P-mags and EI... good idea?
 

Hey Guys,

ok this questions comes a little bit late because i got my engine already. it's an io-375 with one lightspeed plasma II and P-mag istalled on it. to be honest... when i ordered this configuration i didn't spend al lot of thinking about this. anyway... at that time i thought that it doesn't make much sense to install one EI and old style magnetos, because on lower rpm the magnetos, with their fixed timing, would fire before the EI sparks. two EI's are no option for me.

so does somebody has some real world experience with this? if there is no performance/efficiency difference between the EI-Pmag and EI-mag combinations, i would rather sell the p-mags and replace them by slick magnetos just to make it less complex.

thank you...
Kay

Actually...
 

at lower RPMS the EI will fire way before the magnetos. I have a Lightspeed with the cockpit display, and on the ground at idle power the timing is usually around 38 degrees BTDC, vs. 25 for the magneto. Hence the better idling properties.

Vic

This may be a terminology issue as well because P-mag is a type of EI. So, if you have LSE and an P-Mag, you have two EI's.

Having said that, I don't see a reason why this would work any worse than LSE+mag (or P-mag+mag) as long as both are functioning properly.

Just an FYI... Here's a recent post on the P-mag / Lightspeed combo.
http://www.vansairforce.com/communit...mag+Lightspeed

Sam

I believe this was discussed last week...do a search and you will find it.

ok... my understanding was that the lightspeed will fire much less in advance at lower rpm's. somewhere below 25 degrees, but it seems that i was wrong here. i do believe that the combination of lightspeed and p-mags would work. but now i don't see a real benefit here, the p-mags add just cost and complexity in combination with a lightspeed EI. i don't want to say that p-mags are less reliable than slick mags but there should be a higher chance of mishandlng or mistakes during installation for the p-mags.

so, what do you guys think...? is the Lightspeed EI so let's say powerful that it "over-rules" any kind p-mag or slick mag? and if so, from my understanding, the p-mags/slick mags act just as a back up?

Kay, still learning....

@ Radomir:

you're right the p-mag is a EI, although i used the wording EI just for the Lightspeed to bring more confusion into the topic. :-)

you said that the combination of lightspeed and p-mag would work fine as long as they are functioning properly... and this is exactly my concern right now. i just don't know if the p-mags are a higher source of error compared to slick mags.

P-Mag is Lycoming's ignition of choice for the new IO-233, if that tells you anything.

To your original combination, why would you run two different types of electronic ignition. I can understand the single magneto and a EI for those who don't want to jump into the pool all at once, but why two different EI's? I'd dump the Lightspeed and buy another P-mag - much less complicated.

Different failure modes.

p-mags are self powered. lightspeed is not.