P-mags and EI... good idea?

[flytoboat]

Paul, Thanks for the "Mags 101" class. Very interesting!

[elippse]

Don, I try not to push any particular type of ignition, but, instead, I try to put out whatever limited amount of information I have accrued through my experiences. I find that educated decisions are, in the long run, the best! Thanks for your response! Paul

[elippse]

One thing I left out when considering ignition systems is associated with an inductive system that uses a waste-spark distributor-less ignition. As I previously pointed out, the inductive systems have lower rate-of-rise of their high voltage which puts them at a disadvantage in firing fouled plugs. HOWEVER, in the waste-spark system, the two cylinders that are 180? out in the firing order have their plugs fired in series. One cylinder is nearing TDC on its exhaust stroke while the other is nearing TDC on its compression stroke. That means that until the spark voltage has reached enough potential to jump the gap on the plug on the exhaust, there is a possibility that if the plug on the compression stroke is the one that is fouled, the voltage arriving at that plug could possibly be higher due to having to jump the gap on the other plug, somewhat like the old gapped device used to fire oil-fouled plugs!

[G3i Ignition]

I have seen the benefits of a synchronized firing event, which lacks with the ? EI systems. On my home page under ?NEW? is the SC Interface to remove this un-balance firing of the ignition system. Soon I will have available SC Interface for the LSE Plasma 2 & 3 systems also.
Thomas S.
G3i

[RV8R999]

p-mags are far easier and safer to time correctly.

[Walt]

Originally Posted by RV8R999

p-mags are far easier and safer to time correctly.

Easier and safer than what?

[cujet]

Originally Posted by KayS

Hey Guys,

...at that time i thought that it doesn't make much sense to install one EI and old style magnetos,,,,

so does somebody has some real world experience with this?

thank you...
Kay

I've installed, or been involved with a number of electronic ign's. While I'm not the worlds leading expert, I do have a good bit of practical, real world experience.

Remember, the Pmag won't produce self sustaining power at idle. It needs 800 +- RPM. A conventional magneto, of course, does not need ships power at all, ever.

It's easy to envision a situation where at the point where power is pulled back to idle, on short final, for example, "no ships power" would/could mean engine shutdown, with no hope of a re-start or recovery. We all know we had plenty of altitude and there would never be a need for a go-around, right?

By now, probably old news to everyone here, but CAFE foundation has one of the best electronic ign writeups. For various reasons, I feel the best setup is one conventional, healthy magneto and one electronic ignition. According to CAFE, this results in very little loss in peak efficiency, when compared to dual electronics. I prefer the Pmag due to simplicity, ease of installation and the back up, engine driven power supply. I've seen too many failures of other types/brands.

FADEC systems on modern aircraft always have back up power, and/or mechanical backup. Just like the Pmag, there is a good reason for this.

[videobobk]

I had two Slicks when I started flying my 9A. I went to one E-mag and one Slick. I saved one gph in fuel at cruise, got better starting and a little better idle, but gained no significant performance. When I added a P-Mag and removed the remaining Slick, I saved a little more fuel (maybe .2 pgh,) much better idle, and gained about 4 mph top end and cruise. Climb never changed much. As to safety, I make a note to not pull to full idle if the master is off; keep 900 rpm all the way down final, until the landing is in the bag.

Walt: Timing E- and P-Mags is easier than anything! I don't think safer comes into the equation.

Bob

[N941WR]

Originally Posted by cujet

I've installed, or been involved with a number of electronic ign's. While I'm not the worlds leading expert, I do have a good bit of practical, real world experience.

Remember, the Pmag won't produce self sustaining power at idle. It needs 800 +- RPM. A conventional magneto, of course, does not need ships power at all, ever.

It's easy to envision a situation where at the point where power is pulled back to idle, on short final, for example, "no ships power" would/could mean engine shutdown, with no hope of a re-start or recovery. We all know we had plenty of altitude and there would never be a need for a go around, right?...

The P-mags are self powering above 800 RPM + OR -. Each should be tested as tachs are not all the same.

However this is not an issue because on short final with the engine at idle you are typically over that number due to air loads on the prop. You will probably only have a problem taxiing off the runway after the plane slows down and your RPMs drop.

[cujet]

Originally Posted by N941WR

However this is not an issue because on short final with the engine at idle you are around over that number due to air loads on the prop. You will probably only have a problem taxiing off the runway after the plane slows down and your RPMs drop.

I disagree. I can easily get the IO-360 in the Velocity to go below 800 on final. It's also possible to stop a windmilling prop during a stall.

I still believe that one electronic such as a Pmag and one conventional mag is the safer choice. I've had my share of in flight failures. I do what ever I can to avoid them. Even if it means 0.2 GPH more fuel flow (that's within the noise, AFAIAC).