7200 turbo). I forget what stock CO setting is. I suspect reseting the CO to 3-3.5% also increases the fueling about one half to one full point in the mid range up to until the metering plate starts to stall at which point the motor will still go lean quickly.

Not an expert, must what I believe so far.
Old 11-21-2009, 01:10 PM
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