5 ms·

The EPA tests are interesting. They do simulate stop and go driving, and that’s why on a gas car the city number is worse, but the steadier highway test shows b

The EPA tests are interesting. They do simulate stop and go driving, and that’s why on a gas car the city number is worse, but the steadier highway test shows better numbers. One of the weird things with an EV is that the highway numbers are actually worse (as other posters have commented). The tests definitely trade off realism for consistent reproducibility though. This article describes it in detail, it’s really interesting: https://www.caranddriver.com/features/a15388892/the-truth-about-epa-city-highway-mpg-estimates/ https://www.caranddriver.com/features/a15388892/the-truth-ab...

kenhwang 6y ago
The test is absolutely insane and it totally makes sense why EPA estimates can vary so much from real world numbers. It would practically ignore the effects of aerodynamics and I'm not even sure weight plays a role given both of those are supposedly accounted for by a simulated drag on the rollers.
- avs733 6y ago
  weight is inertia and aero drag is a speed dependant force...both are just forces that can be simulated really easily on a dyno.
avs733 6y ago
I was going to write something longer and then got distracted and this thread went bonkers, so sadly your post is not going to get the attention it deserves. I've actually toured a fuel economy lab for a Tier I/Big 3 auto manufacturer. The testing procedures described there are correct...account for as many variables as possible. The lab I toured had the dynos in temperature and humidity controlled rooms. Exhaust vents were standardized in length to ensure consistency, etc. MPG is serious business with millions on the line. Most interesting story I had was that they have several drivers they use for different purposes. Some are super consistent and used for repeatability tests. Others specialize in maximizing mileage. They quoted a 5% improvement by certain drivers over others on the SAME TEST. which already has incredibly precise time/speed windows that the drivers must stay in between. Every time, someone is manually controlling the throttle and brake pedal. Although they can use a computerized control for other testing. They will run the test until they get the best possible test and then ship that to the EPA.

kenhwang 6y ago

The test is absolutely insane and it totally makes sense why EPA estimates can vary so much from real world numbers. It would practically ignore the effects of aerodynamics and I'm not even sure weight plays a role given both of those are supposedly accounted for by a simulated drag on the rollers.

avs733 6y ago
weight is inertia and aero drag is a speed dependant force...both are just forces that can be simulated really easily on a dyno.

avs733 6y ago

I was going to write something longer and then got distracted and this thread went bonkers, so sadly your post is not going to get the attention it deserves. I've actually toured a fuel economy lab for a Tier I/Big 3 auto manufacturer. The testing procedures described there are correct...account for as many variables as possible. The lab I toured had the dynos in temperature and humidity controlled rooms. Exhaust vents were standardized in length to ensure consistency, etc. MPG is serious business with millions on the line. Most interesting story I had was that they have several drivers they use for different purposes. Some are super consistent and used for repeatability tests. Others specialize in maximizing mileage. They quoted a 5% improvement by certain drivers over others on the SAME TEST. which already has incredibly precise time/speed windows that the drivers must stay in between. Every time, someone is manually controlling the throttle and brake pedal. Although they can use a computerized control for other testing. They will run the test until they get the best possible test and then ship that to the EPA.