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Aerodynamics/Drag Coefficient of Coupe vs. Sedan

22K views 25 replies 23 participants last post by  yomama's butt-front  
#1 ·
Hi, everyone! This is my first post here.

Currently I am in the market for a new car and am curious to know about the drag coefficient of the coupe vs. the sedan. And why is the spoiler different on the SI coupe from the SI sedan? Knowing one is more aerodynamic than the other probably isn't going to be the deal breaker for me.

Just curious if anyone knows. Thanks.:dance:
 
#3 ·
One of the keys to aerodynamic coefficient of drag is frontal area. The two cars are essentially the same, so that is a wash. The next area to measure would be the air going over the roof. Because of the boundary layer of air being attached to the body, the longer sweep of the sedan roof would give ever a slight advantage.

The last area to look at is the rear deck. Because the coupe rear deck swoops down while the sedan has a higher deck with more of a Kamm effect, I would again give the nod to the sedan.

Finally, for just aerodynamic numbers, the lower sedan spoiler would probably show better aero numbers while the coupe spoiler might give just a little more downforce.

In the end, the differences would have to be miniscule, with perhaps a slight advantage to the sedan due to its longer, gently arched roof and higher rear deck.

I would not buy the car based on which one is more aerodynamic. If that is the deal breaker, then get a G35, which has one of the lowest coefficient's of drag of any car out there today. My '03 G35 Sedan has a drag coefficient of 0.26.

Buy the car based on how it looks and feels to you. I was torn between the coupe and sedan and went back and forth many times before finally getting the sedan. I still have a real soft spot in my heart for the coupe and would love to have one in addition to my sedan.
 
#9 ·
neluck finding out the number value to the coupes coefficient of drag?
one of the dudes found out how to figure it out urself (long dragged out test)
but i wanna do that after getting a professional number to test it
if my test runs up within 5% error of the professional number, ill begin a few mods and see what helps
they include:
lightweight rims
lower an inch
cover underbody with aluminum plating (to prevent bumper drag and front drag)

and nething else i can think of lol
let me know if u find a professional number
 
#18 ·
Frontal Area and Drag C-efficient

I downloaded a performance measuring application for my iPhone "Track Day". It required the frontal area and the drag co-efficient. I have both a 2009 Honda Civic Coupe and a 1997 Miata so I did a search on the Internet. The Civic coupe is listed as 2.237 sq meters and 0.27. I don't remember the exact source but I checked several. The Miata was 1.829 sq meters and 0.38.
 
#21 ·
These are all 2006 model numbers:
Hybrid: 0.27 (wiki)
Sedan: 0.31 (wiki)
Coupe: 0.34 (2006 model launch tech data)

The Hybrid has underbody aero worth the extra 0.04, and the coupe's tail costs it 0.03. The spoiler on the sedans after 2008 is to reduce drag, the spoiler on the base coupes is to reduce lift it has little effect on drag.

Honda released a DX-GA model in Canada in 2008 that used the Hybrid's underbody covers, the Dunlop SP31's, and switched to the electric steering. They did this to qualify for a government backed incentive program that gave cash back for cars rated at 6.5L/100km or less.

-SWRT
 
#23 ·
These are all 2006 model numbers:
Hybrid: 0.27 (wiki)
Sedan: 0.31 (wiki)
Coupe: 0.34 (2006 model launch tech data)
That's actually a huge difference, Just like MPG when 31 or 34 might not seem like that much until you realize it's almost 10%, and every 10th time you fill up it would be for free.

I am really surprised if those numbers are correct that the sedan is 9-10% more aerodynamic.

Another thing is that I wonder with the sedans if the difference between the 08s and 09s with the extra cut outs in the bumper makes it better/worse? One would think that even though it's not as nice to look at because it's a vast sea of plastic, the outer edge of the 06-08's lower bumper is probably better for airflow.