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Not always the case, because you have to factor in the ICE efficiency which is not linear.
For many cars, ICE efficiency peaks at the torque peak RPM level, whereas extremely low and High RPM will yield very bad efficiency.
It is my understanding that most cars will be in their sweet spot at around 2000 RPM at the tallest gear, as ICE already has a good % of its optimum efficiency at that rotation speed. 2000 RPM will translate into 45-50 mph in a small engine car and 75 mph in a big engined car (my previous 740i for instance) .
Of course wind resistance is a key factor, and becomes the main reason for mpg drop over the sweetspot.
Better meaning quicker, safer, more comfortable and cheaper. This clearly needs huge investment.
I think a good mass transit system also needs a strong integration of all of its parts together, so that it will be easy to switch from one line to another.
The French SNCF is currently working on a 245 mph commercial speed for their trains in France. Some cities that previously needed 5+ hours would be linked in bit more than 2 hours (450 miles) which would drastically cut airplane and car transit.
Currently, train has 90% marketshare against plane for all journey of less than 2 hours. 60% for less than 3 hours, 40% for less than 4 hours and 30% for less than 5 hours. It is difficult to compare train and car marketshare because obviously there aren't any reliable statistics. There are obviously transfers from road to train when train becomes attractive.
Of course, Long distance trains must be complemented by local network of mass transit. There is no sense to a 1 or 2 hours rail journey if one need to drive the car 1 hour to the station.
For instance I would very well see some high speed links between San Diego, LA, SF and more to the north and the other states.
Fare price is an issue. Currently in France travelling by car will be always cheaper from 2 passengers upward. Break even will be 1driver+1 passenger.
I have read about deeded parking spaces selling for $50K or more in the Chicago area.
2011 Hyundai Sonata, 2014 BMW 428i convertible, 2015 Honda CTX700D
You are correct. But, you are incorrect in stating ...
You would have gotten better mpg at 45-50 in the 740.
Air or wind resistance is not the only variable in the calculation. While I can't vouch specifically for the BMW 740's best speed for mpg, the gearing of the car and the rpm and torque-peak are other variables. At 45-50 mph many cars would not shift into OD or into their top gears. A 6-spd automatic that is in 3rd or 4th gear of its 6 gears at 45 mph is not going to be using fuel very efficiently.
If all there was to get higher mpg was to keep reducing the speed to get no wind resistance, then as you went down to 30, 25, 20, ... 0 mph your mpg should be zooming. At 1 mph you would get what - 5,000 mpg? Obviously that is not correct.
Actually, there ARE laws against that. In Texas it's called "exhibition of excessive acceleration" and you can definitely be ticketed for it. My stepdad got that ticket two or three times in the 70s.
In the USA, insurance rates go up across the board slowly but surely when there are a lot of accidents. Sure, the absolute best drivers get the absolute best rates (usually) but we all pay for too many accidents. If the accident rates went WAY DOWN across the population, we would all benefit.
Insurance is also going up because of the horrible cost of repairing the tinny crumple zone cars of today. I was pleasantly surprised to get my insurance bill on the 07 Sequoia. It was $150 per year less than my 05 GMC hybrid. It is $450 less than the 05 Passat Wagon I had. I would surmise it has to do with cost of repair on these new "safer" cars. Just read of a guy with an FJ Cruiser. Said a very minor fender bender was $7500 to repair. His comment was they are not as tough built as his older FJ40s.
PS
The savings on insurance will cover the additional cost of gas over driving a little vehicle. .
Yes but all that does is answer the question for that model. So what is best for an auto. Scion Xb, is not going to be the same for a 6-spd auto. Malibu, is not the same for a PU. Each model is going to be different.
It depends on the gearing, the aerodynamic efficiency (or lack therof) of the car, and the particulars of the engine. As a rule of thumb, the best mileage comes with the engine running about 1/3 of its range between idle and redline, as Honda was kind enough to illustrate here:
In reality, brisk acceleration usually preceeds brisk braking and major loss of momentum.
So with traffic, it makes more sense to acceleration gradually and keep plenty of empty space in front of you. Let off the gas and coast to a stop.
Basically, in practice, the less you need your brakes, the better you mileage. Ideally, you would have exactly enough momentum to let off the gas and coast to a stop at a red light, wasting zero energy with braking.
My van has a trip computer, and it reads out instant MPG as well as average MPG.
Keep in mind vans are HEAVY, two tons plus, with people and gear we're talking probably 5000 lbs rolling down the road.
I have found that if I floor the throttle, my average MPG will drop immediately, by 0.1 to as much as 0.3 mpg, and I can never recover that loss. More often than not I just end up having to brake and losing a ton of energy.
I get much better MPG accelerating gradually and leaving plenty of space in front, plus coasting to a stop at red lights and stop signs.
As for speeds, again, the van has a huge frontal area and is boxy, so MPG takes a plunge with speed.
Instant is not very accurate, because you have to account for elevation changes.
Trips, though, I have averaged as high as 34mpg, but I was doing 46-60 mph, no faster.
At 65mph, I usually get about 30mpg.
At 75mph, that drops again, usually 26-28 mpg.
So for me speed is a major factor, probably the biggest.
Flooring the throttle has never helped, in fact it always drops my average noticeably.
To get peak mileage you have to drive like Grandma, basically.
Sounds boring, but in practice, that's what works best.
Plus, extra wear on the transmission means it might prove to be penny wise, pound foolish.
It is an interesting point, though.
Maybe I'll try it out in the snow, to start out in 2nd gear to reduce wheelspin.
I think the lowest speed I've been able to get my Intrepid into top gear (4-speed automatic), is around 37 mph. In normal driving it'll do it around 45.
I think most automatic transmissions are "smart" enough not to upshift until the conditions are right. And even if you do trick them into upshifting early, like what I described with my pickup, if it's still realistically too low in the rpm range, the moment it encounters enough load, like a hill or too much pedal pressure, it'll downshift again.
For most if not all automatics, it means 1-2. This is why you want an automatic with tap or paddle shifters. You should be driving a manual, but that topic's down the hall.
Actually, even if you forget and leave a transmission in a low gear, if you get revving fast enough, aren't most of them smart enough these days to upshift for you, anyway? For instance, if I left my Intrepid in 2nd, and got out on the highway, wouldn't it eventually shift up to Direct Drive and then finally, overdrive?
They actually had transmissions smart enough to do that back in the 50's, but then in the 60's, I think they started getting "dumb" again.
I would imagine that with the advent of computer controls they would upshift at redline for you, but in the old days if you stuck it in L or 2 or 3 (if you had it) that was all you got.
You can always make the trans upshift at WOT by merely leaping off the gas pedal momentarily, but (even in a Toyota, LOL!) it will eventually downshift again.
The thing to do is pick the average speed you want to be going in order NOT to have to stop at the next light, then floor it to reach that speed and totally let up. The optinmal speed will usually be quite a bit lower than the posted speed limit, except in one or two clued-in communities where they actually took the trouble to phase their lights.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
I do -- a 2007 Honda Civic Hybrid. It has a digital speedometer and a computer that calculates mpg every 10 seconds. On a flat surface with calm wind and a mild temperature, here's what I get:
60 mph .................. 51 mpg
70 mph .................. 44 mpg
80 mph .................. 36 mpg
Note that the HCH has a Continuously Variable Transmission (CVT) that constantly adjusts its gear ratio for maximum efficiency, so it's not directly comparable to a fixed gear automatic with overdrive. But these numbers clearly demonstrate the effect of speed/wind resistance on mpg.
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Dallas drivers aren't much friendlier than those in Nevada.
Around town at 35-45 mph, I get 60 mpg.
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As the 740 engine is rated at 5400RPM, then the sweet spot would be at 1800RPM.
which would correspond to 65-70mph.
Anyway, my bord computer readings were pretty similar between 50 mph and 75 mph. While the sweetspot center may be lower than 75 mph, it is pretty flat and could extend between those 2 extremes. Below 45 mph and above 75mph the mpg start noticeably decreasing.
Once, I tried a highway economy run at a medium speed of 80 mph (75-85mph extremes, as light foot as possible) on the 740 and the board computer displayed a result of about 24mpg, slightly improving the official figures. It was the trip computer so allow a margin of error of course. Boring to death.
All my efforts over 50 miles went in smoke when I stupidly got stuck for 20 minutes in a jam because of a poorly managed toll at the highway exit. My mpg dropped to 20 , which is what I generally achieve when I set the cruise control to 100 mph flat (in Germany of course).
I have a 1978 600cm3 Citroen Ami 8 which tallest gearing is of about 14 mph / 1000 RPM. My observed sweetspot is at about 35 mph middle with a stretch between 30 and 45 mph. Engine need to be maintained above 2000 rpm (Flat-2 engine). Looks like some US speed limits were set using this car as a reference...
I estimate my Fit sweetspot at around 50 mph (2000 RPM at that speed, CVT transmission)
How would you best name the range of speed where fuel consumption is the lowest in a car ?
I'll pause for a moment to let the uproar of laughter die down.
Okay, now I'll continue. Seriously, the most fuel efficient speed for a car is specific to each car. It's generally the lowest speed in the highest gear or overdrive. That means you're going as fast as you can while the engine is turning the lowest rpm that it can. That's efficiency.
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I think he meant that "sweet spot" applies more to a passive, inactive object like a tennis racket or baseball bat, where you can lay your finger on an actual place on the object. A machine is complex with parts swirling all about.
But we understood what you meant anyway. :P
I do! I commute in a Miata. :shades:
The only van with a manual is the Mazda5, and it was too small for my needs and not really all that fuel efficient for the sacrifices you make.
I think we'll see pigs fly before Toyota puts a manual trans in a Sienna. They just removed that option from the RAV4.
Pigs lack the aerodynamic surfaces to control their direction along the three axes of flight. Thus, they tend to impact the ground at a high rate of speed.
And that's not nice.
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They had to do this, of course, because auto makers were too stupid to figure out that a 50 mph car crash would be bad for the occupants.
I'm sorry, perhaps that's a bit harsh. Maybe auto makers were really smart. Maybe, instead, they were a bunch of sick perverts who got a thrill by mutilating and killing helpless animals ..... you know, the same way budding serial killers start out.
Years later, they mass-marketed exploding Pintos.
Coincidence?
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I do -- a 2007 Honda Civic Hybrid. It has a digital speedometer and a computer that calculates mpg every 10 seconds. On a flat surface with calm wind and a mild temperature, here's what I get:
60 mph .................. 51 mpg
70 mph .................. 44 mpg
80 mph .................. 36 mpg
Note that the HCH has a Continuously Variable Transmission (CVT) that constantly adjusts its gear ratio for maximum efficiency, so it's not directly comparable to a fixed gear automatic with overdrive. But these numbers clearly demonstrate the effect of speed/wind resistance on mpg
Coming to work today I did the same SOTP trials in a new Prius, 230 miles.
Set the cruise and eyeballed the Insta-Readout
50 mph - most readings were between 49-60 mpg with spot readings as low as 39 and high as 73 over a 5 mile stretch of flat or gentle inclines/declines
60 mph - most readings were between 45-52 mpg with spot readings as low as 36 and as high as 73 over a different 5 mile stretch.
70 mph - most readings were between 40-45 on a flat stretch for about 2 miles.
80 mpg - asking to go to jail with $3500 fine and $1100 penalty for the following 10 yrs - not attempted.
The writers over there are on strike, you lookin' for work?
But don't count on it. Remember, the pattern is never up, up, up. Gas prices shoot up, then retreat slightly, then shoot up even higher. And the higher they go, the easier it is for prices to go even higher.
When gas went from $2 to $3, that was a 50% increase. A boost from $3 to $4 is only a 33% increase. From $4 to $5 is a 25% increase. And so on.
But it was a $15 a tank increase for me.
A boost from $3 to $4 is only a 33% increase.
But its still a $15 a tank increase for me.
From $4 to $5 is a 25% increase.
But its still a $15 a tank increase for me.
And so on.
And so on.
2011 Hyundai Sonata, 2014 BMW 428i convertible, 2015 Honda CTX700D
No relief here.
And diesel is still $3.69
(more in Report Your Local Gas Prices Here).
Then if the price of gas goes to $4 I will just stay at home and watch the goldfinches and humming birds feeding.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)