mpg vs. speed - Metro graph
 

(Originally written May / 06)

Took a break this afternoon because it was good testing weather ... http://www.gassavers.org/images/smilies/smile.gif

http://images6.theimagehosting.com/m...art.371.th.gif

Bi-directional averaged 1.7 km long runs on my level "test course"

Conditions at SUPN6 as of (3:00 pm EDT) 1900 GMT on 05/03/2006:

Wind Direction (WDIR): NNE ( 30 deg true )
Wind Speed (WSPD): 3 kts
Wind Gust (GST): 4 kts
Atmospheric Pressure (PRES): 29.94 in
Air Temperature (ATMP): 58.8 °F (this temp. avg'd with another land-based station)

raw data fyi:

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

This is with the following "mods" in place:

- grille block, wheel skirts, smooth wheel covers, tires @ 48 psi

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 car 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) is 112 km/h / 75 mph! that's nuts.

FYI - for those who were interested in this thread, I've (finally) posted a summary, with some new cleaned up images, at MetroMPG.com:

• Speed kills: testing MPH vs. MPG in top gear

I like the presentation of the info. Makes it easier for others to see that if you slow down, you use less gas.

Now only if I could get away with driving 40MPH on the Highway. In MN, the lowest allowable speed on the highways is 40mph, but that is asking for serious trouble since most people go about 10MPH above the speed limit.

Example:
55mph limit means go 65
60mph limit means go 70
70mph limit means mash the go pedal till you see God, then slow down a little.

Sounds like Missouri.

Here in California they have a slightly different variation.

50 means go 57 (even as you pass the regional CHP headquarters)
65 means go 70 if you're in a sedan, coupe, minivan or small truck
65 means go 80+ if you're in a 3/4+ ton diesel truck, a Hybrid or a VW bus

65 means go 55 if you're :turtle:

sounds like everywhere i've lived. NO ONE but me:) goes the speed limit or even below. on interstate 95 in richmond they actually call it "The Virginia Autbahn" . But i like the phrase" mash the go pedal till you see God then slow down a little" .:thumbup: May I use it? It's perfect for my coworkers. Thanx. S.:D

Yep, pretty much sounds like Missouri.
Here In IL, the law is,

If it says, ex.55, 60, 40, 45. you can go 5 over without getting pulled over. Once you hit MO, you can go 10-20mph over, even faster if you have a police scrambler and radar detector. Go as fast as Possible without getting shot in East St. Louis, and when the speed limit says 70, go 85 to prevent getting smashed in the rear from a honda going 95. Autobahn Courtesy rules apply :thumbup:

Yup, when I drove from Regina SK to Edmonton AB, that was pretty much the situation... even with snowy weather in the posted 70-mph zone. First I followed a Colbalt that was doing 80mph, then a Corsica that was doing about 82. A huge Ford truck towing a trailer flew by doing around 100, but I couldn't keep up to it. Then I followed another Ford was doing 90 and later an Infinity that was doing the same speed. Finally, the fastest I followed was a buick century that was doing 95 and the Geo barely kept up.

The other interesting thing is that 3/4 of all these fast cars were from Alberta. I guess they can afford to get 7 mpg at those speeds (the Geo gets around 30 mpg).

It's interesting to see just how straight line your plot is MetroMPG. No Excel here, so no graphs but flattish roads have allowed a better idea of my envelope which would be typical of any overweight slushbox with piss poor aerodynamics.

MPG is almost flat between 38 and 50 MPH at around 32 MPG, and it drops sharply below that due to TC slippage if you try and drive steady state.

52 - 31
55 - 30
60 - 28
65 - 25
70 - 21

I take it this was data collected on the great FLA trek of 2007/08?

It's really good data to have.

I wish this type of detail was available from the government agencies (EPA/NRCAN) - in addition to the "city vs. hwy" simulations (which is all they are), I'd like to see an actual plot of fuel economy at various steady state speeds. That, I think, would tell us more in the long run.

More from driving around and going over to my cycling start points than the actual drive down which was my big quest to hit 30 on a long trip and failed. :rolleyes:

Half the gang is in the land of Treb and that big famous rodent today while I recover from a New Years Day century ride which luckily occurred before the same cold system as you have there hit here. It's only 44° outside... yuck!

I head back up on Friday...

Yea I hate that I'm always going down 94 going to detroit michigan. And someone in a honda is doing 95 tailgating me. The best is when the cut you off and almost cause an accident to save a minute.

Interesting how it's about linear...

After the taller trans it starts to look less linear.
http://metrompg.com/posts/photos/mpg...t-z-b4-aft.gif
Speaking of which, have you thought about tracking down a set of taller wheels/tires and running another one of these tests Darin?

I feel for you, I live in MI, and 94 is said to be the worst road ever. I believe it is actually a drug route from Chicago to Detroit.

Anyway, what's the point of measuring speed in km/hr if you're giving your fuel economy in mi/ga?

Don

I know. Not what I was expecting to see. Projecting the slope, apparently at about 210 km/h the car would be getting 0 mpg. :D

In fact, I the day I did the original (green) plot, I was collecting one more data point @ 110 km/h, but I discarded it because one of the bi-directional runs was ruined (I think I caught up to another car and had to brake - speed limit is 80 on that road). But the one "good" data point was around 43.x mpg, which would have started to suggest a more expected plot, more like these:

http://www.metrompg.com/posts/photos/gcc-autobild1.gif


To see if it gets better still than the taller final drive? I hadn't considered it (mostly because I don't know anyone with the same bolt pattern - 4 x 114 or something).

Because I have to drive in Canada, but I mostly talk about fuel consumption with Americans. ;)

Really, I'm tri-lingual: MPG (US) for the bulk of the conversations, L/100km for the enlightened Canucks, and MPG (Imperial) - still - for the majority of the unenlightened Canadians.

MPG imperial, US.... oh man, I feel for you, but I understand now.

Do you live in town? How do you deal with the snow up there?

Thanks!

I live in a small city, yup. I deal with the snow by building luge/toboggan runs in the back yard for the neices and nephews! :)

http://tbn0.google.com/images?q=tbn:...ts/bobsled.jpg

That, plus snow tires. We're having a good old-fashioned winter this year, aren't we?

We indeed are! Out here in west Michigan we've gotten a fair amount, but it's the drifting that hits us. Our East-West road has a couple S-turns that drift badly, and my 1/3 mile long North-south driveway drifts VERY bad.

I used to have to plow as much as twice per day to get my car in and out... I actually saved money selling my tractor and buying another 4x4 and getting rid of the car.

We're trying to sell this money pit of a house... we have a showing tomorrow. Let's hope!

West Michigan - I was in Muskegon a few years ago. Drove there to join a tall ship and sail up & over the peninsula & back down to Bay City. Traveled about 500 miles by water to go 140 over land :)

The dreaded N/S driveway! My mom grew up on a farm with a 1/4 mile N/S lane. She was telling me just the other day that they often left the cars at the road and walked in & out, because plowing it only made the drifts deeper as the banks got higher.

Good luck with the sale.

Ahhhh yes, you feel my pain!

My father in law came down with his big plow last year and made banks on either side that were about 3.5-4 feet tall.

Well.... you want to guess how tall the drifts were the next day? Uhg!

I'll have to get some pictures some time. Three times last year I had to use the GMC to literally pull my car through everything to the end of the driveway to go to work (back when I was still a tech consultant).

The problem is that there is Nothing to block the wind or snow for about two miles to the west, then RIGHT on the east side of the driveway, there's a woods.

Okay.. rants over!

Pat

Pretty much. It looks like engine eff is increasing proportionally to the car's energy requirements increasing. Ideally, if your engine is operating at peak eff at ~55mph, it should be more like the other maps you posted from GCC. Maybe I'm being too optimistic but I think you still have way more available in terms of mileage at a slow highway cruise w/ your setup.

Calculator
 

Great thread. Yeah, it's crazy how much speed affects your mileage. For those that don't believe, check out http://www.mpgforspeed.com/ It has a calculator that will show you exactly how much you can save.

Its interesting how the graphs have a linear reduction in efficiency and not a exponential reduction. I guess for an electric car we would get graphs like the ones I've attached. I thought a internal combustion car would still have similar results but I guess not.
Ian

Historical fuel consumption vs. speed graphs
 

From my previous car's owner's manual, drivers were enlightened with the attached little tid-bit.

This was in the 1956 Beetle owner's manual. And, I believe in prior and very few subsequent years.

It shows a litres/100km (un-labeled) vs. speed graph where the consumption goes up (nearly linearly!) as speed rises. As well, there is a weight penalty plotted!

Note: the maximum speed of these cars was/is 68 mph!

[First post... Glad to be part of the movement!]

Great first post, co_driver. Nice image.

Got to love the language in that manual:

Welcome to the forum.

Yeah I'm in MN also.. in rural mn its like more like 5-10 mph depending on the driver, then again cops will give a ticket if you 10 over no questions asked... but the twin cities is nuts.. go the speed limit and people are flying by you like your standing still.. but there cops usually just go after the "boy racer" types.. the ones thinkingthe roads are race tracks.. and leave the 10mph overs alone