Teardrops and wind tunnels: A look at the world’s most aerodynamic cars

Inspired by VW's ARVW concept, we look at the cars with tiny drag coefficients.

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[yticolev]

All of those listed Cd's are suspect as they were all tested in different wind tunnels with different methodology and cannot be peer reviewed in any meaningful way. In addition, virtually manufacturer lists the CdA of there cars. This number at least could be correlated against mpg and HP numbers and speed to determine if the underlying Cd is realistic or not.

Area (the "A" in CdA) is a huge factor in efficiency or top speed. I was struck looking at all these pictures how narrow most of them were.

Edit: I too missed the sidebar.

 

[yticolev]

Check out the AeroVelo Eta, the speed bike that I worked on in university. It currently holds the human powered speed record - nearly 90 mph just with a buff guy pedaling.

I once hit 50mph on a Specialized Rockhopper hardtail mountain bike with 2.2" knobbly tyres, powered by nothing but a skinny 16 year old... with a little help from the Earth's gravity. It was a very steep downhill, which is why I chose it. My tyres were squealing round the bends, I wanted to slow down but I was too afraid to brake, so I had to ride it out. I passed two cars!

That would indeed be scary on knobby tires! My personal terminal speed on a upright bicycle as tested over 50 years or so appears to be 46 mph on road tires, tucking or pedaling. That is not seeking out the longest steepest roads or wearing skin suits and just what I find along the way on normal rides.

 

[yticolev]

Honda Insight (gen 1) was a cd wonder when it came out: 0.25 according to Wikipedia. We had a few in the motor pool. I got well over 60 mpg on the highway - close to 70, and on a nearly pure stop n go trip to SF (clogged, on both freeway and city streets) got about 60. Had to retrain myself to shift when the light said to, which appeared to lug the engine a lot but gave the electric motor something to do (a pool car with a stick shift ... even though they only had a few, one was almost always available for checkout).

In 2013, Mercedes optimized the already slippery 2013 CLA—Cd 0.23—a little further for the CLA 180 BlueEfficiency, fitting different mirrors, wheel covers, serrated spoilers, and a few other tweaks here and there to reach a Cd of 0.22.

https://www.caranddriver.com/features/a ... ison-test/
I was sure this Car and Driver wind tunnel comparison article article used the original Honda Insight as a baseline car. However, it did have a relevant car from this Ars article, the Mercedes CLA 250 (2014 model year). It measured the Cd at .30, far from Mercedes official .23 number. In the same set of wind tunnel tests, the 2014 Prius (Gen3) was measured at .26, a number that I believe was the official Toyota number.

Same test revealed the actual CdA numbers of these cars. Looks like Toyota numbers are more trustworthy than Mercedes. Perhaps you don't get what you pay for.