How the EPA tests - and doesn't test - fuel economy of new vehicles

[ghosthunter]

How the EPA tests - and doesn't test - fuel economy of new vehicles



By Sebastian Blanco
Posted Nov 5th 2012 6:00PM

Doesn't the EPA test the fuel economy of all new vehicles? Actually, no.

Last week, Hyundai and Kia announced that they had each made errors in the way they tested the fuel economy of their new vehicles. "Honest mistakes" and "human error" were made during their in-house process for determining fuel economy figures that overestimated the rate at which vehicles like the Veloster and Elantra burn fuel. While most models were off by one or two MPGs, highway numbers for the Kia Soul were revised down by six MPGs in one instance.

At this point, you might be saying, wait, automakers get to test their own vehicles? Doesn't the Environmental Protection Agency (EPA) do that?

Actually, no.

Most new cars and trucks in the US never see the inside of the EPA's National Vehicles and Fuel Emissions Laboratory in Ann Arbor, MI. Instead, they are tested by the manufacturers themselves, which often use pre-production prototypes in "a standardized test procedure specified by federal law," and then report those numbers to the EPA. Only 10-to-15 percent of all new models, or about 150 to 200 vehicles per year, are re-tested by the EPA to verify the automakers' numbers. Keep reading below for the full story.

Over the decades, this system has worked well and there's no hint that there are widespread issues of faulty test data being reported back to the EPA and used as official MPG numbers seen everywhere from TV ads to window stickers. Sharon Basel, from GM's Environment, Energy & Safety Communications department, told AutoblogGreen that the "EPA requirements do include a complex series of test and procedures. GM works closely with the staff at EPA to make sure that we have a common understanding and interpretation of those requirements." There is, though, "an ongoing investigation," the EPA says, without giving more details, so we might learn that errors are more widespread than anyone now suspects.

Here is how the government and automakers are supposed to test fuel economy for all non-plug-in vehicles (plug-ins – as well as hybrodgen-powered and other alternative powertrains – are a more complicated, separate-but-related issue). The vehicle is placed on a dynamometer in a lab and then put through a series of tests to simulate "typical" trips that represent five different drives: city, highway, high speed, air conditioner and cold temperature. The speeds that the wheels must be spinning are specified, as are the distances and number of stops, and the carbon emissions are measured to see just how clean or dirty the vehicle is. There's a chart detailing these procedures below, and you can get a more detailed description of the EPA's tests here.

Even though the test was updated for 2008 model year and later vehicles, it is still not perfect. If you want to know more, there are two detailed PDFs about the test procedures (1, 2). Jay Friedland, the legislative director at Plug In America, told AutoblogGreen that, "The trickiest issues around EPA testing are the fact that they are indeed self-reported homologation and that there are a number of ways to manipulate the results." Friedland said that the tests are inaccurate enough that the EPA needs to have a "fudge" factor, "which further reduces the combined mileage by a factor of .7 to make the data better match the real world."

source: How the EPA tests - and doesn't test - fuel economy of new vehicles

[dr. d]

the description of the city schedule, is a far cry from our local actual city driving experience. their city schedule might pass for our actual highway (edsa, slex) experience. heh heh.

[niky]

Actually, EPA highway numbers match weekend SLEX and NLEX numbers very well.


The big issue is not only do they not do the test, the test procedure has so much fudge in it that it basically doesn't mean anything. Everything is done in laboratory conditions, then drivetrain and aerodynamic losses are calculated after the fact and plugged into an equation that has extra fudge numbers in it just to make it "realistic". The back-calculations are where Hyundai/Kia had issues, so it's not surprising that the most unaerodynamic Kia, the Soul, was the worst affected by the re-test.


Another loophole is "pump gas". Most US gas is E10, but the EPA allows testing on regular gasoline, which gives better economy.


Worse, the EPA demands an exact acceleration load, which handicaps small cars with small engines. Small cars struggle to hit 40 mpg in the EPA, where compact cars do it easily. In real life, it's easy to use those same small cars to hit 45-60 mpg at a steady 55 mph, whereas compacts will "just" do 40 mpg, whatever speed you drive at. To cope with this, manufacturers have to install artificial torque limits and pedal response into their cars just to beat the EPA. Want to know why the pedal response on your new car is so sluggish at 2500 rpm? Blame the EPA.


In the end, a lot of US consumers will complain about poor mileage, because they drive much faster than the virtual EPA test, use worse gasoline than in the EPA test, and drive with the AC on 90% of the time, unlike the EPA test where it's off most of the time.

[Bitulo]

source: How the EPA tests - and doesn't test - fuel economy of new vehicles

Agree that it is practically impossible to capture actual driving conditions in a laboratory or testing simulation to come up with accurate reading of the fuel consumption per kilometer. But the value of the test is the comparability of the testing results. In other words, a small cars can be compared with another small car under the same test condition. A sub compact compared to another subcompact under the same test condition. This way, the tendency of manufacturers to just pronounce the most favorable FC of their cars based on very unrealistic conditions. The comparability of the FCs figures would be of help to prospective buyers who make FC a very important consideration. Hindi porque hindi 100% accurate ay wala ng silbi.Since dumaan sila sa magkatulad na testing protocol, then the results are comparable.

[naganogo]

You have mentioned very nice information, I found some very interesting points.

[pyramid00]

In a mythbuster episode, it was noted that the EPA had tested 104 fuel-saving devices for the last 20 years and found 7 which had slightly improved efficiency (max 6%). I had emailed EPA to ask what were the drive cycles implemented to test the said devices.

Their reply: "The only acceptable test procedures are the Federal Test Procedure (FTP), which is
a simulated city drive trace used for emissions testing, and the Highway
Fuel Economy Test (HFET), which is a simulated highway drive test for fuel
economy calculation." This document is available on our web site at:
www.epa.gov/otaq/consumer/b00003.pdf.

Americandrivingcycles

FTP-75cycle
The FTP cycle (for Federal Test Procedure) has been created by US EPA (Environmental Protection Agency) to represent a commuting cycle with a part of urban driving including frequent stops and a part of highway driving.

Here are the main characteristics of the cycle:
Distance 11.04 miles (17.77 km)
Duration 1874 s
Average speed 21.2 mph (34.1 km/h)

HighwayFuelEconomyTestcycle
The Highway fuel economy test (HWFET) is used to assess fuel economy over highway driving cycle.

Here are the main characteristics of the cycle:
Distance 12.26 miles (16.45 km)
Duration 765 s
Average speed 48.3 mph (77.7 km/h)
Other test cycles
In 2007, EPA decided to add 3 more cycles to the existing ones, in order to better reflect real world driving conditions.
The first one is the US06, which is a complement to what is missing in FTP-75 cycle. Indeed, this cycle has a higher top speed of 80 mph (130 km/h) and some higher acceleration which represents a much more aggressive driving behavior.
The SC03 is another added cycle which particularity is to be performed at 35°C ambient temperature. This is needed for taking into account the air-conditioning in fuel consumption and emissions calculations.
The last added cycle is the “cold cycle”. This is in fact a FTP-75 performed at -7°C ambient temperature.

The drive cycle test used by UP-VRTL at the moment is the Japanese 10-15 mode.

[lala31]

a lot of US consumers will complain about poor mileage, because they drive much faster than the virtual EPA test, use worse gasoline than in the EPA test Xender Discord Omegle