3 cyl. yamaha engine, fuel only or fuel and ingnition?

[stsubaru]

Hi.

i have a 3 cylinder turbocharged yamaha snowmobile engine.
im going from carbs to fuel injection. it has coil on plug ignition.


the big question is, leave ingnition stock, and let microsquirt control fuel.
or microsquirt fuel and ignition control???

after reading the repair and service manual from yamaha.
the only pickup for the ignition is this. (see picture)

[dontz125]

Yes, that's the pickup coil. Can you post a pic of the rotor and the teeth?

[stsubaru]

here are som pics...

[EWflyer]

Looks like another one of those goofy Nippon Denso corp trigger wheels. Those guys are certainly marching to the beat of their own drum.

[dontz125]

Please confirm that's a 6+1 wheel. If so, you'll need to remove the odd tooth and one of the regularly-spaced teeth, making it a 6-1. The uS should work nicely with that.

[stsubaru]

white marks where the teeth are.

so if i remove the two teeth thats close to eatch other.
it would work?
ill end up with the total of five?

[dontz125]

That should do it. Some inline-4s get a little finicky about where the missing tooth is due to compression slow-down when cranking, but those are generally 36-1 or 12-3 wheels on 180 degree cranks (1-4 and 2-3 come up every 180 deg). With 3 cyls at 120 degrees and a 6-tooth wheel, I don't think you'll have the same problems.

[stsubaru]

Although the crank spacing is 120 degrees, the actual
firing is staggered at 240 degrees.

http://www.mtukrc.org/download/ketterin ... r_2011.pdf
see page 7....

[dontz125]

Ah - 4 stroke. Gotcha. Still, I don't see an issue.

Interesting paper - thanks for attaching it. One question that sprang to mind, reading the paper from the 2011 team - did they actually try starting at -40 using E85? The comment on 'hotter' plugs was also a bit dodgy; while the plugs may be cleaner, burning the electrode back isn't going to help your cold start performance any ...

[stsubaru]

i know there are some tuners in that run e85 on snowmobiles in cold conditions.... cold start is the problem, nut sure how they solve it.
im planning on running my sled on Avgas 100LL
it's a great alternative to racefuel. and it's at the same price as pumpgas.
only downside is it kills air/fuel sensors since it contains lead.

http://www.statoilaviation.com/en_EN/pg ... 100ll.html