5 MPH ISN’T MUCH, SO WHO CARES?
Try this simple exercise.
While paying attention to safety, drive your car at 30 mph and stick your hand outside the window with your palm facing the wind. Takes some effort to do this, but easily manageable.
OK, now try this at 60 mph. A lot more effort involved! When you think about it, while you’re driving at 60 mph, it took more than twice the effort to hold your hand in place.
That’s the whole point! Twice the speed doesn’t mean twice the effort – it actually means a whole lot more.
Even just a 5 mph difference is a big deal!
WANNA BET? LET’S DO SOME MATH!
OK, some geeks banged their heads together and came up with a basic mathematical formula for the amount of power it takes to move your car at certain speeds. Here’s the geek formula:
Driving load = av + bv2 + cv3
– The “av + bv2” part has to do with how much power it takes to overcome the resistance due to parts that scrape together in the regular operation of your car – like pumps, pistons, ball bearings, brakes, and the road resistance your tires need to overcome to get the car rolling at a given speed.
– The “cv3” part has to do mostly with power required to overcome wind resistance (or “drag”) while driving.
– When doing this formula, your replace a, b, and c with the speed you’re driving at. Let’s assume this speed is in miles per hour (mph).
For those of you who know anything about math, the “power of 3” aspect of this formula means that wind drag will be the largest force your car will have to fight with. Make sense?
Remember your hand? What if you sat up there on the hood and had to deal with all that wind at any speed? That’s a lot of wind! And your car works hard to fight against that wind.So the point is: wind resistance is what kills your car’s fuel efficiency.
So, back to the math. Plug in the speed, in this case 60 mph:
Driving load = 60 + 602 + 603 = 219660 units
These “units” could be anything – horsepower, Newtons, Joules, whatever. They just provide a measureable number to compare with.
Based on this formula, the amount of power required to drive at 60 mph is 219660 units. Based on the same formula, the amount of power required to drive at 65 mph is 278915 units. The difference is 59255! This is an increase of about 27% more effort your car has to make just to drive 5 mph faster!
See Image 1 for a graphical representation of how this effort loads up as you drive faster.
Notice:Twice the speed means more than twice the effort!
EFFORT VS EFFICIENCY
Depending on how your car’s engine was designed, it will drive with better efficiency at certain speeds more than at others. For most cars, this peak efficiency lies somewhere between 40 and 60 mph. See Image 2 for all passenger cars in general.
Want a real example? I measured my car, it seems to be around 50 or 55 mph. See Image 3.
Wind resistance kills car fuel efficiency. Drive slow!
WILL 2 MINUTES KILL YOU?
In a rush? Do the math again, and you’ll think twice! Let’s assume you drive:
– 20 miles to work at 65 mph. This means you will drive about 18 minutes.
– 20 miles to work at 60 mph. Then you will drive only 2 minutes more!
Will 2 minutes kill you?
It will sure save on wear and stress for your engine! And it will save you fuel, too.
Try driving at least 5 mph slower.
Read John’s other articles at: http://www.associatedcontent.com/johnmelendez