Re: 505 Noises - solved
Senen Racki (sracki@dow.on.doe.ca)
Mon, 28 Oct 1996 15:48:59 -0500
> There's generally 2 systems. Vacuum in which the level of advance tracks
> the amount of vacuum. There's are two states of high vacuum which of
> course means there's 2 potential high advance states. At idle and barely
> cracked throttle, the butterfly in the throttle is closed and vacuum is
> high. Here, advance can be high as there's little load on the engine and
> if retarded, the engine would run hotter. Once the vacuum goes down, you
> want advance to more or less track RPM. Too much advance at low RPM/Low
> Vacuum would be a throttle open trying to accelerate condition and with
> too much throttle, pinging. So RPM is tracked to advance the timing. In
> old engines, that'd be via centrifugal advance with weights/springs in
> the distributor. These days, it's via "Motronic Magic" and the like where
> that Mechanical Advance is adjusted by the Black Box "watching" the RPM
> and doing that advance thing. At Crusing RPM, you'll have a little of
> each type of advance in action to yield the most efficient power and thus
> best mileage.
I'm confused. Are you saying that the timing will be retarded with
increased RPM? At idle, the microswitch cuts out the supply of
vacumm to the advance unit. Am I thinking about it in an opposite
way? I thought that as you increased RPM, vacuum would increase,
advance diaphragm would pull distrubutor and advance timing. Too
much advance at throttle would cause pinging (predetonation), which
in turn would eventually cause heat buildup.
Comments anyone?
Senen.