<VV> turbo distrubutor

[Jim Burkhard]

And if this was the case for the Cosworth Vega, leaving the vacuum advance
off it was stupid too.  The absence of a V.A. is fine for a WOT-only car,
but if it will ever need to be operated at part load, it's a terrible
mistake. Performance, driveability, and fuel economy all suffer. It's a
triple loss.

Jim Burkhard

> -----Original Message-----
> From: virtualvairs-admin@corvair.org 
> [mailto:virtualvairs-admin@corvair.org] On Behalf Of Anthony 
> Buck Hansen
> Sent: Saturday, April 24, 2004 1:29 AM
> To: VirtualVairs@corvair.org
> Subject: Re: <VV> turbo distrubutor
> 
> 
> 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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