MPG

[Grant Lenahan]

gotta assume same gearing, same car, same road, same temp, same gas,  
blah

so, yes. I just commented on your trio

but you rightly point out why gearing and rpm have such an impact -  
its pumping and compression, not simply some abstract idea of slow  
spinning engines.

Good point

Grant
On Nov 20, 2009, at 11:21 AM, LL - NY wrote:

> You forgot RPM. At steady state, the lower the RPM (therefore rate  
> of air/fuel throughput) the lower the fuel consumption. That  
> explains why the low numerically geared V8 monsters (like,  
> surprisingly, 6sp 'Vettes and neu-Camaros, and the latest Mustangs)  
> can actually get near 30 MPG on the highway. They're barely ticking  
> over 1800-2200 RPM at full highway speeds.
>
> On Fri, Nov 20, 2009 at 11:12 AM, Grant Lenahan  
> <glenahan at vfemail.net> wrote:
> Weight - absolutely  F still = MA
> Driving style - sometimes, and rarely when on the highway
> Engine size - very relevant - defines effective  compression ratio,
> pumping losses, and combustion efficiency, assuming some small power
> is required to maintain a body in motion at say 70 mph
>
> Counter intuitively (unless you think like carnot or otto), a driver
> who accelerates foot to floor, and then cruises at maximum vacuum to
> maintain speed, will do better than one who accelerates slowly and
> then maintains the same speed.
>
> Grant
>
> On Nov 20, 2009, at 10:57 AM, Louis-Alain Richard wrote:
>
> > Kent,
> >
> > I bet all these cars are about the same weight.
> >
> > Fuel consumption is closely related to weight and driving style
> > more than
> > engine size.
> >
> > Louis-Alain
> >
> >
> >
> > -----Message d'origine-----
> > De : quattro-bounces at audifans.com [mailto:quattro-
> > bounces at audifans.com] De
> > la part de Kent McLean
> > Envoyé : 19 novembre 2009 16:55
> > À : quattro at audifans.com
> > Objet : Re: MPG
> >
> > victor norman wrote:
> >> I have a 2000 A4 2.8 quattro and never seem to get more than  
> 20mpg in
> >> mixed town and highway driving.
> >
> > I get in the low 20s (22-23), but that's without a lot of stop- 
> and-go
> > traffic
> > slowing me down.  That's about the same as I get with the 20V and
> > the V8. Go
> > figure.
> >
> > --
> > Kent McLean
> > 1990 V8 w/5-speed and other mods
> > 1991 200 TQA #3, with mods
> > 1999 A4 Avant, V6 Tiptronic
> > gone: '91 200 TQA x2, '94 100 S Avant, '89 200 TQ "Bad Puppy"
> >
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> >
>
>
>
> Grant Lenahan
> glenahan at vfemail.net
> (201) 602-4702 mobile
>
>
>
>
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Grant Lenahan
glenahan at vfemail.net
(201) 602-4702 mobile