SeaGeo
Well-Known Member
- Thread starter
- #1
There have been a lot of discussions surrounding EPA testing methods for range (fuel efficiency). I'm providing some links for people so that there are fewer excuses for people to guess.
Summary:
-there are a few different ways manufacturers can test their vehicles.
-The EPA itself only tests a few vehicles. Most are certified by the manufacturers.
-The tests are completed on a dynamometer, and then adjusted for real world conditions using a couple of approaches. The cycles run on the dyno are available here:
https://www.epa.gov/vehicle-and-fuel-emissions-testing/dynamometer-drive-schedules
- Most manufacturers apparently use the two cycle method with an automatic 30% deduction to range (multiple the dyno range by 0.7 basically). This is less expensive, and generally seems conservative for range.
-manufacturers can do the 5 cycle test. This is more rigorous, and expensive. It also seems to generally give longer range values (which appears to be what Tesla does). It should (in theory) be more realistic as well.
- When using the 5 cycle test, manufacturers can use default coefficients, which are provided in the third link below, or submit their own based on real world testing (quickly scanning these, they appear to basically be aero coefficients). The formulas are provided in the cornell link below, and the coefficients are included in the fourth link. They can also use adjustment factors from in-use data, but that requires EPA approval.
- "Manufacturers may voluntarily lower fuel economy values and raise CO2 values if they determine that the label values from any method are not representative of the fuel economy and CO2 emissions for that model type." -- my understanding is that Porsche does this. So when people look at Tesla's combine rating coming in lower than 70 mph highway tests, but other manufacturers coming in much closer to the rated combined range on the high it could be that the other manufacturers used the 2 cycle test and it's conservative, or that the manufacturer is willingly "sand bagging" it as someone put it. Which really is that they're trying to make sure that the rating people see is a lower bound estimate of what they should expect when the consumer actually cares about range (ie, highways). That would be expected from say, Porsche, who is known to have always reported values from very conservative testing conditions (like 0-60 for ICE on meh tired and at 5,000 feet elevation).
https://www.torquenews.com/2250/how-epa-determines-electric-vehicle-s-range-not-simple-it-sounds#:~:text=The EPA uses five drive,speed cycle (US06), an
https://www.fueleconomy.gov/feg/pdfs/EPA test procedure for EVs-PHEVs-11-14-2017.pdf
https://www.law.cornell.edu/cfr/text/40/600.210-12
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=35113&flag=1
Summary:
-there are a few different ways manufacturers can test their vehicles.
-The EPA itself only tests a few vehicles. Most are certified by the manufacturers.
-The tests are completed on a dynamometer, and then adjusted for real world conditions using a couple of approaches. The cycles run on the dyno are available here:
https://www.epa.gov/vehicle-and-fuel-emissions-testing/dynamometer-drive-schedules
- Most manufacturers apparently use the two cycle method with an automatic 30% deduction to range (multiple the dyno range by 0.7 basically). This is less expensive, and generally seems conservative for range.
-manufacturers can do the 5 cycle test. This is more rigorous, and expensive. It also seems to generally give longer range values (which appears to be what Tesla does). It should (in theory) be more realistic as well.
- When using the 5 cycle test, manufacturers can use default coefficients, which are provided in the third link below, or submit their own based on real world testing (quickly scanning these, they appear to basically be aero coefficients). The formulas are provided in the cornell link below, and the coefficients are included in the fourth link. They can also use adjustment factors from in-use data, but that requires EPA approval.
- "Manufacturers may voluntarily lower fuel economy values and raise CO2 values if they determine that the label values from any method are not representative of the fuel economy and CO2 emissions for that model type." -- my understanding is that Porsche does this. So when people look at Tesla's combine rating coming in lower than 70 mph highway tests, but other manufacturers coming in much closer to the rated combined range on the high it could be that the other manufacturers used the 2 cycle test and it's conservative, or that the manufacturer is willingly "sand bagging" it as someone put it. Which really is that they're trying to make sure that the rating people see is a lower bound estimate of what they should expect when the consumer actually cares about range (ie, highways). That would be expected from say, Porsche, who is known to have always reported values from very conservative testing conditions (like 0-60 for ICE on meh tired and at 5,000 feet elevation).
https://www.torquenews.com/2250/how-epa-determines-electric-vehicle-s-range-not-simple-it-sounds#:~:text=The EPA uses five drive,speed cycle (US06), an
https://www.fueleconomy.gov/feg/pdfs/EPA test procedure for EVs-PHEVs-11-14-2017.pdf
https://www.law.cornell.edu/cfr/text/40/600.210-12
https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=35113&flag=1
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