Smart Fortwo Cd - Fuel Economy, Hypermiling, EcoModding News and Forum

PA32R · 04-18-2009, 03:27 PM

I've been looking into why the Smart Fortwo gets relatively poor fuel economy. This site explains that it has a Cd of 0.38 because the vehicle is made to be high enough to put drivers at the eye level of more normal cars and for some sort of increase in crash safety and thus suffers high drag at highway speeds.

However, this site, among others, gives the Cd as 0.29.

Does anyone have an explanation for the discrepancy and/or authoritative information on the true number?

Rob

Cd · 04-18-2009, 03:38 PM

Yes, makes you wonder if they just throw any old number in there doesn't it ?

I would go with the higher figure. It is similar in shape to the Scion Xb.( which was .35 if I remember correctly )

PA32R · 04-18-2009, 03:42 PM

Quote:

Originally Posted by Cd

Yes, makes you wonder if they just throw any old number in there doesn't it ?

I would go with the higher figure. It is similar in shape to the Scion Xb.( which was .35 if I remember correctly )

And now I see here that it's 0.34.

You're right, they just make 'em up I guess.

SVOboy · 04-18-2009, 06:10 PM

It looks more like the Toyota iQ I think, which I've heard has a .299 Cd or some such nonsense.

I will try to contact someone official at SmartUSA and get the real number.

PA32R · 04-18-2009, 06:13 PM

Quote:

Originally Posted by SVOboy

It looks more like the Toyota iQ I think, which I've heard has a .299 Cd or some such nonsense.

I will try to contact someone official at SmartUSA and get the real number.

Of course, Cd varies with Reynolds Number, which varies with flow velocity so...

But that would be great, I'd appreciate it. Thanks

SVOboy · 04-18-2009, 06:18 PM

I emailed my contact at Smart, if he doesn't get back to me by monday I'll give a call.

winkosmosis · 04-18-2009, 08:01 PM

I bet 90% of these cD numbers are made up

Cd · 04-18-2009, 10:07 PM

( SVO, Perhaps you might also ask why the car gets such bad FE .)

SVOboy · 04-18-2009, 10:20 PM

Well, they'll probably say a few things:

- compared to other cars, it's great
- euro testing standards are different
- euro emissions standards are different

But if I find someone receptive to it I might try to have a conversation about the subject.

PA32R · 04-18-2009, 11:36 PM

They say "it's the highest mileage gasoline ICE vehicle in the United States." But you give up a lot (two seats, luggage area) for a little (a couple of m.p.g. at best compared to, say, a Mini). The diesel available in Canada is in a different class altogether. But still, it seems like the Smart Fortwo should do better.