using the frequency of spark on one plug?

I'm getting 430Hz average on one plug wire. Multiply by 60 for shots per minute and divide by 4 because it fires on every cycle, right?

At least I thought that was the case. Using those numbers I'm getting double RPMs I should be getting, and it just aint so.

Do some V-twins skip an ignition phase on alternating cylinders? Like, on say, a two speed (Load/No Load *high rpm/Low rpm* generator?

7/28/2014 11:55:07 PM

it fires on every 4th stroke of the piston, but that's only every other rotation of the crank. in other words, you're calculating how many times the piston goes up or down, but that's not what RPM is. It moves twice for every 1 revolution of the crank. Divide those strokes you've calculated by 2 to determine the revolutions per minute of the crank.

7/29/2014 12:48:03 AM

Thanks for the input, man.

I think this machine works on a "wasted spark" ignition system. It sparks at the end of the exhaust stroke with no fuel to ignite.

it's a generator and they're sort of built around simplicity so it sparks at TDC of the OTHER piston as well, splitting the current instead of adding a second coil.

That would make for 4 sparks per complete cycle. 4 sparks, 2rpms. 2 sparks per rpm.

that's still four times the factory max RPMs and roughly twice the number needed to fragment the engine. It actually works great and sounds fine, im trying to fine tune it and am just curious as to why i'm getting 4 times the spark frequency I "think" i should be getting.

Do you suppose maybe it's a super-redundant (just made that up) sparking? perhaps it is designed to give spark to the chamber at each "dead center" (top and bottom) point of the piston? If so, combined with the split current... that would be an astounding 8 sparks per cycle. 4 sparks per revolution
430Hz*60/4 = 6450Rpm
Still double the suggested range max.

WTF

lol... does freaking anything work like that though?

7/29/2014 1:35:53 AM

i think you're turning 3200 rpm with a normal spark pattern near the top of the compression stroke, which sounds about right.

re-read my first post. you are calculating the number of piston strokes per minute (on one cylinder), which is indeed 6450...but the piston goes both up and down for every revolution of the crank. you need to divide that number by 2 again to find RPM (which is 3225).

[Edited on July 29, 2014 at 9:28 AM. Reason : ]

7/29/2014 9:26:13 AM

holy crap you're right

mark that one down as straight up ignorance on my account. my bad.

thanks dude

7/29/2014 11:30:37 AM

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7/30/2014 1:33:11 AM