GM HEI 8 pin module with Microsquirt

[Andy_Stprbeck]

With Bruce's recent post about V2 Microsquirt strenuously urging not to use the internal ignition drivers I figure I should follow his advice, so I'm looking for a good way to do this. My application is a dirt bike (single cylinder) so something that is compact and somewhat resistant to water dirt etc... is needed.

So possible stupid question but the GM HEI modules are one way to do this right? Is there some really obvious better way to do this that I don't know about?

If I use an 8 pin HEI module wired as shown here:

http://www.megamanual.com/ms2/GM_7pinHEI.htm

Except:
1. where this diagram says DB37 pin number 36 I would wire to Microsquirt pin 12 (Ignition output #1)

2. where this diagram says DB37 pin number 24 I would wire to Microsquirt pin 30 (optoin V+)

3. HEI module pin "B" on the HEI goes to Vref

4. Set ignition output jumpers in Microsquirt to logic level.

Questions:
1. To what would I attatch optoin V- ? I'm guessing the ground pin of the Module, together with another wire from ground pin on module to ground near battery with all of the other grounds? Or maybe optoin V- goes to nothing in this situation?

2. I have a single cylinder wasted spark setup, since this thing is good for 6000 rpm+ on a V-8 it should be good for well above the 10-11000 ish rpm of my single right?

3. My single tooth input is at 75deg btdc, so I can't use the cranking override thing, and I'm not sure what the advantage of that would be anyway??? So if I don't want to use it I can just hard wire to Vref rather than using the relay right?

4. Since the whole point of this is to minimize noise I would want the module mounted as close to the coil as possible so the wires from module to coil are as short as possible and as far from any other wiring as possible, right?

5. Using the connectors available for this module it should be pretty rugged, resistant to weather and some moderate heat. Right?

Thanks for any help
Andy

[Matt Cramer]

OptoIn V- would need to be grounded. I don't see too many problems with this other than the rather low resolution of a 1 tooth trigger setup.

[old guy]

Why not just use an LS1 coil. Can't get much easier.
http://www.megamanual.com/seq/coils.htm

[Andy_Stprbeck]

Old guy, I have no idea why i wouldn't use an LS1 coil. Is there some potential advantage to the LS1 coil over my stock coil and the HEI module?

I do kind of want to keep the original coil though. It is a coil on plug type coil and it is used to seal up the "hole" down into the cavity where the spark plug sits in the engine. Also, I figured I'd leave the option open to later attempt using the built in Microsquirt ignition drivers for a somewhat cleaner install, but to start out try to eliminate sources of trouble.

[old guy]

The advantage to using the LS1 coil is that you have the whole ignition system in one unit. You should be able to find another motorcycle plug cap that will work on your engine. Also as stated in a recent post you are better off using an external coil driver as there are more chances of noise problems using the internal driver. Plus the LS1 coils are really cheap.
Just my 2 cents worth.
Read the last post in this thread, it explains everything about the internal coil driver problems.
http://www.microsquirt.com/viewtopic.php?f=87&t=23064

[Andy_Stprbeck]

Hmm... I thought the HEI module WAS an external ignitor, hence the logic level output from the Microsquirt. That's pretty much the whole reason I started this thread and asked the question. I read the thread in the link Old Guy posted, came to the conclusion I wanted to use an external ignitor, but I didn't want to build the circuit that Bruce described because I wanted something sealed and didn't want to build it myself. Pearing through the megamanual it looked like I could:

1. Use the LS1 or LS2/truck coil

2. Use the Bosch 0 227 100 124 module

3. Use GM HEI module

4. Use any of the various coil pack type modules (EDIS, DIS, etc...) which doesn't make sense on a single

Only 2 and 3 keep stock coil which I kind of want to do,I found the HEI module on Ebay easier then the Bosch, and somebody posted in another thread that the GM module somehow seems to interpret the VR sensor signal "better" than the built in microsquirt circuit. I figured even if that's not true it's just another option.

Am I mistaken here?

[old guy]

What tpe of engine is this on. Chances are that your COP is made for a CDI that will not work with an inductive ignition. I don't know what they get for an 8 pin HEI module, but you can get LS1 coils on E-bay in the $20 range. Just my opinion but the LS1 coil seems like a no-brainer.

[Andy_Stprbeck]

The bike is a Yamaha WR450, four stroke single cylinder dirt bike. It has electric start with all of the associated parts; battery and a decent charging system. It is a dual overhead cam (5 valves) type engine so there is the big "hole" where the plug fits down into the head, and the coil fills the hole and seals it off, thus my desire to keep the stock coil.

Maybe this is a good time to ask what the difference is between "CDI" and "inductive ignition"?

The wiring diagram for the bike shows the coiled wire inductor symbols for the primary and secondary coils of the coil so I think is the "inductive ignition" variety, but this is educational, good info to know.

I already bought an HEI module from ebay for ~$20, but if it doesn't do what I need I'd happily eat the 20 bucks and go the better route.

[old guy]

A CDI coil usually has a real low primary resistance, less than 1ohm, inductive coils are usually in the 1.5 to 4 ohm range. I can tell you right now that the Yamaha coil is a CDI. An inductive coil makes a spark when power is removed and magnetic feild collapses. On a CDI ignition a capacitor is charged to around 400 volt and when the ignition fires it dumps the full charge into the coil. If you look at a plug cap from a Suzuki TL1000. it will probably work for your application. So the LS1 with the coil and ignitor all in one package for around $20 still looks like a winner.
Just as a side note a CDI and an inductive coil will look the same in a schematic.

[Andy_Stprbeck]

Using my el-cheapo multimeter I get ~0 ohms on the primary coil which is certainly <1 ohm. Looks like you are right Old Guy. Guess I should go shopping for an LS-1 coil.

Guess I should have asked abut this BEFORE I purchased the parts.

I'll look into the TL1000 wires, I think Honda 600 F2/F3 wires might have a seal type deal that might work too.



Now that this has been pointed out to me, out of curiosity I checked the Yamaha web site and it even lists the ignition type as CDI on the specs for this bike.

Thanks Old Guy, you probably saved me a lot of frustration, and possibly some fried electrical components.