Quote Originally Posted by Bitsyncmaster View Post
A many tooth tach wheel on the crank would give you much faster RPM response readings even with an even fire engine. The odd fire engine you have to use two ignition pulses to measure RPM which even slows down response more. Fast response is helpful getting a better idle.
I used to handle turbo ignition timing exclusively with the MSD box + a MAP sensor. This actually worked fairly well but I'm sure was a bit laggy compared to a crank & cam wheel.

I tried to see if a similar thing would work with Megasquirt. The ideas is to set the ignition map to a static value across the board, adjust the distributor until base timing is correct, then use the 100Kpa+ areas on the ignition map to retard timing. I sent some emails and the answer was "maybe" but it sounded like there were some questions about sync with an ever-changing RPM signal.

Quote Originally Posted by dn010 View Post
I am under the impression you need both crank position AND cam position to have sequential injection. This is why even with the ECU knowing cam position, with EDIS the ECU has no idea what stroke the engine is on (since it doesn’t get a 36/1 signal from the crank sensor) thus sequential is not possible.
I would assume so. A single cam wheel with an asymmetrical pattern and adequate resolution could probably do it but I have no experience there.

It really probably isn't worth the effort to convert an existing batch firesetup to SFI. I'm sure injectors / spray patterns play in to the value equation as well. I happened to get lucky with experimentation and find 30lb injectors that fit the K-Jetronic heads and bullseye the intake valve with a nice fanned spray of fuel. Under these conditions I'm thinking there is an opportunity to capitalize on injector timing and keep fuel as atomized as possible. On a map that is very quick to jump rich under load I was still able to get about 25MPG at an 80MPH average speed with the AC running.