I'm considering the purchase of an T-409 MBRP 4" stainless exhaust system, which seems to be among the more quiet/refined systems available. As I understand it, this can be from tailpipe to 1) four bolt flange, or 2) to/near the turbo via downpipe.

QUESTION : How much LOUDER is the downpipe? I really am not (NOT) looking for noise... just lower EGTs... less noise the better (at least for me). Follow up question: How much difference does the downpipe make in lower EGTs? Is it worth an extra $125, in your opinion?

QUESTION : I'm told that a resonator can be added to the 4" downpipe to reduce noise.... Does anyone have this, and can anyone share before/after experiences with sound reduction? Again, is this worth $120?

Will be using truck to tow a 13000 lb (loaded) fifth wheel up steep mountains in high altitude... would like to be able to talk to my wife while doing so, as opposed to screaming over high drone, jet engine sounds,...etc.

Thanks guys...
Paul.

Paul- The pipe you are talking about is the front-pipe. Replacing it will give you minimal gains as you have an LB7 and no CAT. I would go with the standard system and hold off on the front-pipe. The noise level will be louder than stock, but by no means LOUD. Hope this helps.

If it's a CA truck, it will have a kitty. Even our gas cans are smog-controlled in CA. Yep, weed-wackers too!

If it's a CA truck, it will have a kitty. Even our gas cans are smog-controlled in CA. Yep, weed-wackers too!

My truck does not have a kitty... --Paul.

Yup, leave the front pipe alone then.

Mcrat....Do you get an SES light if you take the cat of your weed wacker....wonder if Fingers has a fix?:D

Naw, they make it so you can't adjust the carb, so when it gets old and starts running poorly, you throw it away instead of adjusting it.

I'm waiting for manditory vapor recovery systems on our toilets. That'll be a gas. :eek:

Paul, I had the same concerns as you. I replaced my Cat and full system with an MBRP 4" system. Outside the truck it is defintely louder. I also installed the mufler the opposite way that MBRP recommends in hopes of making it as quiet as possible.

In the cab it is almost as quiet as before. There is only slightly more noise. I don't find it objectional at all and there is no drone. My wife hasn't even noticed yet :)

I say go for it and if you find it too loud you can add the resonator but I think you will like it as is.

In my opinion changing the front pipe won't change the sound much if at all but it should help in reduce EGT's. If that is your main goal you probably should do the front pipe right away as well.

Replacing it will give you minimal gains as you have an LB7 and no CAT. I would go with the standard system and hold off on the front-pipe.

Yup, leave the front pipe alone then.

Paul, I had the same concerns as you. I replaced my Cat and full system with an MBRP 4" system.... In my opinion changing the front pipe won't change the sound much if at all but it should help in reduce EGT's. If that is your main goal you probably should do the front pipe right away as well.

Thanks for all of comments, and thanks for the PM Tony (Max Power)-- I read your article and enjoyed it. There appears to be differing views (quoted above), but I'm wondering if there is really an underlying harmony. The impression that I'm getting is that if you HAVE a kitty, then it would be definitely worth removing the front pipe (as Tony did), but if the stock truck does NOT have a kitty then it adding the front pipe will not provide much benefit in reducing EGT's. It would seem then that it's more an issue of removing/replacing the KITTY than adding a front pipe... is that correct?

Thanks,
Paul.

That is absolutely correct. Changing downpipes on your truck should have no difference in sound and a minimal change in egts since it does not have a Cat on it already. You would be going from a 3.5" downpipe to a 4.0".

I agree with Maxpower. I would go on and change the downpipe with the rest of the system.

Ok, lets add a new twist to this...

I replaced my front pipe & cat with the MBRP, bolted to my stock muffler and rear pipe. My main concern was keeping noise down as well, but it sounds like the full MBRP system is reasonably quiet. What gains could be expected if I were to finish the job with the rest of the exhaust system? I doubt egt's will be a big concern since I typically only tow about 8000 #. Or, I could stop being a tight wad and just do it...

sammy- I have heard gains of up to 25 HP with the system. Someone had a dyno sheet around here, maybe they will post it again. Noise is definately not an issue with the LLY as the VGT keeps the exhaust note very tame. At an idle there is a low rumble, but upon accelleration it turns to more of a whistle. Hope this helps.

The front pipe is another 4 1/2' of 4". Of course it is going to make a difference. Is it going to make $125 worth? That is a personal decision. I have not seen any numbers posted either way. Later! Frank

I would agree with Frank et al, the front down pipe is going to have minimal affect on noise or EGT. I have seen a stock muffler cross-sectioned and I've got to believe that at least three fourths the exhaust resistance in right in there. As far as my 4" system is concerned, I wish it was a tad quieter in the cab under load. It might be my 5" double walled resonator tip (not MBPR) though since I have not heard any complaints about other MBPR systems. From reading many post here it would seem that the TSS 4" exhaust system appears to be the quietest. It has a Donaldson-designed flow-thru muffler which is pretty huge by comparison to MBPR, Banks, JK, etc.