Don Henley

I didn't see a specific category for this, so I'm posting it in here..

Has anyone fiddled with underbody panels for our cars? I'm talking a panel under the front, and rear bumpers to reduce the drag, increasing mpg, etc.

And yes, I realize a light weight / smaller set of wheels will also help with a drop, I've got all that covered. I'm only/mainly looking into the diffusers.

baron340

iTrader: (4)

Just make yourself one. All you need is a pop rivet gun and some sheets of plastic. Just be careful where you are attaching it underneath the car.

lightningslp77

i dunno about that, i think the reason there isn't a topic is because our cars already achieve 38+ mpg as far as mileage goes and in the long run unless you're running a 10 second car it won't really do anything but take a millisecond of ur 1/4 mile time if u intend track use.

it might help if you put on diffusers and have an aftermarket suspension and intend in playing around with it on curvy roads or time attack events but other than that i personally don't see a reason for it.

if you have a lowered car and smaller rims and you intend to put panels on i think its really gonna suck for daily driving in terms of bottoming out lol.

baron340

iTrader: (4)

If its a flat pannel right on the bottom of your car, bottoming out shouldn't be a big deal. I call bs on the 38+ thing. I can see 34-35 on average, but are you really seeing 38+ daily driven? I think it would be a cool idea to test out. There has to be a reason porshe and lexus do this to most of their cars from the factory. Aerodynamics can have a much bigger effect than you would think.

lightningslp77

daily driven i'm seeing 27-32 depending on what enviroment i'm at.

when i'm cross country driving i did at some sections of my trip get an awesome 38 mpg on cruise control...could've been on a decline but i continued on that rate for about 200 miles. i know that other users before have gotten similar results but again gas mileage is completely dependent on driver habits and the enviroment ur in.

i'm sure aerodynamics do come into play at certain points but you're not going to notice anything when driving from the grocery store back to your house.

personally it would just make it harder for me to get under my car and work on it especially with time contraints having to break pop rivets everytime lol.

if u come out with any results share the wealth

Don Henley

Well R&Ding an optimal performing diffuser requires the use of wind tunnel testing, which is VERY expensive; not worth it when designing a car that's $15K brand new..

However, it's been proven (Mugen, J's Racing, etc companies that actually use wind tunnel testing for their aero products) that drag/aerodynamics start to take effect @ 55MPH. Most of us drive beyond that speed daily, probably more often than not. I think with a diffuser, a drop, and some lighter wheels, upwards of 40mpg would be attainable.

I'm getting something around 32-34 on a stock 2005 sedan, and I wish to increase this dramatically since I plan on driving this thing into the ground.

I have a set of coilovers and lightweight wheels and all that jazz, so it's time to move onto maybe more unconventional methods..

Thanks for the suggestions, I'll probably try and get a friend who does some custom work to help me out.

I'll be sure to post anything I can R&D (probably everything will be off the butt dyno though..)

baron340

iTrader: (4)

An underbody panel doesn't have to be very sturdy. Any kind of stiff sheet plastic will do it. Just find some points to bolt it to in the front behind the front bumper and in the back, covering up the big gap that turns the rear bumper into a parachute. Take into consideration that it will need to be removable and you should be good. I would be very interested to see the results on this. A splitter might also be a good investment.