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dannichols1474 dannichols1474 is offline
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Join Date: Sep 2019
Location: Milpitas, CA
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Quote:
Originally Posted by Showdown View Post
Does/did the 1977 CIS adjust for fuel pressure, fuel temperature and air pressure and air temperature.

Not a sarcastic comment, I really want to know- I can't remember since it's been a while since I had a CIS...
Hi Julian,

My 75 CIS system did not monitor and adjust for air temp, air pressure or fuel temp, but the CIS system is controlled by fuel pressure and there were no O2 sensors, so no Lambda control.

I read Scott's (Winders) comment to be directed toward the EFI ECU control capabilities. I am running a MegaSquirt2 ECU so air pressure (BARO) is measured by the MAP sensor when the engine is key on / engine off, the air temperature is measured by IAT sensor, and both air pressure and air temp are compensated for in the fueling pulse width calculations.

Fuel temp and fuel pressure are not monitored directly, although air temp could be considered a proxy for fuel temp as delivered to the injectors (not accounting for cooling effects due to the latent heat of vaporization when the injector sprays fuel into the intake port).

On the flip side, my system is running closed loop (when it is warmed up and within upper / lower limits of MAP and TPS) as I have the EGO (exhaust gas oxygen) Correction enabled and the ECU monitors the actual AFR against the target AFR and makes corrections to the fuel injection pulse width in real time.
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Dan
1975 911 Carrera

"CIS to ITB EFI conversion" thread
Updated (2) Table of Contents pg17 post 339
Old 06-13-2025, 07:47 PM
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