To improve my gas milage and hp on my 95 150 does the diamiter of my pipes matter? I have 2 1/4 in now.

 

the bigger the pipe size the better it flows which makes more power. what motor do you have?? 4.9 5.0?

 

bigger is not always better...stick to 2 1/2 "...or you will lose to much low end torque...... i have 2.5 sido...50 series

 

Changing the piping diameter will shift the rpm of the torque peak. The rule of thumb is that a larger diameter will shift the torque peak to a higher rpm. It will also reduce backpressure. Optimizing your torque curve for to match your driving style will improve your mpg and also help your overall acceleration.

 

Stay with the 2-1/2" and exit with a 3 in tip. Any larger and it will get "blapppy" you know what I mean.
I have an '03 F-150 with a flowmaster 430402 chevy application (89-350) 3inch in dual 2-1/2 out to 12 inch X 3inch stainless tips slant cut.
I get compliments all the time on the sound. Better a compliment than a complaint.
I made a run down to Houston last weekend and once your over 75 (2000 RPM) the sound dies down until you hit 95 (2400 RPM) then it comes back.
Thats running P-265-18's on 3.55 gears, yep 2k at 75 MPH and plenty of pedal left
And believe it or not but with Mikes 1750 programmer I got from him in '03 and the program I asked that he put in on the stock (enhanced stock Mike calls it) program I was getting just under 19MPG a gallon at those speeds.
If I stay at the speed limit it will get over 20 MPG.
Of course the city ratings suck because I hate driving with everyone else.
See 'ya

 

x2-=thats why i did my dual exhaust on my 8klb van in 2.25- to maximize tq- i make 320 ftlbs at 2500 rpms and it stays in the 300's till 4300- where it obviously starts to drop-phil

 

You're ok with 2.25". That's what I use on mine from the head-pipe back. It has lot's of torque paired with a free flowing Magnaflow si/do.