Sea-doo Bombardier, Руководство пользователя, Страница: 45 / 123

03-16
SECTION 03 - ENGINE PREPARATION
CALCULATING THE
COMPRESSION RATIO
Uncorrected Compression Ratio
The uncorrected compression ratio of an engine is
the volume of a cylinder plus the volume of the
combustion chamber divided by the volume of
the combustion chamber.
C.R. =
WHERE:
C.R. = Compression Ratio: 1
V
1
= Volume of the cylinder
V
2
= Volume of the combustion chamber
π
= 3.1416
B = Bore (cm)
S = Stroke (cm)
1. BDC
2. V
1
3. TDC
4. V
2
5. Stroke
EXAMPLE:
B = 76 mm
S = 64 mm
V
2
= 27.6 cc
C.R. =
C.R. = 11.5: 1 UNCORRECTED
Uncorrected Compression Ratio of Production
Engines
• 11.5: 1 engine type 587
• 12.2: 1 engine type 657
• 12.25: 1 engine type 717
• 11.25: 1 engine type 787
• 11.75: 1 engine type 947
Corrected Compression Ratio
In a 2-cycle engine, a portion of the stroke is
opened to the atmosphere via the exhaust port.
The corrected compression ratio is calculated as
the piston closes the exhaust port.
C.C.R. =
WHERE:
C.C.R. = Corrected Compression Ratio
V
3
= Volume of a cylinder with piston just closing
the exhaust port
V
2
= Minimum combustion chamber volume
1. Exhaust port just closed
2. V
3
3. TDC
4. V
2
5. Stroke
V
1
V
2
+
V
2
-------------------
B
2
S
π × ×
4
--------------------------
F01D6NA
5
1
2
3
4
V
1
7.6
2
cm 6.4 cm
× π ×
=
4
---------------------------------------------------------------------
290.3 cc
=
290.3 cc 27.6 cc
+
27.6 cc
------------------------------------------------
V
3
V
2
+
V
2
-------------------
F01D6OA
5
1
2
3
4