I have been looking at MAD industries, and all the different relay kits they sell and have a question. If you need a full 12 or 14 volts for the HEI system, why not use a relay and get full power? Am I on the right track or would that be too much? I am running a 6AL and an in-cap MSD coil and was thinking about wiring it up similar to the headlights or fan.

Anybody did this before? Did you notice a difference?

Thanks

I've found the IGN terminal on the fuseblock of a first gen Camaro to be more than adequate.

the relay couldn't hurt- i might do that on my car. i think a relay pulls a couple amp draw to activate it- a lot less strain on the ignition switch. you can also unplug the relay when you park it somewhere, as a theft deterrent.

If you wired it correctly, the relay won't have any benefeit for an MSD.

The heavy red wire on the MSD box should be connected directly to a 'hot at all times' 12V source. Since the unit can draw 10+ amps on this line, I like to wire them directly to the starter solenoid battery cable. This eliminates the voltage drop you would get from the 10-20 feet of 14 gauge wire in the Chevy harness.

The switched ignition wire on the MSD is just a "tickler". That is, all it does is turn on a MOSFET switch (a transistor) that powers the rest of the box. The voltage on this line can probably be anywhere from 8-16V and the unit draws nearly zero current on this wire. The MOSFET switches are much better than relays as they generally have less voltage drop than the contacts of a relay and don't have any moving parts so they never wear out.


Derrik- Automotive relays generally only need about 100-200mA to energize them. They do exactly what you described though. They lessen the load on the switch that drives the circuit through the relay.

Just my $.02

Paul D.

So what you're saying, is that the MSD is pretty much it's own relay. Thanks for the help.