tonymil
Posts: 274
Joined: Mon Apr 16, 2012 6:50 am
Location: Latham, NY

Comparison of Aerodynamics

Thu May 29, 2014 11:00 am

I just came across this article that compares the aerodynamics of the Tesla model S, Nissan Leaf, Toyota Prius, Chevy Volt, Mercedes CLA 250 and a 2001 Honda Insight for Hybrid.

http://www.greencarreports.com/news/1092373_aerodynamic-tesla-model-s-electric-car-wins-the-wind-tunnel-wars

The Tesla did impressively well, but this quote really surprised me, especially considering the Tesla is 1400 pounds heavier:

The numbers get even more interesting: Did you know, for example, that a Model S requires just 14 horsepower to maintain 70 mph, 4 hp less than a Leaf?

skyemoor
Posts: 20
Joined: Wed May 28, 2014 10:32 am

Re: Comparison of Aerodynamics

Thu May 29, 2014 11:34 am

Rolling resistance wasn't addressed, so weight won't make a difference in aerodynamics. The real world is different, though.

I noticed an old Insight was tested, though if it is like my 2000 Insight, the undercarriage panels are either missing or 'air grabbers'.


tonymil wrote:I just came across this article that compares the aerodynamics of the Tesla model S, Nissan Leaf, Toyota Prius, Chevy Volt, Mercedes CLA 250 and a 2001 Honda Insight for Hybrid.

http://www.greencarreports.com/news/1092373_aerodynamic-tesla-model-s-electric-car-wins-the-wind-tunnel-wars

The Tesla did impressively well, but this quote really surprised me, especially considering the Tesla is 1400 pounds heavier:

The numbers get even more interesting: Did you know, for example, that a Model S requires just 14 horsepower to maintain 70 mph, 4 hp less than a Leaf?

tonymil
Posts: 274
Joined: Mon Apr 16, 2012 6:50 am
Location: Latham, NY

Re: Comparison of Aerodynamics

Thu May 29, 2014 12:10 pm

skyemoor wrote:Rolling resistance wasn't addressed, so weight won't make a difference in aerodynamics. The real world is different, though.


The comparison of horespower to maintain 70 mph would not have come from the wind tunnel test. I think it was thrown in to show "real world" effect of aerodynamics.

skyemoor
Posts: 20
Joined: Wed May 28, 2014 10:32 am

Re: Comparison of Aerodynamics

Thu May 29, 2014 2:15 pm

All I was trying to say is rolling resistance wasn't covered, so weight wouldn't matter in a calculation to estimate horsepower requirements to overcome wind resistance. So we are on the same page.

Here's a nice calculator on this subject;

http://ecomodder.com/forum/tool-aero-ro ... stance.php

tonymil wrote:
skyemoor wrote:Rolling resistance wasn't addressed, so weight won't make a difference in aerodynamics. The real world is different, though.


The comparison of horespower to maintain 70 mph would not have come from the wind tunnel test. I think it was thrown in to show "real world" effect of aerodynamics.

NeilBlanchard
Posts: 356
Joined: Tue Jun 19, 2012 11:26 am
Location: Maynard, MA Eaarth
Contact: Website

Re: Comparison of Aerodynamics

Thu May 29, 2014 5:02 pm

The most important factor is the efficiency of the drivetrain. Then aerodynamic drag, Then weight, and then all other friction.

Aerodynamics swamp all other drag at ~30MPH, and weight doesn't enter into it when driving at a constant speed.

Case in point is the Edison2 VLC - the version that won the X-Prize was ~840 pounds and a Cd of 0.164. It got ~102MPGe.

They then made an electric version, that raised the weight to ~1,140 pounds (an increase of almost 36%) and it got ~245MPGe.

Another example is a Honda 125cc motorcycle - stock weight is 231 pounds and MPG is ~90MPG, but with 80 pounds of aerodynamic shell and taller gearing - it gets 214MPG.

http://ecomodder.com/blog/diy-aero-fairings-honda-125cc-motorcycle-214-mpg/
Sincerely, Neil

http://neilblanchard.blogspot.com/

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