Volvo 819 E - Fuel Injection System Control Unit

Group 28 Ignition sys t ems
Des ign and fun ct ion E ngine load in f ormation
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2 \.----t-rT
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F uel injection system control unit (LH-2.1. LH-2.2. LH-2.4)
The fuel syst em con trol unit (1j supplies the ignition system control uni t (2) with info rmat ion on engine load. Th is
based
on signals from an air mass meter (3), th e quan t ity of induc t ion air being used as a measure of th e l oad.
Signal
The air mass mete r con t inuously measures the quant ity of air drawn into the engine and delivers a variable signa l to
the injection system control uni t, in which the signal is conve rted into digital fo rm and used to compu te th e quantity
of fuel to be injec ted. The signal is also relayed to the ignition syst em cont rol uni t. The digital signal co nsists of a
series of
current pulses (4) of a durati on (5) proportional to the load.
Advantages
This type of load info r ma t ion is used in E2-K systems with LH-Jetronic fuel injec ti on and Rex-I systems w i th th e Regi-
na injec ti on system, and is more accurate than that supplied by a vacuum line fr om the intake manif old. In addition,
the air mass meter responds more quickly and is no t subject to measurement e rr ors caused by variations in air den -
sity. (In o
ther words, it is independent of air temperature and heigh t above sea leveL)
• Should the fuel system control unit fail. for any reason. to supply
th e ignition system control unit with a load signal, the latter will
compute the timing on the basis that max. load conditions prevail when the throttle
has opened.
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