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Multi/Missing tooth triggering + Cam sensor


Grant Baker
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Hi Guys,

I'm setting up an engine that has a 36/1 crank trigger and a cam trigger with a single tooth.

I've used the help files, but just to confirm...

Crank trigger set so that gap is at (for example) 90 deg BTDC no1.

Cam trigger set so that the tooth edge is at TDC no1 on same cycle. This is 90degrees (or 25%) after the Crank trigger gap.

Is that correct?

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In the help files it says otherwise ;)

Search for Trigger 2 Sync Positioning.

On some trigger setups a Trigger 2 Sync is required for the ECU to accurately calculate engine position. Trigger modes Multi-tooth and Multi-tooth / Missing have a setting called Sync Mode that is used to specify the type of Trigger 2 Sync being used. There are some important requirements for the Trigger 2 Sync, failure to follow these requirements may lead to trigger errors occurring and the ECU being unable to calculate the engines position and speed.

 

Multi-tooth Requirements

 

·When the Trigger Mode is set to Multi-tooth the sync tooth edge must occur within a green 50% zone as shown in the image below. It does not matter which trigger 1 teeth edges the sync tooth edge falls between.

 

Multi-tooth sync position

 

 

Multi-tooth / Missing Requirements

 

·When the Trigger Mode is set to Multi-tooth / Missing the sync tooth edge must occur within a green 50% zone as shown in the image below.

 

·The sync tooth edge(s) must also NOT occur in the 'missing tooth gap' or within 30 degrees (crankshaft revolution) of the tooth after the gap.

 

Multi-tooth Missing sync position

 

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I will add a little more info just for user knowledge:

  • You generally want your gap to be in an area of least crank acceleration.  For a 1, 2 or 4 cylinder, 90deg before or after TDC is a good position.  For most engines 5 cylinders and up the crank acceleration is smooth enough that position is less critical (ignoring odd-balls like flat plane V8's).
  • You generally dont want the gap to be within your normal running ignition timing range.  For most engines this means you dont want the gap in the range 0-40 deg BTDC.
  • Number of teeth on the crank trigger should be divisible by the number of cylinders.  So for instance 36 teeth is good on a 4 cylinder but not ideal for a 5cyl.
  • I have never observed the "sync tooth position" being quite as critical as the help file makes out (within the 50% window would be very difficult to achieve on a 60-2 set up!), but it is certainly always advisable to have the sync tooth nowhere near the crank "Gap". 
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