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For all the super charger owners. What kind of AFR do you show when you are in vacuum (below 0psi). Just got a Innovate MTX wideband hooked up and I am seeing all kinds of crazy readings. 14.8 to 15.2 when cruising arround in the 1500 to 2200 rpm range.

Is this normal or should I start to look around for vac leaks or other problems?
 

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sounds normal, mine bounces all over the place with different loads/rpms. the ecu plays with the mixture after listening to the o2s. 14.7 is stoitch it should settle near there(but still bounce around) if everything is equal
 

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Thats good to know, I was afraid the free FMU mod was restricting fuel when in vacuum. Ok, time to start tuning the URD AIC.
 

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when the engine is warmed up sufficiently and under 80% throttle, the ECU will operate in closed loop mode, relying on the o2 sensor to provide mixture corrections. when it is started and cold, or when at greater than 80% throttle, it will operate in open loop mode, relying on lookup tables. aside from getting the URD piece that will allow you to hack into closed loop mode, the ECU will always strive to make the AFR 14.7 in closed loop. If the ECU has to provide more than 25% trim correction to the injectors to lean or enrich the mixture (like in the case of running bigger injectors uncorrected by an FTC) it will throw a code. hope this helps! Tony
 

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A O2 sensor only knows 14.7 or more or less. So when in closed loop on a O2 sensor vehicle it will oscillate above and below 14.7 AFR perfectly normal.
 
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