Check out the bottom of the civic hybrid
 

check out the bottom of my dad's civic hybrid. The Cd is supposedly .27, and it has a partial belly pan under part of the front of the car and near the back. It is suspiciously missing sections on either side behind the rear wheels.

Wouldnt there be less drag with these areas covered? it doesnt seem like it would cost very much to cover these areas, if they were already putting a plastic panel in that area. Any guesses why they wouldnt cover those areas?
At least on one side, it wouldnt be anywhere near the exhaust...even on the exhaust side, some improvement could easily be made. also, the lip of the rear bumper is a sharp edge that sticks out and overlaps the belly pan, it looks as if it would catch some air.

A couple wild guesses
-It doesn't matter. With air flow exiting near the low pressure trunk area anyway, there's no point to smoothing the air stream right before turbulent separation.
-They also may want to induce some turbulence right before the back of the car, so that some of the air flowing under the car will curve up into the low pressure area behind the trunk, and the separation of airflow over the top/sides of the car wouldn't be influenced as much.

All I could make out from that picture was an upside down coil spring....

yeah, sorry the pic is upside down. what you are looking at is the back corner of the vehicle, looking toward the rear wheel.

Could be that they left it like that to create turbulence. Initially, I would have thought that Honda would have optimized everything on the car, but after seeing the aero results of Phil Knox and Bajoos, I am starting to give everything a closer look.

Another wild guess

-Some bean counter wanted to save about $1 off the materials costs without regard to the impact on the car's quality, basically telling the engineers to **** off.



Happens all the time in industry.

Heh, yeah... VW uses plastic water pump impellers, plastic! :thumbdown:

I almost wonder if something is missing? The only reason i ask this is there is that empty circle ring thing, looks like it could be used to attach another plate, same with the bolt hole in the corner. The wheel spoilers also seem as if they were designed to work with more underbody. Hmmm

Yeah,
Maybe honda will just start adding the panels in a couple years, as the MPG competition between the hybrids gets more intense??
I just wish they would have done a better job with it...I dont think my dad would like me putting coroplast under there!

red91sit -

Maybe the circle ring thing is for a ground effects kit for a non-Hybrid Civic sedan. Maybe the new Si.

CarloSW2

Theres always room for improvement even on supposedly very efficient cars. A first gen Prius (97-99, never sold in US) owner in Australia was able improve fuel economy at 100kph from 42mpg to 47mpg with a simple front belly pan. You would think the manufacturers would have installed on it from the factory if they were trying to build the model of efficiency.

He went from this
https://us1.webpublications.com.au/st.../2456_22lo.jpg

To this
https://us1.webpublications.com.au/st.../2456_32lo.jpg

In the end every component goes through a cost vs benefit analysis. Filling in that area behind the rear tire will probably improve fuel economy by a point or two but it wasn't worth it to Honda. It might be to you.
I still find it outrageous that hybrids like the Prius and Civic don't come with rear wheel skirts from the factory.