lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> John writes <<I have a single electronic ignition (EI by Klaus Savier) and a mag with both ignitions set at 24 degrees BTDC at manifold pressures greater than 25" <<snip>> I believe that detonation should be even less likely in my configuration then standard dual mags. I do like the system, however, it could be the source of my heating problems during climb. I'm open for any suggestions.>> How do you know that both plugs are firing at the same time? The magneto is set at a static timing point of say 20 DBTDC but that isn't when the plug fires. When the engine is running there are mechanical and electromagnetic delays that cause the plug to fire later. How much later is a good question. With two mags, you can assume that the delay is the same, so how long it is doesn't really matter, but with one mag and one EI, who knows? Your fuel flow is dropping because your charge density is falling due to heat (the intercoolers can't keep up). Remember that you can maintain manifold pressure while charge density is dropping as the charge gets hotter. IMHO, if you increase you fuel flows and fly 10-20 KIAS faster in the climb your ROC will be about the same but cooling will be improved. I suspect that in the mid 20s FLs you will need to drop your VSI to 500-700 FPM. If this doesn't work then you are back to ignition timing and/or improving cooling through the engine. I tested 25 degrees static advance early in my flight test program and saw detonation at altitude. I also know that many conventionally baffled engines have had to resort to increasing the discharge area ("Dolly Parton" cowl) to get adequate cooling. Cooling on the IV is marginal, so small changes in speed and attitude can mean a big change in engine temperatures. During flight testing prior to the cross country race I would see a 10-20 degree rise in CHTs after a 180 degree standard rate turn at FL270 and 94% power. Talk about touchy. Regards Brent Regan LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com.