Modern Engines & Ignition Systems

Discussion of aircraft electrical system design, construction, and problems.

Re: Modern Engines & Ignition Systems

Postby Gordon » Thu Jan 25, 2018 10:32 am

Ignition Systems Comment........

Dale.......you are "spot on" with many of your comments. When it comes to horsepower in airplanes....more is always better. I put 500 hours on my RV-6 with 180 hp and a constant speed prop and that high power saved the day on a couple occasions.

My Hummel engine in my Onex (yet to be flown) has a Slick 4220 mag on one side (with an impulse coupling) and a Dyna S electronic ignition on the other (google it and check it out). It is used on motorcycles, like Harleys, etc. It is claimed to work very well on these VW engines.......we'll see.

Gordon.........Onex.......Hummel 2400
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Re: Modern Engines & Ignition Systems

Postby lutorm » Thu Jan 25, 2018 1:32 pm

If we're talking reliability, classic mags are terrible. If I recall correctly, the MTBF for a magneto is something like 500 hours.
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Re: Modern Engines & Ignition Systems

Postby daleandee » Thu Jan 25, 2018 6:23 pm

lutorm wrote:To be fair, putting a relief in the piston tops is my solution to the problem given the heads that I have. Of course getting new heads, that supposedly have better quality control, would be a better "fix", but if it comes to buying a new set of heads vs cutting a little dish in the pistons when I'll have them mounted in the mill anyway, I'm going to go for the latter.


I do understand the reason you are taking this approach and it's good to know that you are using a mill. Still this involves removing the heads & jugs, and then the pistons. I'm not sure how deep you need to go and it will take some careful measurements to ensure that you have adequate piston crown to do this. Also re-balancing the pistons as a set will be necessary. That is a lot of labor that should not need to be done. I believe I'd have a conversation with the supplier of the heads (assuming you bought them new) about replacing a defective product.

Would it be possible to have a welder build up the spark plug hole and then machine it properly? Is there a shorter plug that could be used?

Dale Williams
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Re: Modern Engines & Ignition Systems

Postby lutorm » Thu Jan 25, 2018 6:37 pm

I'm already rebuilding the engine. If I didn't already have everything apart, it would be a different question.

For the price of any machine work I can't do myself, it would probably be a better idea to just buy new heads. And I doubt the holes are weldable, that would be a lot of material to add. It would likely warp the heads way out of shape.

If the original builder had discovered this when he got the Aerovee kit back ten years ago, I agree it should have been returned. It's a bit late now...
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