[SEL] The McVickerish Engine

[jbcast at charter.net]

---- "Kangas wrote: 
> Thank you Arnie and Patrick but I'm still a little puzzled. If neither the exhaust nor intake valve is opened at any time while the engine is missing wouldn't that be like a Diesel using it's Jacob brake? The compression without firing will stop the engine very quickly if it was not for the vehicle's momentum forcing the engine to keep turning over.

The jake brake was invented because a Diesel has little braking on it's own. A gasoline engine has a throttle plate and vacuum helps slow the engine. Exhaust brakes use a butterfly in the exhaust to restrict flow and build back pressure. Modern variable displacement engines close both valves on a cylinder, the compression acts as a spring and uses very little energy.
J.B. Castagnos
Belle Rose, LA