View Single Post
Old 09-14-2015, 10:55 AM   #1 (permalink)
MetroMPG
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,530

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 54.46 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car Mirage - '14 Mitsubishi Mirage ES (base)
90 day: 62.14 mpg (US)
Thanks: 4,078
Thanked 6,978 Times in 3,613 Posts
Why hydrogen powered cars will have poor drag coefficients

Why? Well, have a gander at the gaping maw on this thing:


(Toyota Mirai hydrogen vehicle: a face only a mother could love)

Hydrogen vehicles need big grilles for cooling and also to take in air to process in the fuel cell:

Quote:
...cooling is a challenge, because fuel cells run at far lower temperatures--perhaps below 100 degrees Centigrade--than do internal-combustion engines.

The huge temperature differential between ambient air and the temperature of the engine coolant means [IC] engines are easy to cool: You can shed heat more easily from a given amount of airflow.

To shed heat from the [fuel cell] stack coolant at the lower temperature differential requires a greater amount of airflow--hence the large cooling inlets.
Source: 2016 Toyota Mirai Hydrogen Fuel-Cell Car: A Few Things We Noticed

And the Mirai's drag coefficient?

0.293

Oof! Not exactly class-leading. In fact, pretty far from class-leading.

One of the great things about (battery) electric cars is they don't need big cooling systems or exhaust systems, so you can dramatically cut drag using smooth underbodies and no (or much smaller, or fake) grilles.

Tesla Model S is a good example:



The Model S actually has a pretty big grille on its snout, but it's fake. It's just there for styling.

The car's 0.24 drag coefficient is actually top of the class for a production vehicle.

Attached Thumbnails
Click image for larger version

Name:	$$$$$mirai.jpg
Views:	301
Size:	49.1 KB
ID:	18717   Click image for larger version

Name:	tesla-unveils-2015-model-s-p85d-3.jpg
Views:	674
Size:	68.6 KB
ID:	18718  
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following 3 Users Say Thank You to MetroMPG For This Useful Post:
aerohead (09-14-2015), BamZipPow (09-14-2015), Daox (09-14-2015)