As for the 55 mph speed limit, there is no singlesweet spot as the gearing
varies from car to car. I made a 6000 milecoast to coast trip in my vette -
never re-setting the avg. MPG button- and got 30 mpg. In 6th gear, at 85 mph,
it was turning 1700 rpm. Togo 55 mph, I would have had to drop 2 gears at
least and would probablyturned more RPM..... I dare a Prius to try to get 30
MPG across Texas,air on, (radar detector on) at 85 MPH! As I recall, whenthey
passed the 55 MPH limit in the 70's. the big rigs got worse fueleconomy
because they had to drop 2 or more gears to comply, which putthem out of their
optimum operating range. As Tom mentions, thereis no substitute for prudent
driving.....
Ed
-----Original Message-----
From: Tom Bryant [mailto:saltracer@awwwsome.com]
Sent: Sunday, July 20, 2008 02:36 PM
To: land-speed@autox.team.net, BWANA343@aol.com
Subject: Re: [Land-speed] Tires,Mileage,etc/non LSR ?
My thinking on this is that altering from the engineered gearing will
likelyresult in no gain, or worse, a decrease in mileage. Some years ago, I
had atransmission tech that got involved with building an overdrive system (on
mytime I might add). He eventually went into production. His primary marketwas
motor homes. He found that in many cases the mileage would improve for ashort
time and then go back to the previous mileage. Computers have alearning curve
and will adjust themselves to do what they are designed to doand quite often
the engine is more efficient in a lower gear. Loaded engineshave lower vacuum
and lower vacuum is a computer's signal for more fuel.Todays' computers are
even more sensitive to changes of inputs and some willnot tolerate changes in
gearing, etc.Each month, I write a short article for the local newspaper (an
ad) and haveresearched different ways to improve mileage and have seen
references tobigger, usually heavier wheels & tires resulting in decreased
mileage. Ihave cautioned people to be wary of mileage scams that are now
rampant. Ihave also decided to research some of the more promising "scams"
byinvesting in them myself and see what the results might be. I purchased
theRun your car on Water + Fuel" material; 104 pages of detailed instruction
onthe construction of the device which looks to be something that will
work,but, there are disclaimers warning about compatibility with
computersystems and what has to be done to make it work with them. Plus it
isprobably illegal, at least in California. Most add-on devices are!In the
past, I have also doubted that the proposed 55 mph limits on vehicleswould be
effective with todays more streamlined vehicles, but from materialI recently
read about the throttle sensors now being used (no physicalconnection between
the throttle pedal and the fuel system) it seems that theengineering is
focused on 55 mph as the desired speed "sweet spot" for mostall vehicles.
Having said all this, it appears that the most useful thingyou can do is to
drive sensibly. Excessive use of heavy throttle and/orbraking is
expensive.Tom, (Hot & Smokey) Redding CA - 216 D/FCC
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