Single cylinder "distributor" question

wes kiser · Post by **wes kiser** » Sat Oct 06, 2007 11:22 am

Some of you may remeber some questions I had asked when trying to get a single cylinder KTM engine squirting last year.

I am back to helping the UNCC FSAE team, and have a question about an interim ignition pickup. Ultimately they will be doing and "external" toothed wheel built into a supercharger drive.

Basically, the KTM has a single tooth and a VR sensor. The stock engine has a CDI box, that does do some degree of advance. THe only way I can see this working acceptably is if the tooth comes up a relatively long distance before TDC (like say 60 degrees or something), and then the coil is fired as a "this cylinder" kind of thing. This way, it only would have something like a 40 degree crank window to incur an error.

If as an interim solution, can I use this single tooth pickup and dizzy mode? The only problem I see is the "ignition offset" becomes the maximum advance value instead of the minimum (and I don't know if this is OK in the code). When reading up on standard MS2 dizzy code, the offset is equal to the minim advance possible, so that wouldn't work. If it is fired as a next cylinder, I can see lots of error being incurrend in the 300 or so degrees of crank rotation the would pass.

The reason I posted this in the development forum is because I would be using the beta code (as that is what my most recent experience is with), and felt it was more a specific code question about dizzy mode.

wes kiser · Post by **wes kiser** » Mon Oct 08, 2007 1:39 pm

I was able to verify the tooth location relative to TDC. The leading edge is 40 DBDTC. This verifys my theory as to how the CDI ignition worked (as the maximum advance is 38 (from a KTM engineer).

Post by **jsmcortina** » Thu Oct 11, 2007 12:56 pm

Try it out on the stim first. "This cylinder" mode should work fine, but the single tooth may cause a problem as you note.

James

wes kiser · Post by **wes kiser** » Thu Oct 11, 2007 8:18 pm

This is a microsquirt, so the stim is a bit difficult. I no longer have my mustang, so my squirt is gone as well. One of the team members is building one, so hopefully we can test on his (ms 2).

As long as there are not code issues with offset being greater than maxium advance requested, I think it will work ok. It appears KTM set it up as a "trigger return" tooth as well, as it is quite wide. Falling edge appears to be about 10 dbtdc.

Thanks, I will let you know how it goes.

racingmini_mtl · Post by **racingmini_mtl** » Thu Oct 11, 2007 8:28 pm

A JimStim would allow you to test a microsquirt more easily.

Jean