There are probably several factors that affect fuel economy, the largest being transmissions and differentials. It would be interesting to see how many gears each one has and what the final drive ratios are. All other things being equal, having a final drive ratio that allows the engine to run at lower RPM while cruising will improve fuel economy.
One of the things that surprised me is that the AE10x generation of Corollas got BETTER mileage with the larger engine and the 3+OD automatic tranny than the smaller engine with the 3 speed auto. The best I'm getting out of my AE104 is 31-32 on the highway. I pushed the old AE109 up to 39 mpg once.
I knew a guy that put a V8 in a '66 Ford Econoline van and got better mileage than with the 6. The engine could run at lower RPMs and move the thing around more efficiently.
The 0-60 times vs the weight could give you an idea. Without knowing what the engine hp ratings are, I would say that some of them use a high final gear ratio which would give better hwy mileage. Most of the city mileage figures are pretty close to the same with just the Corolla and the Fit above the mid to high-teens.
As for similar weight, you're looking at a difference of around 450 lbs between the lightest and heavest cars. That's a large difference in wet curb weight for small cars but these figures don't give you enough information to be able to answer your question.
The Nissan had a CVT, the Hondas had 5-speed automatics, and all the rest were equipped with 4-speed automatics.
I don't understand how some of those cars got both much lousier city and much lousier highway fuel economy than others, especially cars from companies that are struggling to meet their CAFE requirements.
I think the Japanese car companies have had a lot more experience designing cars and drivetrains with an emphasis on fuel economy rather than on performance, as the Detroit 3 have. The Detroit 3's offerings generally have an edge in performance, which is useful when customers prefer performance over fuel economy, but when consumer preference moves away from performance towards fuel economy the Japanese have the edge. The Korean car companies were using mostly Japanese designs until recently, so they have some catching up to do in both performance and economy, using low purchase cost to get consumers to buy their products.
From what I've read in Automotive News, the GM and Ford have released or are close to releasing engines with improved fuel economy that should match the current generation of Japanese engines, which should level the playing field until someone comes up with something even more fuel efficient. Chrysler seems to have put their eggs in the performance basket and doesn't appear to have anything close to being ready for market so they are looking at partnerships with the imports to supply engines until theirs is ready. Chrysler was smart in recruiting Jim Press, one of the smartest car guys I've ever met, and if they follow his advice and have some patience, they will have products that can compete in a market where fuel economy is preferred over performance.
"larry moe 'n curly" wrote in message news: snipped-for-privacy@b5g2000pri.googlegroups.com...
The interesting thing about these number is that they can be somewhat misleading. Consumer Reports also usually lists "overall" mileage and
150 mile trip mileage for the cars tested. There was somewhat less difference in these numbers: EPA Overall 150 mi Trip city/hwy Hyundai Elantra 27 32 28/36 Toyota Corolla 32 39 27/35 Ford Focus 26 32 24/33 Chevy Cobalt 24 31 22/31 Nissan Sentra 26 32 29/36 Honda Civic 28 34 23/32 Honda Fit 32 38 31/38 (5 speed automatic) Chevy Aveo 28 33 26/34
Only the Corolla and Fit really standout if you compare the 150 mile trip numbers. The Fit is smaller, has a much smaller engine, less performance, and has a five speed automatic, so I can understand why it is so much better. That leaves the Corolla as the exceptional car in its class as far as fuel economy is concerned. The Corolla has the smallest standard engine (1.8L) but even with the smaller engine it performs above average for the class. The smaller engine is likely to give superior fuel economy to the 2.0l engines in most of the other cars (except the Civic, which also has a 1.8L engine, and the Cobalt which has a 2.2L engine). So, it seems to me that the determining factor is engine size...all the cars with 2.0l engines had an overall average of 26 to 27 mpg and a 150 mile trip average of 32 mpg. The cars with the smaller displacement engines got consistently better mileage on both the 150 trip and overall. So what is the trade off? I am not sure that there is one. The performance numbers for the 1.8L engines are on par with the others (or better). Of course performance numbers can be misleading. Without actually driving the cars if is hard to tell how they "feel" on the street. I've had cars that would deliver really good performance numbers that were a chore to drive in traffic because of the power curve. Other cars, that "tested" slow, easily kept up with traffic with minimal effort. It might also be that the smaller engines will not be as durable as the larger engines, but I suspect even if this is true, it is irrelevant for most buyers.
Not really. You don't have enough information to make a valid judgment about mileage. Everything in automotive design is a compromise and you don't give any info about what compromises where made by the designers. You don't list the engine displacements, the engine horse power, the final drive ratios, the tire sizes, how many speeds the transmission has, etc. All of these things effect mileage and without knowing what they are, you can't make a judgment call as to why one car gets better mileage than another.
Its like saying that apples are red and grapes are purple. I wonder why grapes are better for you?
I mentioned the number of speeds of the transmissions -- all 4-spd automatics, except the 5-speed autos for the Hondas and a CVT for the Nissan.
Why is it necessary to know the HP when weight and acceleration times are given, from which HP can be derived? And what purpose would knowing the engine displacements serve?
I don't disagree about drive ratios, but why did GM choose to make the Chevy Aveo get lower MPG numbers, both EPA and real life, than the Honda Fit or the heavier Honda Civic and Toyota Corolla? How was the Aveo compromised to make it thirstier without making it more powerful?
What? A better comparison would be between two 5-lb bags of oranges where the oranges in one bag yield more juice than the oranges in the other bag.
HP cannot be easily derived from weight and accleration times because there are many other variables, including wheel and tire size, tire rolling resistance, gear ratio of each of the gears in the transmission, and the vehicle's coefficient of drag. HP and torque produced by an engine varies with engine RPM, and they vary between engine designs. For example, over square engines, where the cylinder diameter is greater than the length of the piston stroke tend to develop peak HP and torque at higher RPM than engines where the stroke is longer than the cylinder diameter.
Vehicle and drivetrain designers have to balance performance, fuel economy, cost, and manufacturing capability. A vehicle can be geared for better acceleration at the cost of fuel economy or for better fuel economy at the cost of performance.
The Aveo has a 1.6 liter, 16 valve, DOHC I4 engine with a 9.5:1 compression ratio that produces 103 HP at 5800 RPM and 107 ft-lb torque at 3600 RPM. Curb weight for the 4 door sedan and automatic transmission is 2,542 lbs. Pounds per HP is 24.7
The Corolla has a 1.8 liter, 16 valve, DOHC with variable valve timing with intelligence I4 engine that produces 132 HP at 6,000 RPM and 128 ft-lb at
4400 RPM. Curb weight for the 4 door sedan with automatic transmission is
2,822 lbs. Pounds per HP is 21.4
But isn't (curb weight in kilos)/(0-66 MPH acceleration time) close enough, especially for those of us who can't test with a tail wind to neutralize air resistance or with a dynomometer? ;)
But the Corolla gets better fuel economy in both the city and highway tests, despite the having practically the same acceleration time.
Horsepower is a measure of the ability to do work, not acceleration. Curb weight divided by 0-66 MPH acceleration time will give you curb weight per
0-66 MPH acceleration time, not horsepower. For example, a very strong man with the strength of 1 horse is riding a 10 speed bicycle, and we measure the time it takes for him to ride frrom 0 to 66 MPH, allowing him to use only 1st through 5th gears, then after he has rested, we measure the time it takes for him to ride the same bicycle from 0 to 66 MPH using only
6th through 10th gear. In this example, the man's power hasn't changed, and the weight of the bicycle hasn't changed, yet the 0-66 MPH time will be different because of the difference in the gearing.
The Corolla is also heavier. The Corolla gets better fuel economy despite the same acceleration time and weighing more because the engine and drivetrain use the fuel more efficiently than the other cars, or there is less aerodynamic drag. An engine that is more efficient will convert a greater portion of the energy in the fuel it uses into power at the crankshaft. A drivetrain that is more efficient will deliver a greater portion of the power delivered to the transmission input shaft (or torque converter in the case of an automatic) to the ground.
I'd like to add that, while some manufactureres might rate the fuel economy of their vehicles CONSERVATIVELY, others might take a more aggressive approach in thier numbers. My '01 Civic EX Coupe commuter car (100 miles per day since purchased new; 250+ K- miles to date) has consistently delivered 38-40 mpg at interstate speeds. Around town, it's 34-36mpg. These numbers are higher than the manufactureres estimates. so, as you state , how and where the care is typically driven will make a significant difference.
The currrent 2008 Chevy Cobalt TV ads claim that the Cobalts 36 mpg highway mileage exceeds that of the Honda Civic. However, I know of several people who have purchased 2007 and 2008 Honda Civic Sedans which are getting close to 40 mpg on the highway. Comparing the two using the
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web site comparator supports this, and clearly shows that the Honda Civic is the higher rated vehicle.
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