MoTeC Global Forum

I'm setting up an old M4 Pro on a Suzuki G13B. The G13B has no crank sensor so we're looking at adding one using the sensor and trigger from a G13BB. That's a simple enough operation as the later parts are a simple bolt on replacement.

The question I have is how I'd configure the reference. I've attached an image showing what the trigger wheel looks like. As you can see it has two solid sections of different lengths. I'm guessing the ecu would see these as missing teeth. The solid section is the equivalent of three teeth on one side and double that on the other side.

If the ecu was configured for ref/sync 93 ( missing 4 times/cycle ) would this work or would the length of the blocks throw things out? I have the option of using another trigger wheel with 6 evenly spaced teeth but I assuming the 36 tooth wheel would be a better option if it can be configured. I'll have an additional sensor on the end of the cam for sync.

Thanks

Hi Sam,
There is no ref/sync mode in the M4 that will work with this trigger pattern that I can see.
From a quick google it looks like you could possibly use a 6 tooth wheel off a G16, but you would also need a single sync tooth on the cam or in the distributor.
If you dont want to use a sync sensor then you will really need to do something like a 36-1 type wheel on the crank.

Hi Adam,

I'll have a hall single tooth sync on the cam so I don't see any reason why the crank trigger wheel with 6 evenly spaced teeth won't work. I guess the trigger wheel pictured could be cut to 36-2 or 36-1. I've read that the ecu will work better with more teeth on the reference but I'm unsure of how much practical difference that makes and whether it's worth the cost and trouble?

Thanks
Sam

sam7 wrote:Hi Adam,

I'll have a hall single tooth sync on the cam so I don't see any reason why the crank trigger wheel with 6 evenly spaced teeth won't work. I guess the trigger wheel pictured could be cut to 36-2 or 36-1. I've read that the ecu will work better with more teeth on the reference but I'm unsure of how much practical difference that makes and whether it's worth the cost and trouble?

I don't think the pictured wheel could be easily modified to 36-1 or 36-2 since the OD is no longer round where the existing missing teeth portions are. Unless you mean to completely machine it down smaller OD then re-cut new teeth. Also note you don't want welds on a trigger wheel as that upsets the magnetism so don't go welding it up...

Yes, a 6 tooth wheel will be perfectly fine for an engine like this. I have tuned some quite serious 4cyl, low inertia, high comp engines that had just 2 teeth on the crank with no drama. The biggest effect a low tooth count will have is scatter during cranking and some small drift from target ign angle during high crank acceleration.