OPERATION No MA.IE. 144-00
: Chnract~~ristics o/ the H I,-jctrortic P dectrnr~ir
/i/c,1 iujcctim splcm.
Op. MA.IE. 144-00 17
SUPPLEMENTARY AIR CONTROL ( 1 ) :
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At idling speed and when cold, the engine must produce more torque so as to counteract increased resistance
caused by friction. In addition to an enriched air fuel mixture, the engine also needs, when starting from cold
and during the warming-up period, to be supplied with supplementary air. The E.C.U. compensates for this
supplementary air by providing more fuel; the engine therefore has a larger amount of mixture at its disposal
to reach normal running temperature. The supplementary air control fitted in parallel with the throttle butterfly
supplies the supplementary air. The supplementary air control is heated only when the engine is running, and
its heater winding is supplied electrically as long as the ignition is switched on.
The location of the supplementary air control ‘on the engine block was selected for its good heat transfer charac-
teristics, and so as to subject the unit to the changing ambient temperature of the engine.
The opening section of the supplementary air control is automatically .adjusted according to the temperature, so
that the required idling speed is maintained regardless of engine temperature. When the latter increases, the air
channel is gradually reduced, until it is completely closed when the coolant temperature reaches approximately
+ 60” C.
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The supplementary air control is situated at a representative spot fo.r engine running temperature. A bi-metal
spring actuates a rotary valve thereby altering the size of the air passage. Electric heating has the advantage
of allowing the. supplementary air to be adjusted at pre-set times.
SWITCH ON THROTTLE BUTTERFLY SPINDLE :
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The switch on the throttle butterfly spindle contains two contacts the idling speed contact, and the.full load contact.
The control contact, which.slides along a slot, closes the idling speed contact or the full load contact for a given
position of ‘the butterfly. The’ E.C.U. analyses the signals received so as to adjust the duration of injection.
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