[Diy_efi] The Hunt effect

[dh at busb.com]

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