I have to agree with Mark L. We discussed this I believe a year ago and all agreed that the typical auto engine used in a plane has way more compression, and in our KR's a much smaller prop than our brother certified engines with big 70 inch props or so, and low compression. Auto engines that keep rotating after shut down are typically in a straight shift car, which makes the load on the drivetrain great enough to overcome the compression of the engine. It can also happen in automatic cars depending on their design and speed the engine quits. More typically the transmission loses pressure and disconnects the couple to the engine, allowing the engine to stop rotating. In much the same way, the prop being small, and engine with more resistance due to higher compression, it stops regardless why the engine loses power, ie: fuel, ignition, internal, etc...
Certified engines will do the same given the right circumstances. The nice thing about ours quiting is that the prop drag is reduced, making an effective glide better. Also it has been my experience that if a good battery is on board, a higher compression engine (within reason say 8 or 9 to 1) will start easier than our certified cousins. Fewer rotations is typically required to restart. Your results may definitely vary... Colin N96TA
