You may have gained torque at the peak but I'd like to see what it did under the curve.

 

if u have the intake airflow and u can get enough fuel in the engine, u can run 3" and make good tq and hp

 

tq was up 8rw at 2500 rpms compared to 2.25 not 2.5. dyno didn't show below the 2500 curve. Definitely has wayyyy more 1000-1500rpm tq compared to my long tube dual 2.25 no x pipe set up, dd wise.

It is most likely due to the 2 xpipes creating back pressure. Most tq loss 3" in exhaust systems are due to trure duals where on our trucks means the driver's side exhaust tube has an extra 2 ft of tubing an slightly higher back pressure than the driver side. But if the old school x or h pipe is introduced then pressure "will almost" equal out.

 

Why is it still believed that backpressure creates torque? If that was the case people would just slap on some 1.5" pipe for towing duty and call it a day. What you do need is an adequately sized pipe for your setup (and headers will most likely have 3" collectors, meaning 3" will be the ticket) and an x or h pipe to improve the scavenging effect. Honestly I think it's a waste of time to measure the exhaust flow and perfect the scavenging on anything but a full blown race build, but there are people that do it and find extra power.

Id really like to see a dyno run to prove it if you think it's true, but the number of runs Ive seen to prove it false leads me to believe you cant.

Then again Ive seen quite a few dyno runs where guys lost hp with a flowmaster, but people keep buying them because they sound like performance. All about the marketing?