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LP Engine G430(3.0L) Igntion System
Because it takes less time to reach full current, coil
saturation can be obtained at much higher engine
speeds. Also, since the current is much higher in the
HEI system, heat generation must be controlled so the
module can live. This is done by the dwell control
circuit in the module. What this circuit does is
electronically sense the primary current to see if
maximum current was reached in the last dwell period.
If maximum current was reached and no current
limiting took place, the dwell period will remain the
same. If current limiting did take place, the dwell
period will be shortened by turning on the primary
circuit later. Since the turn-ing off of the circuit is
always at the same time, the dwell period is shorter. If
maximum primary current is not reached, the primary
circuit is turned on soon-er giving a greater dwell
period allowing maximum current to be reached.
By using this circuit, the HEI system is able to put out
35,000 volts to speeds above 3000 engine RPM while
the conventional ignition system's maximum voltage is
reached about 1000 engine RPM and then begins to
fall off. Also, by using dwell control to reduce the time
that the current limiting is taking place, the operating
temperature of the system Is reduced, further
increasing the reliability and life of the HEI system.
Ignition Coil
So far we have only talked about the magnetic pickup
assembly and the module's role in greater available
voltage and energy, but the design and construction of
the ignition coil also affects the system's output.
The design requirements for the HEI coil was that it
would have a low primary resistance for reasons we
have already covered and have a size and shape that
may be mounted in the distributor cap. The primary
resistance was decreased by reducing the length of
wire used in the primary windings. Resistance of a
wire is determined by its length and diameter. As
length increases, resistance increases and as
diameter increases, resistance decreases. So by
reducing the length of the wire used in the primary
winding, low resistance is possible with a reasonable
wire diameter. In the oil-filled ignition coil used with
conventional ignition systems, the primary winding is
wrapped around the secondary winding and the
secondary winding is wrapped around the iron core
(figure 6-7). The HEI coil has the secondary winding
wrapped around the primary winding and the primary
winding is wrapped around the iron core. The HEI coil
is not oil filled, the windings are covered in an epoxy
compound for protec-tion against moisture and arc-
over within the coil.
Figure 6-7 HEI and Conventional Ignition Coil Construction
131-063
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