Tested: speed vs MPG - 2006 Toyota Corolla automatic
 

While I was in Ontario over the holidays, I borrowed my dad's car to collect some speed vs. fuel consumption info.

I learned a couple of interesting things about the car...

http://ecomodder.com/forum/attachmen...1&d=1231533701

Temperature was cool (-4C), and there was a breeze. I'll post the full details a bit later...

Raw numbers: (posted Jan 13/09)

Conditions, route & methodology (reposted Jan 14 from further down the thread):

Weather conditions: -4C, wind E 9km/h, pressure 103.32 kpa, humidity 68%

Route: 2 lane highway, straight, dry & almost level (11 feet elevation change over 1.6 km / 1 mi.) The road runs SSW/NNE and can be found here: iroquois ontario - Google Maps

Methodology:

Speed was set once per pair of bi-dir runs with cruise control, cancelled with the brake between runs. Car was brought up to speed & leveled off before passing a "start" marker (road sign) where the ScanGauge (not calibrated to this car) was reset. Reading was taken after passing a "finish" marker and cruise was cancelled.

Traffic conditions: There was no traffic in my lane and very little in the oncoming lane. (More than a few runs were done with me being the only car on that stretch of road.) If anyone caught up & overtook me, or if I caught up to another car, I ditched that run and did it again to avoid aero interference.

See also:

• http://ecomodder.com/forum/showthrea...05-a-9841.html

• Tested: speed vs. MPG in top gear (1998 Geo Metro / Pontiac Firefly)

• Honda Ridgeline MPG vs speed graph: fuel economy with & without cargo trailer

Very nice. Look forward to the full details.

I just wish the automakers would release this level of info for new vehicles (standardized lab conditions of course).

I'd rather see this than some kind of simulated trip to grandma's house, which is what the EPA does. Or let's say "in addition to".

Thanks Darin.

I'm always amazed with the straight line between mph and mpg.

I second the wish to have such data with the car. The normalized conditions should be difficult to find as temperature, humidity and wind do have an influence.

Denis.

curve
 

Darin,between 70 and 120 km/h the "curve" is very linear,just as auto engineers claim.Any ecomodder who established a baseline for their own car at any two distinct speeds,and drawing a straight line between those two points on a graph,ought to be able to interplolate or extrapolate mpg at any speed for their car,with a fair degree of confidence.-----------Another valuable tool! Your great graphics and presentation intimidate the hell out of me! "I am not worthy," Thanks mucho,Phil.

What kinda trip mileage are you getting from the Corolla?

Phil: I wonder if we're seeing the slope of the Corolla graph getting less steep as speed increases to 120. That would be consistent with other graphs I've seen, eg:

http://metrompg.com/posts/photos/gcc-autobild1.gif
( source: Speed kills: testing MPH vs. MPG in top gear - MetroMPG.com )

That graph suggests to me what we're seeing is the engine approaching the best BSFC zone as speed, load & RPM rise.

roflwaffle: I didn't really do a lot of driving in the car. I did a couple of mostly rural trips in cold weather (-5 to -10C) that netted mid 40's MPG (US). Left to his own devices, my dad's mileage was 22.4 mpg in wintertime 100% sub/urban driving (from: http://ecomodder.com/forum/showthrea...rolla-546.html ). Not sure what he's getting on the open road.

What kind of road conditions? How long at specified speed was needed to obtain the average? Traffic?
Too many variable my friend. While my GP may lockup at 38mph, here in MT that will not net me the best mileage due to the hills and mountain passes. Dropping my speed from 75mph to 70mph lowered my mpg, just from the decrease in inertia attacking the passes and rolling hills.
I'm guessing you used a scangauge? My dad bought one this last fall, and at 9mpg in the truck he is very motivated to increase that, but has been unable to just because he is already as the limit of his conditions for FE.

Don't take this as an insult or negative comment. Just some of us live in places that just don't allow for amazing FE. :( Would be nice to hit 36mpg with a full size car, but its just not possible where I live and my driving conditions.

2 lane highway, straight, dry & almost level (11 feet elevation change over 1.6 km / 1 mi.)

Weather: -4C, wind E 9km/h, pressure 103.32 kpa, humidity 68%

The road runs SSW/NNE and can be found here: iroquois ontario - Google Maps

However long it took to drive the 1.6 km between markers (road signs) at the given speed. :)

There was no traffic in my lane and very little in the oncoming lane. (More than a few runs were done with me being the only car on that stretch of road.) If anyone caught up & overtook me, or if I caught up to another car, I ditched that run and did it again to avoid aero interference.

That may well be. Depends on what techniques you throw at the geography though.

The purpose of the test was to rule OUT as many variables as possible and present some baseline data.

One thing I couldn't avoid was the wind on this day. I'll post the raw data later that shows this.

I drove through your general area this summer on a road trip I took and got some amazing mileage (43+ mpg) driving through the mountains with my Matrix filled to the brim with 4 people and luggage. Its totally possible to get great mileage in the mountains.

I would bet fuel economy is better at higher elevations. You get to open the throttle wider and the air hitting your frontal area is thinner.

Sounds like my grandpa. He has a 2002 and pulls ~25-30+mpg (~40/60 city/highway?) driving like everyone else in pretty nice weather.

Revised graph!

Added the car's official highway fuel consumption ratings that also shows the constant speeds at which those figures were attained in these conditions.

Shows EPA "new", EPA "old" and NRCAN. I was surprised to see the Canadian rating so much higher - I was under the mistaken impression that they were nearly the same as the "old" EPA figures.

http://ecomodder.com/forum/attachmen...1&d=1231854565

One of the things that surprised me about the car/graph was the point of best fuel economy at 40 km/h.

That speed happens to be pretty shortly after the transmission shifts into 3rd gear (of 4), so the engine is turning fairly slowly. It surprised me because it's the first speed vs. fuel consumption graph I've ever seen where the best performance isn't in top gear.

You can tell from the graph that the shift from 3rd to 4th (with torque converter lockup) happens between 60-70 km/h (shifts right in the middle at 65 km/h or 40 mph, actually).

It's possible to bleed speed down to 60 km/h and then hold 4th gear there, which would have raised that MPG point on the graph quite a bit, but I didn't. The transmission will downshift at the slightest prod under those conditions.

Thanks for collecting and posting this data. This is motivating me to do a similar test for my car.

This sounds just like my car. There is a straight and relatively flat stretch of road about 1 mile long in my daily commute. The speed limit is 35 mph, I try to go just fast enough to get the TC locked and keep it there, which is about 37-38 mph (~60 kph) at just a shade under 1500 rpm. This requires a very delicate touch with the throttle, and careful monitoring of the TPS. On my way to work the car is not fully warmed up yet, usually just hitting the 150*F coolant temp required for lockup, and the road is very slightly uphill in this direction, and I see mpgs in the low 30s. On my way home the car is fully warmed up and has the slight grade working in it's favor, and I see low-mid 40s, as high as 50 mpg in warm weather with summer fuel.

I was wondering if you would mention the TC Lockup between 60kph & 70kph.
I can force the TC to lock up in my wife's car at 55kph, by turning off OD then when I hit 55kph turn OD on. The trans will go straight to lockup, but as you said any extra load at this point drops it immediately out.
Nice work, Thanx,
S.

Graph looks about right. Too bad I can't get the "no traffic" conditions.
Good baseline info right there :)

I've noticed the best straight/level/low traffic MPG I can get is at about 33/34 MPH on one stretch of road near my house. Once in third gear it gets pretty high (needs-more-calibration 'Guino reads between 60's and 70's).

Don't let me stop you. :) That would be interesting to see.

Oh - that's a neat trick! I didn't try that. It would sure save the extra energy spent getting to 65 kph just to get it to lock and bleed back down to a slower cruising speed.

IME it's also more likely to lock-up at lower speeds if you give it a bit of gas, say going ~5mph above the lock-up speed, and then setting the cruise control as you let off the gas.

Where can I get raw data for one of these cars in the high-speed runs? I'd like to plot fuel consumption (gal/mi) versus speed and versus speed squared in the 50-85mph range, among other things.

I used data gathered by MetroMPG on the Blackfly and the 06 Corolla to find the optimum speed to drive each car, based on the premise that saving gas is good, getting to your destination sooner is good, and depending on how much you value your time and your fuel, there is a correct balance. So I assigned a dollar value to time and to gas.

I pay something like $2/gal, but I feel obligated to save gas like it was much more expensive. I value it at $6/gal. Getting there sooner also matters to me, to the tune of about $12/hr.

I plotted the cost per mile for each of MetroMPG's data points, and I had Excel fit a parabola to the result. The optimum speed to drive, considering only time and fuel consumption, is the speed where the cost per mile is the lowest. For me, that would occur around 67mph in the Corolla, and around 62mph in the Blackfly.

However, suppose I was running late for work and I'd be willing to pay $.50 for each minute earlier I arrive, but I still care to conserve gas to the tune of $6/gal. Under these conditions, I'd drive the Blackfly at 68mph, or the Corolla at 78mph.

This is very much back-of-the-napkin. A better optimization problem, like the one that runs in my head whenever I'm behind the wheel, would take in to account that some speeds are not as safe as others (whether too slow or too fast), cars probably wear out faster at higher speeds, and that it's fun to post large MPG numbers. Also, these data only apply to steady-state cruising in economy cars on flat roads with the A/C off, in top gear.

Bottom line: drive faster to save time. Drive slower to save gas. For me, the balance appears to be around 65mph.

I don't think the raw data is available. The chart came from here: Green Car Congress: Fuel Consumption at Higher Speeds

I'm new here but is this graph saying at 70kph the vehicle gets 51.x9 MPG? And at 40kph it gets 57.2?

I own an 05 Corolla CE Automatic and it gets nowhere near these figures at those speeds... you stated you borrowed the vehicle so I would assume that means its stock (unmodified). I'm confused how you arrived at these MPG ratings, unless I'm just totally missing something here.

Hi Milkman - yes, the figures posted are correct and the car is unmodified.

But note the test conditions the readings came from, in post #9. FYI, you can't compare real world (round trip, cold start etc.) mileage to these figures. They're simply "constant speed" numbers for a warmed up car under pretty ideal conditions.

Have you done a similar test (level road, cruise control, no traffic etc) and come up with different numbers?

This is fascinating to me. I have a 2004 Matrix XR, FWD, Automatic. I had assumed that my best fuel economy would come in my highest gear, after torque lock-up, at the lowest possible RPM--this equated to about 37 mph. Then, empirically (without a scan-gauge), I found that a slightly higher speed than the lowest possible RPM speed in this condition produced a better result--45 mph or so yielded better fuel economy. Your test results concur with my rough finding. What is astonishing about your result is that 24.9 mph--which must occur prior to torque lock-up--is an even better efficiency speed! Remarkable. Please tell me if I'm interpreting your results incorrectly. I know have 25 mph and 45 mph marked in my mind as my efficiency target speeds. Thanks for the work. Steve

Hi, Steve

I wonder if what you saw is the difference between optimal (flat road, constant speed) testing conditions vs. "real world" driving where it sometimes makes more sense to cruise a bit faster than the lowest speed at which top gear/lockup engages just to avoid automatic downshifts on hills, slight acceleration, etc.

I've seen this in a few vehicles -- but only ones with automatic transmissions. Even though it isn't in top gear, the aero load is reduced enough at 40 km/h / 25 mph that it comes out ahead. If you could manually shift up to the next gear, the "dip" seen in the next 2 data points would disappear.

Darin

Yup, I see that same phenomenon in my Echo, too.

I'm confused though, it sounds as though you were saying it shifted into 4th AND lockup at the same time? That doesn't sound right. Should hit 4th at around 30ish and lockup at 37-38mph.

You're right. It didn't change to 4th and lockup at the same speed.

Cool. Did some digging and the transmissions are nearly identical for my Echo and the Corolla, the difference being final drive. Both are of the U3xx family.

Corollas and Echos are remarkably similar in their FE performance, nod to toe Corolla for carrying extra weight and displacement. And both positively rock with stick. Neat stuff.