Current, Pulse width, Duty cycle – MoTeC M84 User Manual

Page 27: Ignition system, Ignition system types, Cdi distributed

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MoTeC

Installation

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will operate correctly at 2.5 bar (29 psi) and some will operate up to 5 bar (73
psi).

Current

Different injectors require different operating currents. The ECU injector drives
must be programmed to suit the injector using the Injector Current setup
parameter.

Pulse Width

The amount of time that the injector spends open during each injection pulse
is called the Injector Pulse Width and is measured in milliseconds
(thousandths of a second), abbreviated as msec.

The injector pulse width is controlled by the ECU according to the ECU,s
calibration data.

Duty Cycle

The Injector Duty Cycle is a measure of the ratio of the time the injector is
open (pulse width) to the available time per engine cycle. For example, if the
injectors were on for half the available time then the duty cycle would be 50%.

The maximum allowable duty cycle is about 85 percent, beyond this the
injector does not have time to open and close and is therefore open
continuously and cannot deliver more fuel.

The ECU will set a Diagnostics Error if the duty cycle exceeds the maximum
allowed duty cycle.

Ignition System

Ignition System Types

Many different types of ignition systems are available with some better suited
to different applications than others.

CDI Distributed

CDI systems are suited to high revving engines with 8 or more cylinders and
are generally capable of at least 12,000 RPM on an 8 cylinder. CDIs are also
good at firing fouled plugs.

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