Manual

F10A and F10A-8 ONLY

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

stepp er motor may also be programmed to incr ease 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 sp eed stepp er motor∗

∗∗

∗; OR

a suitable Byp ass Air Control Valve∗

∗∗

∗

- an idle air circuit by p assing the throttle plates;

- F10A programming software and cable.

∗

∗∗

∗NB: use only a bipolar stepp er motor with two sep arate windings (four wire), each with at

least 30 ohms resistance. Your Haltech

representative can supply you with a suitable motor.

Use of three- wire stepper motors may damage the F10A 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 outp uts 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 sp eed motor p inches off the air into the engin e. When the engine is below

the desired idle sp eed, the stepper motor's p lunger 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 by p ass aperture is sufficiently

small so as to not over-rev the engine when stepper motor is fully retracted.

Fitting a lar ge idle air valve to a small capacity engin e can lead to p oor idle

control and dangerously high engine rpm with no throttle control.