ignition drivers

[Analogue]

So there's a Bosch COP 4 cylinder ignition module that is used on some VWs and some A4 Audis. It is the unit recommended by Motec for 4 cylinder COP control.

Does anybody know if the input of the ignition box is 12V or 5V logic? There must be several people running these; I know I saw Auburn with this module.

Keith

[Analogue]

So there's a Bosch COP 4 cylinder ignition module that is used on some VWs and some A4 Audis. It is the unit recommended by Motec for 4 cylinder COP control.

Does anybody know if the input of the ignition box is 12V or 5V logic? There must be several people running these; I know I saw Auburn with this module.

Keith

[BeaverGuy]

They are 12V as it is the same 12V source that powers the coils.

[T]

We use the aem drivers ($120, a rip). I am making another one right now ($12).

In our setup the coils recieve a constant high from the battery (12v) and then the path to ground is created by the ignition module. In our case the aem outputs either 5v or 12v to the gate/base of the transistors, which then create the path to ground by allowing a channel to form between drain and source.

until i had read this thread I believed our was triggered by 5v pulses, but now that I come to think of it, it might indeed be 12volts.

[Analogue]

An AEM ignition module will never go on our car again. PM me if you want to know why.

Be careful when making your own. I chopped up a Huco module (pin compatible with Bosch, but cheap enough to sacrifice). Inside is 4 BUB323Z darlington transistors sitting on a beryllium oxide substrate. For those unfamiliar with ceramics that will kill you, BeO is an electrical insulator with the heat conductivity of copper. Cool stuff, literally.

This particular module appears to be current limited. When the collector voltage reaches a certain level, some smaller transistors pull down the gate of the coil driver. This puts a lot of heat into the transistor. If you don't do any current limiting, then you will need good dwell control. Bad dwell control and no current limiting will destroy your drivers fast. Forcing the transistors into dealing with the excess energy is a reasonable solution.

Moral of this story is this: beware of heat dissipation if you make your own. The AEM unit is actually quite good in this regard. You certainly won't have access to BeO substrate, and aluminum core circuit board has it's own set of issues when standing off 400V, aside from the high prototyping cost. On every ignition transistor that I am aware of, the tab is the collector or drain, not ground. It can be up to around 400V if fired without a spark plug.

Now my electronics knowledge runs out before dealing with darlington pairs, or even BJTs for that matter. If I had it my way, I would use logic level IGBTs for this job. Unfortunately, I'm lazy and would rather use a commercial module, and not the AEM unit. This leaves the Bosch.

The darlington is current controlled (this is why IGBTs are amazing), the question is how much to feed it. The datasheet for the '323Z seems to suggest that I could feed it as many as about 100 mA to the base. With a 30 ohm resistor (measured, internal to module) ahead of each one, I find that I would get maybe 150 mA at 5V. This seems excessive. I am beginning to think that open circuit voltage would be fine at 5V, but I might end up with an extra resistor in the ECU to tame down tbe base current.

Thoughts?

Keith

[raska]

I just poted this yesterday in another thread, but it is Bosch p/n 0227 100 211. Used on all 1.8T engine I believe among others, if you're looking for it.