BRP ski-doo MACH Z 1000 SDI, Руководство пользователя

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SECTION 05 - ENGINE PREPARATION
MMC2005-001_05A.FM
05-7
1. Squish area
If the squish clearance is increased, a loss in pow-
er will occur while too small a squish clearance will
lead to detonation.
The squish clearance can be measured by insert-
ing a piece of rosin core solder into the combus-
tion chamber, rotating the engine through TDC, re-
moving the solder and measuring the thickness of
the compressed solder.
The solder should be inserted above and in line
with the wrist pin. Measure the squish on both
sides of piston as it may vary from side to side.
1. Solder
2. Flattened area
CAUTION: Do not use acid core solder; the acid
can damage the piston and cylinder.
OPERATION OF THE RAVE VALVE
NOTE: Rave stands for Rotax Adjustable Variable
Exhaust.
Theory
For a two-stroke-cycle engine to have high power
capacity at high crankshaft speeds, a high volu-
metric or breathing efficiency is required and the
fresh charge losses must be minimized. The result
is achieved by opening the exhaust port early
(94.5° BBDC) and utilizing the resonant effects of
the tuned exhaust system to control fresh charge
losses.
When an engine of this design is run at a medium
speed, efficiency falls off quickly. The relatively
high exhaust port effectively shortens the useful
power stroke and because the exhaust system is
tuned for maximum power, there is a large in-
crease of fresh charge losses. As a result, the
torque decreases along with a dramatic increase
of the specific fuel consumption. Higher torque
along with lower fuel consumption can be ob-
tained at lower engine speeds if the time the ex-
haust port is open is shortened.
BOMBARDIER-ROTAX has patented a remarkably
simple system to automatically change the ex-
haust port height based on pressure in the exhaust
system.
1. Guillotine
2. Diaphragm
3. Return spring
4. Exhaust port
5. Red plastic adjustment knob
Located above the exhaust port is a guillotine-type
slide valve (item 1). This rectangular valve is con-
nected by a shaft to a diaphragm (item 2) which is
working against the return spring (item 3). Two
small passages in the cylinder just outside the ex-
haust port (item 4) allow exhaust gas pressure to
reach the diaphragm. As the throttle is opened and
the engine begins producing more power, the
pressure against the diaphragm will overcome the
pressure of the return spring and the RAVE valve
will open.
F01D5WA
1
F01D64B
2
1
A18C01A
1 5
3
2
4