Toyota Corolla, boat tail - Fuel Economy, Hypermiling, EcoModding News and Forum

Sulfuric · 08-05-2010, 12:01 AM

So I'm making a partial boat tail for my 1994 Corolla. I haven't really been home all summer and now that I am, I've decided to try some "improvements". Unfortunately I can't do any scientific testing because I have no way to read instant mpg. Anyway, I have some flat, bendable metal strips and plexiglass and/or polycarbonate pieces that I have drilled and fashioned into a partial boat tail. It is connected at 3 points on top of the trunk, 3 points underneath the car (below the trunk), and 2 points on the bumper that reinforce the outside bottom 2 supports. I will be adding more soon: some aluminum to the sides, connecting to the "tail".

The sloping angle isn't as gradual as the ideal teardrop shape I would like, but it is certainly an improvement over the drag my car would create without any modifications.

I will try to add pictures when it's finished.

I'm averaging 45-50mpg, depending on how fast I drive - if I can consistently average 50+ than I will (almost) know that it is working).

skyl4rk · 08-05-2010, 07:40 AM

Sounds interesting, have you gotten any comments from other drivers?

Sulfuric · 08-05-2010, 06:31 PM

I've gotten a lot ok looks today - probably 5x as much as when I added my rear wheel skirts, though it could be a combination of having both . . .

NeilBlanchard · 08-05-2010, 10:02 PM

Can you post some pictures, please?

Sulfuric · 08-05-2010, 11:50 PM

Maybe tomorrow. Bug me if I don't

Sulfuric · 08-06-2010, 03:05 PM

Added pictures, though they look like a red x to me. Hopefully its just me. If you cant see them, look at my garage pictures.

ChazInMT · 08-06-2010, 04:09 PM

Great Job! Hope it works well for you. Tons of work into I'm sure!

skyl4rk · 08-06-2010, 04:55 PM

So can you tell if it is helping? Maybe try a coastdown time test in neutral from 60mph to 40mph, comparing tail with no tail. Of course you would have to take it off to do that.

Sulfuric · 08-06-2010, 05:06 PM

Well, it seems like I can coast just a little bit further. I have a road of about ~1 mile between lights, and I used to be able to get to almost 50mph, and then coast to the light and be at about 30ish before I would go through it or have to brake. I did the same thing today, and I was still at almost 40mph at the light, but it could be some other variable like a tail wind or maybe I started closer than usual.

I think it is helping but it could be the placebo effect.

Also, I really don't want to do ABA testing. Not very scientific, I know, but it was rather hard to get the screws in that connect the bottom part to the underside of the car. I did fashion it so the trunk is still able to be opened, though; you can see the wingnuts in the third picture. I just screw them off and it disconnects enough to open the trunk.

I think I'm going to add a little bit more, to have the tail become more of a point.

Edit: I also have a question. I found some 14 hubcaps on craigslist, but they are to a 70s chevy nova . . . do you think they would fit? I have 14 wheels but I'm not sure if all "same" sizes are really the same.

Sulfuric · 08-07-2010, 12:59 AM

I added another plexiglass or polycarbonate panel to the bottom. The air from underneath the car should now stay attached farther back, hopefully creating less drag.
I drove to a an outside beach movie tonight (just got bacK), and I think it coasts longer. I've been making .5+ mile glides much more frequently now and sure seems like I keep my speed longer. That gradual "slowing down feeling" (negative g force?) is much smaller.

Pictures tomorrow, maybe. I might even add more.