IO-540; Which Mag To Which Plugs?

[Geico266]

I am replacing an EI with a Slick Mag and I need to know if there is a correct position of the plug wires in relation to the cylinders? The EI had all car plugs on top & Slicks plugs on the bottom of each cylinder. I know Lycoming has a pattern to it, but I just just can't remember.

Maybe a better way to ask the question is; The left mag serves all six cylinders, but which side is top and bottom? Does it make a difference? Is it necessary?

BTW, what is the reason for staggering them?

[AMURRAY]

When you bank the airplane to the left, the left wing is down and the right wing is up. When you bank to the right, the right wing is down and the left is up. On the 540 it is the same, the right mag runs the right lower and left upper. The left mag runs the left lower and the right upper. Lycoming calls this the optional wiring, but almost all lycs I have seen are wired this way.

[N941WR]

Larry,

I was talking with Brad at E-mag Air and he said they are in the process of testing their 6 cylinder P-mag's on two different 540's.

Just thought I would mention another option should you ever want to go back to EI.

[f1rocket]

So I'm guessing there's a story there somewhere????

I have a Lightspeed in my Rocket. It's been flawless for over 200 hrs. Mag runs bottom plugs, EI runs top plugs.

[RV10inOz]

I am not a Lycoming expert .....YET!

In other engines and I assume the Lyc is no different, you want the flame front to be timed the same across the front of the pistons to be the same.

So the left mag should go to the top or bottom ....on ALL cylinders, and the right to go to the other on ALL cylinders.

This is because the timing of both will never be absolutely identical, so whichever one fires first innitiates the flame front, and if the next cylinder fires ever so slightly different, it will be rough. In other words the timing between each cylinder is not equal, some will have bigger and smaller gaps in the firing.

I have corrected some rough running engines by doing this in the past, they usually ran rough only at full power, and not violently just roughish. Fix up the plug lead sequences and smooth as a babies backside!

Hard to get your head around at first...... but its real!

Cheers

David

[dav1111]

Bendix Mags have each plug location marked on the plug connector, I am sure about Slick's.

[Geico266]

Originally Posted by RV10inOz

I am not a Lycoming expert .....YET!

In other engines and I assume the Lyc is no different, you want the flame front to be timed the same across the front of the pistons to be the same.

So the left mag should go to the top or bottom ....on ALL cylinders, and the right to go to the other on ALL cylinders.

This is because the timing of both will never be absolutely identical, so whichever one fires first innitiates the flame front, and if the next cylinder fires ever so slightly different, it will be rough. In other words the timing between each cylinder is not equal, some will have bigger and smaller gaps in the firing.

I have corrected some rough running engines by doing this in the past, they usually ran rough only at full power, and not violently just roughish. Fix up the plug lead sequences and smooth as a babies backside!

Hard to get your head around at first...... but its real!

Cheers

David

This makes more sense to me than staggering them.

[osxuser]

Ok, another tidbit. Put the EI on the bottom plugs and the Mag on the top. The EI runs a larger gap in the plugs, so you end up with a smaller chance that the bottom plugs will foul with the EI, AND it should be easier to burn off with the hotter spark.

[f1rocket]

Ideally that's true, but most of the EI systems mount the coils on top of the engine so getting the ignition wires to the bottom plugs become problematic. It just works easier to hit the top plugs than the bottom ones.

I know you can mount the coils on the firewall, but that creates problems too and I like to keep my firewall as clean as possible.