#1 window is longer on optical sensor trigger wheel 4 ka24de, how about the 83'dizzy?

[Guest Kapower]

Hello everyone, My name is Jason Merritt. Long time reader, first time poster.

 

I'am researching for the proper input circuit construction on my V2.2 board with msextra 029q, and have a couple of questions.

 

I will be using the O.E. optical sensor, with a 12v pullup circuit for a 1991 ka24de from a 240sx.

 

The trigger wheel/disc on my Dizzy has 4 windows. (4cyl) (and of course the 360 slots on the outside) The #1 cylinder window is LONGER then the other windows.

 

The trailing edges of the windows are aligned. But the front edges are not becuase of the longer window for #1 cyl.

 

Does the trigger wheel/disc on the 83 dizzy also have the longer window?

 

If so then I'll just use the same input circuit that is recomeded in this forum.

 

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as you can see ^^^ I need to trigger from low to high to get a stable tach/input signal. high to low would be bad...

[Mack]

the 83 doesnt, but all maximas and 300ZXs share this trait. I have a 300ZX disc in my 83 dizzy and it seems to run just fine.

 

what I am wondering is if there is a way to use this to run a coil on plug set-up or possibly for sequential injection later on when the router board gets up and running. Can the wheel decoder decode that longer slot to mean #1 cylinder?

[Guest Kapower]

This is a little of topic, but...

http://www.autronic.com/page_files/trigger_disks.htm

 

Have you seen these trigger discs from autronics? The easy way may be to make one of those work.

 

I have also wondered what it would take to trigger the Megasquirt using the longer slot.

 

I got my car running tonight, checked my timing and it looked a little shakey. I'll play with the fixed angle feature to confirm the inconsistant timing tomorrow.

 

I must say that it does start up better then when I had MSII. ( I was triggering of off the leading edge with msII, oops... did'nt know any better I broke my starter from the kickbacks while cranking and the engine ran ruff...)

 

Maybe I got lucky, I think MS1 extra may already be triggering of of the trailing edge of the signal.

[mobythevan]

As long as one edge of the windows aligns (first edge, or trailing edge like you say) then in theory it can work OK. It just needs to be setup so that the input trigger to MS happens when the opto encoder shuts off (which usually means the TACH signal goes high. It may be too much trouble to figure out if you are not comfortable with the trigger circuit.

 

I would verify the TACH line goes high at the trailing edge of the disc window. Then verify that the trigger input circuit will provide the MS processor with an acitive trigger (low signal I believe) when the TACH line goes high.

 

Then it is easy to check that it is working by using the timing light on each cylinder if need be to make sure timing is steady and one cylinder is not getting a skewed timing from the larger window.

[Guest Kapower]

"It may be too much trouble to figure out if you are not comfortable with the trigger circuit."

 

I'am not comfortable with any of this stuff, but it's too late now...

 

I need to invest into a scope...

 

With the trigger circuit being pulled up to 12V until a trigger from the optical sensor which pulls the signal low at the leading edge of the window, then at the trailing edge of the window it goes high (back to 12v) That should "usually trigger the opto isolator".

It sounds right to me...

 

I'am using the standard v2.2 hall input circuit recomended in the MSM.

 

 

So, I need to set the fixed timing to 20 BTDC and hook the inductive pickup from my timing light to every spark plug wire, and check to see that I'am getting a steady 20BTDC.

 

Thats a great idea, Thanks.

 

-Jason M

[mobythevan]

I think you'll need timing tape around the entire damper so you can calculate where each cylinder should be firing as you move down the line.

[Guest Kapower]

^^^ Ya, I could only check cyl #1 and cyl #4, and they only varied by about .5 to maybe 1 deg, so it was steady.

 

If I use a scope to verify the trigger is stable should I look at the output to my MSD 6A or should I look at the IRQ pin after the opto isolater?

 

If the timing is stable at a fixed value of 20deg BTDC then

The output signal should be evenly spaced. But what else could I look for?

[mobythevan]

Either place would work, just keep in mind that at the input active low IRQ pin you still only want to compare the low going edges, the high going edges will vary because of the larger disc window.