|
hey Dan,
u sure u
never thought about this before????
ur answer is dead on the
money bud...
----- Original Message -----
Sent: Saturday, June 08, 2002 8:16
PM
Subject: Re: [Chevelle-List] Advancing
Timing
Keith,
Just a guess here, but even as low as
1500 RPM, the time it takes for a piston to go from 12 degrees BTDC to TDC has
got to be milliseconds. So, if you fire it at say, 6 degrees BTDC, and figure
the time it takes for the air/fuel mixture to fully ignite, there's a
possibility that the piston may actually be on its way back down the cylinder
bore before any power is applied, wasting some of the power stroke. Firing the
plug earlier, at 12 degrees BTDC, gives you the time needed to fully ignite
the charge while the piston is at or near the very beginning of the power
stroke.
Lets do the math. 1500
RPM equals 25 revolutions per second. That's 9000 degrees of travel every
second. Assuming that a 350 mouse motor is a 4" stroke, ( I'm not sure ), 12
degrees BTDC equals roughly 1/8". That's 10.8 milliseconds before TDC.
And that's at a fast idle....imagine 4 or 5 thousand RPMs.
OR, I could be way off base with these
figures. I never thought about it before, and its the best answer I could come
up with quickly. Take it easy, its nice outside.
Dan McIntosh
65 Malibu
|
