I am the proud owner of a 05' GMC C/C 4x4 diesel. My questions are these, would it be worth my time just to replace the factory muffler with an aftermarket one for the time being? Also does anyone know the laws regarding catalytic converters here in the great state of California? Lastly I have seen many posts about exhausts and I am still left wondering which aftermarket exhaust is the best for the price?

If you want to remain legal, especially in CA, you better leave the cat in place. I wouldn't fuss with a muffler only, go with an MBRP or similar cat back exhaust that is 4" in diameter or larger for lower egt's. Also, Welcome to the Diesel Place:welcome2:

contact MarK Craig at DPPI... www.dieselperformanceparts.com

California,,,,, dont ask dont tell. They have not yet started completing smog checks on them,,,,,, YET

Going through the same problem with the exhaust in California...

the problem is not the eventual state check for the cat, the problem is the CA truck throwing codes and engine light and possibly compensating for the codes and damaging truck.

I have a 4" turbo back exhaust kit in the garage and afraid to put it on. I have been talking to exhaust shop about cutting the cat and welding the 4" pipe on it. However, if it screws up the exhaust I will have to spend $400 on a new cat and then new exhaust. So far, I am thinking about returning the turbo back and buying cat back. Also, I have heard many people say that after putting on the 4", the truck ran like crap and they went back to stock. Can't really put it back on if I adapt the cat to 4" inlet/outlet. (Anyone out there have a kitty that they want to put up for adoption, I will paypal you for shipping)

It seems that after about 8 hours of reading all of the post regarding exhaust on the LLY engine, that it is the luck of the draw if your truck will throw codes without the Cat. Just don't feel like taking the risk if it is my daily driver. There seems to be a 50/50 chance if it will be good or be bad! Maybe we can put up a survey of CA LLY owners that have done exhasut work?

Truthfully speaking, for my towing and etc. the 4" cat back did not make any difference. However, when I finally got the 4" down pipe installed they dropped significantly and I rarely get over 1100 degrees now and thats uphill with a load. So I would recommend a full 4" front to back, or just stick with what you have. The cat-back is just not worth it. Thats my opinion anyway.

Occitiger,

Do you have an LLY or LB7? Do you have a CA truck? seems to make big differences.

mines a CA truck. I say do what i did and cut em all off, no need for the cat or muffler and it really isnt that loud. hell its quiet compard to a derge with a straight pipe. Ive also been pulled over 2x since doing it and neither time was for the exhaust. Neither time did I get a complaint or question about it either. Who knows when Ca will start smog checks on diesels, when they do Ill move.

Hey jmg,

I see you fingersticked and did the block off...any problems with that? install or problems with the engine? How long have you had it blocked and sticked? Thanks.

If I had to live in Calif. think I'd leave everything in place as it came from the factory.

So it sounds like i should leave the cat in place, but look for a whole new exhaust from the turbo back. Does any company make a turbo back exhaust or are they all downpipe back? Also is there a system that includes the cat in it's application if it does come from the turbo back?

Hey BCHN,

I have been doing some serious checking and it seems that all turboback systems eliminate the Cat. Only way I have seen to put the full system on is to take the Cat to a muffler shop have them cut off the ends and open it up to 4", reweld the 4" pipe on it and then re-use it. But then, you have to be careful that it will fit under the truck. I am still debating if I am going to do all of this, b/c if the cat gets screwed up it'll be $400 out of my pocket. I may just do cat back, but I hear it isn't worth itas far as EGTs and performance. I wish there was someone out ther that has done the 4" exhaust and maintained the Cat on a CA LLY, been looking for hours, well days actually.

Nrgreen: If I understand it correctly you are wondering if anyone has gone to a 4 inch exhaust from the turbo back while however putting the cat back in place. I just dont understand why anyone would do that. "Its like wipin before you poop it just dont make sense"-Larry the Cable Guy. In all seriousness I understand why you are concerned about the cat. The whole purpose of getting rid of it though is for the egt reduction. To put a four inch system on and then put the cat back on would in my opinion be defeating the whole purpose. I currently have the MBRP cat back system on. However next week I will be replacing that with the four inch turbo back and installing the fingers stick to keep the codes in check. I am doing this for two reasons. Better sound and egt reduction. Hope this helps.

Eric

Thanks Eric...actually I want to keep the cat for a few reasons...

Legality of it all,
Don't want to switch everytime I go to dealership and possibly void my warranty
Don't have a clear answer if the fingersticks and (mostly)EGR blocker will cause long term damage to the truck.

I would love to just go 4" with downpipe, but I just want to get a system done that I don't have to worry about being fined or adapting everytime I go in for dealership work. I want to do it once and be done. I don't want to do anything to throw codes. I know, I know, most people don't really care about the codes, but I do.

Believe me, I have asked my self the same question about putting the cat back on, and I totally agree with your analogy, but I only need to drop EGTs a little and I think the new muffler and exhaust will do what I need.

But seriously, thanks for the input, every opinion helps!

Nrgreen: I hope you were able to wade through my bs. I am in law enforcement in Ca. I have never heard of a diesel being checked for a catalytic converter. I have heard of rice rockets being checked. I personally feel if your dealer will void a warranty for that, then you need to find a new dealer. You do know that you can install a fingers stick without installing the egr blocker plate. That is what I intend to do. PLEASE do not misinterpret my opinions on diesels being check for the cats. I am just relating my personal experience with that matter.

Eric

nrgreen, keep us updated on your exhaust choices. thanks for the input, too bad we have to deal with these cats, but i guess this is our punishment for living in such a beautiful place.

Thanks 1Sast, no problem, just trying to do the right thing that will save me potential problems later. My understanding on installing the fingersticks without the EGR blocker is that the truck will try to compensate in some way for the low backpressure. Now, I don't know what it will do to compensate or what damage could occur if it does try to compensate for the low backpressure ( I don't know engines enough to answer that question, I have heard it can ruin the turbo)....thus, my dilemna...I saved for a long time to get my truck, I am kinda skitish about doing anything "iffy" ya know?


I have read so many postings over the last few days and it seems 50/50 if it is good or bad. I think I would feel better if I did something that didn't throw codes, the question is what?

I have had my truck fingersticked and plated for almost 20,000 miles now and I have had nothing but great results. I have been pulled over twice and to the dealership twice and no one has said boo about my muffler and catless 5" exhaust. No one voided my warranty, nothing. I say straight pipe it and fingerstick it and plate it, there are only benefits to be reeped.

Thanks JMG,

Definitely good to hear from someone who has done it and had it like that for a while. I guess what has made me leary is all the people out there that said they went with the new exhaust (4") and then the trcuk ran like crap, so they went back to stock. Wish we could find out what happened with them and why that happened to their trucks.

Well I did it! Went ahead and put the 4" exhaust on the 4.5 LLY CA truck. Put on aftermarket muffler and removed the Cat. So here are the results for ALL of the CA LLY people wondering:

1) Definitely a little louder, finally sounds like a beast when I hit the gas, not much louder when just cruising. I did turn some heads when I hit the gas:)
2) No exhaust drone or weird noises :)
2) EGTs dropped about 50-100 running on Edge *** lvl 3. Just enough to not set off my 1250 degree alarm going up hill.:)
3) Doesn't respond as fast (sometimes) from low RPMs when I down the pedal, and sometimes shifts up a gear instead of down. Responds well when I down the pedal and already at 1500 RPMs or higher. Not necessarily bad, just have to get used to it. It does pass a lot faster though.:) :(
4) And the one everyone is waiting for....NO CODES!!!!:ro) No fingersticks or EGR blocker installed.

So I am about 90% happy and being that I only spent about $300 on exhaust for the full system, I am ok with the results. Definitely would not be as happy if I spent $700 on the exhaust, didn't make THAT much of an improvement.

Running AFE Stage 2 intake, Edge with attitude, 4" turbo back exhaust no cat, replaced muffler. Definitely happy with the combo together!

Sounds like everything has worked out well for you. Keep us updated cause I am very interested to see how your truck holds up. Where did you get your exhaust from anyways?

just do it .... you will like it.

I got it from RPM outlet. I wouldn't suggest going there though. I got a package deal for all three mods for a really good price, but pieces were missing, the edge was scratched and missing parts, sent me the wrong exhaust. They are a total pain to deal with. I used the exhaust cause it was such a pain to send back and I would have been out $40 on shipping, just got lucky it worked out the way it did. i had to go to Edge to resolve Edge problems as RPMOutlet told me, "We don't do customer service, its how we keep our costs down." WTF?!? So they wouldn't send me the EGT probe that was missing unless I paid for the shipping. Edge sent it next day air and told me that they were pulling their products from RPMOutlet because of numerous complaints. If I had to do it all over again, i would go to Marc at Deisel Performance Parts. I will be doing the rest of my shopping with them.

Be careful with Kitty's in CA. They have stepped up to having a more comprehensive checks with new smog machines, at least with in the bay area, and are getting more failed checks (usually older vehicles). Of course you will get a couple years of no smog with a new vehicle, but, I'd be worried if you do not have an "in" with a dealer who will assist you with codes due to missing cat or mod exhaust problems (warranty void)!! If you get pulled over by a savy LE Officer, and they check mods and notice a missing Cat, you will be black flagged and cited. You will then be forced to get your vehicle checked at a "state smog referee", who will in turn, go through your ride with a fine tooth comb for ANY mods that are not C.A.R.B approved. my .02

You are correct DirtAndSand, this is why I am having the exhaust shop fit my Cat onto the 4 inch pipe tomorrow. Thanks for the input.

Well, cat went back on the truck, it started to run horrible and after 5 days it threw codes and light. That seemd to be a little bit longer than most people. I think that the money spent on the exhaust is not worth it, not enough performance increase to make it worth dealing with the hassle. Should have just gone Cat back.