WAVEFORMS - INJECTOR PATTERN TUTORIAL
RELATIONSHIP BETWEEN DWELL & DUTY CYCLE READINGS TABLE (1)
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Dwell Meter (2) Duty Cycle Meter
1
ø
.................................................... 1%
15
ø
.................................................. 25%
30
ø
.................................................. 50%
45
ø
.................................................. 75%
60
ø
................................................. 100%
(1) - These are just some examples for your understanding.
It is okay to fill in the gaps.
(2) - Dwell meter on the six-cylinder scale.
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THE TWO TYPES OF INJECTOR DRIVERS
OVERVIEW
There are two types of transistor driver circuits used to
operate electric fuel injectors: voltage controlled and current
controlled. The voltage controlled type is sometimes called a
"saturated switch" driver, while the current controlled type is
sometimes known as a "peak and hold" driver.
The basic difference between the two is the total resistance
of the injector circuit. Roughly speaking, if a particular leg in an
injector circuit has total resistance of 12 or more ohms, a voltage
control driver is used. If less than 12 ohms, a current control driver
is used.
It is a question of what is going to do the job of limiting
the current flow in the injector circuit; the inherent "high"
resistance in the injector circuit, or the transistor driver. Without
some form of control, the current flow through the injector would
cause the solenoid coil to overheat and result in a damaged injector.
VOLTAGE CONTROLLED CIRCUIT ("SATURATED SWITCH")