Straight Pipe for LLY

[BrewMaster]

I'm looking to remove my cat and muffler on my '06 lly and replace with straight tubing. I figure this would be cheaper than going with a turbo-back exhaust which is essentially the same thing. The turbo-back that i was looking at was the MBRP 4" but have decided to just go the cheap route for now. My question is, has anyone done this and what are your opinions, also does this void out any warranty's? Thanks in advance.

[DmaxMaverick]

Welcome aboard!

I helped a friend do something similar a couple days ago. Have a look at THIS THREAD (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=34530). You may able to do something like this. This was on a CA truck, so your emission class may be different. The forward pipe with the cat is a real piece of work. In front of the cat, it's stamped/welded pipe, with normal exhaust tubing out the back. I've seen several attempts to delete the cat with a section of pipe, and in every case, the welds wouldn't hold to the forward section. Maybe you're a better welder, or the material is just too foreign. It isn't round, so you can't clamp it. Maybe they designed it this way. I dunno.

Anyway, you can purchase front pipe sections without a cat, to fit your truck. If your state ever begins Diesel emission testing, you'll need that cat back in there. Otherwise, replacement is north of $500. With the stock size pipe, removing the muffler only makes more noise. No appreciable gain. In the end, it is far and away better to just replace the entire system with a better flowing 4" system, if you want something different, or for performance reasons. IMO, performance gains with stock diameter pipe isn't worth the time/effort.

[Duramaster]

BE CAREFUL when doing this modification. I have had a few trucks come in with MAF sensor codes because of the now LACK of exhaust back pressure. Make sure you get an exhaust system that was/ is designed for the LLY and not the LB7. Otherwise you might have to figure out how to add restriction to your new free flowing exhaust.

[BrewMaster]

Guys, Thanks for this info!

[OhmEye]

I have had a few trucks come in with MAF sensor codes because of the now LACK of exhaust back pressure.

Sure doesn't see like a bad thing to me, the lack of back pressure I mean. The code doesn't sound good, though. If I get the code will it show up as a check engine light or is it just hidden away somewhere until retrieved?

DmaxMaverick and I wrung it out some after the conversion and I've done some around-town driving since but haven't seen anything yet. Under what conditions would the code most likely show up? Can you recommend a fix for the code other than choking the exhaust back again?

[DmaxMaverick]

Sure doesn't see like a bad thing to me, the lack of back pressure I mean. The code doesn't sound good, though. If I get the code will it show up as a check engine light or is it just hidden away somewhere until retrieved?

DmaxMaverick and I wrung it out some after the conversion and I've done some around-town driving since but haven't seen anything yet. Under what conditions would the code most likely show up? Can you recommend a fix for the code other than choking the exhaust back again?

This isn't something you'll see with the CA LB7. The exhaust pressure, temperature and gas content isn't monitored.

[OhmEye]

This isn't something you'll see with the CA LB7. The exhaust pressure, temperature and gas content isn't monitored.

Excellent news! :cool:

Thanks again, Greg. Can't tell you how much I appreciate your help.