Intake And Exhaust System; Intake System; Breather System (A Reductor To Intake Air System Of Blowby Gas) - Yanmar 3YM30 Sevice Manual

7. Intake and exhaust system

7. Intake and exhaust system

7.1 Intake system

Air enters in the intake silencer mounted at the end of
the intake manifold (rocker arm cover). It is fed to the
intake manifold and then on to each cylinder.
Exhaust gas goes into exhaust manifold (in the fresh
water tank) mounted on the cylinder head outlet. After
cooling, the exhaust gas enters the mixing elbow, which
is directly connected with the exhaust manifold, and is
discharged from the ship along with seawater.
When the inside of the intake manifold becomes dirty,
intake air resistance is increased and reduces engine
power. Periodically check the inside of the intake
manifold. In the same way, the intake air silencer
should be checked for dirt periodically and cleaned.
Care should also be taken to insure there is no air
leakage.
Do not operate with the intake air silencer removed.
7.1.1 Breather system (A reductor to
intake air system of blowby gas)
Emitting blowby gas is harmful to natural environment.
Therefore blowby gas reductor is adopted as breather
system.
Some of the combustion gas passes through the
clearance between cylinder and piston, and flows to the
crankcase. This is said as blowby gas. While it passes
into cylinder head and rocker arm cover, the blowby gas
mixes with splash oil, and becomes oil mist-blowby gas.
The gas passes through the baffle plate inside a rocker
arm cover. And it passes through a diaphragm assy,
and reaches a intake silencer. The gas is reduced in the
combustion chamber.
Pressure inside a crankcase is controlled by the
function of the diaphragm assy, and suitable amount of
blowby gas is reduced in intake air system.
[Disassemble]
When a rocker arm cover is taken off, check whether
oil or the like enter the diaphragm space from a small
hole on the side of a diaphragm cover or not without
disassembling the diaphragm.
Intake pipe
Diaphragm cover
Spring
Center plate
Diaphragm
Breather baffle
Baffle plate
(Breather system component)
Blowby gas
(Blowby gas flow)
149
Cylinder head
Intake silencer
Rocker arm cover
Intake manifold
Diaphragm
Spring
Diaphragm cover
Baffle plate
Rocker arm
cover
Cylinder head