gyre wrote:Nothing unusual.
Just good design.
1.3 litre Fiat tuned to hit peak efficiency at high rpm, fine tuned with the distributor advance, 9.5 compression down from normal due to smog years, and milder cam.
Better mileage if I had changed to a stock euro cam.
Typical mileage was 35-40 mpg on premium on the highway, days of real leaded premium, without the ethanol gas tax which loses about 35% for most cars.
20-25 mpg in town if I was hammering it.
I get 25 mpg with the 408ci, but so do many other people.
12.5 compression, mild cam, 3.25 rear end, extremely aero daytona body.
Mileage probably doesn't vary between 55 and 100 mph.
Check out the hypermiler forums for the really shocking claims.
I got 26 mpg with a full size van once in the mountains, four speed manual overdrive, 318.
That probably depends a lot on wind, but it always did well.
Mileage runs in the fifties used to routinely break 50 mpg using all the tricks.
I can't beat 25 mpg in my volvo or ranger.
My ranger should get 36, but with ethanol and age, may not be possible.
The volvo is compression limited in those years and high drag.
Im curious about your statement about fuel consumption not varying between 55 and 100 mph. Can you support this? Higher speeds require more work. More work requires more energy. Without getting into the formulas, basically if you double your speed, you will need to more than double your horsepower. It is not a linear increase.
NR I have to disagree with "need to double your horsepower". Higher speeds do not require -much if any- more work. The work is in reaching that speed and in overcoming any additional friction losses. Additional friction could come from increased turbulence or possibly a hotter engine. You do not need to increase your horspower to maintain a speed. This is how the car companies can advertise gas mileage that no one else can get. Take it sllllloooowwwlllyyy to 55 on a smooth road with overinflated tires and drive at one speed for 10? hours and your average mileage will be great.
You have clearly never attempted to attain high speeds in a car.
Power to overcome air drag =FA x CD x 0.00256 x mph cubed/375
The cube of the top speed is related to the coefficient of drag (CD), and so altering your CD from a typical 0.45 to a more sporty 0.30 (a reduction of 30%) only results in a 12% increase in top speed. 100 mph to 112 mph.
This is a noticeable gain for sure. But to double your speed youre gonna eventually increase your power. Volkswagen, the makers of the 1100 hp Bugatti Veyron realized this to attain their 220 mph top speed.
A better example is a Mitsubishi 3000 gt vr4. This car has 320 horsepower, and can reach 160 mph in 5th gear at 6000 rpm, with 1000 rpms to go before redline, and a whole unused 6th gear. (this particular car is power deficient rather than drag deficient, so it is a great example for our formula)
If you apply the above formula, it would take around 625 horsepower to reach 200 mph.
A wise man gets more from his enemies than a fool does from his friends.