The underside of the floor, the muffler, the engine, the electrical system and computer controls, etc are all exposed to road dust and water and other crud, especially in northern climates where they salt and sand the roads. Why don’t manufacturers put body panels or covers across the bottom of the car, and provide air ducts for cooling if needed? It seems to me that the car would last longer, work better, and be more aerodynamic as well.
The panels would only provide the benefits you mention as long as they are new. They would soon develop into a collection point for the dirt crud and salt that you want to keep away from your vehicle. IMHO it would be next to impossible to clean there. I can only remember two of my cars that ever developed holes in the foot wells indicating that the present method works prety well. I have owned some real “Jewels”
Race cars don’t even use “under panels”. I would guess that is because they are afraid of the lift they might cause.
Have you ever worked on a car before? You have enough crap to deal with without having to crack open a shell. Plus you have deal with the heat buildup if this all self contained.
Jaguar did this with the E-types. A few other British marquis did also. One major problem (above and beyond john_e’s comment) with them is that they collect dirt and dust (as stated above) and MOISTURE. Moisture sitting on metal is always bad news. Especially in snowy climes where salts are used on roads. Trapped salt water or metal is a recipe for corrosion.
BTW, another problem specific to the Jags is that the builders tried unibody construction and had partial framing. This allowed for wonderful road handling (car can bend torsionally without creaking or popping). Problem is that unibody construction is not that strong. Especially with two heavy-ish people in the car. It tends to bend.
British Leyland tried this (around the same time) with the TR-4, a much shorter car, with the same problem. I recall our neighbor sitting in her TR-4 and having to slam the car door shut. When she wanted out, the door would not budge. Luckily, it was a convertible and she could drop the top and climb out. Otherwise, one would have had to jack up the middle of the car to take the strain off the top of the door.
I had a very nice :rolleyes: Renault Alliance that had something similar to what you describe. It was a plastic sheet that covered most of the bottom of the engine compartment. It was a pain in the ass for all the reasons mentioned above, plus the holes where it screwed to the car tore through leaving it hanging. Ripping it off solved all my problems (other than the car being a POS).
All the more, none of this stuff really ever goes bad as a result of exposure in a reasonable amount of time. New, stainless steel exhause components will problably give you 10 years of life. Electrical wires are not as exposed as much as they used to be, but they’re insulated. The engine? It’ll in all likelyhood outlast the rest of the car. What computer controls? The sensors? Maybe that’s a good point, but they go bad eventually anyway.
Also, adding all that extra sheet metal would DRASTICALLY increase material and manufacturing costs. Ditto the service costs (image paying $30 for a $15 oil change, for example).