Variable Trigger Settings

[petert 549]

I have been working with Haltech recently on this topic for Motronic 60-2 sensors. It's amazing how much the base trigger angle actually moves throughout the rev range. You often see trigger settings of 112-114 deg for aftermarket setups. Whilst this will get it working, there is a large angle between the trigger angle and the maximum ignition advance of perhaps 35-40 degs. for a road car. In the past I have been using 96 deg, with a tooth offset of 3. This gets the trigger point around to 78 degs. (96 - (3*6)), but its possible to get the trigger angle down to <50 degs. Keeping the trigger point closer to the timing reduces the lag time between flywheel speed and timing variations. Locking the timing and mapping the timing point with a timing light will reveal the fluctuation throughout the RPM range. It's significant! When you think you have 30 deg @ 7000, you actually only have 27. If you'd like the full scale drop me a line.

[wicked 103 3 Cars]

Doesn't it come down on which ECU you use?

If an ecu uses every teeth for the ignition (and gap only to get the right reference) then it wouldn't be an issue to have a large trigger angle.

Probably the Haltech only uses the gap as trigger and previous trigger to estimate the next ignition.

 

iirc does the vems use every teeth for timing reference, but I'm not sure.

[petert 549]

It has to start counting somewhere, thus the two missing teeth. Then it counts down using each tooth ( 6 degree steps). Thus the tooth offset figure. If you had 114 deg with no tooth offset, yes it would be a very large angle.

[wicked 103 3 Cars]

If you see 3 degrees diff, then I assume that your ECU does indeed start a timer on the missing tooth detection and rpm, because 3 degrees diff in 1 teeth count (=6 degrees) is a huge acceleration....

When every teeth is used for timing reference, it is not important what the trigger angle is, since it will continuously be updated.

 

Or you have other issue, like varying delay through your coils (from coil trigger to spark), because of varying dwell, cylinder pressure or what so ever...

(All based on reasoning, as I have no experience with Haltech)