[Diy_efi] The Hunt effect

[Ulmer, James D - Denver, CO]

My off-hand test with my '94 Cadillac NorthStar yielded just under 2 mpg
difference. 16.9 verses 19.5. For me, the better gas is clearly well
worth the cost. When prices peaked at $3.00 a gallon around here, I
thought I'd save a little money and switch to the lower octane. Went
back to the better stuff and the trip computer showed the difference
within just a few miles of driving.

Big Jim 

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
On
> Behalf Of dh at busb.com
> Sent: Monday, October 03, 2005 5:13 PM
> To: diy_efi at diy-efi.org
> Subject: [Diy_efi] The Hunt effect
> 
> Took a trip to Washington a couple of weekends back.  Told my Prius
> driving
> Texas friend (From Austin) that he should start purchasing 89 instead
of
> 87
> octane.  That's 'cause it would cost him less.  Well, partner, he said
he
> would try it if I paid the bill, which I did.  We shared driving
duties
> and
> sure 'nuff the car got 51 mpg instead of the previous 48 mpg.  We did
this
> averaging over 80 mph (while moving) and with two drivers.
> 
> How does 3mpg save money?  Well that is 3mpg divided by 48mpg which is
a
> whopping 6.25% improvement.  Big deal? Well yes!  You see that gas
cost 10
> cents more per gallon which is 3.22% more.  Since I'm an accountant I
> noticed that the 3% increase in cost (because gas is quite expensive
now)
> was giving a 6% increase in mileage.  That, folks, is a 3% reduction
in
> gas
> price per mile.
> 
> Don't mean squat in a non-computer controlled car, but in engines that
> have
> high compression (over 8.5:1) and 'bouncing' engine management (where
the
> ignition is repeatedly advanced until the engine pings and retarded
> slightly) you can expect the same gains.
> 
> Please, try this for yourself and report the results.  Especially
those of
> you that have a consistent route to work and don't run into a lot of
> traffic
> in-route (both of you).  Report your results here, in public.
> 
> In reality, it should also work for even older engines with lower
> compression.  I first noticed the effect with an 83 Olds with computer
> controlled carburetor and that was NOT a sophisticated engine control
> system.  With that car the engine got about 6% better fuel mileage
making
> it
> breakeven even at $1.50 per gallon.  With the wonderful side effect of
> being
> able to pull the hills of North Alabama without pinging.
> 
> I call this phenomenon the Hunt Effect.
> 
> dh
> 
> 
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