Two cylinder two-stroke?

DannyP · Post by **DannyP** » Thu Aug 20, 2009 8:15 pm

I have a friend of a friend who races snowmobiles. To the best of my knowledge, the engine is a 2 cyl 2 stroke, so it would have 2 events per crank revolution, as I would assume(uh-oh) they are evenly spaced at 180 degrees from each other. It is an inline twin, not a V.

EDIS is set up for 4 events per 360 degrees, so I don't think you could make that work. But is there 2 stroke capability in Megajolt 2? If you used the individual coil drivers and just left two unconnected, I think so. Wasted spark wouldn't work, it has to be COP, sequential.

Also, a question on rpm. I know EDIS is good to almost 10,000 rpm, but these motors go up to somewhere around 13-15K. How high could we realistically go?

motowrecker121 · Post by **motowrecker121** » Fri Aug 21, 2009 2:01 am

Hi Danny Its Ben the friend of a friend. i am no expert on the ignition i am triing to learn and see if i could make this work.

Basicly what i am looing for is an ignition that will fire every 180 deg. that i can program myself. i beleive a 4 cyl setup could work because it will fire 2 per revolution.

can i etup each bank to fire an individual coil?

also i need it to be stable and accurite to atleast 11,000 rpm

any help is greatly appreciated

thanks
Ben

DannyP · Post by **DannyP** » Fri Aug 21, 2009 2:19 am

Hey Ben, how goes it?

I am hoping Brent fields this one, at least as far as Megajolt2's capabilities.

The current version of Megajolt wouldn't work I think for you. On a 4 cylinder, they usually fire 1-4-3-2 which is even fire. So drop out 4 and 2 leaving 1 and 3 at 180 degree intervals. EDIS based system uses the same coil output for both cylinders, 1 and 3. So you would have to use one two-post coilpack, which gets us into the rpm issue. Will wasted spark work on a 2-stroke? I think not, as one cylinder would fire and the other would fire also, but at bottom dead center with a full, noncompressed intake charge.

Post by **brentp** » Fri Aug 21, 2009 3:30 am

for an existing EDIS setup I'll have to think about it again- The last time I discussed this was here:

http://www.autosportlabs.org/viewtopic. ... roke#10595

this was for a 1 cyl 2 stroke engine. My logic was that since the wasted spark design fired in the exhaust stroke as well as the compression stroke it could work for a 2 cycle engine- unless I'm (embarrassingly) missing something?

Yes, megajolt 2 could probably do anything- even nonsensical stuff since we'll have full control of the spark sequencing.

TwoSheds · Post by **TwoSheds** » Fri Aug 21, 2009 4:57 am

Since a four-stroke four fires twice per rev, evenly spaced, and a 2-stroke 180deg twin fires twice per rev, evenly spaced, don't we just need to get rid of the extra plugs but make "their" sparks do some work?

So run one HT lead from each coil directly to a solid earth and the other to a plug - hence that plug fires the same as it would normally on an EDIS system (on every approach to TDC) but the previously wasted spark is now doing some work.

Simples!

[scratching_head] I must be missing something[/scratching_head]

Roger

(p.s. for those not blessed with UK TV, 'Simples' is not a typo

)

DannyP · Post by **DannyP** » Fri Aug 21, 2009 1:37 pm

So the consensus is it will work, as demonstrated by that link to a 2 stroke twin(Thanks Brent). The only problem would be the rpm issue, which will hopefully be fixed by Megajolt2.

motowrecker121 · Post by **motowrecker121** » Sat Aug 22, 2009 4:08 am

the curent set up on the sled has 1 coil with 2 plug wires and they both fire every 180 so wouldn't that be wasted spark?

what drives me crazy is the current set up is completly programable by the factory but not by myself. i would like to not be at there mercy and hope that they put in the timing curve that i request. they are known for changing things a little here or there and not telling you.

when will the new setup be available.

thanks
Ben

DannyP · Post by **DannyP** » Mon Aug 24, 2009 12:31 am

What about a 72-2 trigger wheel and two single coilpacks? Each single coil would be wired to each coil output. Since EDIS is set for a 4 cylinder, would it not work to fool it into thinking it is firing a four cylinder?

Then the rpm limit of 9-10,000 wouldn't affect it, the EDIS would think it was only half the rpm. The idea is similar to those that have mounted a 72-2 wheel on a camshaft, which travels at half crank speed, but in reverse. Think about it and let me know guys, I think this could work for Ben.