Log sec Trig without using it.

[Benzmac16v]

Hey,

I kind of stumbled across a possible trigger for a secondary trigger (basically a lobe for a carb pump).  I would like to test if it could work as a sec trigger, but I have no idea when it would trigger or even if the sensor will see it through the cover.  Obviously this is kind of a curiosity experiment, final version would have a new custom cover/sensor mount installed for a reliable sensor and signal.

Jim

[mattias]

This is done all the time on the red block Volvo engines. Usually you must grind the lobe to look more square (sharp beginning and end) for the sensor to distinctly see it, usually you must approach close with the sensor (1.0-2.0 mm).  The Honeywell GT1 Hall sensor is a good candidate.
The signal must not race with the primary trigger teeth on a simple trigger, with missing-tooth primary it must not race with the missing teeth.

[Benzmac16v]

What are the consequences of not grinding it down?  I ask because there are easier ways of creating a sec trigger than the work that would be involved in getting that sprocket out...  This, however, would be incredibly simple and probably a worthwhile endeavor because of the simplicity.

When you say the signal must not race with the missing tooth, do you mean occur at the same time?

Also, is there a way to have the signal show up in a trigger log, but have it ignored from a functional stand point?  That way I can play with it and ensure it creates a reliable signal throughout the engine rpm without worrying about the consequences of a missing trigger.

thanks,
Jim

[mattias]

You can always try without grinding it down, the signal may drift a bit depending on when the sensor considers the signal strong enough.

When I say race, I mean exactly what you asked. If it occurs at the same time, there is no way to know if it was the previous or next cycle in which it occured, which directly determines the ignition order.

You can disable the fuel/ignition, enable  the cam sync, make a triggerlog (tools menu) and just check it out visually.

[Benzmac16v]

Ill give it a shot and see what happens.  Pretty sure it wont work without the custom bracket, but we will see.

Why does it matter what cycle it happens on?  I know you are keeping track of what phase the engine is on, but why couldn't the range be set to between 600 and 100 degrees (assuming the missing tooth is at 0, 360 degrees).  In a 4 stroke engine you always have 720 degrees of rotation...  If you know the cam sync comes between 600 and 100 you should be all synced up... Just have the ecu count degrees based on the primary after it sees the secondary once, why does it matter if the trigger comes at 719, 720 or 0 degrees anymore than it matters if it comes between any other range?

Im not familiar with how vems counts or uses the secondary, so probably something I am not familiar with.

thanks,
Jim

[mattias]

The filter function for the secondary trigger is made just for what you describe, to set an allowed range - but the ECU must first sync up if you have a missing tooth trigger, or else every 360 degrees look the same.

If you think a couple of times about this, it can't be done in that many ways, still this trigger code supports a very wide variety of triggers.