what makes cars fuel efficient? - Chicagoland Sportbikes
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post #1 of 17 (permalink) Old 06-21-2006, 08:47 PM Thread Starter
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what makes cars fuel efficient?

I know it sounds stupid and there are 1000 different reasons but I can't understand why comparing apples to apples from different makers mpg can vary so much. For example:
Suzuki Forenza
23 mpg city / 30 mpg hwy
2.0L I4, 16 valve, 126 hp @ 5600 rpm

Toyota Corolla
32 mpg city / 41 mpg hwy
1.8L I4, 16 valve, 126 hp @ 6000 rpm

Hyundai Elantra
27 mpg city / 34 mpg hwy
2.0L I4, 16 valve, 132 hp @ 6000 rpm

All are econobox cars in the same price range but the mpg differs a good amount. Okay the engine size is a tad different but still. What makes the mpg differ, is it all in the fuel managment computer? Does Toyota have a secret the rest of the auto industry not know about. Not planning on buying a new cage anytime soon, just seems strange how the mpg is so different among seemingly even matched cars.

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post #2 of 17 (permalink) Old 06-21-2006, 08:56 PM
 
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Do you have any more info? How about vehicle weight, aerodynamic drag, wheelbase, gear ratios, etc.
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post #3 of 17 (permalink) Old 06-21-2006, 09:23 PM
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excellent point
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post #4 of 17 (permalink) Old 06-21-2006, 09:26 PM
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Quote:
Originally Posted by Richard James
Do you have any more info? How about vehicle weight, aerodynamic drag, wheelbase, gear ratios, etc.
+1, you also have to take things like torque into consideration. Producing lots of torque eats gas more than HP. Also mechanical efficiency, example, it's a lot harder to spin a 20" wheel and tire compared to a 15" wheel and tire. AWD systems use up power, etc.

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post #5 of 17 (permalink) Old 06-21-2006, 10:07 PM
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so, so, so many factors that have a effect on MPG that we could discuss it for pages and pages.

a bunch of it is gonna be in engine size, fuel delvery, gearing, and weight.

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post #6 of 17 (permalink) Old 06-21-2006, 10:11 PM Thread Starter
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Quote:
Originally Posted by Dr. D
+1, you also have to take things like torque into consideration. Producing lots of torque eats gas more than HP. Also mechanical efficiency, example, it's a lot harder to spin a 20" wheel and tire compared to a 15" wheel and tire. AWD systems use up power, etc.
I hear ya, but without going inot every detail, the examples are physically very close, ie. weight, length etc.... LEt's see if this spec comparo page works:
http://autos.yahoo.com/newcars/compa...specifications

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post #7 of 17 (permalink) Old 06-21-2006, 10:14 PM
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most of it has to do with torque and horsepower in relation to the weight of the car and specifically the rolling masses. Most of the time the weight of the rolling masses is determind by the quality of the product. So the cheaper the car is the cheaper the material the heavier it is. That means it has to have more power to be competitive in its class. More power is produced through more aggresive cam profiles and more aggresive tunes, making the car less fuel efficiant

or something
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post #8 of 17 (permalink) Old 06-21-2006, 10:21 PM Thread Starter
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Quote:
Originally Posted by Monster231
most of it has to do with torque and horsepower in relation to the weight of the car and specifically the rolling masses. Most of the time the weight of the rolling masses is determind by the quality of the product. So the cheaper the car is the cheaper the material the heavier it is. That means it has to have more power to be competitive in its class. More power is produced through more aggresive cam profiles and more aggresive tunes, making the car less fuel efficiant

or something
Makes sense.

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post #9 of 17 (permalink) Old 06-22-2006, 09:29 AM
 
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Quote:
Originally Posted by Monster231
most of it has to do with torque and horsepower in relation to the weight of the car and specifically the rolling masses. Most of the time the weight of the rolling masses is determind by the quality of the product. So the cheaper the car is the cheaper the material the heavier it is. That means it has to have more power to be competitive in its class. More power is produced through more aggresive cam profiles and more aggresive tunes, making the car less fuel efficiant

or something
Look at the comparo......the Elantra weighs the most, has the most power and still gets better mileage than the Suzuki.........and forget height as the Corrola is 2" taller(should create more drag) than the others yet still manages better mileage(although the 200lb weight savings must cancel that out).


BTW, forget those numbers......they are averages. You may or may not get that mileage depending on your driving habits.
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post #10 of 17 (permalink) Old 06-22-2006, 09:48 AM
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Quote:
Originally Posted by taziscool

BTW, forget those numbers......they are averages. You may or may not get that mileage depending on your driving habits.
That's true, but these are pretty good reference points while comparison shopping. They all test to the same standard.

For consideration, my Mazda 3 w/ 2.3L gets about 28mpg mixed, 32 or so highway, depending on how lead footed I am. The base engine is supposed to be a bit easier on gas, but isn't an option on the hatchback. It's rated at 32 highway, 26 city (I think).

Back when the GTP was only 75,000 miles old, it could get about 30mpg on the highway while keeping it at 80 and no AC.

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post #11 of 17 (permalink) Old 06-22-2006, 10:24 AM
 
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Quote:
Originally Posted by Grover
That's true, but these are pretty good reference points while comparison shopping. They all test to the same standard.

For consideration, my Mazda 3 w/ 2.3L gets about 28mpg mixed, 32 or so highway, depending on how lead footed I am. The base engine is supposed to be a bit easier on gas, but isn't an option on the hatchback. It's rated at 32 highway, 26 city (I think).

Back when the GTP was only 75,000 miles old, it could get about 30mpg on the highway while keeping it at 80 and no AC.
That reminds me, you have to take into account the accessories on the vehicle. Heavier duty charging systems, AC, water and oil pumps tend to drag on the motor. Also, think of the drivetrain efficiency. Front engine, FWD vehicles are much more effecient than their Front engine, RWD counterparts. Furthermore, a vehicle with 6 feet of drivetrain will produce more friction than one with a 2 foot drivetrain.
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post #12 of 17 (permalink) Old 06-22-2006, 10:31 AM
 
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With variable valve timing automakers can inflate the PEAK horsepower number ALOT. I'd rather street drive a VW with a nice flat torque curve (power throughout the torque range) than a Honda that's a dog until you hit 5800 rpm.
Average Jane (especially if equipped with an auto tranny) will never ever hit 6000rpm.

My Honda Crx came with only 62 horsepower @ 4500rpm. But that is o.k. because it weighs exactly 1819lbs. I replaced the engine (and more importantly the transmission with a tighter gearbox) for an engine with only 130hp. It's rare I lose a race.

Last edited by areacode312; 06-22-2006 at 10:38 AM.
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post #13 of 17 (permalink) Old 06-22-2006, 10:38 AM
 
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Quote:
Originally Posted by Grover
That's true, but these are pretty good reference points while comparison shopping. They all test to the same standard.
and what standard it that? I've always wondered if there is such a thing. I know I've heard several car manufacturers make claims and when their cars were tested by a third party lab, it produced up to 50hp less than what the claim was. Back in the day a lot of the muscle cars use to claim lower hp because of the insurance companies. Who regulates these numbers? Is there a standard for mpg but not hp, or the other way around? not trying to start a battle here, just curious if anyone has any insight to this stuff?
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post #14 of 17 (permalink) Old 06-22-2006, 11:07 AM
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FWIW, there is a movement starting that is going after the manufacturer's claims on MPG. There is no independent testing facility that gives those numbers, so they are not a good way of comparing MPG. Reality is, most of them never come close to the claimed MPG, not even the new hybrids.

I was reading an article on this a couple of weeks ago, might have been on here, not sure.

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post #15 of 17 (permalink) Old 06-22-2006, 11:11 AM
 
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Quote:
Originally Posted by Wink
FWIW, there is a movement starting that is going after the manufacturer's claims on MPG. There is no independent testing facility that gives those numbers, so they are not a good way of comparing MPG. Reality is, most of them never come close to the claimed MPG, not even the new hybrids.

I was reading an article on this a couple of weeks ago, might have been on here, not sure.
I knew that they were trying to come out with some sort of regulations about what the manufacturer claims and how the vehicle actually performs. I just didn't know if it had already taken place. That's why all these numbers don't really me squat to me.
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post #16 of 17 (permalink) Old 06-22-2006, 11:31 AM
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The numbers are BS at the moment. Nothing has been done to certify an independent third party to test ALL the vehicles so that we can have some numbers that mean anything.

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post #17 of 17 (permalink) Old 06-22-2006, 07:56 PM
 
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There ARE Federal regulations that force automakers not to lie about car specifications.

But for some reason Mazda is too stupid to abide by them.
They fudged the horsepower output on the Miata.
And they didn't learn their lesson and fudged the horsepower output of the current RX-8 saying it makes 238hp at the crank, but in reality it only makes 180hp to the wheels, ROFL. My Nissan 240sx with a stock engine (albeit from a Skyline) makes a stated 250hp at the crank, I've dynoed it the 210hp range which is in keeping with the rear wheel drivetrain loss rule of thumb of 15%.
Quote:
Because of the descrepency in the HP numbers, Mazda is sending out letters to every new registered owner of the RX-8, any pre-sale customers that haven't received their RX-8 yet, telling them of the error in the advertised rating, and giving them two options:

1. Mazda will provide free scheduled servicing for the duration of the standard warranty plus a $500 debit card.

2. Mazda will make arrangements to buy back the car.
Here's an interesting article, lol.
Quote:
Toyota, Honda must fess up to less vroom
New testing standards force carmakers to reduce claims
Nick Bunkley / The Detroit News / March 13, 2006

It turns out Toyota Motor Corp. isn't as strong as it appears in at least one area -- under the hood.

Testing under stricter new horsepower standards reveals that most of the models in Toyota's lineup have less oomph than the company has advertised. Even though the engines are unchanged, the automaker had to lower the horsepower ratings on all but few 2006 Toyota, Lexus and Scion models. The reductions range from 4 to 20 horsepower compared with 2005 models.

Honda Motor Co., the No. 2 Japanese automaker, also has downgraded the horsepower ratings on several models, including most of its Acura luxury brand.

But while the Japanese automakers overstated their power, an analysis of data compiled by Edmunds.com shows domestic vehicles have generally been testing at or slightly above previously stated horsepower. The testing suggests Detroit's automakers may have suffered unfairly in the battle of perceptions.

While drivers may not notice the difference, said George Peterson, president of consulting firm AutoPacific Inc, "it does matter to the manufacturers because each one is engaged in what I would call a brochure war where they're competing for the best specifications. And the average American likes a bigger horsepower number than a smaller one."

Most notably for Toyota, the rating for its top-selling Camry, when equipped with a 3.3-liter V-6 engine, had to be reduced to 190 horsepower from 210.

The V-6 version of Toyota's Highlander sport utility vehicle dropped from 230 to 215, and the Lexus LS and SC 430 decreased by 12.

The revised ratings comply with standards adopted by the Society of Automotive Engineers.

The standards specify which components and accessories should be on during testing and what kind of oil and fuel to use. To claim an SAE-certified rating, an automaker also must conduct tests in the presence of an independent witness.

"The intent of the revision was to tighten up the specifications," said Gary Pollak, an SAE program manager. "There were a lot of areas that were loose and subject to interpretation."

Peterson doesn't expect Toyota or Honda to face the same kind of backlash that Hyundai Motor Co. did after inflating the horsepower ratings of its U.S. vehicles by as much as 10 percent for more than a decade. The South Korea-based automaker agreed in 2004 to pay $30 million to settle a lawsuit filed on behalf of 858,000 owners.

But for consumers who covet powerful engines and allow horsepower ratings to influence which vehicles they purchase, the revisions could chip away at Honda and Toyota's reputations.

Consumers haven't taken kindly to overhyped claims.

In 2001, Nissan Motor Co. came under fire after overstating the acceleration of its Infiniti Q45 sedan. Ford Motor Co. admitted overstating the horsepower rating of its 1999 Mustang Cobra R, and Mazda Motor Corp. did the same with the 2001 Miata roadster. Buyers of both cars were offered compensation.

The new rating also could make some vehicles less appealing to consumers who start shopping by researching specifications on the Internet. The V-6 Camry's 190 horsepower pales next to competitors such as the 221-horsepower Ford Fusion, although that will change soon when the 2007 Camry is introduced with 268 horses.

Toyota spokesman John McCandless noted that the company was proactive in testing all of its vehicles under the new standards.

"We've never really been big on promoting horsepower," McCandless said. "The proof in the pudding is driving the car."

Darren Seeman, who runs the Web sites ToyotaLife.com, LexusLife.com and ScionLife.com from home in Portland, Ore., doesn't think people who bought a Toyota before the latest tests were conducted will feel misled or cheated. "Honestly, I don't think a lot of people buy a Toyota brand for the horsepower," said Seeman, 29. While Toyota and Honda have subjected their entire lineups to the new standards, Detroit's automakers are mostly retesting vehicles with new powertrains.

Eventually, all vehicles are expected to be rated according to the new standards.

"What we put in place were pretty much common practice at GM, and at Ford and Chrysler as well," said Dave Lancaster, a technical fellow at General Motors Corp. who chaired the committee that developed the standards. GM has submitted results from 11 engine lines -- covering popular vehicles such as the Chevrolet Malibu and Impala, Pontiac G6 and Cadillac DTS -- to SAE for certification. The tests bumped up the horsepower ratings for the Malibu, Impala and G6 by 1 for 2006.

DaimlerChrysler AG has retested its higher-performance vehicles, including the Dodge Viper and those equipped with a Hemi engine. The Viper went from 500 horsepower to 510, while the ratings for most others changed less than 4 percent, Chrysler Group spokesman Cole Quinnell said.

Under the previous guidelines, Quinnell said, "a lot of times we chose to publish a number that was lower than what another manufacturer might choose."

Ford has found virtually no changes in testing under the new standards. Company officials say the new 3.5-liter V-6 planned for the 2007 Ford Edge, Lincoln MKX and Lincoln MKZ will provide at least the 250 horsepower it has promised.

"It's not in our best interest to give customers an inaccurate picture of what kind of power their car has," Ford spokesman Nick Twork said.

Honda saw the horsepower ratings on the Odyssey minivan and Pilot SUV fall from 255 to 244. The CR-V and Element went from 160 to 156. Various Accord styles had slight gains. Six of the seven Acura models were downgraded, including the RL, TL and MDX.

Honda spokesman Chuck Schifsky said the company wanted to be up-front with customers by retesting all of its vehicles, even though that meant reducing many of the horsepower ratings. "We're still pretty darn competitive with all of our vehicles, even with the new specs," Schifsky said.

Honda and Toyota have been educating dealers about the changes. Dan Hurd, a salesman at LaFontaine Toyota in Dearborn, said, "They're more concerned with the drive and the fit and finish."

Seeman, who operates the Web sites, said he doesn't feel any differently about his Lexus SC 430 knowing that it was downgraded from 300 horsepower to 288. "I'm still going to tell people it's 300."

Last edited by areacode312; 06-22-2006 at 08:08 PM.
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