I just joined the board yesterday. Nice. I bought an 03 GMC Sierra with a 5.3 in it last week.

Im kind of on a budget now and want to do a few small mods till I can recover from my big down payment I just made. I bought a k and n drop in for $10 today from some lady at my shop that didnt want it in her truck.

Anyhow I know on some engines if you put dont put a muffler on, the engine sounds good but something to do with low backpressure can kill power.

A few of my friends have trucks with the side exit exhaust...I think I want to go that route. Both of them have cats still but no exhaust. Sound mean as hell and where I live, nobody cares. So will I lose power if I just run cats and no muffler? Or should I use cats and a bullet style muffler? Or gut the cats???

Just want the most power and fuel efficiency while still sounding mean.

Thanks

 

If you really want to know what the sound and power loss will be like, just un-bolt the flange after the Y-pipe. Don't worry, it's a ball and socket flange so it'll reseal in a pinch, just don't lose those nuts or you'll be sorry like me!!! Pretty damn loud on my 4.8L, but I lost a significant amount of torque. Although I did gain a bit top-end, it isn't worth it on a stock motor in my opinion. Also, after driving around for an hour or two, the drone begins to kill the fun from the exhaust note. If you're gonna run it without a muffler, at least run the pipes to the axle or out the back. But, like I said, just try unbolting the Y, and have at it!

 

I have an lq4 6.0, I welded 3'' tubing in place of the cat and muffler. And after removing the rear o2s from the computer and a little timing I gained lots of low end and it sounds like no other HD around here. There is a bunch of other tuning that went in to my truck but for the exhaust you have to remove(delete) the rear o2s.

 

I dont think I can afford the tuning now. So whats my best bet? Should I just throw on my friends used 40 series? Thanks

 

*Shudders at thought of another flowmaster on a truck*

If you wanna sound like every Ford in town, go right ahead! Grab a spintech muffler if you wanna sound badass AND unique!

 

Yeah I really want it to sound unique. How should I run it? Like with or without cats, out the side or out the stock location, which spintech muffler should I get if they have different ones.

Im from Austin, now living in Midland. I used to go to your part of town all the time. My exs rents had a house on the river there.

 

Keep the cat till you can delete the rear o2, and the stock location is a good spot and less work and you can still pull off the side exit. It will just be right befor the rear tire. I had a 3' spin tech itll sound different but not loud. As I told you I have 3'' full length exit now and it sounds like a pro stock truck. But a duel in single out spintech will sound different then everyone else. I only put it on for kicks my ls1 buddy gave me one there too pricey for me new I think there like $140 for 1.

 

How do you delete the rear cats? Also yeah $140 is a little steep. Especially when my buddies run straight pipe around here. We live in west Texas, nobody cares. What about just doing a cut out? How do those do on these 5.3 engines?

 

Not the cats the rear o2 there is two o2s in the system the befor cat and after cat, and you'll have to delete the after o2 for the truck to run correctly. $140 is for a spin-tech and like I said there too expencive. But yeah straight 3'' tubing from the cat to the back is just fine. But to get rid of the cat the correct way you have to delete the rear o2 from the computer, witch means it will use only the info from the first one to trim the fuel. Hope this helps.

 

Ok yeah I just mixed my wording there. So heres the plan.

1.Keep the cats and get a single 3 inch straight pipe to the back.
2.Get my computer tuned and at the same time delete my rear o2 sensors
3.Gut my cats and see how it all sounds.

How do I actually get rid of the rear o2s? Just cut the wires and shrink wrap them once my computer deletes them?