MoTeC Global Forum

I had some questions about ignition timing and reference offset when using a MAP sensor compared to a cam position sensor for reference position and speed. We are running a 2013 KTM 450 SXF and were previously using a cam position sensor for synchronization but we recently decided to switch to MAP. We are using Crankshaft One Missing Four Stroke as our reference mode. We corrected the engine speed reference offset by 14 degrees. When we were testing, there were a lot of backfires occurring. We get pattern lock which switches to cycle lock after about a second of cranking. Would this be an issue with the engine speed parameters such as reference offset etc. or is it more likely a problem with transferring over the ignition map directly? Or is there something that we are just missing completely? Is there maybe some parameter I should change but haven't considered yet? Any advice on this would be greatly appreciated!

I have attached the package I have been working on.

I've worked on two KTM 450 SXF (2016 and 2021 models) using MAP for sync, and they needed Engine Speed Reference offset of 346 - 351 deg. Why would yours need to change (by anything other than 360 deg) when changing sync location?

When using a MAP sensor, you do need to set Engine Synchronisation Ignore Mode to Enabled, with Engine Synchronisation Ignore Speed to something pretty near idle (1200 RPM worked for us).

We had to make a clear panel in a side cover (old pair of safety glasses) so we could verify the timing with a timing light. Here is a picture:

The Reference Offset value is the crank angle from the Reference Tooth to TDC Compression Cylinder 1.

In a missing tooth mode this is the Edge after the Missing Tooth Gap so a change in the Synchronisation method will not change this angle.

A multi tooth (no missed or extra teeth) mode will potentially be affected by a change in the synchronisation method, as these modes use the edge before the Sync tooth as the Reference Tooth, so if the new Sync point moves enough that it is after a different tooth, then the Reference Offset will be affected.