Hyundai may be inflating MPG figures - UPDATE: busted by EPA

[MetroMPG]

Originally Posted by niky

as how the less aerodynamic cars with smaller engines (Soul, Veloster) lost out more, I'm betting most of the fudge was in aero versus coastdown...

Hyundai and Kia said Nov. 2 the flawed mpg ratings were the result of how engineers in South Korea conducted the EPA’s “coastdown” test. The test, in which a vehicle accelerates to about 80 miles an hour on a flat, straight road, is put into neutral and then allowed to coast down to about 9 mph, wasn’t done correctly, the companies said.

Source: Hyundai Fuel-Economy Flap Seen as Turned Tables for Honda - Bloomberg

[niky]

How do you control for wind in that? SAE? I thought the coastdown was dyno only, to get rolling losses, then aero numbers were plugged in.

The numbers make perfect sense now.

[mort]

Originally Posted by niky

How do you control for wind in that? SAE? I thought the coastdown was dyno only, to get rolling losses, then aero numbers were plugged in.

See here And go to the attachment I, on page 25. All the gory details.
In short: wind speed, air temperature, and barometric pressure must be recorded for each coastdown run.

The test road or test track should be straight, smooth, and level for a sufficient distance to obtain the necessary data. The necessary distance will vary depending on the vehicle type, the test surface grade, and the ambient conditions; however, the anticipated minimum necessary road or track length is 0.5 to 1 mile (1 to 2 km).
...
Tests must be conducted on the road or track in both directions with minimal interference from other vehicles during the data collection periods. During the data collection period, the track surface and vehicle should be dry, the track should be free of obstacles or significant irregularities. The absence of intermittent wind barriers near the road or track surface is preferred to reduce positional wind variations.

Coastdown runs are pairs in opposite directions one immediately following the other. At least 5 paired runs are averaged. Wind, grade, tire temperature, and air density are corrected for mathematically.

This procedure yields a road load equation. The coastdown time between 2 speeds, 55 to 45 mph for instance, can be found. Then the dyno load can be adjusted by dyno coastdown tests between 55 and 45 mph so the dyno load matches the road load at 50 mph.

-mort

[gone-ot]

FWIW, such "road load" dyno numbers are actually available at EPA in each manufacturer's "Request for Certification" documents--that's where/how I got such info on the 2011, 2012 & 2013 Cruzes.

If anybody is interested, contact me and I'll show you the "path" to finding them.

[MetroMPG]

Hyundai Gets Caught Fudging Fuel Economy Numbers Again

It appears that Hyundai didn’t learn its lesson the first time around (which cost is nearly $400 million), and has admitted to another “error” in calculating the fuel economy for its redesigned, home-market Sonata.

Hyundai had initially stated that the revised sedan saw its fuel economy improve by 6 percent compared to the previous model. However, government testing showed that the improvement was only 2 percent.

[Daox]

Yikes, after 400 million I'd surely learn my lesson.

[niky]

News Flash: Turns out Hyundai does coastdown testing with KDM variant with rear fender skirts, 14" wheels and Bridgestone Ecopias pumped to 80 psi. KDM variant also weighs 500 pounds less due to not having the US market subwoofer.

[MetroMPG]

I'm embarrassed to say I can't tell if you're joking.

[niky]

It would explain things nicely, wouldn't it?

On the other hand, perhaps they're not doing coastdown with GPS? Just finished a Hyundai test drive, and the speedometer was off by several mph at a mere 60. While most cars are off, that one's a huge difference.

[Hersbird]

I don't know about incorrectly figuring some complex federal system that sounds like navigating the tax code but as to earlier posts about why Honda owners seem to beat estimates, while Hyundai owners come up short, I'd say is almost entirely owner demographics. Who buys the cars, when, where, and how they use them, and the propensity to complain. The last thing many Honda buyers will do after spending more is admit maybe it wasn't worth the added expense. This was so obvious in the late 90s Oudacity vans and their transmission woes. Hyundais are rode hard and put away wet by many owners, especially when backed by a 10 year warranty.