<VV> turbo distrubutor

[Anthony Buck Hansen]

GM had no vacuum advance on the 75-'76 Cosworth Vega, and it wasn't to keep
it simple. For those who don't know, it was GM's first car that combined all
of these features: four valves per cylinder, dual overhead cams, stainless
steel headers, and electronic fuel injection. If you're only talking about
turbo cars, sorry.
Tony Hansen
permanent email address: corsaconvertible@yahoo.com

----- Original Message ----- 
From: "Jim Burkhard" <burkhard@rochester.rr.com>
To: <UltraMonzaWest@aol.com>; <VirtualVairs@corvair.org>
Sent: Friday, April 23, 2004 8:23 PM
Subject: <VV> turbo distrubutor


> Bah!  You can't "eliminate" the need for vaccum advance UNLESS you are
doing
> ALL full-throttle driving. Mechanical advance only is fine for a race car,
> but on anything that is driven anytime part throttle (including all
streeted
> cars), you will be underadvanced and the throttle response & fuel economy
> will suck.  All spark ignited engines need to increase the spark advance
at
> part throttle loads. There's no way around it. If you crank up the static
or
> centrifal advance to (ahem) "compensate" for the lack of a vacuum advance,
> you will then be over-advanced at full load (prone to knock and/or losing
> torque from the optimal timing).
>
> The fact that GM didn't have a V.A. on the turbo distributors was only
> because they were trying to keep the whole deal simple and having BOTH a
> pressure retard and vacuum advance would have made things more expensive.
> But one level of spark advance (reardless of load!) at all engine speeds
up
> to 4,000 rpm (or is it 4400, I forget...) is no way to run an engine,
> though. No modern car dispenses with load-varied spark advance. Sure, it's
> all done electronically (no distributor), but the optimum spark advance
> ALWAYS varies a lot with load. No way around it whether a turbo engine or
> not...  To not do so means you lose part throttle torque (feels
unresponsive
> and you have to go deeper into the throttle to make the car move) and also
> fuel economy (on account of a drop in indicated thermal efficiency from
the
> mistimed combustion).
>
> Jim Burkhard
> Air, Fuel, and that other one... Now what was it...?
>
> ----------------------
>
> Patio Matt wrote-
>
> > You can also "modify" / re- curve  the existing unit [
> > change the springs /
> > remove ONE spring, etc.]  if you understand what you're
> > doing...and even
> > eliminate the NEED  for the VA  to get full advance...
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