exhaust hurting my MPG?

[Belto]

I have a XJ 4.0L,, with a stock exhaust till the cat witch is 2.5 then I have a cherry bomb style muffler and cut down.. thats it,,,

 

its it hurting.. bc it sound mean as hell...and I love it..

 

just to know

[ifixit8]

I doubt that system is hurting your mpg, if anything it should help it.

[Eagle]

The stock cat is 2-1/2" but the stock system from the cat back, including the muffler, is 2-1/4". Yes, the larger exhaust is hurting your mileage. The first replacement exhaust on my '88 Cherokee was a 2-1/2" cat-back with a Walker turbo muffler. I lost about 2 or 3 MPG and I could definitely feel the loss of low-end torque. It was the first time in my life I was actually hoping for an exhaust system to rust out, and that I celebrated when it was time to replace it.

 

I went back to the stock size and I've been much happier.

[Belto]

see again,, to some it helps to some it hurts,, damn it ,,, lol

[BLHTAZ]

You have to be very careful with a 4.0L engine. AS Eagle said...if you take too much back pressure away from a 4.0, it is detrimental to it's performance and economy. A lot of people like a big "free flowing" exhaust, but you will have to be willing to sacrifice something for the sound. I am going to replace my broken muffler soon with a flow master 40, but I am not going to change the pipe size.