Ned Hibberd's Blog

Saw the report and sad for me, I agree with the song, I cant drive 55

I agree with yah. I drive a Mustang and people bear down on me in an effort to get me to speed up.

The problem with thinking slower speed limits will save gas is you're comparing the average cars of the early/mid 70's to todays cars. There's NO comparing the two.
Back then it was dang near impossible to buy a car with "overdrive" (a final gear ratio of less than 1:1) and today it's dang near impossible to buy a car that doesn't have overdrive.
Every engine will have a point of maximum efficiency, normally around it's peak torque but not always. At this point the engine will require LESS throttle to maintain speed and thus burn less fuel. Todays cars are geared from the factory for maximum efficiency at a certain speed. Slight variations can effect it (tire size changes are the most common) but normally not much. However, a 15 to 20 MPH change can and will effect it quite a bit. Ex: A bogging car will require more throttle to maintain speed and will always seem to be on the verge of down shifting (if it doesn't constantly) and it will also be more prone to pinging from the lack of octane requiring the owner to either buy a higher grade of gas or have the car re-tuned to run with less ignition timing or a fatter fuel curve to prevent engine damage.
It will be interesting how many of the classroom smart geniuses will try and tell all of the hands-on mechanics and engineers how changing speed limits will save the world TONS of fuel. Especially since they've really stuck their proverbial foot in their mouths when they released the data showing dairy cows are worse polluters than the average automobile..

xlacious,
At typical highway speeds, wind resistance isn't a major factor at all!! Especially when we're only talking a 10-20 MPH change. Airflow is a different science in-and-of itself. If you've ever been involved in any wind tunnel testing you would see every vehicle forms a pressure wedge in front of it that air begins to flow smoothly over. Secondly you'd realize that EVERY car/truck/SUV basically acts like an airplane wing (longer flow path over the top than the bottom) which creates lift. That's why even newer cars are fitted with air dams under the core support to "spoil" that effect and add stability to the vehicle. More importantly since cars don't have much of a grill these days it creates a high pressure area in front of the radiator/AC condenser to aid in cooling efficiency.
Testing done in NHRA ProStock has also shown little to no effect in actual pressure differentials using different hood scoop shapes and sizes. However, at speeds over 200 MPH they have seen a difference in overall vehicle wind resistance so the actual size and shape of the scoops have gotten smaller. Mind you the findings of SLIGHT differences in wind resistance at 200 MPH would equal -0- difference to a vehicle at typical highway speeds.. The same findings have been made in NASCAR, Winston Cup, USAC, and several other sanctioned bodies.
I would much rather concentrate my efforts to making the vehicle run more efficiently than worry about the difference in wind resistance at 10-20 MPH. A difference that would probably compare to having a single typical 8-10 yr old in the back seat (ad

I am not complaining about the cost of fuel and I will not drive 55 on our state highways...

...unless...

...it is the law.