A question about the IMRC system.

[97ReoCobra]

I purchased a 97 Cobra at the end of last year. Being new to the 4.6 4V engine I've been reading as much as I can about them. I find the IMRC system intriguing. I have not seen any information on whether or not the fuel injectors are affected by the IMRC system. It would seem to me that when they open and increase the air volume, it would lean out the engine considerably if additional fuel was not also added. Does anyone know if the computer adjusts the fuel injectors when the IMRC's open and close?

Thanks in advance for your time and attention!

 

[racecougar]

Not in the method that you're thinking of. Airflow is determined by the MAF, and fueling is adjusted accordingly, with feedback given by the upstream O2's. The IMRC opening/closing doesn't play a direct role.

 

[97ReoCobra]

That makes sense. They have an indirect affect in that their opening and closing changes the amount of air flowing through the MAF, which has the direct affect on the fuel injectors.

Thanks racecougar.

 

[mwolson]

The O2 sensors are only monitored in closed loop operation, typically idle and part throttle. In open loop operation, typically at WOT, the fuel is delivered based on a table with RPM on one axis and Load on the other. (Load is calculated primarily from the MAF data.)

Since the the MAF reports a lot more air coming in when the secondaries open, the PCM knows to add more fuel to keep the AFR where it should be.