Yanmar EF-494T, Technical Manual

Page: 97 / 239

3 ENGINE 3 ENGINE
EF494T TM 06/2011 edition 89
3.2.3 Revolution timer
Clean exhaust gas is assured over the entire
range of engine speeds by changing the fuel
injection timing according to the engine speed.
At low engine speed
Fuel injection is less affected by the viscosity of
fuel and starts after the sub-port has been
closed. (At a low engine speed, the injection
timing is delayed.)
At high engine speed
Fuel injection is affected by the viscosity of fuel
and starts even if the sub-port is not closed.
(A) Low
(B) Engine rpm
(C) High
(D) Delay
(E) Timing
(F) Advance
(G) Sub-port
(H) Plunger
(I) Main port
(J) Load timer
3.2.4 Load timer
The fuel injection timing is changed in
accordance with the load condition of the engine,
thereby optimizing the injection timing over the
entire range from the no-load condition to the full-
load condition and making exhaust gas clean.
When the upper leading part of the plunger goes
beyond the main port, fuel injection starts.
Once load is applied, the plunger starts operating
and the stroke length of the upper part of the
plunger increases. The fuel injection timing is
delayed accordingly. (The injection timing is
delayed when load is applied.)
(A) Upper leading part
(B) Main port
(C) Fuel
(D) Main leading part
(E) Plunger
(F) Fuel increase
(G) Fuel decrease
(H) Load increase
(I) The injection timing is delayed and the stroke
length of the upper leading part increases as the
load increases.