I'm thinking of replacing my stock muffler with a Magnaflow. My goal is improved fuel efficiency. Magnaflow will stand behind a 10% increase in HP (which I don't mind) but will not guarantee improved mileage.

I drive conservatively, most of the time, and tow trailers in the summer up to 2000 lbs. I have an '02 stock 4.7L auto with the tire and handling group (I only include that because I can't remember if it included special exhaust components).

So what do you think? Am I likely to see a mileage improvement if driving style stays the same? Any pitfalls you've experienced?

 

If they guarantee 10%, I'd put that sucker on a dyno. Your engine makes, what, 235 hp? You're NOT going to get 23 horses out of a muffler. Maybe 5-10.

Edit: regarding fuel mileage, I don't think you'll see much of a measurable improvement.

 

Usually a muffler will help because you do have improved performance but you will probably start to race it because of the muffler lol. Cause less millage.

 

Yeah............Happened to me

 

LOL, yea I think the same for me too, wonder how it will be with the new motor LOL.

 

yeah..the manufacturers claim HP gians, as well as fuel economy. I don't believe either. I noticed maybe a little more throttle response outta mine, but other than that......idk

 

Thanks a lot, guys. I'm going to wait until my stock muffler NEEDS to be replaced and then put a Magnaflow on. It's actually cheaper than Mopar, through Canadian Tire, anyways.

 

strait pipe adds like 12 hp and ALOT of responce (cat and muffler less)

 

Well, Straight pipe is worse than a muffler. Most engines need some back pressure.

 

I think that's a fine plan. Or...replace it just because you want to...for the sound...whatever. But don't replace it for power or economy because you'll likely not be able to measure in increase in either. But their "guarantee" sounds intriguing. What are the details? You said they guarantee 10%. What will they do if it doesn't? Buy the muffler back? Or pay for it and let you keep it?