Brodhead Pietenpol Association

Original Posted By: Patrick Panzera
Is there any good reason not to let the mags fire also on the exhauststroke if speed of rotation is such that this happens? It seems that themags on Danny Mains Piet are set up this way.Phil ________________________________________________________________________________

Original Posted By: John Greenlee
My last post an hour ago my fingers got ahead of my brain and said this " and sincethe mag runs off the cam, which runs at half of that speed" The mag runs off the crank ( usually)waltMy last post an hour ago my fingersgot ahead ofmy brain and said this and sincethemag runsoff the cam, which runs at half of that speed The mag runs off the crank (usually)walt________________________________________________________________________________

Original Posted By: jmcnarry(at)techplus.com (John McNarry)
Subject: Pietenpol-List: Re: to correct my last post>Is there any good reason not to let the mags fire also on the exhaust>stroke if speed of rotation is such that this happens? It seems that the>mags on Danny Mains Piet are set up this way.>PhilMany of the newer electronic ignition systems on four stroke automobiles doexactly this. Well almost, they fire on overlap. TDC inbetween exhaust andintake while the cylinder is scavenging. Sometimes referred to as the "wastespark system" this system uses no distributor but instead has a coil foreach pair of "companion cylinders". The secondary winding of each coil has aspark plug connected at each end. A six cylinder engine would need threecoils. A four would then require two. Interestingly the polarity of eachplug in a pair is opposite. Coil polarity used to be a big item in the autoworld. Mags fire every second plug at the opposte polarity as the armaturewindings cut across the flux lines the opposite direction each halfrevolution of the mag.John Mc________________________________________________________________________________

Original Posted By: walter evans
Subject: Pietenpol-List: Re: to correct my last post>Is there any good reason not to let the mags fire also on the exhaust>stroke if speed of rotation is such that this happens? It seems that the>mags on Danny Mains Piet are set up this way.>Phil>________________________________________________________________________________

Original Posted By: walter evans
Phil Phillips wrote:> > Is there any good reason not to let the mags fire also on the exhaust> stroke if speed of rotation is such that this happens? It seems that the> mags on Danny Mains Piet are set up this way.Perhaps premature wear of the ignition system?Pat________________________________________________________________________________

Original Posted By: Phil Phillips
Phil,I'm not sure. But if this will help, my Rotax 447 ( and all 2 strokes Ithink) fire both cylinders at the same time. This means one is incompression and the other down ready to exhaust.walt-----Original Message-----