Single Pmag and Slick Mag?which holes?
 

My o-320 is set up with the standard two slick mags crossing over (2 top and two bottom plugs)

When I replace the right side mag only with a pmag and auto plugs, should I leave the crossed config? Or should I put all the autoplugs together on top (or bottom) and the same with the standard plugs?

Appreciate the advice!

All Pmag / autoplugs bottom. Allegedly they are less susceptible to fouling, have better spark and should burn fuel at bottom of cylinder better rather than fouling out the bottom aviation type plug / mag (which may be firing later).

That seems logical...
 

I'll roll with that until I have another $1500 to do the other one! :)

New Engine Configuration
 

I'll be the first to say that I know less about these engines than virtually everyone on this site. However, I just unboxed my brand new Lycoming YIO-320-D1A (from Van's) this weekend and it is configured as follows: pmag on the right, Slick on the left, aviation plugs on top of cylinders 1 and 3, and on the bottom of cylinders 2 and 4.

There must be a reason why, just don't ask me what it is.

Chris Hrabe
RV-9A

That is how a typical dual magneto setup is set up. Probably six in one and half dozen in the other for PMAG/magneto setups currently flying. I wonder if this might give less variation on RPM drop across the two ignitions when running them seperately, like during a runup check? Maybe it was easier for them to pull a mag and install the pmag without re-routing the other mags plugs/wires.... That did add some time to my initial single pmag install.

Bottom line however, lets say your flying along in cruise and your PMAGs are firing at 35 DBTDC... The magneto is still firing at 25 DBTDC and and at that point is probably doing nothing as the fuel has already ignited off the pmag spark. (A six pound oil plug at that point is what i recall Emag referring it to) Why would you want two cylinders running off the top plugs and two running off the bottom plugs? Assuming this same condition, heat rises, wouldn’t firing off the bottom plug allow the flame to propagate across the face of the cylinder from bottom to top, better than top to bottom?

The differences are probably not noticiceable in feel/flight but it would be best to Call Emag and ask them how to set it up.

Just a heads up; consider where your RPM sensor is coming from. If it is coming off one of your magnetos, it may be easier to replace the magneto that doesn?t have the rpm sensor. I installed my first pmag on the right and had to move my rpm sensor to the left mag, which required removing the left mag and then a half day episode of trying to reinstalll / re-align the gears/timing.... shortly thereafter i installed a second pmag and ultimately ended up taking the rpm indication from a pmag to the g3x.

Auto plugs fit far better on the top. And are much easier to service and torque.

Aviation plugs work very well all on the bottom and are easy to service.

The motor has no problem with this arrangement.

The cross wiring (2top, 2 bottom) with mags is scheme used to to equalize plug wear. As you rotate the avi plugs IAW the Lyc rotation schedule you?ll get a reverse of polarity on the plugs, which will equalize the electrode wear.
So you can keep that wiring scheme if you want to prolong electrode wear, or put all top/bottom as you please. If your engine is in reasonable shape it won?t make any difference if the EI is top or bottom or split.
As for which hole. I?d suggest you get rid of the impulse coupler, there is a history of them coming unglued. You?ll want to wire your non impulse mag so the starter won?t activate if it?s not grounded.
Tim Andres

I have a single magneto and a single LightSpeed EI. For the LightSpeed the manufacturer states as follows:


Question Which spark plug location do you recommend for a single Plasma CDI installation?

Answer A single Plasma CD system keeps the entire combustion chamber clean so it does not matter much if the Plasma CDI is on the top or the bottom. It is best if you use your first system on the top and the second on the bottom plugs. Since even a single Plasma CDI will keep the spark plugs clean, the systems should not be crossed. Use either all top or all bottom plugs for each system.

I would think that the same advice would be applicable to the PMAG.

Contrary to previous advice on this thread I'd advise that if you're keeping one magneto (and that's the smart move) then I'd keep the impulse coupled mag. That way the engine can still be started by hand propping in the event that you have a flat battery. It just gives you more options.

I decided to install one Lightspeed EI and one magneto too.... but since I don't need the impulse assembly and since they do fail occasionally (which can destroy the engine)... I decided to install the non-impulse mag alongside EI.

I will not go flying with a dead battery, so I don't need the ability to hand prop. Some have said to me "What if a hurricane is approaching your airport, the power is out, and your battery is dead? Or, if you are at a backcountry airport and your battery is dead?" Those are good questions...but...

I won't go flying with a dead battery. For me, the dead battery could be the first link in a bad chain of events. My non-impulse magneto will help guarantee that I don't go flying with a dead battery. For others, the dead battery is fine... and I won't argue that its either a bad or good idea to go flying with a dead battery... its really aircraft and pilot dependent.