[Diy_efi] RE: 60-2 Toothwheel - Kalman Filter or ( EKF )

Bruce A Bowling bbowling
Wed Apr 11 17:51:21 UTC 2007

>How much of a difference does injector timing make at
>idle?  And in practice, where did any differences show
>themselves?  Obviously, if you have a really big cam
>and idle is very "lope"-y, with a lot of intake
>reversion and charge dilution with exhaust gases,
>you're going to make things a little more tolerable at
>idle by using timed sequential injection, but I have a
>sneaking suspicion that there is a small but
>noticeable difference at idle, and possibly at small
>throttle opening cruise (high gear, low road speed). 

I should have done a bit of qualification on the statement on injection timing relative to crank position at idle.

>From what we have found on MS installs, one can obtain a decent and reproduciable idle quality. That is, for a steady-state situation at idle, a tune based on AFR will reproduce if all other parameters are in line - and the batch injection phase is the same.

Now, is this tune the most optimal with respect to fuel consumption and emission output? In other words, batch injection over a properly phased sequential injection?

Go to www.sae.org and purchase the following paper, SAE 800467, by O Glockler, H. Knapp and H. Manger (1980). I cannot reproduce here due to copyright laws, but I will speak to it (from my memory as I do not have the paper in front of me). This was a paper outlining testing that Bosch performed in the late 1970s in regards to injection phase relative to intake valve position. What they did was to move the injection event thru a full 720-degree engine cycle and monitor the engine torque, HC and CO out, at a idle situation. For the most part the measured parameters are pretty constant. But, at the point where the injection event corresponds to an open intake valve there is a change in CO and unburned HC output and torque dropped off a slight amount. IIRC, the torque dropoff was under a few percent. So, you suspiction jives with the data presented in this paper.

Also, this paper is referenced in Heywood (pg. 299)and the following comment appears:

"Sequential injection timing, where the phasing of each injection pulse relative to intake valve lift profile is the same is another option. Engine performance and emissions do change as the timing of the start of injection relative to inlet valve opening is varied. Injection with valve lift at maximum, or decreasing, is least desirable."

- Bruce

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