OK, I think I am going to try the MBRP exhaust on my new D/max. It is a 2005. Do I remove the cat or not?
Yes, I have read all the threads, they are not all the same! Some say yes, there is much to gain others say no. :eek:

So, what is the real deal?
Will it throw codes with no cat?
What is to be gained by taking out the cat?
What is the down side to taking out the cat?
Lets break it down really simple for a diesel noobie :ro)
Thanks guys!

:help:

aquaelvis,

Positives:
Removal will net you 20-30 degrees lower EGT, 2-4 HP and more exhaust note vloume.
Negatives:
More exhaust note volume, possible engine SES light, slightly higher EGT's, potential dealer warranty issues unless you replace it for dealer trips.

We always reccomend getting the cat back system 1st, if you find you need the extra 20-30 degrees EGT drop then add the front pipe and see if you get a light or not.

Mark @ DPPI

You may or may not throw codes, only one way to find out. I would go with the cat-back system first then you could add the front-pipe later if you want to.

It all about what you want. The gaiins are small but when your looking for every last little bit it counts. As Mark said about 20 - 30 degrees temp drop under load and about 3 Hp are the gains. Negatives is louder exhaust,its illegal to remove, it will void your warrenty if brought to a dealer, it will set codes in computer and may or maynot turn the CEL on.

Thanks for the feedback guys, I think I will go with a cat back system for now. I really don't want a drag truck and I don't need the headaches of a dealer problem.
If the gains are small it does not seem worth the potential problems.
I think the only mods I am going for (other than lift) are the Edge w/ Attitude and exhaust.
We'll see about the electronics, don't want dealer trouble. They seem pretty popular though and worth the cash. I want one ):h
Now I gotta find the best price and get it ordered, my truck won't be in until next week! :(

cat deleted here and i LOVE the sound...and NO LIGHT! Rip er out!

let us know how it works I'm thinking the same cat back system. It's susposed to gain mpg also.

I am going to get a exhaust and was mainly thinking of removing the cat because you are supposed to get better gas mileage with it removed. So does removing the cat get you better gas mileage? How much louder is it?

badass- In theory, removing the cat will get you better mileage as a restriction in the exhaust is being removed therefore creating a more free flowing system. Will you actually SEE a mileage improvemnt? Don't hold your breath. What you will get is quicker spool-up, lower egt's, and a lower exhaust note.

badass- In theory, removing the cat will get you better mileage as a restriction in the exhaust is being removed therefore creating a more free flowing system. Will you actually SEE a mileage improvemnt? Don't hold your breath. What you will get is quicker spool-up, lower egt's, and a lower exhaust note.

What results if I just replace the CAT with a test pipe? If sound level only goes up 1 dBA with 4" cat back AND test pipe, back pressure should be greatly reduced with test pipe only. Of course I'll bet the flanges won't work very well on the back end of the test piece where it's supposed to match up with the 3 1/2" stock.....

Ed

bettered,

The biggest restriction is the stock muffler, then the cat is number 2. Removing the cat alone is a minimal change at best! The flange on our MBRP front pipe bolts right on the stock system but you do have a slight lip where the 4.0 bolts to the 3.5 sections etc.

Mark @ DPPI

bettered- I would go with the cat-back system and then later add the fron-pipe if you think it is necessary. You will get a noticeable gain with just the cat-back.

I just ordered the 4' cat back MBRP system. (single, alum) I will let everybody know how it works. (dealer, install, sound, etc)
I am getting my d/max tomorrow, the dealer just called and said it is at LineX now, it'll be ready tonight. (I have to tow my trailer tomorrow morning so I will go get it after that)
I can't wait! :ro)

bettered- I would go with the cat-back system and then later add the fron-pipe if you think it is necessary. You will get a noticeable gain with just the cat-back.

I think that's in my future, but I'm bummed by the 3 dB cabin increase. That's going to be notably louder. (I know, 3 dB doesn't sound like much, but 10 dB is twice the noise level - so I'm underenthused about 1/3 louder in the cabin.) Thanks for being honest, though. I don't know what the effect on cabin noise is with Banks "Monster Exhaust", but I'm betting it's similar.

Thanks for the reco.

Ed

I noticed a significant noise gain when I decided to delete the muffler and make it a true straight pipe. I might have to add my muffler back in when I tow. Either way, you'll get use to the noise rather quickly.

I added temprorary kitty delete (its in the corner of the garadge now).

Negatives:
Louder (inclusing turbo whine and some form of hissing in the exhaust)
prior to the kitty delete the exhaust was "clean - like a gasser". It now really smells like a diesel - aka eye watering / tick off the neighbors with idles.

Positives
faster turbo spool / take offs
lower EGT

I think that's in my future, but I'm bummed by the 3 dB cabin increase. That's going to be notably louder. (I know, 3 dB doesn't sound like much, but 10 dB is twice the noise level - so I'm underenthused about 1/3 louder in the cabin.)
Ed

Hmmm, 10*LOG(2) = 3. Seems 3dB is twice as loud. 10 db would be 3 1/3 times as loud. Or did my calculator break?

Jim

No cat here and love it. Sounds awsome, turbo now when floored always hits 25-26. When I first installed it the check engine light was on for about 15 miles or so then went off same thing happend when I installed my edge.

What is a way around the SES light with the cat and muffler removed? I just ordered the 4" downpipe and am looking forward to a real diesel sound. All my Cummins powered rigs were straight piped and I loved the overall sound and perofmance gains it gave me.

I
Negatives:
Louder (inclusing turbo whine and some form of hissing in the exhaust)
prior to the kitty delete the exhaust was "clean - like a gasser". It now really smells like a diesel - aka eye watering / tick off the neighbors with idles.



For a lot of people, those are the positives...

What is a way around the SES light with the cat and muffler removed?

Do a search on "Finger Stick" it will solve the SES light for you

Good summary info on the finger stick here. (http://dieselplace.com/forum/showthread.php?t=21428)

I think that's in my future, but I'm bummed by the 3 dB cabin increase. That's going to be notably louder. (I know, 3 dB doesn't sound like much, but 10 dB is twice the noise level - so I'm underenthused about 1/3 louder in the cabin.) Thanks for being honest, though. I don't know what the effect on cabin noise is with Banks "Monster Exhaust", but I'm betting it's similar.

Thanks for the reco.

Ed

3 dB is TWICE the sound level (intensity) and 10 dB is 10 times louder! The dB sound measurement scale is logarithmic.

Thanks for the feedback guys, I think I will go with a cat back system for now. I really don't want a drag truck and I don't need the headaches of a dealer problem.
If the gains are small it does not seem worth the potential problems.
I think the only mods I am going for (other than lift) are the Edge w/ Attitude and exhaust.
We'll see about the electronics, don't want dealer trouble. They seem pretty popular though and worth the cash. I want one ):h
Now I gotta find the best price and get it ordered, my truck won't be in until next week! :(

Just got an 04 myself and I'm wonder which to go with. I like sound, Mileage, and boost. But I don't like trouble. I'm interested in what you find out. I'm looking to buy within the next couple weeks myself.

Thanks, great forum.

I removed the cat on 05 LLY and got 3 codes and went into limp mode. Repaired that, blocked the EGR, stacked the boxes, installed air intake system and full 4" exhaust. Started at 17.3 MPG and now have 26.1 MPG with adverage MPG at 43 in mixed driving.

lostbuckaroo- If you go with a cat-back system you will NOT set any codes. Problems arise when the cat is removed (P0401 & P0404). Insufficient EGR flow is what it boils down to. Go with a cat-back and you will have lower egt's, better sound, and zero problems. Give us a call if we can help.

I want a truck that runs well, but don't want it to belch smoke or be loud and shout "DIESEL" to everyone within hearing distance. My '04 LLY has an MBRP system that I did in stages, just to see the changes. Starting with a cat back, the exhaust was only a very slight bit louder...hardly noticeable. This is surprising because when you look through an MBRP muffler it's almost like looking down a straight pipe. Those louvers aren't very big, and you install them open side back, so it's hard to imagine a straight pipe being much louder. Yet the truck is very quiet. And honestly, there was very little difference in felt power. After a couple months I put on the frontpipe and got rid of the cat. There's no smog check here. The exhaust is now a little bit louder, but still it's nearly nothing. Without the cat it does make a vacuum cleaner-like whoosh at idle that wasn't there before. Supposedly that's the VV turbo. Without the cat, right away I noticed the turbo seems to spool up quicker and be a little more responsive at low speeds. But drive the truck a couple months you get used to it and don't notice things as much. Theoritically it may have started getting better fuel mileage, but I didn't notice any difference. There've been no code lights.

One thing...the stock pipe has a bend near the transmission oil lines, while the MBRP pipe is straight. Before installation it looked like the new pipe would come a lot closer to those oil lines and maybe transfer heat, so I wrapped the front pipe with insulating exhaust tape. I doubt that it did much.

Hmmm, 10*LOG(2) = 3. Seems 3dB is twice as loud. 10 db would be 3 1/3 times as loud. Or did my calculator break?

Jim

I was using my slide rule. Sorry..

Ed

I have the banks monster on my O3. Negligible increase in cabin sound. I like a quiet diesel since I drive a loud one all day at work. AFE intake produced a slight turbo whistle, Van Aaken chip, I'm good to go. Leaving the cat in also changes the that vile diesel stink!!!!

Hmmm, 10*LOG(2) = 3. Seems 3dB is twice as loud. 10 db would be 3 1/3 times as loud. Or did my calculator break?

Jim

Your calculation is correct Jim.

I have the mbrp exhaust, I got it in 2 parts, first the cat back, the front pipe was backordered. So I drove around awhile with just the cat back, if thats all I would have bought I would have been unhappy. Didnt seem to make the sound more agressive, only a little bit. But when I added my front pipe mmmmmmm that was the sound I was looking for. The turbo whine sounds amazing!! I love the way it actually smells like a diesel now. I really like the jet sound at idle. But im thinking about adding the muffler delete, will it make much of a difference cuz the mbrp seemed pretty free flowing??

I've had the MBRP front pipe on for quite a while, and really like it. I've checked it quite a few times for codes, and never had any. Unfortunately, tonight, just for the heck of it, I check it, and @#$^ got PO404 and 401.

o well...... thought maybe my truck would be the exception to the rule...

guess it's fingers stick time. Wonder if he'll have a boost stick/fingers stick discount.!?;)

OK, mahalkita, bettered, and NOTNSUV, forget about your abacus and slide rule, a 3dB change is about the minimum change in sound level that most people can perceive. A 10dB change sounds about twice as loud.

http://www.teamcombooks.com/mp3handbook/11.htm (http://www.teamcombooks.com/mp3handbook/11.htm)

What if anything does the 401 and 404 code cause that would be bad overall? I just installed my MBRP catless pipe yesterday and so far no SES lights even after a 70 mile trip of varied driving.

If your not getting codes or a light, don't worry about it.

How can you check for codes? If you get codes and no SES then why worry about it. What exactly does the finger thing do?

Thanks

The codes mean nothing unless the CEL is illuminated. I have had them (P0401 and P0404) since getting rid of the cat with no ill effects. Those that get the CEL however, have issues and need the fingerstick.

Hmmm, 10*LOG(2) = 3. Seems 3dB is twice as loud. 10 db would be 3 1/3 times as loud. Or did my calculator break?

Jim

10 times more sound energy==> 10*LOG(10) = 10 dB. 10 more dB is 10 times more energy.

I first put on the MBRP, and the sound was nice. Then I added the cat pipe and it got louder still. I might go back with the cat. At 1800ish RPM, it's a bit annoying, unless, of course, you like that sort of thing.

At least noone comments about the diesel clatter anymore.

I have an 05 lly I installed straight pipe exhaust, no cat no muffler, all ran good until I installed the Bully Dog air intake. After that EGR flow insufficient code poped up. So I put air box back to stock. A week later the light came back. Guys at Bully Dog said it was because I removed the cat. Put in a magnaflow diesel cat and reinstalled the Bully Dog air box, code came back. Anyone have any solutions as to how I can run the Bully Dog box with straight exhaust??

Ive got an 05.Imputting edge attitude w/juice/Afe stage 2 & mbrp duals on. I have a friend that builds custom 5in.duals to .not sure if i should try his work.Although he builds alot of ford & dodge exhaust.

OK, mahalkita, bettered, and NOTNSUV, forget about your abacus and slide rule, a 3dB change is about the minimum change in sound level that most people can perceive. A 10dB change sounds about twice as loud.

http://www.teamcombooks.com/mp3handbook/11.htm (http://www.teamcombooks.com/mp3handbook/11.htm)


Your are correct regarding the physiologically hearing (of the same sound or noise). But the measurement of sound level is not done with the ear hearing curve in mind but just a spl meter that doesn't care how it really sounds to the ear. So a 3 dB increase might give you a big unpleasant drone because the frequency changed completely.... I am not saying you are wrong but I also don't want people to think 3 dB is nothing - its a lot comparing car noises with each other and might be very unpleasant in certain frequency ranges producing a drone. Its relative as most things, some will like it and some won't.......

OK, I think I am going to try the MBRP exhaust on my new D/max. It is a 2005. Do I remove the cat or not?
Yes, I have read all the threads, they are not all the same! Some say yes, there is much to gain others say no. :eek:

So, what is the real deal?
Will it throw codes with no cat?
What is to be gained by taking out the cat?
What is the down side to taking out the cat?
Lets break it down really simple for a diesel noobie :ro)
Thanks guys!

:help: Well if you just want to be completely legal keep the cat like what I did. If thats not a big deal to you. Kill the kitty!!! I absolutely hate having one on my truck, but every time i see a cop i am glad i dont even need to think about any problems. I think basically everyone is oblivious on whether diesels have a cat or not, so from what ive heard there isnt much to worry about if you get rid of it.

3db increase is twice the signal strength (watt /square meter), 6db is 4 times, 9db is 8 times 12db is 16 times...
3db decrease is 1/2 the signal strength, 6db 1/4.. you get the idea..
http://arts.ucsc.edu/ems/music/tech_background/TE-06/teces_06.html

Your are correct regarding the physiologically hearing (of the same sound or noise). But the measurement of sound level is not done with the ear hearing curve in mind but just a spl meter that doesn't care how it really sounds to the ear. So a 3 dB increase might give you a big unpleasant drone because the frequency changed completely.... I am not saying you are wrong but I also don't want people to think 3 dB is nothing - its a lot comparing car noises with each other and might be very unpleasant in certain frequency ranges producing a drone. Its relative as most things, some will like it and some won't.......

You are correct a SPL meter is looking at a frequency range as a whole. Two different exhaust may exhibit the same loudness or SPL level but at a completely with different tone (frequency).

For comparison the meters need to be weighted the same and set to “C” weighting. (“A” weighting measures 500-10,000 Hz, and “C” measures 32-10,000 Hz). I would not be surprised if a dealer/manufacture compared exhaust systems to the factory exhaust using the “A” weighing, which completely discards the lower tones/bass from the readings.

3db increase is twice the signal strength (watt /square meter), 6db is 4 times, 9db is 8 times 12db is 16 times...
3db decrease is 1/2 the signal strength, 6db 1/4.. you get the idea..
http://arts.ucsc.edu/ems/music/tech_background/TE-06/teces_06.html

This applies only to the power required to generate sound. For example to increase the volume of a loudspeaker 3dB you need to double the power.

If you home stereo amplifier is 100 watts and your speaker is playing at 90dB, you would need a 200 watt amplifier for the speaker to output 93dB.

a 3dB change is about the minimum change in sound level that most people can perceive. A 10dB change sounds about twice as loud.
Correct.... and it takes a doubling of amplifier output power to effect a 3db gain in SPL.
That's why volume controls are "audio" or log taper... turning the volume knob from "4" to "8" changes the resistance a lot more than turning it from "2" to "4".

[quote=MXdiesel;667657]Well if you just want to be completely legal keep the cat like what I did. If thats not a big deal to you. Kill the kitty!!! I absolutely hate having one on my truck, but every time i see a cop i am glad i dont even need to think about any problems. quote]
My concern is the annual emissions check I am required to do to register the truck. Is there an aftermarket cat that flows free, but still meets the legal requirment to have a cat?
When I do go off-roading, how long does it take to put the cat-replacement pipe on before heading out, and then how long to replace the cat when back on the road?

Is it possible to build a cat delete pipe that is removeable so that you can replace the cat for warranty work at the dealer?

AFAIK, that's how most systems are set up and sold. The cat cutout is a separate $100 item (for stainless) and can be swapped out.

The attachment on the '06 is different. The 4-bolt flange has been replaced with a sleeve coupling.

If you're going to an aftermarket exhaust system, what does .03 decibles matter? You obviously want it louder and free flowing. Take the cat off. Mine has been off since mile 500. No ses light. Been to the dealership prolly 10 times and not once did anyone ever ask anything about it. You do not void the entire warranty for the vehicle. It only covers the exhaust system. Dont worry about cops either. Most dont really care about a catless truck or not. Most dont care about aftermarket exhaust systems anyways. California, I'm sure is the exception. We have way better things to do than pick on respectable guys with a mean sounding diesel. I, for one 'am more concerned with the '84 caprice rollin on 24's with a money green paint job thumpin down the street. So, take it off and enjoy it.

California cops don't care either... it's the CARB that I'm concerned about, that, and not knowing if the Finger's Stick will work with the '06 electronics has me a little nervous.

I'm still not clear on smog requirements for CA... on a 3/4 ton truck, Diesels may very well be exempt (for now).

For anyone outside of the smog-nazi states... :grd:

BTW: Glad to see you pulled through and have power. Yes... I know southern LA is a big area.

leave it on! horror stories here about taking it off. codes, warranty etc...... my 04 has none from factory

Need to move this to the audio section, LOL.

Blake, it was my understanding that the dB scale was created on the premise of 1 dB unit being the discernible difference in sound volume. about 10% SPL increase. for me 6 dB has always been the apparent doubling of volume. 10 dB appears nowhere except in power requirements. BUT, the freq of the noise in question slants these numbers dramatically.

Anyhow, I reduced hiway SPL in my truck by 12 dB with a very extensive sound deadening treatment, making it quieter than the wifes Expedition. I went with a magnaflow, no cat, after much ado. Never regretted it.


Anyone wanting more find it HERE (http://www.prorec.com/prorec/articles.nsf/b97f38ca2751fda58625680900056bad/ea68a9018c905afb8625675400514576?OpenDocument)