Re: Pug timing sensitivity?

Rebel Moby /
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It is shit. His theory is mathamatically and geometrically impossible. He might think there is 4mm of rotation where he can not detect vertical movement, which there is movement that is very slight, but it is not 4mm of stroke (which is vertical movement).

Flame front initiation is based on the roataion because the crank still rotates forward over the time it takes to propagate the flame, burn the fuel laden air and raise the pressure in order to push on the piston. Because there is a time lag between initiation and the raise in pressure you need to fire the spark before top dead center.

Starting to push the piston too late would be like trying to get a pedal bike to go fast but only pushing on the pedal when it is already part way down.

Trying to push the piston too early would be like trying to get a pedal bike to go fast but pushing down on the pedal before it even gets over the top of its rotation.

Stock setting is a compromise setting so it would spread the the goodness over a wider band. Setting advance from stock would be better for higher speed (at the expense of starting) and retarding it from stock would be better for starting and off the line.

Trouble also is the earlier you set it the more parasitic heat is retained in the motor, so if you have a goodly exhause you can use the heat better in the pipe then in the motor. Lots of people have played with the advance before and have a goodly idea of the range for each set up, basically you can go slight retard from stock if you have a pipe and gain both for starting and some top end when the pipe starts over stuffing the combustion chamber.

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