" Aerodynamics doesn't begin to have an effect until 60 MPH "

[Isaac Zachary]

Originally Posted by racprops

Can you translate that to Miles and MPH and MPG??


Please.

Rich

Energy per mile can be derived from
EPM=½ × p x V² x Cd x A

You don't have to do the math. Just plug in the numbers here: https://ecomodder.com/forum/tool-aer...resistance.php

I couldn't find the Chevy Express's coefficient of drag nor it's frontal area. But the late model Chevy Astro, which is similar in shape, had a drag coefficient of .40 and a frontal area of 34.1 square ft. Of course the Express would have a bigger frontal area, but probably a better coefficient of drag, although probably not by much.

But just using those numbers and 6,000lbs weight and the other defaults (including a 22% efficient engine) and I got 20.3mpg at 60mph according to the calculation. Obviously you can mess with the numbers and get any result you want.

The point I was making is even if a Chevy Express gets 15mpg, there are vans that hold 15 passengers. That's 3 or nearly 4 Toyota Priuses (or Prii). So they'd need to get 45 or 60mpg to meet the same fuel mileage. But some are getting 30mpg in their (diesel) Chevy Express vans! You can get better in a Prius, but you can't haul as many people or as much stuff!

[kach22i]

Originally Posted by racprops

Can you translate that to Miles and MPH and MPG??

ALS posted a PDF (post #33), does this snapshot from it help?

[kach22i]

Originally Posted by Isaac Zachary

The point I was making is even if a Chevy Express gets 15mpg, there are vans that hold 15 passengers. That's 3 or nearly 4 Toyota Priuses (or Prii).

This is a source of angst for me, looking at my beautiful 4-seat coupe the other day all I could think of was the waste.

I've only had a passenger in the car for maybe 5% of the miles I've put on it, and the rear seat may never see use.

This is the tragedy of most vehicles in the USA, at least as daily work commuters consisting only the driver.

[Autobahnschleicher]

Originally Posted by racprops

Can you translate that to Miles and MPH and MPG??


Please.

Rich

160 km/h = 100 mph

6L/100 km = 39 mpg

7L/100 km = 34 mpg

18L/100 km = 13 mpg

Learn metric...

[MeteorGray]

I'm an old man now, but I remember in high school in the 1950s the science teacher said that the US would need to adopt the metric system like the rest of the world had already done for very good reasons: it is so much easier to use and much more logical once you are taught the system.

It was up to the US Congress to do that for us.

Congress failed us.

[freebeard]

Have you not read John Mitchell?

en.wikipedia.org/wiki/John_Michell_(writer)

In 1970, Michell founded the Anti-Metrification Board to oppose the adoption of the metric system of measurement in the United Kingdom. Believing that the established imperial system of measurement had both ancient and sacred origins, through the Board he brought out a newsletter, Just Measure.[50] In 1972 he published the first of his "Radical Traditionalist Papers", A Defence of Sacred Measures, in which he laid out his opposition to the metric system.[50]

http://en.wikipedia.org/wiki/Metrica...ion_opposition

1 Metrication
2 Technical arguments
2.1 Natural evolution and human scale
2.2 Divisibility
2.3 Duplication in naming and usage
2.4 Industry-specific product sizing
3 Political arguments
3.1 Tradition
3.2 Government compulsion
3.3 High modernism and legibility
3.4 Price inflation
4 See also

[not responsible for vBulletin disrespecting clarifying spaces]

Based by the French on a mistaken geodesy

[skyking]

Regarding the OP:
I lump it in there with other misguided generalizations. My favorite one is " my car gets better MPG @70 than at < some slower speed >.
Modern engines are not very sensitive to small changes in RPM. What happens is they get a good tank or two, maybe downwind and downhill
That becomes the new standard and they would rather drive faster than do some real sciencing :P

[freebeard]

The premise does not accommodate head, tail and quartering winds.

What is the effect with a 60 MPH tail wind? Churning in the wheel wells?

[Autobahnschleicher]

Originally Posted by skyking

Regarding the OP:
I lump it in there with other misguided generalizations. My favorite one is " my car gets better MPG @70 than at < some slower speed >.
Modern engines are not very sensitive to small changes in RPM. What happens is they get a good tank or two, maybe downwind and downhill
That becomes the new standard and they would rather drive faster than do some real sciencing :P

Surprisingly I tested a Mercedes Benz E220 D and it genuinly had its best fuel economy at 110 km/h (just under 70 mph).
That was 4,7L/100 km (50 mpg)
However it is a rather aerodynamic car with a 2,5L turbodiesel and very tall 6-speed manual.

[ALS]

I did some testing a few years ago with my 97 Volvo and speed matters with fuel economy. It weighs in at 3450 lbs and has a Cd of.36
EPA has it rated at 25 mpg highway and Euro ratings are 11.7 liters per 100km.

50 mph 35.4 mpg
55 mph 33.9 mpg
60 mph 31.15 mpg
65 mph 28.5 mpg

At 70 mph it seems to run around 25.5 mpg.

BTW this was after some undercarriage mods. Before cleaning up the air flow under the car, it would get at most around 25.0-25.5 at 65 mph with E10. With straight gas the car gets between 29.25 and 29.75 mpg at 65 mph.