Dual PMAG vs. One PMAG

Bavafa · #1 01-31-2014, 10:17 AM

For those who transitioned to PMAG, one at the time, I was wondering how much of a gain/change (if any noticeable) did you experience?

In another word, is it worth $1500 bucks for a person that does not pick up his money on a tree?

Thanks in advance

Capflyer · #2 01-31-2014, 11:04 AM

I have an Electroair and one mag. Can turn the mag off and see little to no difference in flight. I vote for going with dual PMags. That is what I'm putting on the RV8 build. Dollarwise, a new mag with gear and wires will run you about the cost of the PMag and then you'll add another $800 or so at 500 hours when it is time to replace it so really the PMag is less costly.

Omega232Devils · #3 01-31-2014, 11:25 AM

If you are trading in mags for PMags, dont forget to factor in the money from the sale of your mags. That may make the decision a little easier. There are always people looking for standard mags, so you wont have a problem selling them.

As for your question, you wont notice much gain from a dual setup over single, but factor in mag overhaul cost and auto plug versus airplane plugs and you can get closer to justifying the second PMag.

Dan

My 2cents, I went from single mag and electroair to dual Pmags and am happy with the decision.

eddieseve · #4 01-31-2014, 03:02 PM

I originally bought two pre-loved P-Mags and installed them one at a time to make sure they had no defects.

The change to one P-Mag and one Mag was great, installing the second I found amazing.

My aim was to be able to run LOP, the first P-Mag allowed good leaning but eventually a slight roughness would occur, with the second P-Mag I can aggressively lean and it's smooth all the way to engine shutdown.

Definitely worth it in my opinion.

Also why would you want to run two different ignition timings, one variable and the other fixed at 25 degrees?

Cheers

Low Pass · #5 01-31-2014, 03:30 PM

I've used Bendix mags, Slick mags, Electroair and now dual Pmags. In my subjective opinion, you get 80% of the "goodness" from one Pmag. 20% with the second.

I'm definitely a pilot on a budget, so I bought the first and flew a year before buying the second the following year.

Also saved a fair amount of weight with the Pmag. Maybe 2 lbs per side.

Joe Parish · #6 01-31-2014, 03:50 PM

A few years ago at Osh I ask that question and I believe Brad said with one P-mag you would get about 70% of the advantage on one.

Bevan · #7 01-31-2014, 04:14 PM

If one is good, two is better (as long as they are independant of each other which they are).

Bevan

Bavafa · #8 01-31-2014, 04:27 PM

I agree with the notion that two ignition firing at the same time it is better than otherwise and also I do see the benefit of PMAG compared to MAG though not as pronounced as some folks have experienced, perhaps my slick mag is functioning extra good.

I have my slick MAGs for sale as a package and if I find a buyer, I will switch but it does not seem the difference is worth the $$$ if I was going to pay that strictly from pocket, which comes out of my gas money and it would take years to make up for the gas saving that comes with PMAG.

kjlpdx · #9 02-04-2014, 12:04 AM

I installed one pmag last june. took but a few hrs as promised. seemed to run fine and a week later I flew from OR to OH, seeing 10+% improvement on fuel economy as well as a drop in EHT and rise in CHT [meaning more power is being produced]. my plane now starts almost immediately.
years ago I had a jeff rose system which ran fine for several years. then one day it quit. that's when I liked having the slick mag, fat, dumb, and happy, still firing away at 25°, oblivious that anything had changed. with the jeff rose I had a gauge showing advance. rarely can you achieve a large spark advance, typically just a few degrees.

Toobuilder · #10 02-04-2014, 07:02 AM

The 75/25 ratio is a sound bet if you are trying to simply do a cost analysis for fuel savings. However, keep in mind that dual plugs are not there for redundancy- they're there to allow the flame front to get all the way across the piston face. The only way to do that is to start at opposite sides and meet in the middle, thereby effectively halving the distance. This only works if both plugs fire at the same time. Hard to put a cost on this aspect, but significantly mis timed plug firing is "wrong" from a design standpoint.