KA24E distributor trigger wheel(s)

[speedfreak]

First off, I don't have a Nissan and I've never seen the inside of a KA distributor, so forgive me if I say something newbie-ish.

I have the ECU, MAF, injectors, rail, and TB from an '89 240SX. I'm going to chip the ECU and use everything on another engine. I have to recreate the distributor signal for the ECU

1. I've been told elsewhere that there are two different trigger wheels. Is that right?

2. I know that one wheel has four notches with one odd size for the TDC reset. What does the other wheel do?

3. Last, does anyone know the degree spacing of the wheel teeth? Even if you do not, the wheel diameter, cutout widths, and tooth widths will be enough for me to build another wheel from.

[slideways...]

actually i have some knowledge of it, as mine went bad once. but it was a while ago so im kind of fuzzy on details.
as far as i know it has one wheel, with 360 holes around the wheel, plus
4(i think) extra holes. i dont remember if they are on the outside or inside of the ring of holes. oh and i dont have the distributor on me anymore so i dont have a measurement of the wheel.

[speedfreak]

Thanks for the reply.

Yeah, I found out that the one with 360 holes is for crank angle. What I suspect , but have not confirmed, is that the 360 wheel is so the ECU can reference spark advance. If that is the case, I'll have seperate ignition and it will be uneeded. The 4-tooth wheel is obviously for the injector order, but a sequential system must have one space longer than the others for TDC reset. One of the wheels, anyway.

[slideways...]

yeah the 4 hole portion, the TDC hole is either a double hole or wider than the others, dont remember which. and im pretty sure it is used for spark timing reference, because when mine went out i had no spark at all. otherwise the rest of the distributor was still good, and the coil was still good, just the ECU didnt get the signal from the crank angle so it wouldnt tell the coil to send any spark. when i replaced it, everything was gravy again. (not sure how it happened but when i opened up the distributor the disc was all crumpled and mangled...)

but i really think it is only one wheel, with 2 sets of holes.

im not sure about injector sequencing, the only thing i have ever heard of is the wheel is the crank angle sensor, but it is a possibility. actually im pretty sure its a 4 wire connector so that does make some sense...

its just a photo sensor thingy so you could use the signal from just the crank sensor and leave the other wires unplugged i guess.

[speedfreak]

Originally Posted by slideways...

yeah the 4 hole portion, the TDC hole is either a double hole or wider than the others, dont remember which......(snip)......

im not sure about injector sequencing, the only thing i have ever heard of is the wheel is the crank angle sensor, but it is a possibility. actually im pretty sure its a 4 wire connector so that does make some sense...

I'm starting to think the 4-hole is like a 36-1 where the "long" space is twice the length of the other three. I'd like to confirm it before building one, however.

When I mentioned a sequential system, I just meant that the long space on the trigger tells the ECU when to start back on cylinder #1. The ECU probably just does a 1-2-3-4 count until that long space indicates the start over point.

[slideways...]

oh. ok yeah that is how it works.

[speedfreak]

So no one has a picture or detailed description of this thing? I found a really fuzzy and rotten pic looking down on the distributor in a PDF from Jim Wolf, but it is very hard to see the holes in the "chopper" wheel.

[speedfreak]

I found a clearer illustration in an online service manual, but there is still an unlcear spot. I can't see if the 360 crank angle slits have a long "reset/TDC" window like the #1 injector, or if it is just a solid ring of notches.

[slideways...]

hmm cant help you with that. id need to see it in person also...