Good explanation and I agree with everything except the part about RPM not being used by the EC2. Engine speed is a primary input to the system, hence the term "speed - density system".
Ok, if I understand you correctly, Tracy, then RPM IS a computational variable in determining fuel injector pulse duration and not just the "frequency of injection" factor. Is RPM an adjustment for "Volumetric Efficiency" at different rpms or used for a different purpose??
Ed
Guess a little more detail is needed to explain this. The EC2 re-computes the injection requirements in real time. Just before the intake cycle starts, it computes the required fuel for this individual intake cycle. You can't get any more closely tied to RPM than this
The volumetric efficiency is very much affected by the design of the intake system. Since there are no two alike out there (at this time), it is not possible to take VE into consideration as a function of RPM. Detroit has it much easier in this respect because they can control every detail of the engine.
Tracy
Ok, one more time for us slow folks. I understand that the EC2 calculations some "adjustment" to the fuel requirement for each intake cycle. Since the intake cycle is certainly tied to rpm in so far that the rpm determines the number of intake events per unit time. I think I follow that each intake cycle can be different as far as fuel requirement. I had assumed that the fuel injection adjusment is primarily based on the manifold pressure it senses. In otherwords, if the Ec2 senses 17" Hg manifold pressure at a specific intake manfiold air temp it calculates X milleseconds of injection time. I had assumed that this amount of injection time would be the same whether 17" at 3000 rpm or 17" at 5000 rpm but that since the injector fires more times/sec at 5000 rpm than 3000 rpm there would be more fuel injected. In otherwords, I had assumed that since the EC2 does its calculation for each cycle, it didn't know(orcare) whether the cydle was happening at 3000 rpm or 5000 rpm only what the manifold pressure was at each rpm.
Since my assumption is apparently incorrect, then over a beer, you need to explain it to me one more time how the RPM is a factor in the computation of fuel injection time.
I strongly suspected that Ve wasn't really a factor for the reasons you stated, too bad {:>)
Ed Anderson
I think semantics are confusing both of us (or me at least : ). If we look at it in terms of a single intake cycle, rpm does not figure into the equation. If you look at it in terms of CC per minute or gallons per hour, it does. However, in the latest version of the software (which Rusty has), rpm does have an effect in that a different MAP table is used for high and low RPM ranges.
Tracy (who would never accuse Ed of being slow ! )