3 inch single exhaust on a 01 sport?

[Exploder001]

I have a 2001 Explorer Sport 4.0 sohc, and after reading alot of threads i see that the ideal exhaust size is 2.25 or 2.5 inch pipe. But id love to try and get alittle better gas mileage out of it so ive been thinking about getting a custom 3 inch single exhaust after the cats with maybe a cheap 3 inch turbo muffler like a Flowtech Raptor or Cherry Bomb Turbo. Im ok with losing some low end torque if it would get me better gas mileage or would going with that big of a pipe do more bad than good? Thanks.

 

[2000StreetRod]

loud or fuel economy?

In my opinion if you drive for fuel economy increasing the muffler in/out and tailpipe diameters will make no difference except in sound level. With a 3.73:1 axle ratio and normal size tires 80 mph is only about 2600 rpm.

Your engine speed should stay within the range of max torque for best fuel economy. When enlarging the exhaust pipe diameter your muffler selection becomes important. If you're not careful you'll lose low to mid engine speed torque. Below is a plot of my NA torque after installing a full custom exhaust from the manifold outlets back. I was able to slightly increase torque from stock.

However, the Dynomax VT muffler gets loud above 2500 rpm.