Ever check the prices on those things? If the car companies spent that much money on such an unneeded part why would they put it on in the first place? It’s all about making money anyway isn’t it?

These are the few reasons that belly pans are used:

1. Noise: every year the car manufacturers are faced with making their cars quieter, not only exhaust noise, but ambient engine noise also.
2. Clean up the air flow under the car. Better high speed stability and less air resistance = better gas mileage, (another criteria the manufactures are faced with).

The “advice” that I see given is to remove the pan, “it keeps the heat in,” “it cause premature valve guide wear on air-cooled Porsches,” “it’s added weight the car doesn’t need.”

Unless your car is a full-out race car, leave it on (Porsche C2/C4 MB diesels see below).

It cleans up the airflow under the car. If you've ever seen F1 cars, you know they're flat underneath. I know the front spoilers are there to stop air under the car, but it won't stop all of it. Suspension arms, hoses, oil pans, transmission, all these things give a place for the air to collide with, resulting in drag.

“Keeps the heat in” first off heat rises.

I have a customer with a 1997 933, prepped for PCA Driver Education Events. Upgrades: chip, lowered, H&R with sport Bilistens, Fiskes with race tires, light weight clutch, B&B mufflers. This car is road legal. He is faster than most full race prepped cars. A lot of it is his driving, but his daughter kicks butt in this car also. Good genes? Yes. But it's also a stable car at high speeds. All belly pans are on the car. This car doesn’t run hotter than any one without their pans.

Ever look at the complexity of a 928 S4 pan? Lots of slots. Cooling slots for the motor mounts. Blow across an empty bottle, you are actually pulling a vacuum on the bottle. Same principle with the 928 pans (also 944/951/968), there is only a small opening in the front of the car, but the belly pan helps with pulling out air from the engine compartment, (even a very slight down force is obtained). We have had 928s in here that ran hotter at speeds without their belly pans.

“Adds weight,” they don’t weigh much, unless of course it's a full-out race car, then ounces count.

They keep the engine compartment cleaner, your car’s technician will like you.

Bottom line: leave the pans on, they help, not hurt.

The early C2/C4 had sound absorption on them, like Mercedes does with their diesels. This is a foam-like substance and is good at canceling noise but it also works like a sponge. All air-cooled 911s leak some oil (as do Benz diesels) and the sound absorber soaks it up until full, but it also attracts dirt when it’s wet with oil. I advise my customers to remove the foam but leave the pan.