Perhaps the question really relates to where you are getting your vacuum.
In my car the vacuum advance is pulled off the carb inside the butterfly so
that vacuum and advances increases with throttle. The high manifold vacuum
is blocked at idle by the butterfly. At idle advance is zero and goes up
from there.
Jim Altman jaltman@altlaw.com Illigitimi non Carborundum
http://www.altlaw.com/metro/jaltman.html 69-TR6#CC28754L(O) W4UCK
-----Original Message-----
From: owner-triumphs@autox.team.net
[mailto:owner-triumphs@autox.team.net]On Behalf Of Jack Brooks
Sent: Friday, October 15, 1999 8:05 AM
To: Randall Young@pop.mindspring.com
Cc: Triumphs (E-mail)
Subject: RE: Vacuum advance - Clarification
Randall,
The bottom line is that at idle, the vacuum advance is pulled in by the high
vacuum in the inlet manifold changing the timing. When you open the
throttle, you let in more air and bring the vacuum in the manifold closer to
zero, allowing the vacuum advance to move back to it's static position. So,
the question is whether the engine is advanced or retarded as the vacuum
decreases or increase.
Listers, can anyone shed some light on this issue?
Thanks,
Jack Brooks
1960 TR3A
1974 Norton 850 Commando
Hillsdale, NJ
> Jack :
>
> I'm not sure if I said one of those things that "just didn't sound right"
> <g>, but I think Barry glossed over the point that most if not all auto
> vacuum advance systems do NOT advance the spark at idle (unless the engine
> is overheated). Efficiency at idle is not a concern (it's 0 by
> definition),
> and a retarded spark makes for a smoother, more stable idle speed. Also,
> for most engines, the centrifugal advance is no longer working at idle, so
> the idle timing needs to be retarded for the slowest possible speed, not
> just the nominal idle speed.
>
> Randall
> 59 TR3A daily driver
>
> > -----Original Message-----
> > From: owner-triumphs@autox.team.net
> > [mailto:owner-triumphs@autox.team.net]On Behalf Of Jack Brooks
> > Sent: Thursday, October 14, 1999 2:23 PM
> > To: Triumph List
> > Subject: Vacuum advance - Clarification
> >
> >
> >
> > A few days ago I was following a few posts about the way a
> > vacuum advance
> > works. Some of what was said, just didn't sound right.
>
|