Wiring diagram for one CPI and one mag

[plehrke]

I have read several very good posts and threads on CPI installation. Maybe missed it some where in my searches but looking for a wiring diagram for mag on left and CPI on right side. I would like to keep my ACS ignition switch but wondering if I have to go to toggles. I do not have good place to put toggles as I already need to add toggle switch for the set spark advanced for LOP.

A few related question are can I just switch the wires on my ACS switch for L to go to CPI and R go to left mag so I am only starting on the CPI system? I am assuming I only want to start on the CPI system. Do I use a shielded wire from switch to coil pack on the CPI system and if so do I only ground the shield at the switch or both ends like on mag?

[Toobuilder]

When I was running a single CPI, I simply wired it "hot" to the master and left the mag on the existing key switch. Before anyone freaks out at that, keep in mind the CPI needs to be cranked on the starter to get running, so there is no danger of getting it to fire with casual/incidental movement of the prop. I also used a resettable breaker on the ignition which could be pulled if needed.

There is no need to shield the power wires to the CPI coil or brain.

[plehrke]

Originally Posted by Toobuilder

When I was running a single CPI, I simply wired it "hot" to the master and left the mag on the existing key switch. Before anyone freaks out at that, keep in mind the CPI needs to be cranked on the starter to get running, so there is no danger of getting it to fire with casual/incidental movement of the prop. I also used a resettable breaker on the ignition which could be pulled if needed.

There is no need to shield the power wires to the CPI coil or brain.

It is ok to start with both the impulsed coupled left mag and the CPI unit together?
What advance is the CPI firing at during start?
No chance for kickback with the plugs firing at slightly different advances?

[Toobuilder]

If you retain the impulse there is no issue with both on start. While there is no harm, there is also little advantage - The CPI can be programmed to virtually any advance/retard you can dream up while cranking. I use 4 degrees after TDC, so no kickback with mine. Personally, I like to get the impulse coupler out of my engine whenever possible as it presents added mechanical complexity which is made redundant by the magic in the CPI brain box. The only advantage to an impulse coupler in this scenario is the ability to hand prop the engine. That's not an option for my Rocket, so it was easy to let go of that capability.

[rv6ejguy]

We're setting most Lycoming CPIs to 6 BTDC at 500 rpm (uses the 500 rpm setting for everything below 500) and there is about 15 degrees of cranking retard in the software already so you'd be firing at around 9 ATDC. You can change the rpm timing as well as the cranking retard to suit your needs.

Should be no chance of kickbacks and we've not had any reports except where people got the magnets mounted incorrectly or one with a wiring mistake.

The CPI could be wired directly but you should have coil power on a switch to verify operation. Don't switch CPI power off to do a "mag check" and don't switch grounds.

[Toobuilder]

Ross,

You seem to imply that the crank retard is factoy set and fixed in the above post. Is this new, because my units clearly have an adjustable crank retard setting. IIRC, this setting is from zero up to 15 degrees, in one degree increments.

Also, the guidance on turning off the coil and brain seems to have changed, as (again, IIRC) that was once "ok". I have done that a few times and the brain reboots immediately, so no performance issue that I can see. Moot point however, as the coil can be shut down via the CPI brain box's coil check page. Thats how I've been flying all this time. Opperationally, I cant see any need/value to have a switched coil.

[rv6ejguy]

Originally Posted by Toobuilder

Ross,

You seem to imply that the crank retard is factoy set and fixed in the above post. Is this new, because my units clearly have an adjustable crank retard setting. IIRC, this setting is from zero up to 15 degrees, in one degree increments.

Also, the guidance on turning off the coil and brain seems to have changed, as (again, IIRC) that was once "ok". I have done that a few times and the brain reboots immediately, so no performance issue that I can see. Moot point however, as the coil can be shut down via the CPI brain box's coil check page. Thats how I've been flying all this time. Opperationally, I cant see any need/value to have a switched coil.

My bad if it came out that way. Cranking retard is generally set to 15 degrees and is user programmable.

For single CPIs driving dual coil packs, you can use the runup window to check the coils. With dual CPIs, I believe there would be no issues shutting off the CPI power to kill its coil pack as you say. We recommend that coil power be switched off on dual EM-5s to verify spark operation. This is due to the fact that each EM-5 drives one set of coils but injectors can be run by either.

[Toobuilder]

Originally Posted by rv6ejguy

...For single CPIs driving dual coil packs, you can use the runup window to check the coils. With dual CPIs, I believe there would be no issues shutting off the CPI power to kill its coil pack as you say. We recommend that coil power be switched off on dual EM-5s to verify spark operation. This is due to the fact that each EM-5 drives one set of coils but injectors can be run by either.

Ok, this is in line with my understanding as well.

Phil - what this means is that if you have a "normal" configuration of single CPI brain driving a single coil pack (it will drive two), then you have two options of killing a coil pack for the "mag check":

First - and preferred, is the coil check window on the CPI screen. You can press one of the arrow keys and it will kill the "A" coil for 5 seconds - done.

The other, which works fine too, is to simply kill power to the CPI itself with a switch or CB. This may be your best option if the CPI brain box is mounted in a remote location.

[j-red]

Back to the issue of the ACS switch... I don't have the wiring diagram for it, but since mags are "on" when the ground circuit is broken, it wouldn't work to run the CPI through the L or R because the ground would be opened and the unit would shut off whenever you turned to both (or the opposite side of whichever side you wired it up on.) For example: if you wired the CPI or coil pack ground to L, it would turn on when you selected R (grounded), but turn off when you selected L or Both (ground circuit open).

Someone correct me if I'm wrong. I have the slick/cpi setup but went the two toggles route. My EI harness didn't have a shielded wire for power, and it doesn't seem to make any difference.

[rv6ejguy]

We get the question about using the old mag switches for the CPI fairly often. Since they ground to disable, that's opposite to what is needed here. It's easier to replace with toggles although you may have to make a nice cover plate to hide the big hole.