12 May 1997, Roger rgb@exact.com wrote:
>
> I believe I'll have to call BS on this one.
>
09 May 1997 tengel@isd.net had written
> >Yes, emissions, but also a smoother running car at idle for the mass
> >(American) market. An engine running with a lot of advance at idle is
> >difficult to adjust for a smooth even idle. In Europe, drivers are
> >typically more enlightened about sporty cars.
>
> Based on your response, I'd have to agree.
>
> > However, many American buyers bought sportscars because they
> > were cute or had the right image... then expected them to be as
> > smooth and trouble free as their Detroit grocery getter.
>
> As I recall, all the American Iron from the 60's, Mustangs, Chevelles
> have the timing set to 8 to 12 BTDC. The centrifical advance brings this
> up to 25 to 30 BTDC at 3,000 RPM. The vacuum advance adds some more
> advance for cruising, falling off as soon as you hit the gas.
>
> I don't recall ANY American Iron using a vacuum retard during the 60's?
Hmmm. So, read my post again. I didn't say they did. I simply said
that the less enlightened American buyers wanted their sportscars to be as
benign and civilized as their milquetoast daily driver... and that vacuum
retard was one method used that produced a smoother idle. I don't know
how you made the leap to all the rest of this... or justify saying my
post was BS.
Tim
>
> >Vacuum retard pulls off some of the advance at idle only.
>
> And between each gear change, any time you release the trottle and create
> a high vacuum, I'd call this built in hesitation at best.
>
> What I've seen has nothing to do with this design, its the wear in the
> mechanical pieces causing the retard thing to torque the plate, changing
> timing and dwell in the process. With this mess, there is NO way to
> tune the car. The right, original answer is a new distributor. One
> alternative is disconnecting the retard and changing to EI. I like
> this one as it eliminates the "symptoms" and eliminates the timing
flopping
> around needlessly. Given everything else is "normal", this works well.
>
> I'll let some of the physics types explain to you why the best
performance,
> smoothest running, and best gas mileage is produced by firing the plug
> PRIOR to the point of maximum compression. Something to do with the
> propagation delay of an exploding gas.
>
> Roger
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