Ignition advance, was Re: alternative engines, WARPED

[Bruce Plecan]

Kinda depends on the WOT pressure drop across the carb., and spring rate of
the vac, advance used.   Even with the same no. degrees per amount of vac.,
by different spring rates/dia. combinations things could vary.  Going from
6-10 start to 20 something at 700rpm, 30 something at WOT (@3,000 rpm), and
40ish at cruise with a OD kinda hard to do thata way (mechanical).   Hence
the real beauty of ecm's, IMHO.
  Grumpy

|      I could be wrong at this, but what I have seen is, ported vacuum is
dead
| at idle, because it is above the butterfly....and as throttle is
increased,
| vacuum is generated at the "port" and does not go away at full
| throttle,,,,,great for emissions but terrible for performance,,,,,the same
| for MPG....
| -Carl Summers

|   You sure about that?  I have always understood that a vac advance can
|  reads ported vacuum in order to affect a curve that begins as the
throttle
|  is opened and increases as more throttle is applied, up to the point at
|  which all vacuum (manifold and therefore ported as well) fades under
heavy
|  throttle openings, at which point the advance will decline again and the
|  engine will see only mechanical advance.  This is apparently to provide
|  extra advance for economy at part throttle.  Anybody who can further
|  illustrate this concept, please do because if I am wrong here I'm going
to
|  have some serious rethinking to do!
|   Aaron Willis