[Cd]

On a lot of race cars I have seen the exaust routed in such a way that it can be used to energize ( reattach ) any stagnant air behind the car.

Can we do the same sort of thing with our cars ?

I would think there would not be enough force behind our puny exaust pipes to do any good.

Also I'm confused about whether a large exaust pipe and free flowing muffler or a tiny exaust pipe with a stock one is better for fuel economy.
I have seen arguments for both.