Operation Of The Rotary Valve; Intake And Secondary Compression - BOMBARDIER 1996 Ski-doo MX Z440 Handbook

OPERATION OF THE ROTARY VALVE

Controlling the opening and closing of the intake port is also a critical factor in the volumetric
efficiency of an engine. Best V.E.'S are obtained by asymmetrical intake timing (opening the intake
Port at about 140° B.T.D.C. and closing the port at about 60° A.T.D.C.) while also allowing for an
unobstructed intake tract
by a rotary valve inlet.
The rotary valve engine
snowmobile engines.
Simply stated, the design
the same RPM. Because
than a piston Dort enqine, a greater air/fuel mixture supply can enter the engine and remain in the
engine without spitback.
Basically, the rotary valve engine performs the same operation as the ordinary two-stroke engine.
The only difference being the location and operation of intake.
1 ) The intake port is positioned directly in the crankcase.
2) The opening and closing of the intake port is controlled by a rotary valve instead of the piston.
3) The rotary valve is driven by the crankshaft in a counterclockwise direction.

INTAKE AND SECONDARY COMPRESSION

FO1O6TS
1. Fresh charge from carburetor
04-28
to provide maximum airflow into the engine. This is best accomplished
is one of the more innovative concepts to be applied to two-stroke
produces more horsepower out of the same size engine displacement at
the aperture size and de~ree of openina exceed that of a piston port