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Been reading this thread, and can add another data point. IO-540-D4B5. I have an SDS ignition running the top plugs and a mag timed to 25* running the bottom plugs. Most of my flying is local, ~3000' ASL, 23 squared (55%), LOP at 9.5 - 10.0 gph. The SDS is set at 28* for those numbers, and my advance switch adds 4*.
Today I flew these numbers, and every 5 minutes for 3 cycles I threw the advance switch. Analyzed the resulting data and the only discernable change is adding 4 more degrees advance would lower my EGTs across the board by ~20*. CHT did not change. Could not identify any trends in airspeed - 3000' here is flying the valleys and keeping a constant elevation means airspeed fluctuates quite a bit as you move through rising and falling air currents. |
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The benefit for playing with advance is far from linear, but it is certainly there. High and lean, the performance benefit is significant. At least I think a change from 198 to 201 knots at the same FF is significant. And as stated, the ability to build in detonation margin when down low and fat with a retarded timing set is also significant. The big takeaway is what Dan and I and others have been stating for a long time now: Variable timing is no good by itself; you need the RIGHT timing for the condition. There are no "one size fits all" solutions. |
You guys are funny!
When I was a kid my dad you to laugh at me because I knew that one car was 1/10th of a second quicker to 60 than another. Therefor, he should buy the faster car. He knew he wasn't racing his car to church on Sunday so that extra speed wouldn't do him a lot of good. The same thing goes for electronic ignitions. Yes, the can be tuned better and ideally would be tuned to each individual engine. However, the P-mags in standard form are working and working well for 99% of the people who install them. Assuming they are installed and timed correctly. Yes, there are better timing maps and some of the other ignitions out there can be tuned in increments of X RPM's. However, how many people understand the finer points of ignition timing and can time their engines to maximize performance. Not to mention the risk tolerance involved in doing so. Not only do you risk damaging a very expensive engine but possibly risk your life. The P-mags in standard form are a plug-and-play installation, for the most part. Once installed you can fly high, low, LOP, ROP, or whatever you want and they will not damage your engine. The best part is that once installed, timed, and configured properly, they are a never worry about device that keeps your engine humming along happily. While we are a group of "experimenters", not everyone wants to experiment with their engine but they do want better performance. The P-mags provide that and they provide the backup power redundancy most pilots look for in their system. The advantages of electronic ignition, coupled with an internal generator, and easy installation are the selling point of the P-mag ignitions. If the timing curves where so dangerously aggressive, as mentioned in this thread, then there would be melted engines all over the world and that is just not the case. Could the timing curve be better? Yes it could, but it is still a LOT better than a fixed time magneto. |
Oh Bill... :). What was that peak CHT you saw again?
Another shot of coolaid for me please. |
We have dual P-Mags on our 7.
We rock up, pull it out, it starts 3rd blade cold or hot. Uses $8 NGK plugs and flies really well. Because we can now analyse the far end of the fart, doesn't make the fart any better or worse :D:D Why haul a dumb mag and big spark plugs around when you can just enjoy simple, great engineering ? Bill - the EI Commander went on the 8 to a new owner, he says it it is great ! |
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Since Version 40 came out a few years back, the P-mags have been rock solid. Granted, having the ability to monitor and tune them is a bonus! |
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Let the new owner know that they can contact me, if they have any questions. |
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Using a set of P-mags and your EI Commander, Nigel demonstrated that the factory settings are too advanced for ROP, all the way up to 16,000 feet. Facts are facts. You've seen the data. Do you find fault with it? BTW, this is not a hardware or brand condemnation. It's just a poor choice of factory installed timing values. Any ignition, magneto or EI, would offer the same result given the same timing values. The values can be changed with keystrokes, or as in Nigel's example, with an EI Commander. So it really does come down to acceptance or dispute of the data. |
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