Brand of Gasoline

[jlagnese at massed.net]

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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