Rear undertray & front lip spoiler to help MPG.

[Improbcat]

After months of slacking, I finally got around to doing some areo mods to Box.

First up was a new front lip spoiler made from a garage door seal. It is only about 1" tall, but the front is low enough I didn't want more (the bottom of the bumper already has a fair amount of scrapes & gouges).




Next was the big project, as anyone who has looked under there knows. the space under the rear cargo area & bumper is really aerodynamically messy. So armed with some black chloroplast, aluminum flashing & some screws & zip-ties I set about fixing that. I did it over two days, with probably about 4-5 hours in it all total, maybe less. ignore the splashes, I drove through a muddy parking lot between the first & second sessions of working on it.

Before any mods:




Overall shot:


From the left side:


From Right side:


The front edge is tucked above the gas tank, and zip-tied in place. I was very careful to not put and new holes in the body of the car where they might rust. So everything is attached by zip-ties, or screws into the plastic bumper.

Detail of Right wheelwell and around muffler:


I pondered enclosing the muffler, but didn't have a good way to do it and not end up worrying about excessive heat buildup.

Detail of Left wheelwell:


From above:


The little bit of flashing is the only part visible from outside. If you kneel or squat down you can just make out some of the edge of the black chloroplast at the edges of the bumper.

I've driven a bit with it on, and aside from one part of the flashing where the tailpipe passes through touching & rattling it works great. Ironically I don't know what it is doing for my MPG as I've loaned my Scangauge to a friend and won't get it back for a day or two.[/url]

[DarkSide_xB]

i dont get it. all of that work under the rear for what? dont get me wrong i give you props for trying something different and coming up with idea of your own. is there really any MPG for all of that work under the rear of the box??

[jct]

we'll find out after he post some mpg results...

[DarkSide_xB]

Mr. John O, how do you do?

[Improbcat]

The underside of most cars is the least aerodynamically efficient part of the car. I've read that upwards of 30% of the drag is caused by air trying to pass under the car. So theoretically smoothing the airflow under the car will improve my MPG. Whether this mod alone will make a measurable difference I'll know after a few tanks of gas.

For an example of underbody aerodynamics, here is a pic of the underbody panels Toyota installed on on the Prius to help improve it's drag coefficient.

[Big_hungry]

looks good! Shoot theres nothing wrong with trying it out. hopefully it will work :)

[jsingh]

interesting...

[ProjectPerformanceRacing]

i like the idea it just would look better if it were a cleaner job. try dropping the whole think and trying to use a single piece of sheet metal or something.

[WhoKilledTheJAMs]

Nice! I have a sort of front undertray made of coroplast and christmas trees, since I have the Tsunami lip, it was fairly easy to fab up. That and blocking the bottom grille gave me about 2mpg on the highway, for like $7 worth of fasteners and some election signs.

I've been wanting to do something like that the rear, but I haven't actually seen it done before. Even if the mpg gains are minimal, it really can't hurt. The bumper is like a parachute.

[burstaneurysm]

Dropping the car would also improve airflow underneath.

[dmpsk8]

hmmm. wonder if its really worth the work

[burkpe]

I'm thinkin carbon fibre undertray like on say a gtr that would be neat looking i'd rock it


anybody got a wind tunnel?

[WhoKilledTheJAMs]

burkpe wrote: I'm thinkin carbon fibre undertray like on say a gtr that would be neat looking i'd rock it


anybody got a wind tunnel?





NSX's make me think of Pulp Fiction

The Wolf: Now boys, listen up. We're going to a place called Monster Joe's Truck and Tow. I'll drive the tainted car. Jules, you ride with me. Vincent, you follow in my Acura. We run across the path of any John Q. Laws, nobody does a F'ing thing unless I do it first. What did I just say?
Jules: Don't do S***unless.
The Wolf: Unless what?
Jules: Unless you do it first.
The Wolf: Spoken like a true prodigy. How about you, Lash LaRue? You think you can keep your spurs from jinglin' and janglin'?
Vincent: Look, Mr. Wolf, my gun went off, I don't know why, and now you're helping us out of the situation. I'm cool with it, all right?
The Wolf: Fair enough. Now I drive real F'ing fast, so keep up. I get my car back any differently than when I gave it, Monster Joe's gonna be disposing of two bodies.


Oddly enough, I actually saw an NSX in the metal recently. Red, gorgeous, etc.[/i]

[jct]

DarkSide_xB wrote: Mr. John O, how do you do?

fantastic, thanks for askin

[HondAudio]

I was talking about this like, months ago!

[TheCCBox]

Let me know what the MPG gain is and i will also try to fab something better out of plastic or even some black chloroplast if it is worth it LOL!!!

[turbotim]

DarkSide_xB wrote: i dont get it. all of that work under the rear for what? dont get me wrong i give you props for trying something different and coming up with idea of your own. is there really any MPG for all of that work under the rear of the box??
Exactly what he said.... i dont get it
also wow thats a lot of rust under your ride

[WhoKilledTheJAMs]

turbotim wrote: DarkSide_xB wrote: i dont get it. all of that work under the rear for what? dont get me wrong i give you props for trying something different and coming up with idea of your own. is there really any MPG for all of that work under the rear of the box??
Exactly what he said.... i dont get it
also wow thats a lot of rust under your ride

I gained ~2mpg from giving the front of my box a similar treatment. There's at least that much to be gained in the rear, too. Between that, blocking off the lower grille, and not driving like a jerk, my last tank was 37mpg, and that's without really intensive hypermiling. 40mpg is within reach.

Some quick spreadsheet math says that going from 32mpg to 35mpg, driving 10k miles/year gives about $100 in savings every year, at $4/gallon. More money is saved with more miles driven, and more expensive gas.

Also, as for the rust: that's what happens to cars when you live somewhere that has winter. My car would probably give a lot of you guys heart attacks. It's not horrendous, but it's worse than that. I just spent some time last week under my girlfriend's '00 Chrysler, and I was combing rust out of my beard for a day and a half.

[987KEITH]

watching...

[dmpsk8]

40 mpg, lol. My dirving habits will never allow that