Haltech E6K - Manual (Page 87)

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CHAPTER 14 IDLE SPEED CONTROL
14.1 Description
A bipolar stepper motor may be used to control the ingress of additional air to the engine
while the throttle is closed. This is useful for maintaining steady idle under changing load
conditions, e.g. as air conditioner compressors or headlights are switched on and off. The
stepper motor may also be programmed to increase the idle rev-rate just after starting, or
while the engine is still cold.
14.2 Using the Idle Speed Motor
In order to use the idle air control function, you must have the following:
- a suitable idle speed stepper motor
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; OR a suitable Bypass Air Control Valve
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- an idle air circuit bypassing the throttle plates;
- E6K programming software and cable.
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NB: use only a bipolar stepper motor with two separate windings (four wire), each with at
least 30 ohms resistance. Your Haltech
TM
representative can supply you with a suitable motor.
Use of three- wire stepper motors may damage the E6K ECU.
∗∗∗∗∗∗∗∗
NB: If you wish to use a Bypass Air Control (BAC) valve to operate Idle Control, you must
carry out all of the same settings as what one would do for a normal stepper motor. The only
difference is that you should disable Idle Speed in the first entry in the Idle Control software
and select BAC as one of the four PWM outputs instead. This will ensure that you are using a
BAC valve to do Idle Control and have turned the stepper motor output off. See Section 16
for more detail on the BAC option and PWM outputs.
The idle air circuit draws filtered air into the engine around the throttle plate, as suggested in
figure 14-1. Normally this is done via an air bleed into the manifold. A valving arrangement is
used so that the idle speed motor pinches off the air into the engine. When the engine is below
the desired idle speed, the stepper motor's plunger retracts to allow more air to enter the
engine. When the idle speed is too high, the plunger extends. If your engine does not already
possess an idle air bypass circuit, a suitably machined aluminium block is available to mount
the idle speed motor. A balancing system or plenum arrangement should be used if employing
individual throttle bodies, so that all cylinders benefit equally from the additional air.
NOTE: You must ensure that the manifold's air bypass aperture is sufficiently
small so as to not over-rev the engine when stepper motor is fully retracted.
Fitting a large idle air valve to a small capacity engine can lead to poor idle
control and dangerously high engine rpm with no throttle control.