Haltech E6M - Manual (Page 115)

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B.2 Direct Fire Ignition
B.2.1 Ignition Outputs
There are two forms of Direct Fire Ignition. One is to have one coil per spark plug (usually
mounted on top of the plug), where each cylinder is individually controlled by its own coil.
The second method is to use a waste spark. The plugs are paired into companion cylinders
(cylinders with the same TDC but on different strokes). Each coil fires sparks on a pair; one
on the compression stroke and the other on the exhaust stroke (the waste spark). Both
methods mean that the distributor can be discarded.
With either method, the importance of the set-up to the E6H/E6M is the number of coils. Each
coil needs its own igniter and ignition output. On a four cylinder using waste spark, two coils
are used, and, therefore, two ignition outputs are needed. In this case, channel 4 is used as the
second ignition channel, making it unavailable for digital outputs. The six cylinder with waste
spark is similar. It requires 3 coils and 3 ignition channels. For this set-up, channels 4 and 5
become ignition channels 2 and 3 respectively, and neither is available for Digital Outputs.
A V8 becomes a little difficult. It requires 4 coils and 4 ignition outputs, but we have no more
available outputs. Therefore, we take one of the fuel drivers and use it as an ignition channel.
The E6H/E6M uses channel 1 (as marked on the loom) for this purpose. This channel
becomes ignition channel 4. There are some trade offs with this though. Multipoint is the only
available injection mode. The batch fire and staged modes are not available. If 8 low
impedance injectors are used in combination with 4 ignition coils then a Haltech External
Driver Box is needed.
There are some other cylinder configurations to consider. 1, 2 and 3 cylinder engines need 1,
2 and 3 ignition outputs respectively. Alternatively, a two cylinder can use one ignition output
and use a direct fire coil with waste spark; this can only be done if the engine is not odd fire.
Five cylinder engines cannot run Direct Fire as they cannot use waste spark and therefore
need 5 ignition outputs. Also, there are not enough outputs to run Direct Fire on 10 and 12
cylinder engines.
B.2.2 Synchronising
On a distributed engine the E6H/E6M does not need to know the engine position. It is told to
generate a spark which the distributor sends to the correct spark plug. With Direct Fire, the
E6H/E6M needs to know engine position so that it knows what coil to trigger next. To do this,
the ECU needs to receive a Synchronisation Event (Sync. Event). One form of Sync Event is
missing teeth on a multitooth wheel. The most common Sync Event though, is a Home
trigger. This trigger needs to occur before the main trigger for cylinder (or coil) one,
indicating that the next main trigger is for cylinder one. This trigger should not occur at the
same time as the main trigger.
When the engine is started, the ECU will not generate a spark until it receives a Sync Event.
After that, the ECU fires each ignition output sequentially until it gets to the last output. It
then expects to receive another Sync event. If it does not receive this event, it will not fire
another spark until the event occurs. If the Sync event is received, ECU ignition is reset to
coil one and normal ignition results.