Help with spark latency

[thecrew2999]

How and what should be adjusted here? I fixed my timing to 10 degrees and slowly revved the engine up some. I got a jump in timing (retarded) then it ever so slightly looked like it retarded a little more. Maybe 2 or 3 degrees total. But I only revved to about 3 or 4 k rpms.

The jump when I revved it initially was like 2 or 3 degrees then would catch back down. It seemed to happen no matter where I set the latency to. I went up 1 each time till I hit 7 and it seemed to be the same no matter what it was set to.

Should this be a worry or is it normal?

[jsmcortina]

[billr]

Also, where is your "crank trigger wheel", on the crank or on the cam/dizzy? Maybe this is just a "basic trigger" off the dizzy???

[thecrew2999]

Haha thanks

[thecrew2999]

I have a crank wheel and a cam wheel on mine. It's not basic trigger... msq attached thanks

[billr]

Just three teeth on the crank wheel isn't going to give the best resolution/accuracy, but I don't know if it is causing your present problem. I think it might, but that is only a guess. Clarify, is the "crank wheel" mounted on the crank?

[jsmcortina]

Just three teeth on the crank will make it difficult for the ECU to detect changes in engine speed and therefore difficult to predict when to fire the spark during transients.

James

[thecrew2999]

Ok was not sure about the latency and if I should be concerned over

My factory setup is 3 tooth crank and half moon cam. From the factory it works well and it's 80s technology. I know 36 1 is ideal but I don't wanna change my stock setup as its clean and all tucked away. Adding a 36 1 wheel with a vr sensor will clutter up my engine bay and force me to install a wheel in a place that will be exposed to possible issues.

There isn't any way to make the 3 tooth wheel work like the factory ?

[thecrew2999]

Here is a quote I found in some megasquirt archives


3+1. This means one wheel with 3 equally spaced teeth and an additional tooth to indicate sync. (Supported somewhat as Daihatsu 3cyl).

[thecrew2999]

Does anyone think if I cut 3 equal teeth out of my crank wheel it would help? I have 6 cylinders this would help megasquirt figure it out I would hope... i still don't get how this could work so well in the 80s but give me issues on new tech

[jsmcortina]

Did you ever strobe the stock system to compare?

James

[thecrew2999]

I'm going to probe the stock tomorrow to see.. stock setup is wasted spark tho with fully sequential fuel and I did forgot that.
So would it possibly help if I cut 3 more teeth into the wheel?

[thecrew2999]

It's 3 evenly spaced teeth on the wheel. Could I maybe use rising edge and falling edge to count as teeth.

[billr]

Cutting three more teeth will help, "more is better" in this case; however, if you can cut an additional three, why not even more? Make it a missing-tooth type of wheel and things get even sweeter.

[thecrew2999]

Since it's a 3 tooth wheel it's got even missing teeth vs actual teeth so I doubt I can make it a missing tooth wheel

[thecrew2999]

Here's my crank wheel... my cam wheel is a half moon

[thecrew2999]

Had to use a crappy pic because the 1 mb rule.

I really think it would be ok if I could get it to figure that the risking edge is one trigger and the falling edge of that tooth is another trigger until the next rising edge. If you understand what I mean

[dontz125]

Rise and Fall Trigger.JPG

V2 is your sensor input. Use the same voltage feed to the circuit that you have to your Hall / opto sensor, 5v or 12v.

[thecrew2999]

Sorry v2? Is that inside my megasquirt? It's been awhile since I was inside it.

[dontz125]

V2 is a function on the Spice analysis schematic above; it's basically a series of square waves. In real life, this is your crank sensor.