Haltech E6GMX - Manual (Page 92)

E6GMX Manual
92
APPENDIX B IGNITION AND INJECTION OUTPUTS
Ignition
The simplest of ignition systems is the distributed setup. The distributor uses a rotor button
and cap to distribute the spark to the correct cylinder. In most cases the distributor will
contain a triggering device used to trigger an ECU or an ignition module directly.
Rotor phasing (GM Bypass Ignition module)
If the engine is currently fitted with a GM Bypass Ignition Module the Rotor phasing can be
checked quite easily. The first thing to do is to remove the ECU, so that neither the standard
ECU nor the E6GMX is connected. Crank the engine. The Ignition module has the ability to
fire the ignition without the ECU being connected. The Ignition module will fire where it
believes is 10 deg BTDC. If the spark timing is not at 10 deg BTDC, move the distributor
until it is firing at 10 deg BTDC. Lock the distributor and do not move again. Plug in the
E6GMX.
Rotor phasing (No GM Bypass Ignition module)
A common problem that arises when distributors are used is cross-firing. This usually occurs
when the rotor button is not in the correct position when the ignition output is fired. To
correctly set up the distributors “Rotor Phasing” you will need to do the following:
Calculate the minimum and maximum timing requirements of the engine. For this example
we will use the following:
Minimum Timing 10° BTDC
Maximum Timing 40° BTDC
This gives a mid point, half way between the minimum and maximum timing, of 25°. Rotate
the engine to this value (25°) BTDC. Align the centre of the rotor button with the plug lead
terminal for cylinder number one. Lock the distributor into place and do not move it.
Now rotate the engine to 70° BTDC. i.e. move it back 45° crank degrees. This is now the
position where the sensor inside the distributor will need to be aligned with a triggering point.
(This may be a magnetic sensor tooth, or a chopper disc window). Move the plate the sensor
is mounted on so that this occurs (Do not rotate the engine!).
If it is not possible to move the sensor, it will be necessary to rotate the trigger wheel relative
to the shaft and the sensor.
Rotor phasing is not only a problem on distributors with advance mechanisms. Several factory
distributors have their triggers at points outside 60 - 100°. It is not advisable to just rotate the
distributor until the trigger is within this window. Care must be taken to ensure that the rotor
phasing will not cause a problem.