62 Auto Fundamentals
the rotor to “walk” around the fi xed gear when
the eccentric shaft turns. This walking action
causes the rotor to revolve around the eccentric
shaft rotor journal in the same direction as the
eccentric shaft. At the same time, the walking
action keeps all three rotor tips constantly close
to the wall of the rotor housing.
This planetary motion of the rotor con-
stantly changes chamber volume between each
rotor face and rotor housing. The change in
volume is the principle used for engine opera-
tion. Study the rotor movement in Figure 3-30A
through Figure 3-30E. We will follow one rotor
Air filter
Crank-driven spur belt
operates overhead cam
and fuel injection pump
Preheater
(”glow plug”)
Throttle
cable
Injector
nozzle
Fuel lines
to cylinder
head
Belt-driven
injection pump
Engine oil filter
V-belt to
water pump
& alternator
Figure 3-28.
Four-cylinder diesel engine. Note the use of a timing belt
instead of gears or chains.
VW
face through the complete cycle. Note that this
face lies between rotor tips A and B.
Rotary Engine Rotor Cycle
In Figure 3-30A, rotor face A and B has
rotated past the intake port. As tip B passed the
intake port, the chamber volume increased. This
action forms a vacuum, causing the fuel mix-
ture to fl ow into the enlarged chamber area. In
Figure 3-30B, the rotor has continued to rotate
clockwise, and in so doing, reduced the cham-
ber size, compressing the fuel. When rotor face
A-B has turned to the position shown in C, max-
imum compression is applied.
Figure 3-29.
Cross-section of a V-6 diesel engine. Note how similar
this engine is to some gasoline engines.
Jaguar
A
A
A
A
A
B
B
B
B
B
C
C
C
C
C
Exhaust
gases escape
Expanding gases
push on piston
Spark ignites
compressed
air-fuel mixture
Air-fuel mixture
is compressed
Eccentric shaft
Rotor
Eccentric shaft
rotor journal
Intake port
fuel mixture
enters here
A Intake
B Compression
C Ignition
D Expansion
E Exhaust
Exhaust
port
Figure 3-30.
Rotor action within the rotor housing. The rotor internal gear and housing gear are not shown.
NSU