Motor Trend to begin real world MPG testing

[Cd]

http://www.motortrend.com/features/c...mbers_mpg_101/

I noticed the current issue of Motor Trend has an article midway through the magazine in which they detail how that they are now testing cars for real world MPG numbers.

What i found impressive is that the equipment that they use measures variables such as rolling resistance and aero drag, as well as emissions.

BTW, They really are including lots of geeky tech info when they test cars.
I wonder why that they stopped publishing the Cd values for cars like they did up until the early nineties.
Most manufacturers already know the Cd of the cars so it seems all they would have to do is to ask for the data.

Car magazines do sometimes print the Cdxa values for cars, but not as often as in the past.
That's too bad.

[ChazInMT]

Just sort of guessing here, but maybe the downsides outweigh the potential upsides for putting the Cd out there. For starters, how do they do a standardize their Cd determination? If conservative with their methodology, you end up with an unflattering number for the Cd, if they are too aggressive with their methodology, then people can criticize them for having bogus numbers. Sounds like a no win situation to me. There are a lot of variables when coming up with a Cd, it isn't like you can just drop a car off a bridge and see how long it takes to hit the ground. Each wind tunnel has a ton of idiosyncrasies as wsll which would make it maddening to try and standardize numbers.

Also you have keep in mind that to the average person Cd really has no meaning.

[niky]

Lot of new blood in MT, and they're trying hard.

Thought I'd see something in here about them not driving balls to the walls when testing economy, though...

[gone-ot]

Originally Posted by ChazInMT

Just sort of guessing here, but maybe the downsides outweigh the potential upsides for putting the Cd out there. For starters, how do they do a standardize their Cd determination? If conservative with their methodology, you end up with an unflattering number for the Cd, if they are too aggressive with their methodology, then people can criticize them for having bogus numbers. Sounds like a no win situation to me. There are a lot of variables when coming up with a Cd, it isn't like you can just drop a car off a bridge and see how long it takes to hit the ground. Each wind tunnel has a ton of idiosyncrasies as wsll which would make it maddening to try and standardize numbers.

Also you have keep in mind that to the average person Cd really has no meaning.

SIMPLE: just backsolve the Cd value that coincides with ALL of their 'input' variables, ie: Area, weight, velocity, air drag, mpg, etc.

[Cd]

Tele/ Niky
Actually what i meant to say was that MT could just ask the guy that gives them the test car what the Cd is.
The company has already done the testing and all they ( MT) have to do is ask.

[wheelbender6]

Consumer Reports mag used to test all cars on the same 90 mile loop of mixed driving. MPG results of that loop were normally much closer to the city EPA rating than highway EPA rating.