I took Tracy's EFI out of Mike Wills RV4 and can't get it to work on
the bench. It is getting a good CASsignal as I have a drill motor
driven 2nd gen CAS. It was working in the airplane.

I would be nice if Tracy had put a couple of LED's here and there to
reassure something was working.

If I ever design and build and EFI I will surely do that because it
is real cheap.

I am open to suggestions. I checked the wires and they seem OK

Will it work with out the PCM connected?

The relay works that selects one of the two computers.


I want to measure the dwell period  Tracy choose.

Paul Lamar



Paul,

What kind of voltage are you getting out of the CAS?

Joe Berki

At low RPM it is about 5 volts. The higher the RPM the higher
voltage. Typical of variable reluctance sensors. Tracy uses this zero
crossing circuit based on an  LM339 quad comparator. Cost of the chip
30 cents :) It does not care about the amplitude. It will tolerate
voltages up to 36 volts.

Here is a better schematic.

I am starting over on the wiring. Mike used non color coded wire and
it is a bear to trouble shoot.

Paul Lamar


Paul,

I am using the LM2917 Freq to voltage chip for a tach circuit for the arduino engine monitor and wanted to know if the voltage out of the CAS needs a zener.

I could use the LM339 as input to the LM2917.

Joe Berki

What you need for the input is a LM1815. That will tolerate high voltages.
It is specifically design for handing VR sensors. It probably wasn't available
when Tracy designed his EFI so he used the cheaper LM339.


Paul Lamar


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