There are 4 different EOIT modes. Normal RPM is only used for the Cranking routine (this is why it only goes to 4000 rpm while the Boundary table goes to 8000 rpm). I outline the different modes and the formulas used in this video: ua-cam.com/video/FmdJOOUUqQg/v-deo.html
This is a great question and one that I didn't talk about in the last big EOIT video...didn't want to make a long video even longer. I have spent some time thinking about this and have come up with a theory. No idea if I am right or wrong, so let me know what you think. The real question to me is, why did GM define a cranking modifier table (N. RPM) to go up to 4,000 rpms? In my mind this is because the driver may be pedaling the engine trying to get to start. Maybe the engine is old and hard to start, or battery is weak, or who knows. So basically when this happens the engine will roar to life and RPMs will flare higher and faster than the ECM can switch out of cranking mode and before start up flare spark control can be applied. During cranking mode the FA1 multiplier will be in effect making the pulse width longer. As you know a longer IPW at higher RPMs mean the pulse occurs of a longer period of crank degrees. So having the N. RPM table (which I also *ASSUME* is in cam degrees and should be x2 just like the ECT tables) will move SOI and EOIT sooner to align the fueling with the valve events. As we all know, engine start up is the most polluting time of the engine cycle - cats are not hot enough to work and engine is still in OL. So controlling EOIT is the next best thing to try to prevent fuel short circuiting as much as possible, or at least making some attempt at emissions compliance. It could also be to prevent back fires, popping, over heating cats in the case of super rich OL mixtures and retarded timing for RPM flare control. I don't think we will ever know the real reason from a GM source, but this is my theory. What say you?
Awesomeness!!
So, what is normal rpm for, then? Is it part of transients similar to make up?
There are 4 different EOIT modes. Normal RPM is only used for the Cranking routine (this is why it only goes to 4000 rpm while the Boundary table goes to 8000 rpm). I outline the different modes and the formulas used in this video: ua-cam.com/video/FmdJOOUUqQg/v-deo.html
If normal rpm is used for cranking then why are the values at such high rpm?
This is a great question and one that I didn't talk about in the last big EOIT video...didn't want to make a long video even longer. I have spent some time thinking about this and have come up with a theory. No idea if I am right or wrong, so let me know what you think.
The real question to me is, why did GM define a cranking modifier table (N. RPM) to go up to 4,000 rpms? In my mind this is because the driver may be pedaling the engine trying to get to start. Maybe the engine is old and hard to start, or battery is weak, or who knows. So basically when this happens the engine will roar to life and RPMs will flare higher and faster than the ECM can switch out of cranking mode and before start up flare spark control can be applied. During cranking mode the FA1 multiplier will be in effect making the pulse width longer. As you know a longer IPW at higher RPMs mean the pulse occurs of a longer period of crank degrees. So having the N. RPM table (which I also *ASSUME* is in cam degrees and should be x2 just like the ECT tables) will move SOI and EOIT sooner to align the fueling with the valve events. As we all know, engine start up is the most polluting time of the engine cycle - cats are not hot enough to work and engine is still in OL. So controlling EOIT is the next best thing to try to prevent fuel short circuiting as much as possible, or at least making some attempt at emissions compliance. It could also be to prevent back fires, popping, over heating cats in the case of super rich OL mixtures and retarded timing for RPM flare control.
I don't think we will ever know the real reason from a GM source, but this is my theory. What say you?
@SilverSurfer77 that was my first thought but how often do you have a flare on startup more than 1400ish?
@@04silverado6.0 on a properly tuned and mechanically sound car 1400 is normal. But what if you have vacuum lean and/or leaky fuel injector?