Harry Francis sometimes has trouble posting to the forum. He sent this to me and Im just forwarding it. Ed
_____ From: Harry L. Francis [mailto:[email protected]] Sent: Thursday, November 19, 2009 2:14 PM To: Ed Burkhead Subject: Re: [ercoupe-tech] Proper mag check rpm HI Ed, My Continental Engine Overhaul Manual , on Page 109 : Table XXI Test Operating Limits, gives a slightly different view. Form X-30010 FAA apprioved January 1984. Mag Drop at full throttle(RPM) : C-75 C-85 C-90 0-200 75 75 *100 *100 *At 1800 RPM (let temperature settle out before taking magneto drop) I think the lower RPM setting is due to the C-90 and 0-200 have the Marvel Carb, and at full throttle the mixture is very rich, and can cause plug fouling. So by using the lower RPM throttle setting you have not yet attained the rich climb mixture setting of the carb.. ( the extra rich setting provides cooling ofd the engine at climb....apparently needed in the higher compresssion ratios of the C-90 and 0-200). Also the Ercoupe Supplied FAA Approved Airplane Flight Manual created for the D model, but is also applicable for the C and CD models...Stromberg Carb, both C-75 and C-85 engines... Page 6 Before takeoff: 4. full throttle 2050 RPM aprox. 5. Ignition Check -maximum 75 RPM drop either magneto. Complies with Continetal manual. With all that said, probably checking at 1800 is OK, (I really don't know why the difference specified RPMs in the C-90 and O-200.(check at 1800 rpm)...but may be because they have different carburetters. (Marvels), with fuel jetting that goes full rich at full throttle, and at 1800 rpm this full rich system is not yet working. Allowable RPM loss for the C-90 and 0-200 is 100RPM @1800 RPM test. Running this engine (with Marvel Carb) at low loads on a check is likely to carbon up the spark plugs due to full throttle full rich mixtures. When checking the ignition system ( Mags), at full throttle, or at a slightly lower RPM, the engine loss of RPM should be slight, and no more that 75 rpms on either mag, and most importantly the engine should still operate smothly without missing. Regards, Harry _____ From: Ed Burkhead <[email protected]> To: ety <[email protected]> Sent: Wed, November 18, 2009 11:05:42 PM Subject: [ercoupe-tech] Proper mag check rpm I cant cite the source for this first item because I read it in a magazine article. The article went into detail on mag and engine problems and how to diagnose them. The article said that normal mag checks should not be done at a high rpm because, at higher rpm numbers, some kinds of problems are masked. If I remember correctly, they recommended doing the mag check at 1500 rpm. This is the number I used. However, the O-200 Operators Manual says warmup should be done at 1200 rpm and, Increase engine speed to 1700 RPM only long enough to perform the following checks: then it lists the mag check procedure. In the Overhaul Manual for the C-75, C-85, C-90 and O-200, Section VII OPERATING INSTRUCTIONS (page 40), it instructs the operator to open the throttle gradually until the engine is running at approximately 1200 R.P.M. Do not exceed this speed until oil temperature has reached 75° F. In the next section, GOUND TEST, it says to do the mag check but nowhere does it say to increase the rpm above 1200 rpm. http://www.pj260. com/Continental/ O-200%20Manual. pdf <http://www.pj260.com/Continental/O-200%20Manual.pdf> Ed
