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Carl |
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Are the price of a P-mag and one Slick close to the same cost? Shouldn't it just be an even trade? |
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Will someone with a completely different setup experience the same thing? Nigel mentioned that his tests were to see the impact timing changes have on performance and not as a definitive test of the P-mag's timing curve. Someone with a fixed pitched prop might experience different timing variations because their MAP / RPM numbers will be different, meaning the P-mag may select a different timing for each combination. |
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The good news is that you happen to have an available airframe, engine, and prop which are totally different from Nigel's, equipped with P-mags and an EI Commander, which you know how to use. There is data available. Here's what Michael Robinson found...with an entirely different airframe and engine, stock compression, and different RPM: http://www.vansairforce.com/communit...6&postcount=44 Short version: 100% power (0 MSL) 31.1"/2700 no power difference from 20 to 28 degrees Cruise at best power (8,500 MSL) 23"/2300 best timing 27~28 Cruise at Peak EGT (8,500 MSL) 23"/2300 best timing 30 Cruise at 50 LOP (8,500 MSL) 23"/2300 best timing 33 Parallels Nigel's observations very well, i.e. advancing past 30 or so is entirely non-productive when ROP, in particular at high power settings. All you get is less HP and higher CHT...yet the stock P-mag advance was delivering 35 degrees at 23" My own observations (which I'll be expanding in due course) are that when running ROP, my 8.9 angle valve motor may prefer even less advance. At 8500 and 65%, there is no detectable speed difference between 23 and 27 degrees, just a CHT increase, and that increase matches Nigel's observation of 2.5F per degree of advance. Recall that many certified angle valve motors have a choice of 20 or 25 degrees, and Lycoming backed timing down to 20 for a lot of them, including the 390. Maybe it's because they have a dyno, eh? |
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As Dan points out, you are in a perfect position to gather and present data - I'd encourage you to do so. Pmag and some of the other ignitions certainly broke new ground, but its time to get on board with developing a new understanding of ignition timing so we can take the next step. Ross' SDS products are the cutting edge today WRT tunability, but I know he'll add new features as soon as they become apparent. In other words, we've come a long way, but there is still plenty of work left to do. |
Thread Drift !!!
I have 2 P mags on a 150HP 0320 and as expected no problems. I purchased 2 EPI ignitions from Ross for a 8.5:1 0360 but stayed with AFP injection BECAUSE I didn't want to deal with the variety of sensors associated with direct electronic fuel injection ON MY CURRENT PROJECT.
Since then, I read reference to 100LL affects on O2 sensors. At this point I feel justified for not experiencing the cutting edge of performance. So, I hope this stimulates useful dialog... Let the flames begin ! |
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I know a lot about engines, but each time I think I know a lot about something, this group of folks here makes me feel like I know very little about anything. Great discussion. |
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..."customers selecting the E-Mag option, this would include replacing the Plain Magneto (on right of the accessory housing) with the E-Mag System. This would include a fully installed & tested unit at the Lycoming factory with all the required spark plugs, adapters and harnesses of the E-Mag EIS." ... ..."Therefore, each cylinder will have one aviation spark plug (for impulse magneto) and one automotive spark plugs (for E-Mag) installed." ... I did this because I am leaning toward purchasing a New Lycoming engine from Van's for my RV-8 under construction. Have not seen a better value than a new Lycoming from Van's. May be able to pickup at Lycoming factory if I have not built on the airpark lot that I want to buy. |
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