Thread: 3% CO on LM-1
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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
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Quote:
Originally Posted by 911st View Post
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.
What ever became of the dixie cup add-on to the metering plate, to help with early on enrichment? I seems somebody machined one and tried it out. Any concrete results beyond opinions and guesses?
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 11-21-2009, 02:32 PM
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