mpg vs. speed

[MetroMPG]

See: http://www.metrompg.com/posts/speed-vs-mpg.htm

km/h - W mpg - E mpg
55 ... 83.1 ... 82.4
60 ... 77.8 ... 76.3
65 ... 74.1 ... 71.7
70 ... 71.2 ... 70.8
75 ... 67.2 ... 62.7
80 ... 63.3 ... 59.3
85 ... 59.4 ... 56.4
90 ... 55.4 ... 53.9
95 ... 51.5 ... 50.3
100 ... 46.6 ... 46.9
105 ... 44.9 ... 44.0

[Matt Timion]

Looks like someone is going to be cruising at 55 km/h for a while :P

[MetroMPG]

i could drive my '89 accord all day at 95 km/h on cruise control and beat its hwy rating by 20-30%.

[MetroMPG]

Originally Posted by Matt Timion

Looks like someone is going to be cruising at 55 km/h for a while :P

you'd think so, eh?

but actually, nope - i really don't like the way the engine sounds & feels down there. my lowest comfortable cruising speed in 5th is 65 km/h.

i only tested the lower speeds because jan asked about it a while ago.

[Matt Timion]

Originally Posted by MetroMPG

one thing this confirms to me is that the blackfly's highway EPA rating is harder to beat compared to other cars i've driven. meaning, the constant speed at which the blackfly attains its EPA rating is slower than other cars.

i could drive my '89 accord all day at 95 km/h on cruise control and beat its hwy rating by 20-30%.

same thing with my mom's car. i borrowed it (1997 camry 2.2 automatic) and ran the same road after doing the blackfly today. its EPA highway speed (30 mpg US) ... 112 km/h / 75 mph! that's nuts.

I actually remember reading that the EPA estimates are obtained at 60mph for highway speeds.

I think the Geos are more difficult to beat becasue they have smaller engines are are more efficient by default. As we know, it's hard to squeeze blood from a highly fuel efficient turnip..

Wait, wrong analogy.

[MetroMPG]

Originally Posted by Matt Timion

As we know, it's hard to squeeze blood from a highly fuel efficient turnip..

yes! exactly what i was going to say

but surely the prius is one of the most efficient turnips out there. yet its graph shows its EPA highway rating (51 mpg) is achieved at around 68 mph - 8 mph higher than the the fireflea's EPA hwy speed.

too bad we don't know what conditions that prius graph was made under for comparison - the site i found it on didn't have any context either.

if any other scangauge equipped people are reading this, do you know what speed gives you your EPA highway rating?

[JanGeo]

First let me say WOW! I didn't expect the slope to be that negative and would have expected a little peak somewhere where system overhead would have been greater than drag for low speeds.

I don't have a level enough road around this area of the country to do testing at various speeds but will give it a try at some point. Maybe if I can find a test loop somewhere - where is a test track when you need one huh! Would love to just drive in a circle on a level track for a few minutes and get some numbers.

[krousdb]

Originally Posted by Matt Timion

I actually remember reading that the EPA estimates are obtained at 60mph for highway speeds.

The highway test loop is done at various speeds where 60MPH is the max and the average speed is 48MPH IIRC. There is more info at fueleconomy.gov but I am too lazy to look it up. Then beginning in 1985 the highway numbers were slashed by 22% and the city numbers were cut by 10% to reflect more real world driving conditions. The 1984 CRX 1.3L was rated 67 MPG highway. The 1985 CRX HF was rated at 54 MPG, about 22% lower.

Now for the next model year they will be slashing the numbers even further to reflect real world driving conditions. Driving conditions in my world are obviously not "real world" conditions.

[krousdb]

Originally Posted by MetroMPG

yes! exactly what i was going to say

but surely the prius is one of the most efficient turnips out there. yet its graph shows its EPA highway rating (51 mpg) is achieved at around 68 mph - 8 mph higher than the the fireflea's EPA hwy speed.

too bad we don't know what conditions that prius graph was made under for comparison - the site i found it on didn't have any context either.

if any other scangauge equipped people are reading this, do you know what speed gives you your EPA highway rating?

I was actually thinking about the same thing recently, only I was thinking how much easier it is to exceed EPA in the Del Sol than it is in the Prius. In the Del Sol, I can achieve ~80% over combined EPA on my daily RT commute. In the Prius, I can only get 50% over.

I suspect that since the automakers have knowledge of what the test routine is for EPA, that perhaps they "tune" the engine and transmission of the high FE models to produce the best EPA results, which helps to sell the high FE models. On the run of the mill FE models and sporty models they tune for driver satisfaction, which is what helps sell the non FE models.

I dunno. Just a theory of mine.

[philmcneal]

what we need is good power to weight + areodynamics ratio, and the EPA tests never take areodynamics and weight as a factor. Just the engine, as you can see even using it as a "comparason" factor seems kind of out of place due to the differences in cars.