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Anyone know a way to calculate this? I know 4000ft/min is a generally accepted number, but I'd like to know how hard I can push my 360 before "bad things happen"™?
I know how to calculate mean piston speed, I don't know how to calculate at which speed things start to break. I imagine is has to do with crank angles, thicknesses, conn rods, piston weights, etc?
For given stroke, yes, of course (teaches the formula).
Just seemed uncommon to me, maybe you wanted to
build up a stroker engine.
Back to topic, I'm a Yamaha man, can't tell. Normally
japanes engines are much less sensitive to over-revving(?)
than british or european ones.
Thanks, Sven. At some point I'd be interested in a stroker, but I'm actually wondering about revs for my current build. My 360 is only a single valve and so I know breathing will be an issue, but I'm wondering is the breathing will be a problem before the revs will...
it depends on the mass of the piston, pin and conrod, a lighter piston will exert less force on the rod, pin and bearing than a heavier one will, honestly, there are other things in that engine that'll fail long before the rods do.
Stock stroke on a CB360 is 50.6mm. One full revolution is 101.2mm
Convert that to feet, the piston travels 0.332020997 feet per revolution.
Divide 4000 feet per minute by 0.332020997 feet per revolution, and you get 12,047 rpm.
12,000 is a fair guess from the math
Centrifugal loads are the problem
With different ignition and lighter piston, 12,500 isn't really a problem, big end bearings will fail before rods snap, rings will 'flutter' and break pistons around 13,500, although you will get a few thousand miles out of it before re-ringing or blowing up ;D
I use stock cams and about 11~ 11,500 in my 378cc motors although they are past peak power by 10,500 (points 'bounce' around 11,750~12,000)
Cam oiling is the main issue, use 5w/40 full synthetic (Rotella is JASO spec 8) )
Thanks. That's what I thought but didn't have a chance to go back to my old text books to check it. I did have it spelled out in an old BASIC app I wrote at college somewhere but that would have taken even longer to find.
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