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I was wondering what the signifigance of the plastic that runs along behind the front bumper is. It covers the alternator belt is all i can tell, and i assume it prevents snow/mudd buildup in the engine compartment, but will it harm anything to leave it off? I slid backward into a ditch a couple weeks ago and it ripped most of it off. From searching the web all i know is it may be called an Under Engine Splash Guard, but that didnt seem right since it was like 50 bucks and its the same as a fender liner that goes for like 7.

 
Rep Power: 245

It slightly improves airflow through the grill, engine compartment and under the car. It also does keep the belts from getting wet in the rain etc.

You could always replace it with a piece of sheet metal (like aluminum) which would help slighly improve efficiency by reducing drag (albeit a slight bit) while helping the above.

 
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Damn, for some reason, those plastic pieces come loose when I'm driving for long periods and will scrape all over the road and end up eating up the plastic. I think I'm going to need a replacement for the whole underbody.

 
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Lol alright, thx man, i was thinking they werent extremely important since it was pretty flimsy plastic. I might look into the sheet metal when idea when spring rolls around, tho i have to be careful with that idea too since if the metal gets bent at all it could shread the belts off. Otherwise maybe a scrap yard could help me out :-)

 
Rep Power: 245

True, yards are always an option. I'm going to be yanking my old damaged one off and replacing with aluminum by spring. It'd be pretty tough to damage that AND have it somehow have a sharp edge pushed into the belts.

But I live on the edge I guess LOL

 
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Haha sounds like a plan, im considering the aluminum, lol, then maybe it wouldnt rip off next time

 
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Yeah, it should work really well. The only issue is where to attach it. I'd like to go back all the way to just ahead of the drain plug (for aero reasons) but that's seriously a bugger trying to attach that far back.

 
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Just use the same mounting points as any underbody X brace.

I was thinking of doing this a while back. You need to be concerned about air flow to the engine compartment. It gets hot in there... your hood is slammed shut and your front is covered by your bumper, rad, ac.... when air comes in, where will the old air go? If you seal up the bottom without any other vents, your just making the front of your car into a huge open box that you drive straight into the wind- it'll slow you down. Think it through so the air vents, its easily removeable for maint and fluid changes, and that it wont come off when driving and cause major issues.

 
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Good points. For those very reasons (ease of access/heat venting) I wanted to only go back to the middle of the oil pan. I'm definitely not going with Coroplast but aluminum .

 
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i work at a honda shop and all those things do is slightly improve airflow but they mainly just keep things like rocks and road debree out of the engine bay. honestly all they do is get in the way when your changing oil!! if your roads around were you live suck. id leave it on, or if your car is slammed. other than that you dont need it

 
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anyone know of some good places to get a larger sheet of aluminum because i can only find small pieces like 12" by 12"
i checked local hardware stores like homedepot. by the way i live in Chicago.

 
Rep Power: 245

Do a local search, like on Google maps for a steel supplier. Give them a call, most sheet steel suppliers carry aluminum too. You will have to buy a 4'x8' sheet (but they may have some smaller pieces around). It's enough to do two rear under trays, so that'd be at least 1 rear and two fronts.

If you'd rather buy less material, search for a scrap metal yard.

Hope that helps.