Why 56.6mph?
Why 56.6mph?
(OP)
Why is mpg sometimes measured at 56.6mph? I seem to remember this speed was supposed to be the most economical but it can't be the same for all cars so how was it calculated?
thanks
Scrim
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RE: Why 56.6mph?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Why 56.6mph?
Norm
RE: Why 56.6mph?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Why 56.6mph?
Rod
RE: Why 56.6mph?
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Why 56.6mph?
I did find a few sites on google that talk about fuel economy at 56.6mph (mostly reviews) but all in the UK.
RE: Why 56.6mph?
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Why 56.6mph?
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RE: Why 56.6mph?
RE: Why 56.6mph?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Why 56.6mph?
Rod
RE: Why 56.6mph?
Back to the original topic, here's a chart of fuel consumption vs speed, sorry about the awful formatting. d means not measured.
Fuel Economy by Speed, 1973, 1984, and 1997 (miles per gallon)
Speed (miles per hour)
1973 (13 Vehicles)
1984 (15 vehicles)
1997 (8 vehicles)
15
d
21.1
22.3
20
d
25.5
25.5
25
d
30.0
27.5
30
21.1
31.8
29.0
35
21.1
33.6
28.8
40
21.1
33.6
30.0
45
20.3
33.5
29.9
50
19.5
31.9
30.2
55
18.5
30.3
30.4
60
17.5
27.6
28.8
65
16.2
24.9
27.4
70
14.9
22.5
25.3
75
d
20.0
25.3
Very interesting that the more modern cars show a distinct improvement at higher speeds. I am told that this is common. As cars get heavier it is increasingly difficult to improve town mileage.
If you ask me we should be driving at 75 by that data.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Why 56.6mph?
During the 1973 fuel crisis when rationing was almost introduced, the UK Government recommended 56mph for most economical motorway speed.
RE: Why 56.6mph?
Knap
thanks for that info, I was beginning to think I imagined it. Do you know where the figure came from though?
Scrim
RE: Why 56.6mph?
RE: Why 56.6mph?
Interesting list, Greg. Newer vehicles are more streamlined than in 1973, are fuel injected rather than carbureted (I only recall Porsche having FI in 1973), likely have an extra transmission gear, and automatic transmissions 'lock up' in high gear for no torque converter loss. The electronic sensors, platinum-tipped spark plugs, better tires, lower viscosity oils, help too.
But, aerodynamic resistance increases with the velocity squared, so the best fuel economy is at the lowest speed at which the engine can run efficiently in top gear. My old Taurus gave 35 mpg at 55 MPH, with the automatic trans. in overdrive 4th & the engine at 1830 RPM.
RE: Why 56.6mph?
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Why 56.6mph?
1937 Buick Roadmaster (original, ~67K miles)---Los Angeles to San Francisco and back (up on 101 and back on I-5) 10 mpg average (65/70mph).
1930 Model A Ford Std. Coupe (engine rebuilt to OEM specs)---Average 15 to 17 mpg for last 18 years.
1959 Nash Metropolitan (modified with a Datsun 210 carb and a 3.9:1 ring and pinion from an MG Midget...orig. was 4.22)---City, 25+mpg...freeway, 40 mpg max... cruises at 65/70 mph.
1966 Lotus Cortina(stock 1558cc twincam engine)---Long Beach to Amarillo and back on I-40, 21 mpg average.
1960 Austin Healy Sprite (stock 948cc engine)---Long Beach to El Paso and back on I-10, 39.9 mpg average.
Just for 'giggles', 1991 Dodge/Cummins 1 ton duelly, 21/22 mpg for over 200,000 miles and counting. Lowest mileage was towing a 5000 lb trailer to Vegas and that was 18 mpg @ 55 mph. And my 454 BBC powered 27 foot class A @ ~6mpg most of the time (really a killer to the bank account)! :o(
Rod
RE: Why 56.6mph?
Was the Lotus Cortina sold in US?
RE: Why 56.6mph?
Cheers
I don't know anything but the people that do.
RE: Why 56.6mph?
Actually their marketing wanted to put more realistic numbers on the window stickers the law won't let them. They're getting some pissed off customers, but they are forbidden to report anything but the EPA mileage. The reason the numbers are so high in the EPA test is that it only looks at the fuel burned by measuring emissions from the tailpipe. It doesn't account for energy coming from the battery. Obviously any hybrid will get a much better score.
http:
-b
RE: Why 56.6mph?
RE: Why 56.6mph?
The Locor (one of 7 that I have owned) was the U.S. 105 hp version and not the Euro 112 hp. I have owned both. I still have the original, but it was converted to a race car in 1967. My only rhd car was my 63 Austin Cooper (which was destroyed in 2003) and my current 67 Austin Cooper S which is a full race car only.
Thundair.
Neener, neener, neener. I made it from Lake Elsinore to Salt Lake City in 7 1/2 hours, without a ticket, I might add (couldn't come close to that on the way back, lost the AC in Vegas and stopped for repair...it was summer). Car? Much modded 1983 T coupe. Fuel mileage for the round trip was a tick under 20.
Rod
RE: Why 56.6mph?
Some one should have told me how to treat a turbo.
I killed one turbo just accidentally hitting it with water at a car wash.
The small engine turbos are the best of both worlds for mileage and power.. I am excited to see some mods to the Ecotec engine with 162 horsepower could be the new small block Chevy...
I guess I am straying from the original post ...I'll stop
I don't know anything but the people that do.
RE: Why 56.6mph?
Ofcourse the figures are arbitrary but since 90 kmh is the maximum speed on most main roads in Europe and 120 kmh is the maximum speed on motorways in many countries, the mix of the three figures try to convey a real fuel consumption figure to the consumer. In real life the figure you will obtain in practice is usually worse, although the figures are better since all cars are equipped with threeway catalysts that prevent manufacturers running the engines at extremely lean mixtures at the fixed test speeds.
At the moment the tests is no longer run at 90 kmh but only the 120 kmh and the urban cycle have remained
In all EU countries a list is published comparing the various cars available here.
See: http://www.vcacarfueldata.org.uk/index.asp