Can a different exhaust system give you better gas mileage?

I‘m thinking bigger exhaust, more flow out of the engine, breathes better, improved gas mileage. Is that right or is it just the opposite?

This Site Might Help You. RE: Can a different exhaust system give you better gas mileage? I'm thinking bigger exhaust, more flow out of the engine, breathes better, improved gas mileage. Is that right or is it just the opposite?

The engine was programmed and set up from the factory for the back-pressure of the stock system. If you change that pressure without changing other settings, you'd likely actually lose power and economy. With the proper changes to programming, etc., it is possible to increase economy or power, but the exhaust will have only the smallest effect on either.

Lots of people have made the same mistake and wondered why their engine performed worse after the change. The source has a very good explanation of why you can expect poorer performance and fuel efficiency with a larger exhaust. What it boils down to is you want the exhaust to be the same size (including the same cross-sectional area through the passages of the catalytic converter) as the collector size. After the muffler you can go bigger but it makes no difference. Before Corporate Average Fuel Economy standards were introduced in 1978 many manufacturers used substandard exhausts - whatever was cheapest. CAFE changed the economics so even tiny improvements in fuel economy were worth a lot of RD and quite a bit of production cost. All modern cars are engineered to provide the best fuel economy they can get.