Posted by Rob Kleinschmidt on April 21, 2011, 10:29 pm
> I've always liked single-banger motors. Would it be possible
> to modify a BMW boxer motor such that the 2 cylinders'
> power strokes were simultaneous instead of alternating?
> In effect it would be equivalent to a thumper
> but better balanced for less vibes.
> SQ
Xposting to reeky since it's pretty slow
Ought to be a piece of cake on a BMW oilhead,
as there's a separate cam for each head. That may
leave some interesting problems with the fuel injection,
but hey, how hard a hack could that be ?
http://tinyurl.com/3m3x3gr
Reeky eagerly awaits the results of your experiments.
Posted by The Older Gentleman on April 22, 2011, 4:30 am
> That may
> leave some interesting problems with the fuel injection,
> but hey, how hard a hack could that be ?
I'm sure Sean would tell us ;-)
--
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Triumph Street Triple Suzuki TS250ERx2 GN250.
Try Googling before asking a damn silly question.
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Posted by Rob Kleinschmidt on April 22, 2011, 11:19 am
> On 4/21/2011 6:29 PM, Rob Kleinschmidt wrote:
> > Reeky eagerly awaits the results of your experiments.
> Yesterday I phoned Shadbolt Cams Ltd in Vancouver.
> They would need a cam billet because too much material for welding
> would have to be added and then ground to fit in order to relocate
> two of the lobes 180 degrees (that much heat would warp the camshaft).
> However they do have a regrinding master pattern for the 1970 R75:http://www.shadboltcams.com/cycles.html
> The cam lobes are in pairs, but within each pair the lobes are not
> quite parallel; they're a few degrees apart. I can't figure this out.
> At first thought, why would the cylinders seem to have different
> valve timing -- and how would this relate to ignition timing?
> Are the cylinders not quite horizontal and 180 apart, or is it
> (on 2nd thought, duh...) merely because the pushrods are at an angle.
> The ignition fires at (or near) each TDC so there's a wasted spark
> at the end of the exhaust stroke. This feature would give me ignition
> on both cylinders at compression TDC (theoretically).
As I said though, if you could get the injection working,
an oilhead engine might run using absolutely stock cams,
as each oilhead cylinder runs off its own chain driven cam.
I believe the oilhead is also lost spark ignition.
Might even be something that could be cobbled up in the
garage with no machining or electronic trickery. Not sure
what's involved with the F.I. system.
Posted by Mark Olson on April 22, 2011, 11:43 am
Rob Kleinschmidt wrote:
> Might even be something that could be cobbled up in the
> garage with no machining or electronic trickery. Not sure
> what's involved with the F.I. system.
It would be no problem at all to hook more than one injector up to fire
from the same signal as the other injector, you'd need to use a driver
circuit rather than just put the two injectors in parallel[1], but it
would be pretty trivial.
[1] which would probably work for a little while until the output
transistor in the EFI computer blew out.
Posted by Rob Kleinschmidt on April 22, 2011, 12:18 pm
> Rob Kleinschmidt wrote:
> > Might even be something that could be cobbled up in the
> > garage with no machining or electronic trickery. Not sure
> > what's involved with the F.I. system.
> It would be no problem at all to hook more than one injector up to fire
> from the same signal as the other injector, you'd need to use a driver
> circuit rather than just put the two injectors in parallel[1], but it
> would be pretty trivial.
> [1] which would probably work for a little while until the output
> transistor in the EFI computer blew out.
Simple slave setup should do it ?
No per-cylinder feedbacks to worry about I guess.
An 1100 oilhead ought to be about the same price
as an airhead these days.
Go for it Sean. We'll hold your coat for you while you
do battle with this project.
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> to modify a BMW boxer motor such that the 2 cylinders'
> power strokes were simultaneous instead of alternating?
> In effect it would be equivalent to a thumper
> but better balanced for less vibes.
> SQ