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  #101  
Old 04-17-2012, 07:29 AM
zut zut is offline
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Originally Posted by jz78817 View Post
the test method used to rate fuel economy has changed, you can't directly compare numbers from anything before 2008 to anything after.
This ought to be re-emphasized: modern fuel economy numbers listed on the sticker are not the same as those from the 1970s. The underlying tests are the same, but the reported sticker number is adjusted downward to reflect a more typical driver. This pdf details the rationale behind the current calculations.

Many vehicles use the MPG-based approach given on page 103 of that document. Using those formulas, the 1977 Mazda that tested out at 46 highway / 35 city would be stickered today at 33 highway / 27 city.

33/27 isn't horrible, but the '77 GLC weighed just 1750 pounds and had a 1.3 liter, 73HP engine. You can get comparable fuel economy today from, say, a 2012 Mazda2, which gets 34/28, weighing 2350 pounds and with a 1.5 liter, 100 HP engine. And that's not even close to the best fuel economy available; just to pick a few, the Chevy Cruze gets 38/26, the Hyundai Accent and the Kia Rio both get 40/30, and the Prius gets 48/51.
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  #102  
Old 04-17-2012, 12:45 PM
jz78817 jz78817 is offline
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Originally Posted by zut View Post
This ought to be re-emphasized: modern fuel economy numbers listed on the sticker are not the same as those from the 1970s. The underlying tests are the same, but the reported sticker number is adjusted downward to reflect a more typical driver. This pdf details the rationale behind the current calculations.
they actually changed the test procedures for 2008. Pre-2008 ratings were estimated downwards.
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  #103  
Old 04-17-2012, 09:29 PM
carnut carnut is offline
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Originally Posted by obbn View Post
I should clarify that a larger car that Americans want isn't only for safety. I realize that a car doesn't have to be large to be safe, but small cars like the Smart just aren't going too protect you as well when hit by a very large vehicle than a car of bigger dimensions.... .
Yes, but as the racing fiend I bought my R5 from said, "But it's harder to hit such a small target."
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  #104  
Old 04-17-2012, 09:34 PM
carnut carnut is offline
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Originally Posted by jtgain View Post
I'm thinking that the rear wheel drive may have been it. You get the sensation of the car "pushing" you up the road instead of "pulling" you.

Plus the noise. When you wind out the engine it just feels like more power. Sort of the "washed car runs better" fallacy. I'm still amazed.
Oh, some of them had tons of power. It just wasn't applied as efficiently as today. I still love the sound of muscle cars. But I know that a modern Audi is also a wonderful thing, even though it is quieter. It turns corners better too.
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  #105  
Old 04-17-2012, 09:52 PM
jz78817 jz78817 is offline
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Originally Posted by carnut View Post
Oh, some of them had tons of power. It just wasn't applied as efficiently as today. I still love the sound of muscle cars. But I know that a modern Audi is also a wonderful thing, even though it is quieter. It turns corners better too.
just don't own one out of warranty.
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  #106  
Old 04-18-2012, 02:15 AM
zut zut is offline
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Originally Posted by jz78817 View Post
they actually changed the test procedures for 2008. Pre-2008 ratings were estimated downwards.
Sort of. After 2008, the methodology for calculating estimated city and highway mileage changed, nominally to include the effects of additional cycles. Test procedures for the city and highway test cycles have not changed. Moreover, for many vehicles, rather than run the additional cycles, the effects of the additional cycles are derived. That means the city/highway sticker fuel economy numbers are calculated using only the city and highway tests, using the formula I linked to above. These calculations are different than those used pre-2008, but still adjust the dyno test values downward.

So it's still possible to do a comparison between 2012 fuel economy sticker numbers and 1977 fuel economy sticker numbers, so long as you remember to adjust the 1977 numbers correctly. For a feel of the difference, this page has data files containing both unadjusted test numbers (which was what would be on the sticker in 1977) and the resulting sticker number for all vehicles.
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  #107  
Old 04-18-2012, 06:37 AM
jz78817 jz78817 is offline
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http://en.wikipedia.org/wiki/Fuel_ec...e_through_2007

As a means of reflecting real world fuel economy more accurately, the EPA adds three new tests[41] that will combine with the current city and highway cycles to determine fuel economy of new vehicles, beginning with the 2008 model year.[42] A high speed/quick acceleration loops lasts 10minutes, covers 8 miles (13km), averages 48mph (77km/h) and reaches a top speed of 80mph (130km/h). Four stops are included, and brisk acceleration maximizes at a rate of 8.46mph (13.62km/h) per second. The engine begins warm and air conditioning is not used. Ambient temperature varies between 68 F (20C) to 86 F (30C). The air conditioning test raises ambient temperatures to 95 F (35C), and the vehicle's climate control system is put to use. Lasting 9.9minutes, the 3.6-mile (5.8km) loop averages 22mph (35km/h) and maximizes at a rate of 54.8mph (88.2km/h). Five stops are included, idling occurs 19 percent of the time and acceleration of 5.1mph/sec is achieved. Engine temperatures begin warm. Lastly, a cold temperature cycle uses the same parameters as the current city loop, except that ambient temperature is set to 20 F (−7C)
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  #108  
Old 04-18-2012, 07:23 AM
zut zut is offline
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If that was in response to me, then you might want to explain why the section you bolded is different from "include the effects of additional cycles." Or are you agreeing with me?
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  #109  
Old 04-18-2012, 07:45 AM
jz78817 jz78817 is offline
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How is "adding three new tests" not "changing the test procedures?"

Quote:
Moreover, for many vehicles, rather than run the additional cycles, the effects of the additional cycles are derived.
Cite?

Last edited by jz78817; 04-18-2012 at 07:47 AM..
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  #110  
Old 04-18-2012, 11:18 AM
zut zut is offline
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Quote:
Originally Posted by jz78817 View Post
How is "adding three new tests" not "changing the test procedures?"
Quote:
Originally Posted by zut View Post
After 2008, the methodology for calculating estimated city and highway mileage changed, nominally to include the effects of additional cycles. Test procedures for the city and highway test cycles have not changed.
In other words, the same "city" and "highway" tests are run today as were run 10 or 20 years ago: there are no changes to the test procedures for those cycles. The change is is the calculation of the reported fuel economy numbers, which now nominally include the effects of additional cycles.

Quote:
Originally Posted by zut View Post
Moreover, for many vehicles, rather than run the additional cycles, the effects of the additional cycles are derived.
Quote:
Originally Posted by jz78817 View Post
Cite?
40 CFR 600.210-08 - Calculation of fuel economy values for labeling
Quote:
(a) General labels. Except as permitted in paragraph (e) of this section, fuel economy for general labels can be determined by two methods....The second method is the derived 5-cycle method, and is based on fuel economy that is derived from vehicle-specific 5-cycle model type data as determined in paragraph (a)(2) of this section. This method is required for 2008 through 2010 model years (except for medium-duty passenger vehicles, in which case it is optional), and is permitted beginning in 2011 model year under the provisions of 600.115-08.
The derived highway and city formulas are given in the link, and are of the form shown in the pdf above.
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