Ignition Timing Controls; Ignition And Combustion Orders; Ignition Timing; Operations - TOHATSU MFS 60A Service Manual

Fuel System (Fuel Injection)
(2) Ignition Control
ECU's microcomputer is programmed with ignition timings best suited to engine's operating conditions. ECU obtains
information about engine operating state such as revolution speed, throttle opening, manifold pressure (air intake vacuum
pressure) and cooling water temperature based on the signals from the abovementioned sensors to generate ignition
timing signal at the most suitable timings.

1) Ignition Timing Controls

Controls of ignition timing is classified into two controls, which are correction of ignition timing during normal operation
and fixing of ignition timing (at engine starting and when an abnormality has occurred). In either case, ECU corrects
ignition time or fixes it to the base.
• Basically, ignition timing is determined on engine revolution speed and manifold pressure (intake air vacuum pressure).
• Signals that are used for correction of ignition timing includes cooling water temperature, manifold intake air
temperature, change of pressure at acceleration/deceleration under atmospheric pressure, and engine revolution
speed.
• Ignition timing is fixed to the base at acceleration, deceleration, when high speed ESG is on, low speed ESG is on, or
when hydraulic pressure is reduced.

2) Ignition and Combustion Orders

No. of Ignitions : Once per revolution per cylinder (around the end of compression and exhaust strokes)
Ignition Order : #1
Combustion Order : #1

3) Ignition Timing

Ignition timing is set as described below.
Model
MFS60A

4) Operations

• At Engine Starting and During Warm-up
The engine is started, the ignition timing is fixed to the TDC.
The input signal and the engine temperature, manifold intake air temperature, engine speed and atmospheric pressure,
on the basis of the programs stored in the ECU, the microcomputer determines the ignition timing after starting.
• During idling and low speed running
When ECU receives manifold pressure (intake air vacuum pressure) signal and input signal from pulser coil (engine
revolution speed signal), it controls ignition timing so that idling and low speed revolution speeds stabilize.
• During normal operation
Microcomputer determines ignition timing in accordance with ECU's program by using cooling water temperature,
manifold intake air temperature, atmospheric pressure and engine revolution speed as input signals. The maximum
timing during normal operation is BTDC 25°.
• During acceleration/Deceleration
When engine revolution speed changes much and is reduced below (or exceed) a setting value, ECU determines that
engine is accelerating (or decelerating), and microcomputer determines the ignition timing based on the program
installed in ECU.
• At engine over-revolution
When engine revolution speed exceeds the maximum allowable value (6,200r/min), ECU stops feeding of fuel to control
the revolution based on pulser coil signals. This is the state that engine high speed ESG is "ON".
• Engine low speed ESG is "ON".
When any of the following state has been detected, engine revolution speed is controlled to 2,800r/min to prevent or
reduce engine damage. This is the state that engine low speed ESG is "ON".
• Engine is overheating. : Engine temperature sensor detects 100° or higher.
• Engine hydraulic pressure is low. : Oil pressure switch ON (24.5 kPa (3.6 PSi) [0.25 kg/cm
seconds or longer.
4-4
#2 #3 #1 #2 #3
#3 #2
Range of Ignition Angle
ATDC 5° to BTDC 20°
#1 (every 120 degrees of crank angle)
#1 (every 240 degrees of crank angle)
Engine Starting
TDC 0° ATDC 5°±5°
Idling Accelerating
BTDC 20°
2 ] or less) is detected for 5
4st 60 2019