Why not do what they do in Kentucky.
Put 13 in wheels on the front and 15
in on the back.
This way you are always driving downhill.
Then get one of
those secret 200 mpg carbs
that Detroit is hiding.
Dave 90degrees on July
4th..Damn Global warming!
Sent: Mon, July 5, 2010 1:10:14
Subject: Re: [Tigers] Gas milage with different tires?
said too long
The issue of better fuel mileage seems to
periodically pop up, which is
not a bad thing. The Sunbeam's drag coefficient
is published at 0.45,
which amounts to it being a rolling brick. At a
speed, drag, which directly translates to hp and tq needed
to move the
car down the road, you can generally estimate the power needs
the summation of the drag forces. At least to the point where you can
convince yourselves that a change in driving habits is needed for better
mileage, lol. In this case, we'll run some numbers assuming that
speed is done in a gentle fashion and not in some screaming
manner. We'll start here:
frontal area is approximately 17.9 sq ft
Cd is 0.45
We won't use the mechanical or rolling resistance losses since they will
fairly constant is the range of highway speeds we'll look at
Drag = 1/2 *
rho * V * V * A * Cd
rho = air density, in slugs.. and we will use a STP
value of 0.0023718
V = car speed in ft/sec for th etwo cases, we will use
78 mph =
114.4 ft/sec and 70 mph = 102.7 ft /sec.
Plugging in Drag (78) =
0.5 * 0.0023718 * 114.4 * 114.4 * 17.9 * 0.45
= 125.02 lbs
Drag (70) = 0.5 * 0.0023718 * 102.7 * 102.7 * 17.9 *
0.45 = 100.8 lbs
HP(78) = Drag (78) * 114.4 / 550 = 26.004 hp
HP(78) = Drag (70) * 102.7 /
550 = 18.8 hp
As mentioed, mechanical losses and rolling resistance adds to
required. As can bee seen, the power difference is significant. And
that power requires fuel in direct proportion. It all points to the old
of "Speed costs, how fast do you want to go?" The best fuel
mileage can be
had by simply going slower. In this case a drop from 78
mph to 70 will
increase your mileage quite a bit. But, it also depends
on the other two
facors as well. If you have happy feet then it is
going to get worse mileage,
happy feet being the ones that are
constantly twiddling with the gas pedal:
everytime you do that, it pumps
raw fuel into the carb through the accelerator
So, my suggestions?
First, slow down
Second, get larger skinnier tires
as fat ones have a lot more rolling
resistance. In fact maybe some old bias
belted tires that can be pumped
up hard. High tire pressures reduce rolling
resistance in those tires.
Also get skinnier tires on the front and keep them
Third, get an AFR meter, not even a fancy wideband. Just one of
that have led lights and show rich or lean. Then tune the car for as
lean or as close to stoic as you can. Then drive it with the AFR meter
side led lit.
Fourth, maybe get a old timey vacuum meter and put it on the
well. A high vacuum means best economy.
Fifth, keep it tuned. Get an
electronic dizzy or innerds like Pertronic.
I hope this may help. But, as in
all things, your milage may vary..