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Electronic ignition

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  • #16
    I’ve just completed my 100 hr that included replacing the right slick mag on the Lycoming IO360 with a Pmag. Wow, starts well, I can still hand swing it (don’t ask how I found that out) it runs sweet, smooth and generally like a new set of harrows.

    The dinosaur in me wants to keep a slick mag but I’m struggling not to pull the trigger on another Pmag, they are impressive.


    • #17
      I'm not flying yet, but after going through the process of evaluating mags vs EI I really struggled to get past the idea of bolting electronics to a hot vibrating engine. For this reason I went with the CPI2 as the brains are on the cold side of the firewall and they have a nice battery backup solution that is built in. For whatever reason I found that more comfortable.

      I might have retained one mag, but wanted both plugs to fire at the same time, and wanted EI because it can ignite mixtures that a mag wouldn't touch. That goes a long way to prevent hot restart problems and makes lean of peak operations much easier to obtain because you can go so lean that the engine just doesn't make the heat needed to harm itself.

      Side note: Anything that requires wiring/electronics is intolerant to a poor install. You absolutely need to have have good wiring, good crimped connectors, everything tied down, no zip ties cutting wires, etc to this to work.



      • #18
        I've been running dual PMags and have around 140 hours on them now. Last week we set the ignition advance to 25° - I'd left it at the factory default previously. My EGT's are all lower now and it seems to be running at a slightly lower fuel consumption. I'm pretty happy with them. Hot starts haven't been a problem.

        One potential issue for hand swinging with 2 PMags, if the battery is completely flat you do need to connect a small 9v battery to the circuit. I haven't tried that.
        Nev Bailey
        Christchurch, NZ
        YouTube Bearhawk Blog


        • Bissetg
          Bissetg commented
          Editing a comment
          … or plug in your jump starter pack

      • #19
        Interesting... At some point I would like at least 1 EI. At the time I was finishing my build and preparing to fly, PMAG just came out with the 6 cylinder version 1, and I wanted to see more time in service before I went that direction. Currently I have dual slick mags (Right = Slick 6350 non impulse, Left = Slick 6393 retard on a SS1001 SlickStart Booster). Really don't see much help with hot starts from the SlickStart Booster....

        So maybe it is time to go EI... Maybe after OSH...?

        schu how difficult was the installation of the SDI? Is there much "fussing" with the panel mounted programming module?
        Rob Caldwell
        Lake Norman Airpark (14A), North Carolina
        EAA Chapter 309
        Model B Quick Build Kit Serial # 11B-24B / 25B
        YouTube Channel:
        1st Flight May 18, 2021


        • #20
          I have dual Pmags in my RV-8 and am very happy with them. I really like the self-contained nature and easy installation. What I'm not in love with however is the computer grade connectors they use. Seems a bit less than aircraft quality to me, but having said that, there haven't been any issues in about 360 hours of flying. Just follow the installation instructions carefully and make sure the wire harness is robust and properly supported and stress relieved. I love the fact that you can orient them at any angle that works for you best. I'd do it again.


          • #21
            Old school Bendix Mags for me. I am going simple from spinner to rudder… except of the panel and autopilot

            N678C reserved
            Revo Sunglasses Ambassador


            • schu
              schu commented
              Editing a comment
              Begs the question: What is simple?

              Some people define close tolerance mechanical systems as simple. I tend to be more in the camp of less moving parts that interact is simple, thus, a crank position sensor wired to a computer box, with coils and plugs is pretty simple. The only mechanical thing is a magnet spinning, and if you don't like displays and settings just set the timing to be 25* at all RPMS and manifold pressures. In my mind that's way simpler than impulse couplings, gear lash, shaft runout, bearings, points, cams, capacitors, etc all working together in harmony through a range of temperatures and altitudes.

              As for reliability, I think electronics are as reliable as mechanical systems these days as long as they are built to industrial specs, conformal coated, good connectors, and good install.

          • #22
            Ive been running the SDS CPI on my airplane since it’s beginning. It’s literally one of the few things I haven’t had to mess with out of necessity. It just works. I didn’t put much time on my plane last year but when I pulled the plugs, the $2.50 NGKs, they were so clean I didn’t even bother cleaning them. Just checked the compression and put the plus back in.

            I have played with the timing curve to make it so I can run mogas and to add a bunch of timing during cruise to get a bit more speed. It’s kinda fun. Plane starts easy, because timing is retarded to after top dead center while cranking, idles nice at 10 deg BTDC, max power timing is at 20deg BTDC and when running LOP in cruise I’m set at 30 deg BTDC.

            No way I’d go back to mags.
            Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.


            • #23
              Originally posted by robcaldwell View Post
              schu how difficult was the installation of the SDI? Is there much "fussing" with the panel mounted programming module?
              There wasn't any issue, install was straight forward. I like that the SDI has a programable timing curve. Like Whee mentions, you can get smooth idle and more timing at LOP and less timing at full power. Makes a lot of sense.

              The p-mag had early teething issues on the 4cyl, but the RV guys tend to agree that they are ironed out. The 6cyl one is pretty new and much more complex because there must be a mechanical gear in it due to how the 6cyl engine mags spin in relation to the crankshaft. That is why it was delayed so long and there are a number of builtins on it:


              At the end of the day I just stuck with what makes sense to me: crap that isn't bolted to the engine lasts longer. In the case of the SDI, the only thing that must bolt to the engine is the crank position sensors.

              Oh, one last thing, I'd pick NGK plugs over any aviation plug any day of the week. The fact that they are cheap is just bonus.


              • #24
                Oh, CPI won't let you hand prop. Have your battery box handy.


                • Bissetg
                  Bissetg commented
                  Editing a comment
                  Hand prop capability was a deal breaker for me, that’s why I kept the impulse mag. But then again that’s why I went carbed as opposed to injected on my first engine. Now that I’ve found I can swing the injected I’m happy that I’ve gone that way. Maybe I’ll get over myself and go to another Pmag. I haven’t goofed around with the timing curve just gone with the factory default for the IO360, the retarded part of my ignition sits in the pilots seat.

                • schu
                  schu commented
                  Editing a comment
                  Fair enough, but I'd figure out exactly what my timing is. Many times the EI boxes will add more than 25* and most find that when they retard them back to lycoming spec (not EI vendor spec) their engines run cooler.

              • #25
                I chose a Bendix mag with impulse coupling on my Bob carburated 0-360. This was so I can hand prop in the bush. R&B Aircraft rebuilt mags were the cheapest option available for me. For the other side, I’ll use an electronic ignition for reliability, ease of maintenance and efficiency. Probably SDS, since they are local, their reputation is good around here, and I don’t think they require a rebuild like a P-mag. The choice of one mag and one electronic ignition was motivated by experience; my carburated rv9 had one mag and one lightspeed, and it burned less fuel than my 172 with the same engine. Hand-propping was available (never did it though). It’s nice that auto spark plugs are cheaper and seldom require cleaning or replacement.

                The last factor in my consideration was that I wanted the option to burn auto fuel and I intended to get low compression pistons. My engine arrived with 8.5/1 pistons though, so I’m not sure if this will work. I think it might, at a 50/50 mix, but that decision is way down the road after testing and break-in with 100/130.

                I have been advised that you compound the benefits of EI when you have two of them, and this makes sense to me. A mag is pretty much “along for the ride” when you have one EI. However, my build is targeting simplicity over performance, so I will forgo some of the benefit. Still, my anecdotal experience suggests something like .6 GPH or more improvement in fuel consumption. SDS tells me that most of the benefits of LOP are found above 10000 feet, but I’m not going with fuel injection anyway.

                Its hard to fault any choice, if it’s made for the right reason. If I had a fuel injected engine I would go with 2 electronic ignitions for all the efficiency benefits, especially with a 6 cylinder engine. I’d probably match with the SDS injection setup. Since I’m carburated, I’ll accept perhaps 30% of the efficiency benefit and a whack of redundancy, a bit of cost savings, and call it a fair compromise. If you aren’t going to fly much, a couple of mags makes good sense, since they are cheap if you aren’t rebuilding them often.

                I’m also not flying yet. I hope my thought process might be of value to some. Its based on years of flying experience-not on building or maintenance.
                Last edited by Pbruce; 06-17-2022, 09:36 PM.


                • #26
                  I think mechanical fuel injection, EI, full engine monitoring package, and someone that knows how to use the red knob will result in pretty good efficiency. Will it make up for the cost of avgas that mechanical injection requires (no injected lycoming has an STC for mogas due to vapor lock)? Who knows.... I suspect a wash. You could go electric fuel injection, but that has it's own problems, mostly with changes needed to the fuel system.....

                  Pick yer poison......