Originally Posted by
Beeman
My brother in law has a snowmobile that reverses the engine rotation for reversing. Can anyone explain how that's done? It slows down rpms when you hit the switch, doesn't come to a complete stop but does start back up in the other direction. Does it simply fire on an upward stroke instead of downwards?
actually all engines fire while still on the up stroke about 6 to 10 degrees BTDC (before top dead center)
in the snowmobiles it is a computor controled process where it stops the fireing till it sences that the RPM are correct and it is nearly stoped then it fires about 20 degrees BTDC thus being too early it will push the piston down before it reaches TDC and cause it to start turning the wrong way then it immediatly fires at the normal 6 - 10 degrees again but in the oposite direction.
You can do this by accident when you accidently hit the kill switch on a snowmobile and just by luck pull it on at the right time, i think this is how it was invented (note; if it happened to you by accident you instantly realized something was wrong because it ran like crap and nothing happened when you hit the throttle, all you had to do was shut it off and re-start it and all was well)
He who has not cruised the back country in a 6x6 , has not lived life to it's fullest
A Mans level of mechanical education directly corresponds to the level pain suffered while getting it