Will a car run "better" without a catalytic converter or muffler?

Dear Car Talk

Dear Car Talk | Jan 01, 1992

Dear Tom and Ray:

Forgive me for asking a purely theoretical question, but I need to win a bet. Will a current model American car run better without a catalytic converter or without a muffler? Please understand, I have no intention of removing these things and breaking the law (even if I knew how), I am just asking for the sake of mechanical knowledge.

RAY: That's a good question, Kathleen. If by "better," you mean will they run more efficiently and more powerfully, the answer is a qualified yes.

TOM: Think of it this way. A car's engine produces only so much power. When you put something in the way of the escaping exhaust--like a muffler or catalytic converter--some of the engine's power must be used to push the exhaust through those devices. So if you remove them, more of the power can be used to make the car go. That means faster acceleration, and more miles per gallon.

RAY: The reason we qualify the "yes" is that if you remove too much of the exhaust system, you could end up pulling some of the gasoline out of the cylinders before it's had a chance to burn. That would decrease the power and efficiency. And the optimal length of the exhaust pipe would be different for every car.

TOM: But as you probably know, Kathleen, power and gas mileage aren't the only things we want out of life. The small amount of power drained by the muffler is well worth it, as my brother can attest, having worked on too many cars without mufflers.

RAY: Huh? Did you say something to me?

TOM: See what I mean. And the catalytic converter gets rid of un?burned gasoline that would otherwise spew all over the place and cause horrible pollution.

RAY: So if your question is whether cars would run more powerfully and efficiently without mufflers and converters, than the answer is a qualified yes. But if your question is whether we'd be better off without them, the answer is an unqualified no.

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