Civic hatchback aerodynamics

[GasSavers_TomO]

I really like the new tail! I wish I had teh space in the garage to do that myself. But where I live, a civic sitting outside is as good as stolen.

[MetroMPG]

Another thumbs-up job, basjoos. Nice work.

[basjoos]

Originally Posted by Nerds laugh at me

Something I have been wanting to ask you from the start of all of this ..of all the things on a car that are not needed, why do you still have your radio antenna out in the breeze ??
I removed mine and only noted a slight difference in reception. I pushed it down into the antenna hole and had it make contact with the metalbody - acting as a huge antenna itself.
Strangely enough even the tiny wire that serves as an antenna has a small effect on your ,Cd ( Besides there is the base which stick up about a quarter inch. Why not flatten that sucker out ?

The antenna has gotten frozen (rusted?) in the extended position dispite an application of Kroil to try to free it up. I live in a rural area, so I need every bit of reception I can get. Eventually I plan to do something (internal antenna, possibly in the Lexan hatch), but its low on the list of priorities for now.

A vertical stabilizer on an airplane is there to keep it pointed into the wind. I don't really want my car to try to start pointing into the wind every time I hit a strong crosswind.

[basjoos]

Originally Posted by McPatrick

Do you detect any difference in mpg between the old and new boat tail?

Both boattails have the same shape, so there shouldn't be any change in mpg. I haven't noticed any change on the SuperMID or in the car's coasting performance.

[McPatrick]

Ok, just wondered because you have taken the back hatch out and even though the new boattail might be somewhat heavier I figured you still lost some wait on the whole 'ensemble'.

[basjoos]

I did some minor tweaking to my car's aero. Did away with the last vestige of flat surface on the back of my car, the back side of the muffler. I made an aluminum fairing that blends into the bottom of the boattail.
Stock muffler

Faired muffler

Pic of my car

[thisisntjared]

hmm i dont know if i agree with the last bit. its good to have a small low pressure zone behind the muffler to help draw out exhaust gasses...

i agree something should be done to make it better than the way it was and i bet what you have is an improvement, but i think there has to be a better solution.

[trebuchet03]

Originally Posted by basjoos

I did some minor tweaking to my car's aero. Did away with the last vestige of flat surface on the back of my car, the back side of the muffler.

If you make the exit like a flat nozzle -- you'll add a littler energy to the diffuser's boundary layer -- in theory, make it stick a little longer

[Mighty Mira]

Hi basjoos,

I thought I'd say hello from a long absent spell on the forum. Work recently required me to make a lengthy commute and I had a look to see what progress you had made. I was amazed at what you have created! Well done!

My only questions are in regards to the underside of the boattail - have you tested with and without? With mpg meter or tuft testing? I'm not sure that an angle as extreme as that of the top will work (which it appears like it is, correct me if I'm wrong), because the air filling into the gap on the bottom must come from only the sides, as the bottom is road and not a whole atmospheres worth of air. Which is why you see that most solar cars have a flat bottom.

BTW I had some time off recently and resolved to do a bunch of mods because my confidence was such that most of them would work, I can always pull them off later and test them one by one, once I have a supermid or such. I'm most of the way there - full aluminium undertray, grille blocking, front deflectors, partial boattail (extends back 1 metre from the top), left external mirror removed, rear skirts. Pictures to follow soon.

Like you I am noticing the difference in maintaining speed on coasts, increase in terminal velocity on particular hills, increased apparent power at higher speeds, lower throttle required to maintain speed. And I'm also noticing that I'll be about 100km past where I used to have to fill up.

My car also probably generates more conversation and stares than your average Ferrari. I gather this is the case for you too.

[Hateful]

Not sure how far I'm going to take the aerodynamics on my Cavalier, but I'm sure it will be a lot more than if I hadn't seen this site and the work Basjoos has done.No shortage of imagination here I see. Of Course if I payed 50K for a prius I'd be a little slow about mods too. ( shock therapy is a little out dated anyway )