Single Pmag and Slick Mag?which holes?

[Deweyclawson]

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).

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 just added the PMag to the right side. Kept the impulse Slick on the left. Auto plugs on the bottom for the above reasons. Well worth the cost and effort. Now starts almost like a car. Runs smoother. Starts easier.

[Captain Avgas]

Originally Posted by Andrew Anunson

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.

I think your comments are reasonable. I wouldn't criticise anyone for opting for a single non-impulse magneto. However we need to see the reliability of the impulse coupled mag in perspective. Virtually every reciprocating-engined GA aircraft has one of them and the incidence of one failing and taking out the engine is extremely rare. But leaving the master on and flattening a perfectly good battery is extremely common.

[GalinHdz]

Originally Posted by tim2542

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.

It is impossible to "reverse polarity" to the spark plugs unless you reverse the polarity of the ground. Do that and everything electric/electronic in your airplane will fail to work.

[tim2542]

Originally Posted by GalinHdz

It is impossible to "reverse polarity" to the spark plugs unless you reverse the polarity of the ground. Do that and everything electric/electronic in your airplane will fail to work.

Id refer you to John Schwaner’s “Sky ranch Engineering manual” ,pg 171.
And recall the magneto is independent of the aircraft electrical system, one of the reasons we love them so much.
Tim Andres

[skylor]

Originally Posted by tim2542

Id refer you to John Schwaner?s ?Sky ranch Engineering manual? ,pg 171.
And recall the magneto is independent of the aircraft electrical system, one of the reasons we love them so much.
Tim Andres

I?ll add that ?ground? is just a ?reference point? for voltage, and in a sense, the mag is operating like an unrectified alternator. In other words, every other plug is fired with alternating voltage relative to the engine block, i.e. ?ground? which is why the arc occurs in the opposite direction on every other plug.

Skylor

[RV6_flyer]

Originally Posted by skylor

I?ll add that ?ground? is just a ?reference point? for voltage, and in a sense, the mag is operating like an unrectified alternator. In other words, every other plug is fired with alternating voltage relative to the engine block, i.e. ?ground? which is why the arc occurs in the opposite direction on every other plug.

Skylor

Sometimes we forget that a magnet has a North and South pole. Same with the magnet on the mag.

On typical aircraft with dual mags, we rotate spark plugs top to bottom next in firing order. IF someone wants to rotate spark plugs on a single EI / Mag system, just rotate the aircraft plugs next in firing order.

[uk_figs]

Originally Posted by RV6_flyer

On typical aircraft with dual mags, we rotate spark plugs top to bottom next in firing order.

I did not know that you are supposed to rotate the plugs, I have just been checking them and putting them back in the same cylinder. Assume this is done at every annual?
Figs