Brand of Gasoline
jlagnese at massed.net
jlagnese at massed.net
Wed Sep 19 18:23:10 PDT 2012
In Maine we get some winter mix gas. That definitely
drops the mileage.
---- Original message ----
Date: Wed, 19 Sep 2012 19:23:17 -0400
From: Mark Rosenkrantz <speedracer.mark at gmail.com>
Subject: Re: Brand of Gasoline
To: Grant Lenahan <glenahan at vfemail.net>
Cc: John Lagnese <jlagnese at massed.net>,
quattro at audifans.com, Jeff Waterstreet
<jwaterstreet at tds.net>
Grant, modern engines adjust timing VERY rapidly,
to lower emissions as well as improve fuel
economy. Today's engines aren't static like a
"single map" or a "jet" in a carb. It's dynamic,
within parameters. Modern "maps" are ranges, not
a static line. As such, it's certainly plausible
to get a SMALL percentage of improved MPG under
normal driving conditions. Your PV=NRT (I love
the ideal laws!) and logic is only accurate if we
squeeze all of the power out of the incoming
fuel. No variation between slightly rich as a
"fudge factor to stave off detonation as an engine
wears" or running lean of peak, something which is
used to get the combustion chamber hotter, faster.
Now, the likely scenario is that she got
ethanol-free gas. As stated, ethanol have less
BTU's per volume, and will decrease your fuel
economy in ANY engine. Another thought, which may
be quite wrong.... but if the engine maps can't
handle it because it's so far out of parameters,
this would severely limit fuel economy
by reverting to a very "safe" map in the ECU.
Honestly, I forget what car, what altitude (air
density), etc.
Do I believe 50% better economy in a "decently
running car," no, I don't. But if you told me by
switching brands and going to ethanol free fuel...
I'd absolutely believe double-digit improvement as
a percentage.
As an aside- get this- In airplanes where we can
adjust the mixture manually, there is a growing
trend to run the engine lean-of-peak
(significantly so). GAMA has all the write ups
you need if it interests you, but the premise is
this- high quality injectors and (this is key for
an air cooled engine) individual cylinder head
temperature (CHT) monitoring. Over 10% increases
in economy are the norm. Pretty awesome. Of
course, this is in a constant RPM engine... but
the ECUs in modern cars are adjusting multiple
times per ignition cycle and are quite accurate.
Mark Rosenkrantz
On Wed, Sep 19, 2012 at 6:55 PM, Grant Lenahan
<glenahan at vfemail.net> wrote:
No, not exactly. Read all my posts again
Grant
On Sep 18, 2012, at 8:29 PM, John Lagnese wrote:
> Exactly!
>
> -----Original Message-----
> From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com] On
> Behalf Of Jeremiah Curry
> Sent: Tuesday, September 18, 2012 7:02 PM
> To: 'Jeff Waterstreet'; quattro at audifans.com
> Subject: RE: Brand of Gasoline
>
> I am not expert, but isn't it feasible that
with low octane gas in the tank
> you go WOT, maybe to merge on the freeway,
leading to detonation. The
> computer decides to retard timing. Then the
whole time you are on the
> freeway the timing is retarded, leading to
less efficient combustion.
> Whereas if higher octane fuel had been used,
that would not have happened?
> My understanding is that the decision to
retard timing will stay in affect
> for some time.
>
> I am a convert to premium in vehicles that
require it (my Allroad, MR2
> turbo, and Triumph TR3) after having trouble
with my 30v Passat and not
> using premium. However I agree it won't help
on engines that don't need it
> (my 80 series Landcruiser)
>
> Jeremiah
>
> -----Original Message-----
> From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com] On
> Behalf Of Jeff Waterstreet
> Sent: Tuesday, September 18, 2012 4:17 PM
> To: quattro at audifans.com
> Subject: RE: Brand of Gasoline
>
> This discussion reminds me why the snake oil
sellers and "magical magnetic
> fuel savers" find people to buy their stuff.
Most people don't know how
> to properly monitor their fuel usage, which is
evident by many responses to
> this topic. I especially like those that say
"my car just feels peppier"
> when they run premium. Two of my 8 vehicles
require premium (one is a
> 2001 A6Q 2.7T), and there is no difference in
mileage between regular and
> premium, unless driven very hard. (like towing
a boat, with my other
> "premium" eating vehicle, a Toyota
Landcruiser)
>
>
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