Electronic Ignition

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  • #85068
    sworley
    Participant

      I saw that an electronic ignition system is now STCed for some 310s http://www.americanpropeller.com/ignition.htm. Will anyone be getting this? What are the reasons for the efficiency gain claims? My limited understanding is that there is a longer spark, which makes sense why that would improve efficiency, but also advanced timing depending on power settings. In what situations is advanced timing beneficial? Should I be looking forward to electronic ignition in my GTSIO?

      #105109
      rwelsh
      Participant

        I would suspect there might be efficiency in variable timing, but I sure wouldn’t want any advance at over 75% power as the CHTs would be very high. Assuming the computer program has been worked out right for the variable timing, this type of ignition would actually get us in the 21th Century. I see where their model list is for all non-turbocharged. They limit the advance when over 24″ MP. Good Thinking. Now we must wait for them to come up with ones for the turbo’ed twins. The price seems right. I am a little fuzzy how they get the spark to both plugs as I see only one unit with six prongs in the kit picture.

        #105153

        Well, the negative that comes to my mind is in the limitations section:

        ” 4. Must not have propeller de-ice (clearance not adequate, see #2)”

        That eliminates most of us. They do say they’re working on a system that will eliminate this restriction by replacing the crank trigger with a magneto trigger.

        My experience with electronic ignition on the ground has been that there’s no benefit on the ground. Power was basically equal. In the air, however, the electronic ignition seems to have an efficiency benefit, or at least so I’ve heard. This seems to be on naturally aspirated engines where the air is thinner. I’ll admit that I don’t fully understand the phenomenon fully (some of it is advanced ignition timing in such conditions, to be sure), but I have heard enough reports of success first hand from the experimental community that I do believe the claims. On a turbo engine I haven’t heard of benefits, but that might be because there are few turbos in the experimental world, which is where most of these sorts of systems are seen. So, as to your GTSIO-520s, who knows.

        But I wasn’t aware of a certified version for Continental 6-cylinder engines at all, so this is very promising. I’ll have to give them a call and talk to them about the status of a magneto adapter.

        #105154
        quote RWELSH:

        I am a little fuzzy how they get the spark to both plugs as I see only one unit with six prongs in the kit picture.

        It replaces one mag. So you have one normal mag, and one of these.

        #105208

        I gave them a call. Basically they’re working on some certification questions still relative to the mag timing housing on the 6-cylinders. The hardware is complete and it’s now a paperwork exercise. He said 1 month is hopeful, but realistically probably a few more months.

        He also said the turbo systems were in development. So there might still be an option for the GTSIO. Benefits will need to be seen.

        I asked if there would be potential for a group buy discount. This would obviously be for 310 owners only at the moment, but he said that it would definitely be possible and to check back when things are certified. I’d be glad to orchestrate the group buy if it could be arranged.

        #105209

        I haven’t researched this too far yet but, what is the fail safe mode if the regular magneto dies?

        #105210

        The result of the STC is one normal mag and one electronic ignition per engine. So, each cylinder will have one spark plug powered by a different method. If the normal mag dies, the electronic ignition is the only one working and vice versa. Basically, the only negative is that a catastrophic electrical failure will take out one spark plug per cylinder for the entire engine.

        #105211

        I wasn’t sure the electronic ignition was fully operational without the standard mag. It would make sense that it would have to be, I just was’t sure.

        #105213

        Yes. The standard mag is replaced by a “mag timing unit” which provides crank position to the computer. The remaining standard mag operates independently.

        #105215
        sworley
        Participant

          So how does use of the red lever change if you have electronic ignition? Does peak just happen at a lower fuel flow?

          #105217

          Peak EGT has to do with air fuel ratio, not ignition timing. So peak will occur at the same fuel flow, but it will have a lower EGT and higher CHT for points with advanced timing because the fuel has more time to burn before getting dumped into the exhaust.

          However, the theory is that you can run leaner and get the same power because of the better quality spark and ignition advance.

          #105220
          rwelsh
          Participant

            I am still confused how you can have two different spark timings going on in the engine. The standard mag will always be at 22 BTDC and the electronic one will be anywhere from 30 to 15 degrees BTDC. This sounds like something the Cessna 195 had in 1948 except electronic instead of battery powered on one mag. Homebuilts have been running on two electronic ignition sources for many years; some without battery backup. This system is somewhat like Unison was trying to sell in 1993, but for a much higher price, and nobody bought into it because it still had the 1920 vintage mag on one side. Maybe this is a baby step to full electronic ignition–hopefully I will live long enough to see it.

            #105227

            Having two different ignition timings on one engine isn’t detrimental to the engine. Doesn’t RAM do that on some of their STCs? The tractor technology mag on the one side does its job, and the electronic does its job. You will still get benefit from the one because the ignition will happen sooner in that one spot. As an example of this in action, one electronic engine control program I worked on had logic in it that detected if a coil pack went out on a cylinder, and advanced the timing on the remaining good coil/spark plug to make up for it. The result was virtually no loss in power.

            The regulations will not allow only electronic ignition systems unless there is an independent power source that will feed only the ignition. For example, the Lycoming iE2 has a PMA (permanent magnet alternator) that provides power only to the ECU and electronic engine controls. This is how it gets away without a magneto. If this system had similar, then it could qualify. However, having one magneto and one electronic at this point I think is a good compromise, since it prevents the company from being required to add its own power source and increase price further. Homebuilts don’t have the same regulations that we do for these things. The homebuilder can choose to accept increased consequences from a complete electrical failure.

            I’m not saying that I’ll definitely buy this when it comes out, but it definitely will be on my list. Let’s say that you paid the list price and spent $10k and their 1.5-2 GPH fuel savings is 1.5 GPH. 3 GPH since we have two engines. It pays for itself in 555 hours. That’s a pretty quick ROI.

            #105228
            sworley
            Participant
              quote TDUPUIS:

              Peak EGT has to do with air fuel ratio, not ignition timing. So peak will occur at the same fuel flow, but it will have a lower EGT and higher CHT for points with advanced timing because the fuel has more time to burn before getting dumped into the exhaust.

              However, the theory is that you can run leaner and get the same power because of the better quality spark and ignition advance.

              So you pretty much have to run LOP to see the efficiency benefits then? If you are ROP running leaner than usual with already higher CHTs seems no good.

              #105231

              Spencer, you’d likely see some speed gain ROP or LOP because of the advanced timing at the same fuel flows you use today. It would be very slight, though, and I think that you would really see the benefits LOP because the advanced timing will help the leaner (and thus slower burning) mixture more. What it might do is help you run LOP easier if their claims of a stronger spark are true.

              When I was running electronic ignition on dynos at sea level, I found there was no benefit to advancing timing at rated power.

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