Help! need ignitor or GM HEI Ignitor Substitute

loudhvx wrote:

otakar wrote:

What is important to know about this mod, is to stay with the OEM stile module. Do not start using the High performance modules. The Hi-Po modules suck up quite a bit more Amperage. I also like to use a single 1N5408 Diode and not the two in series. By putting two diodes in series you handle double the voltage. The 1N5408 handles 3 Amps @ 1.0KV The DR100 module is about the best one you can use. Also make sure that you mount the units onto a good heatsink.

I'm not sure why you would want to use the 1n5408. It won't provide as high of a bias voltage. According to the data sheet it's about .6v at .01amp. That may make starting more difficult if the engine doesn't crank quickly.

The R1 resistor limits the current to less than .02 amp, so voltage limits and current handling in the diode are not really important. The point of the two diodes in series are just to create a 1.2 to 1.4v drop as a reference voltage for the pickups to control the HEI properly. It doesn't handle any high power or voltage.

The write up is here with notes on how the systems (KZ and HEI) function. The HEI notes explain why the need for the 1.4v reference.

www.geocities.com/loudgpz/GPZgmHEImod.html


(BTW, I chose those diodes, not for their power, or current, I chose them because they are cheap and available and fairly standard across many manufacturers.)

And you are correct, it would be best to stick with the cheap OEM replacement HEI modules. I don't know what will happen with high-performance versions of the modules. Any performance enhancement shouldn't be necessary for firing two cylinders of a motorcycle. For an 8-cyl car, maybe...

There is another little trick that can be used for bikes that have high compression. That is, to use a 5-pin Wells DR137 module. The 5th pin can be grounded during starting, for an easier start. It retards the module by 10*, and puts less stress on the starter. You MIGHT even be able to use it for econo-cruse, but that I am not sure about.

Hay Lou, your point on the Diodes is taken. I just wasn't sure why you would put them in series. I have a ton of 1N4007s laying around. I can use two of those. One of these days we will have to get together, since we are both in the Chicago area. This weekend I will be putting my new top end on the GPz1100 I may even be done by Friday. My brother and I were talking about going on a ride on Saturday or Sunday.

Otto

That 10 deg retard is intriguing. It may be 20 degrees on the KZ, though, since it's crank trigger instead of distributor triggered (which is same as cam speed).

Hope the 1100 build goes well. I'm in the middle of making a kerker K-series replica. We'll see how it goes. Unfortunately, I work weekends, but hopefully will have some time off in the fall.

I just got my hands on a good used "K" series pipe for my GPZ. I had the header sandblasted and will refinish it. You can make a replica by using a MAC pipe as the basis. Adding on an Aluminum cannister is easy.

otakar wrote:

I just got my hands on a good used "K" series pipe for my GPZ. I had the header sandblasted and will refinish it. You can make a replica by using a MAC pipe as the basis. Adding on an Aluminum cannister is easy.

That's basically what I'm doing, but I'm using an old beat-to-hell aluminum canister for the shell.