MoTeC Global Forum

Hi all,

We are a formula student team running a m84 with a KTM 500exc. We are currently trying to get the engine running for the first time, we are able to crank and when using the oscilloscope function in the software we get the graph shown in the image which is the flywheel teeth moving past the sensor. We are not sure what point on the graph indicates the position of the missing tooth/additional tooth.

Currently when on 'every tooth' ignition mode it will spark whilst cranking so we do have enough power to spark. The ecu just cannot spot the additional/missing tooth on the flywheel.

Any help will the appreciated,

Thanks

Can you attach the actual .rsc2 file rather than a screen shot. You might have to put it inside a .zip archive if the forum does not allow the .rsc2 extension

There are 17 small teeth and 1 large one on the flywheel. We are not sure how to get the ecu to detect the large tooth.

Ok, as far as I know there is no OEM mode that matches your trigger pattern. My initial thought is the easiest option would be to grind off the long tooth then it is seen as 18-1. Use ref/sync mode 6 and set number of cylinders to "-1".
However be aware if your long tooth is near TDC that wont be a good way to go. If your long tooth is near TDC then it would be better to "shorten" that long tooth (machine or file accurately) so it is the same as the others, then grind off a different tooth that is near BDC. The reason is you don't want your "gap" near TDC where the crank "slows down".

Mag sensors work best when the tooth width is matched with the sensor width. They can't really detect wide teeth, because the trigger edge is usually the beginning of the tooth. It can however detect missing teeth. You need to have a trigger wheel that has equally spaced teeth, then cut off one of them. That means the gap between the teeth will be the length of two gaps+the width of the tooth.

Here is a screen shot of your ref-sync capture where I've circled the rising edge that I think represents your extra wide tooth. Notice how the other rising edges are all close to vertical, but these two edges are rising slower (one due to the compression slowing the cranking). I don't think your wide tooth is wide enough (even if that would work). It probably needs to be at a minium the width of two teeth plus the gap. How wide is the wide tooth relative to the other teeth?

If it were wide enough, you might be able to make that work with a Hall Effect sensor. So I think you need to decide if you're going to re-machine the trigger to work with your magnetic sensor, or try to change sensors (which still might required re-machining the triggers).

Thanks for the quick reply. We managed to reply to sync it once using a tooth ratio of 25 but that was just a guess and it hasn't synced since. The wider tooth is about double the width of the others. The sensor is a rising edge sensor if that helps.