spark plugs MITSUBISHI ECLIPSE 1990 Service Manual

IGNITION SYSTEMELECTRICAL - Engine Electrical8-25
I
Sensors
Engine control unitlgnltlon switch
Battery
11 IPower transfstor
hhP 1
Ilgnltion coil
C To tachometerTerminal for engine
speed detectton
6ELOO45The ignition system is a two-coil ignition system that
supplies sufficient energy for ignition up to high
speeds. This engine does not have a distributor
since the engine control unit directly activates the
power transistor for ignition timing control.
The functions and controls of the engine control unit
and various sensors that control the ignition timing
are described in the next chapter, IGNITION CON-
TROL SYSTEM.
This ignition system has two power transistors and
two ignition coils. Power transistor “A” controls the
primary current of ignition coil “A” to activate thespark plugs of the
No.1 and No.4 cylinders.
Similarly, power transistor
“B” controls ignition coil
“B” which activates the spark plugs of the
No.2 and
No.3 cylinders. In this way, spark plugs of two
cylinders are activated but actual ignition takes placeonly in the single cylinder that is on its compression
stroke, because the other is on its exhaust stroke at
that time.
Power transistors “A” and “B” are activated by
signals from the engine control unit, that controls
which cylinder is fired at what time.

s’ y _._----,_ - k - ..-_ _ _
ENGINE- Base Engine9-7I
BASE ENGINE
Valve seat
Squish area
Spark plug hole
Exhaust portintake port
Piston O.D.
6EN0076Camshaft lubricatingValve guide
6ENO246Camshaft lubricating
oil passage
6ENO247
(1) The combustion chamber is of the pentroof(2) The spark plugs are located at the center of the
type. The two intake and two exhaust ports arecombustion chambers.
in a crossflow arrangement. There is a
squish(3) The camshaft bearings are placed at six loca-area provided in the combustion chamber,tions on the intake side, and six on the exhaust
which promotes turbulence, further mixing ofside (see next page illustration). The thrust load
the air-fuel mixture, and more efficient
combus-of each camshaft is transmitted to the No. 1
tion.
bearing.
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