ok has anyone had experience with both 2.5" and 3" duals on the same setup

 

Less bottom end with 3" duals.

 

Yes this is the 3" x-pipe kit from summit.. The material used was:

2 U-Bends
2 Straight tubes
1 x-pipe kit

 

seemed to pull harder on the top end, i never get traction down low so i couldnt tell if it hurt down low or not

 

I had dual 3 inch into a Magnaflow muffler with the stock cats and a single 3 inch tail pipe out the back. On Monday I took the cats off and ran dual 3 inch into a dual inlet dual outlet Magnaflow with 2 1/2 tail pipes. It sounds really really good but I can tell I lost some TQ down low. I have a small cam, Gibson shorty headers, UDP, tune, KN FIPK, electric fans, and an LQ4 in a 1500 HD. I will in the next week or so be swapping to long tubes, TBSS intake, 31 lbs injectors and having the tune updated. I am hoping to get some of my bottom end back. I changed the exhaust thinking the motor I am build 475-500 hp would need more flow. I can't really tell if it pulls harder up top or not, if so it is so slight it is hard to notice. The only true way to tell if for me to take it to the track but I don't have time this weekend. If I wasn't building such a hot motor I would have left the exhaust on there alone but I read that my hp level would need more flow.

 

Well I think the answer is pretty simple. If you are after the fastest track times, 3" is the obvious answer. My personal preference is to 2.5" pipe. Gives more kick down low.

 

I went threw the same problem a couple months ago...

My truck is a 04ecsb 2wd VHO(LQ9) with 228r, pulleys, fans, cold air box, tb bypass, LT's, nelson tune

The truck came with dual 2.75in from the factory. Its a funny metric size between 2.5in and 3in. Anyways when I ordered the LT's I figured a local shop could hook it up the factory pipes and it would be fine. Well they did a hack job so I ordered the pacesetter ORY. Im with you guys, i like the duals but good single is proven to be the same. It didnt make since that the ORY went from dual 3in to a single 3in so when it came in I cut it up I fabbed a 3.5in pipe so the dual 3in pipes went into a single 3.5in instead of the single 3in. After that I welded a Borla XR-1 3.5in and it sounds awsome. I recomend this setup to everyone...I love it

Heres a clip- b4 cam
http://s417.photobucket.com/albums/p...6/ls1%20truck/

 

OH yeah, got the truck on a dyno the day after the finished exhaust in DFW
With a mail orded nelson tune(not tuned for the LT's), cold air, e-fans, and LT's
336whp 407wtq

It made a huge difference

Good luck bud,
Chris

 

See mine isn't really 3 inch inlet it is whatever matches the stock diameter the best. The muffler is a 2 1/2 inlet and outlet muffler and the inlet side is opened to match the stock size piping and the outlet is just standard 2 1/2. I think removing the cats is what ulimately what killed the bottom end the most

 

Tell me more about the 228r idle and driveability. That's the same exact cam I have sitting here waiting to go in the 6.0 and I'm wondering if maybe I should step down in size. Thanks