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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Frank beat me to it.

964 cams have more lift, duration(which also means the intake valve closes a little later during the beginning of the compression stroke so you loose some compression and air fuel mixture at idle >"pumping loss"), and overlap than stock or SC cams and because of that the motor needs a little richer mixture to idle smoothly.
Anywhere in the 13's is OK if the motor doesn't drop below idle speed and come back up after you blip the throttle and you like how it runs.

It can also mean you have uneven injector spray from some injectors and running richer masks that at idle if it's really bad.

I have 964 cams and I have idle AFR around 13.5-14:1, cruise hovers around 14.7:1 and boost is around 12:1 depending on rpms and air temperature.

Don't worry about the intake valve closing late and causing loss of some compression and torque at idle and low speeds.
At high rpms this cam and valve timing fills more air into the chambers because of the inertia of the high velocity airflow coming in the ports continues to fill the chambers even though the piston has started coming back up the cylinder and the intake valve is closing.
Then with boost that situation is accentuated even more.
Old 03-31-2010, 04:44 PM
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