maybe a dumb question, or one that has been answered before but I will ask anyways....

Can a cat back exhaust increase fuel economy without a tune?

I am reading reviews on Stage 3 MotorSports about the link below and seeing reviews say they saw 1-1.5 mpg increase but wanted to ask here.



http://www.stage3motorsports.com/49-...ess-Steel.html

 

Cat backs on these newer trucks do nothing for mpg's or power. Tune is not needed for cat backs. It's all purely sound. You would be better off just getting custom tunes. More increases per dollar with a tune.

 

.....enter Flowmaster who will claim fuel mileage and horsepower gain....

 

Earlier trucks and cars had very restrictive mufflers that would make an engine feel like it was trying to breathe through a straw. Not so much the case any longer. The stock muffler on these trucks is about as good as you can get as far as being a straight thru muffler. The pipes that run inside the muffler perpendicular to the flow within the individual chambers are tuned to cancel sound waves.
What makes aftermarket mufflers different is the inlet/outlet diameters, and the interior designs change to tune the sound into something more aggressive. A catback system with a performance muffler will sweeten the whole deal in the aggressive sound department, but not by a whole lot. Stock muffler cutaway pic below:





Borrowed image from ecoboost forum.

 

Just figure it is slim to none. Do it for sound, looks and better quality steel in some cases.