5.7L Vortec - Idle RPM?
- Thread starter sparg93
- Start date
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SunlitComet
OBS Jedi-Do Good
Computer controlled. Or were you looking for something more in depth then that?
When you first start the truck, the computer is controlling the engine fuel mixture based on a factory map and sensors, but not the O2 sensors because they are not hot enough yet (open loop). After a minute or two, the sensors start to read and when all the requirements are met.......coolant temp, run time, O2's hot, etc. it goes into closed loop and uses the O2's to control the mixture. (closed loop)
If you just start up a cold truck with cold trans, the idle maybe different +/- 100 or more rpms.
In closed loop the computer tries to maintain 14.7 to 1 at all times.....except decel.
Anything over say ~80% throttle you go into open loop and the O2's are not used by the PCM to calculate mixture because you need more like 13 to 1 to make good power and regular O2s are not wideband and are not precise enough. It instead goes to its map which it uses for power using all the other sensors (MAF is important for this). This is why you need to change the tune for WOT if you have power adder bolt on stuff, because the PCM is not able to check the O2 sensors for rich or lean and adjust. You have to make the adjustments in the tune.
If you just start up a cold truck with cold trans, the idle maybe different +/- 100 or more rpms.
In closed loop the computer tries to maintain 14.7 to 1 at all times.....except decel.
Anything over say ~80% throttle you go into open loop and the O2's are not used by the PCM to calculate mixture because you need more like 13 to 1 to make good power and regular O2s are not wideband and are not precise enough. It instead goes to its map which it uses for power using all the other sensors (MAF is important for this). This is why you need to change the tune for WOT if you have power adder bolt on stuff, because the PCM is not able to check the O2 sensors for rich or lean and adjust. You have to make the adjustments in the tune.
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