You could calculate the cam position from the crank sensor if you really wanted, but it could also be 180 degrees off. It would work with a wasted spark system,

I can see it telling where top dead center is but how does it advance and retard the spark? Starting a car from full advance is not as easy as the retarded base timing. Not retarding the spark is what broke arms in hand crank starting engines and kick back on old Harley's.

A short search said that your EFI was batch fired so didn't need a position.

 

Disregarding any thoughts about EFI, which is not part of the project, the Ford EDIS module, when there is no input from an ECM, fires on the 9th tooth after the missing tooth (36-1 trigger wheel) when the rpm are less than 400 (starting rpm). As soon as the rpm are 400+ (engine is running), the module fires on the 8th tooth, giving the limp home configuration a static 10* advance. I have indexed the trigger wheel/sensor mount another 15* to give a static 25* advance when the engine is running at 400+ rpm. Further, my plan is to use multiple sensors and a rotary switch to select the appropriate sensor. Therefore, there is a 0*/10* sensor (for starting) and a 25* sensor for normal operations. There is no dynamic ignition advance. It's a static advance within the sensor parameters.

Some gullible folks like me have projected that the limp home instructions to the coil-plugs, while precisely advanced, fires the coil-plugs robustly throughout the practical rpm range. That remains to be seen - maybe the Ford engineers didn't want the limp home mode to be robust above a certain rpm? If we had the original Ford engineers at hand to query, then we'd probably get an easy answer. Failing that, trial and error will ultimately flush out the answer.

Cheers,
Larry

 

I can see it telling where top dead center is but how does it advance and retard the spark?

It the missing tooth is top dead center of number 1 cylinder 90 degrees later is TDC of number 3 then another 90 degrees would be TDC of number 2 then another 90 degrees would be TDC of number 4. Once you understand that it's just basic math. Detroit diesel run off the crank sensor to this day. The cam sensor picks up a bump on the back of the cam gear to sync everything. Since the can turns half the speed of the crank you would need twice as many teeth to get the same resolution as a crank trigger.

For someone accusing others of living in a fantasy world you seem to be missing fundamental aspects of how timing works

Edit...
Wrong firing order... I think it was 1 4 3 2 if I remember right

 

Limp mode is generally set up for low power, less advance, and a bit rich to avoid spark knock and to make you get it fixed.

 

Another thing I found while experiencing with my own project a few years back... A VR sensor will transition at the same point when the tooth meets the pickup, but the transition back will vary depending on speed.

 

I just realized I made a mistake... On a four cylinder it would fire 180 degrees apart of crankshaft rotation.

And a better way to put it...
1) Crank engine
2) Time pulse frequency from crank sensor.
3) One you have a time gap representing the missing tooth you are at TDC of number 1
4) Next trigger is 10 degrees after top dead center
5) Measure time between pulses over and over again and you will have 35 pulses 10 degrees apart and one pulse 20 degrees apart.
6) From there it's just basic math to figure out where the crankshaft rotation is which is all that matters in a wasted spark / batch injection system... the cam doesn't mean a thing.

 

For someone accusing others of living in a fantasy world you seem to be missing fundamental aspects of how timing works

My comment on fantasy world was meant for the TS claiming spark advance wasn't needed or wanted.

The cam sensor picks up a bump on the back of the cam gear to sync everything.

A VR sensor will transition at the same point when the tooth meets the pickup, but the transition back will vary depending on speed.

Which points directly back to my saying the cam sensor is a needed thing. Diesel timing has little to do with spark timing though. And the VR quote points to what I said earlier about how the EDIS must get its spark advance.

I'm a GM guy not a Ford guy, and Ford does some things that are way outside the norm.

 

My comment on fantasy world was meant for the TS claiming spark advance wasn't needed or wanted.

Which points directly back to my saying the cam sensor is a needed thing. Diesel timing has little to do with spark timing though. And the VR quote points to what I said earlier about how the EDIS must get its spark advance.

I'm a GM guy not a Ford guy, and Ford does some things that are way outside the norm.

I understood your comment, but was a bit irritated...

A sequential injection system would need to know the cam position, but the rest not so much. It's just a matter of timing the crank sensor pulses.

Edit...

Actually if it weren't for the missing tooth a cam sensor would be needed. I suspect most engines with a cam sensor have all the teeth on the crank which would leave you counting x number of degrees each pulse, but no reference as to where the crankshaft actually is. I'll be done now.

 

Actually if it weren't for the missing tooth a cam sensor would be needed. I suspect most engines with a cam sensor have all the teeth on the crank which would leave you counting x number of degrees each pulse, but no reference as to where the crankshaft actually is.

Gm uses a missing tooth on the crank, and started out with 24- but then went to 56-.

All of my comments so far about crank position and type of pick up result from something I read years ago:
"Crank trigger controls spark. You can make them anything you want but anything except what's correct will mean a non running engine." From - https://www.hotrodders.com/threads/crank-trigger-and-cam-sensor.152869/

 

Okay All, I'm back to the project. Sorry to be away so long but life can get in the way.

Below is an example of a Hall crankshaft sensor that I'd like to adapt to this ignition project. As with almost all automotive Hall sensors, it's biased (no magnets needed). The input is 5V and the output signal is a square wave that swings between about 5V and 0V. Again the goal is to convert the output signal to a bipolar signal that swings between +2.5V DC to -2.5V DC. The bipolar conversion does not have to be that perfect - as long as the square wave goes to an obvious negative voltage then I think the goal is achieved.

I can't give you frequency or impedance information - somewhat over my head or knowledge base. But here is the operational environment: there is a 36-1 trigger wheel and at 600 rpm, the sensor is sending a signal 360/second or 21,600/minute. At 2500 rpm, the numbers are 1,500 and 90,000 respectively. From this information, can we guesstimate the components needed to create a simple high filter?

I have automotive Hall sensors at the hangar and will be there in two days (April 30). Any readings I can take with a multimeter that will be helpful?

Thanks to all,
Larry

 

While I follow your logic, I still think you are making it more complicated than it needs to be. The VR sensor will trigger at exactly the same point every time.

You can feed a square wave into a GM HEI module instead of the normal pickup and get it to work that way. I don't have the link off hand, but there is a page somewhere online where they did it to a motorcycle using the original points and a transistor. I have never tried with a Ford module, but it may be worth a shot. Good luck.

Edit... Ford designed the EDIS to work with a VR sensor and it will have any correction circuitry / programming needed to adjust the signal. Connecting a square wave may in the long run introduce more error than a VR sensor would on it's worst day.