Edmunds.com | Inside Line | Auto Observer Your Account | Help | Directory
You are here:
![[F]](http://a332.g.akamai.net/f/332/936/12h/www.edmunds.com/media/townhall/webxicons/site.gif){kind=small}
Forums
Automotive News & Views Should the US government bring back the 55 mph max speed limit again?
1418 messages, Last post on Dec 16, 2008 at 11:21 AM
You are in the Automotive News & Views Forum. Your Hosts are steve_ & claires
|
Replying to: steve_ (Nov 10, 2008 10:50 am) If an Orwellian nanny-state like England can have faster highways, why can't a land that basks in the claim of freedom and liberty?
|
|
|
Replying to: fintail (Nov 10, 2008 10:56 am) I think 70-75 mph is a good fuel saving speed. 55 mph is asinine, beyond stupid. Even modern 4-cylinder cars can cruise at 80 mph serenely, safely and with power to spare.
|
|
|
Replying to: lemmer (Nov 10, 2008 11:08 am) Here is a web page with a number of graphs plotting MPH vs. MPG
|
|
|
Replying to: cdn_tch (Nov 10, 2008 12:18 pm) |
|
|
|
Maybe if we all drove less (stayed home once in awhile, combined errands, take the bus occasionally) we could save as much or more fuel than drooling along at 55.  55 was an almost arbitrary solution 35 years ago (see my earlier post regarding the origin of '55'). Surely we can do better than that now & keep traffic moving at pace. Cheers! Paul |
|
|
Replying to: cdn_tch (Nov 10, 2008 12:18 pm) Now I have a Mazdaspeed 6 - 6 speed with an engine that can produce about 4X the power. I can't even get into top gear at 55 mph on any sort of hilly environment, and the car is not geared that tall. And here's the other thing - I'm happy with my mpg, if I wanted better mpg I wouldn't have bought the car I did and wanted to slow down. If I wanted better mpg I would have bought a car with higher mpg and still drove it faster than 55! 
|
|
|
Replying to: kernick (Nov 11, 2008 5:23 am) Some are not sold in North America, most are (Toyota Prius, Golf GTI, Golf TDi, BMW 535, MB 180 Kompressor and Geo Metro). And the ones which are are much more representative of what is on the road than a Mazdaspeed. ALL curves show the same shape. Reason: wind resistance quadruples for each doubling of speed. To over come windresistance requires power, power comes from gasoline. A given curve may shift slightly to the right because of gearing but it will not change tha fact that the faster you go, the more fuel you will burn. You have made a choice that you can and want to afford lower MPG, but that does not make it a good choice for everyone since it is not just about the fuel used but the pollution that is created when it is burned.
|
|
|
Replying to: cdn_tch (Nov 11, 2008 10:59 am) |
|
|
Replying to: cdn_tch (Nov 11, 2008 10:59 am) The vehicles listed in that report are OLD. I think one was from the 1980's! I listed my car not to say it is typical, but to say that if someone wants better mpg, then they can choose a higher mpg model - not having to worry about driving an archaic 55mph. I don't know where you live, but I can honestly say I haven't seen any of the cars you listed in months. If you want to show graphs put up some real-world mpg ratings for the new 6-speed cars that are out - Malibu, Camry, 5-spd Corollas ... Reason: wind resistance quadruples for each doubling of speed. To over come windresistance requires power, power comes from gasoline. Yes but depending on what the number is, doubling it might not matter much. If you have 2% drag at 55mph and 3% at 65 mph then you haven't changed much. But if your cars gearing is 10% different between 5th and 6th gear then you end up with a net increase in fuel economy by going a speed in which you can stay in 6th gear. If it was simply aerodynamic drag that affects mpg, then similarly you would expect mpg to continue to increase as you went slower ... 45, 35, 25, 15mph? does a 30mpg car at 55mph, get 60 mpg at 15mph? So it is aerodynamics, gearing, engine rpms, weight, which all interact in the equation of what speed your car is going to run at to get optimum mpg. A 3-speed auto '75 Malibu and a 6-speed auto '09 malibu are not going to get optimum mpg at the same speed of 55mph. Also I don't see where you are going with the pollution thing, as cars emit very little pollution. With the amount of pollution put in the air by all the other sources in the world, man-made and natural, 1 mpg makes no difference. If you want to stop pollution you may have an issue, since the goal of the world economy is to expand. Population growth and world economic growth = increased waste products. I would like a world with less pollution, but it's not going to happen by me getting 35mpg or 20mpg, when there are billions of people striving to use more resources.
|
|
|
Replying to: kernick (Nov 11, 2008 12:15 pm) Yes, aero drag is not the only thing since we have multi speed vehicles, but generally speaking they will all be in top gear by 55 MPH on flat ground. So, if we make the assumption that a given vehicle is in top gear at 55, we then look at what it costs (in HP) to go faster. Take an average sedan with a Cd of .3, total rolling weight of 3750 Lbs and a total frontal area of 22 sq ft, we get HP losses to aero drag of: 55 MPH = 13 HP 65 MPH = 19 HP 75 MPH = 26.5 HP 85 MPH = 36.5 HP Again, that horsepower must come from gasoline, you will burn more the faster you drive (once you are in top gear). Polution: NHTSA states that there are about 3 trillion vehicle miles driven per year. If we simplify the numbers and say that on average the sum of all vehicles driven average 30MPG, the savings in gasoline by increasing that to 31 MPG would be about 3.2 Billion gallons. So would a 1 mpg increase make a difference? I'd say that it would. |
|
You are here:
Forums
Automotive News & Views Should the US government bring back the 55 mph max speed limit again?
New? Join Now!
Forum Tools
Search Forums
Browse by Vehicle
Browse by Board
Browse by Topic
Today's Chats
