Hi, I am new to this forum, but I have been reading here for quite awhile now. I have a Chevy Silverado 1500 RC/SB Stepside. My truck is all stock currently except for my muffler being removed and replaced with just a pipe.

I wanted to get true duals with no mufflers put on my truck. The piping after the cats is 2.5" and then it merges into one 2.75" pipe that goes out the back. There is an O2 sensor located in one of the two 2.5" pipes about six inches before the 2.75" pipe.

The guys at the muffler shop gave me the same old story about how the back pressure created in the Y is what makes the O2 sensor work properly and that I will hurt performance and fuel mileage by changing the exhaust.

What I wanted to do was cut the pipes before the Y and after the sensor, and just go with two 2.5" pipes out the back. Has anyone done this? Will it really mess things up?

Someone told me they did it on a truck similar to mine and the fuel milage went down for awhile, but the computer relearned and it went back to what it was before. Does this sound true?

Thank You
Justin

 

I got the 4.8 too, i cut both cats, had them run 2.5 pipes into an x-pipe into 2 flows. Everything was smooth for a while, then the SES light came on due to no cats. As far as gas mileage goes though, mine did drop for a bit, but it's up to about 22 in the city now. But the only downside to doing what i did was the SES light, but no biggie, just aggravating as crap.

 

With the lil4.8 and no other mods I think you would hurt your performance more than really help. You can get some O2 sensor sims and it will take care of the ses light. My fuel milage dropped but I think it has more to do with my right foot. I would do it just for the sound. You can see my setup in my sig I have had the setup you are talking about and numerous others but without the cats it really pulls alot better up top. The copmuter will relearn a little a remap some of the a/f stuff but its up to you. I would do other power mods first then do the exhaust like you are talking about. Or you could get a stall and not notice the loss of bottom end and get all the benefits up top thats why I like my setup.

 

ya im going lt headers to a x-pipe to two single chamber mufflers than side mount the pipes before the tire...

I dont think it will hinder your performance at all... if you cut off the cats it will flow that much better and also unlock some more power... just get some o2 sims or get a tune to delete the cats and than you dont have to worry about it at all

 

Thanks Guys. I was thinking of keeping the cats, i really don't want to mess with them. So would it be an alright move to go from a 2.5" after the cats to a 2.25". I know the kid at the muffler shop that wanted to do my truck figured I should go to a 1.75", but I think he's full of crap.

I was also thinking of going to dual cherry bomb mufflers turned the loud way. Is there a big sound difference between cherry's(the loud way) and no cherry's (both with cats)?

Thanks
Justin

 

I have dual 2.5 all the way out

 

I have basically what you're wanting to do except 2.5's all the way. Yes, it will work fine. No mileage change on mine, but you may notice a little drop in low end power but you'll get more after 4k. I recommend going with some type of glasspack muffler (Cherry Bomb will work, I have Dynomax race bullets) over straight pipes. The straight pipes will be annoyingly loud and raspy. Keep your tailpipes short after the mufflers, no more than 2-3 feet (don't go all the way out, gets to poppy sounding) and point them away from each other for separation. The stereo exhaust effect from true duals can't be touched by any single exhaust, or 1 into 2 muffler sound. You'll love it.

 

Thanks Guys, I just got back from the city today where I got it done. I went off the two 2.5" piping and kept on going, I put in a set of Blue Bottles 12" Glasspacks and ended it with side exits behind the tires. Sounds pretty good. Not too loud but it has that sweet true dual deep tone. I am pleased with it overall.

I am thinking of reversing the blue bottles to get a louder sound.

Thanks
Justin