For those of you newbies/veterans wondering if it will fit or what it looks like or whatever, here you go. I ordered this frontpipe from Mark Craig at DPPI (http://www.dieselperformanceparts.com (http://www.dieselperformanceparts.com/)) and the part number is GMS9401 and is an MBRP product. It arrived 2 days after I ordered it. As you can see from the pics the flanges do in fact line up just fine and just retain the gasket that came on the stock pipe as well as retain the band clamp at the turbo down pipe side.

The ONLY thing you will need to do to remove the stock pipe is remove the 2 bolts holding the hanger and bracket onto the side of the tranny. There is one clamp on the turbo side with one nut, you will reuse this. There are 4 bolts on the rear. Once that is removed you can slide the entire stock cat pipe out the front with no problem at all. This works for 2wd adn 4wd. You don't need to remove crossmembers on either.

In gear at idle with the stock pipe my EGT's were 400+..since the EGR is active only at idle and highway speeds I sat in the truck with it in gear for 15 minutes. The temp never got above 342, so that is an immediate 50+ degree drop just at idle.

http://home.***.net/~boquinn/frontpipe.jpg
http://home.***.net/~boquinn/frontpipe1.jpg

Nice. Good to know it did lower EGTs.

Will This Change Work On A Ca/ Ne Emissions 2005 Lly Without Throwing Codes Thank You

Thanks briano! :grd: I am going to be out of town this week, so I will probably be doing this next week. Thanks for all the info and your help last week! I too am seeing EGT's at about 400 at idle in gear, I can get down to 325 or so in park/neutral, but my worry was this summer when I start pulling my 5er. Do you know how much they have reduced temps during 'normal' driving? Have you seen -200 deg like I've read in other posts?

Good job Brian. Do you have the drone noise that we have been talking about on this thread HERE (http://dieselplace.com/forum/showthread.php?t=24776) ? If so, did changing the pipe change the noise at all?

Also, how long did it take you to do the conversion? Did you have any trouble getting to the flange bolts / band clamp up by the turbo side?

Throwing codes...from what I have learned and been told, as long as there is some sort of back pressure the EGR should be ok. I will find out for sure though and let you know. I retained the stock muffler so that should be enough.

I will also find out today about normal temps driving around. I have been monitoring them for a while so with this pipe installed I'll be able to tell if there is in fact a drop.

Time it took... the entire process including washing hands twice, getting camera, removing cat pipe, installing LB7 pipe...less than an hour. No problems removing any flange bolts or band clamp at all. Its a very easy install. Reinstalling the band clamp on the turbo side can be difficult if the rear of the pipe is not supported. either on the hanger or losely put a couple bolts on the rear flange.

Drone... I am not sure if I ever heard this drone noise before. I hear the normal workings of the motor and exhaust, but never really considered it to be droning at all. maybe I am one of the lucky ones.

I have to travel to San Antonio today to get my car so I will be doing highway and then some towing so I'll let you all know what temps I see and I also am bringing my OBDII scanner along with me and check for stored codes whenever I park.

Very nice write-up on the front pipe installation, I just installed one yesterday and the installation went equally as well. I purchased my pipe from performancetruckproducts.com, who I believe is a site sponsor. I like to say that the quality of the pipe and fit were outstanding. If anybody is interested I own a 2004.5 and luckily haven’t had any of the issues that I have read about on this form except the raw fuel smell at idle. The dealer re-flashed the computer with the latest updates, it did quiet it down at idle and smooth out the power delivery during normal driving. This is just seat of the pants tuning, but I was disappointed in the re-flash because I felt a flat spot whenever I accelerated moderately, when tipping the peddle slightly, the truck just wasn’t as responsive and I still had the smell of raw fuel at idle. I’m posting this message to say that after installing the new front pipe I don’t have that raw fuel smell and the truck really came alive. No more flat spot and the truck runs and accelerates cleanly. I didn’t detect any difference in the noise level. The finger stick and EGR plate are next. This form has been very informative, Thanks

Can you install the downpipe with an aftermarket exhaust and not install the fingers or EGR plate? Will this throw codes?

I have already swapped out my entire exhaust a few months ago and yes it did throw codes, its basically a straight through system, no restriction. I did not have fingers or egr plate.

I talk to Mark at DPPI and he said as long as there is some restriction it should be fine. I just kept the stock muffler. So far the sound has not changed and the temps actually don't seem as low as I had originally thought, but still are about 20 degrees cooler.

I'll know more after my trip today.

i did mine and the hardest part was taking out the old pipe. i do have the fingers stick and egr blocker plate as well. it is just for the added bonus of cleaner oil longer and clearing any possible codes if I go all the way with the exhaust.

I know if anyone wants to try this, i used a 7/16 ratcheting boxend wrench for the clamp. Mine is short so it worked real well in the tight spot.

Thanks for the Info Briano, Looking forward to your update from San Antonio..!!

NCMIC, did your modifications inprove your fuel mileage?

Well, back from towing my car up from San Antonio. I have gone about 200 miles today half of it with empty trailer, other full. I used tow mode the whole time along with Edge on level 2. I watched the temps the entire way and the only time they spiked was going up hill where the load is greater. The highest it went was 1034. Empty is about 1800lbs and full is almost 5000lbs.

I am not sure about mileage at this point, but from the looks of my guage I got ok mileage. the truck seems just a bit smoother on acceleration, EGT's seem just a bit lower..not much. Other than the more audible turbo whistle I can't really see any difference. I am hoping the city mileage increases.

Not sure exactly if this is what ya'll wanted to hear, but that's it. I guess I was hoping for more, but we'll see.

OH..and so far no codes, but its only been one day. I checked the codes before I left and when I got there.

Keeping my fingers crossed. Thanks for the update.

By chance did your front pipe come with a new 4 bolt flange gasket? Is there any gasket on the other end?
DAN

By chance did your front pipe come with a new 4 bolt flange gasket? Is there any gasket on the other end?
DAN

it does not come with a new gasket as you can use the stock gasket on the 4 bolt flange. there is no gasket on the other end, only a band clamp that is also reused from stock.

Is the Lb7 pipe an aftermarket pipe that also works on the LLY engines? This isn't the old stock pipe that GM changed on the new engines correct?

Is the Lb7 pipe an aftermarket pipe that also works on the LLY engines? This isn't the old stock pipe that GM changed on the new engines correct?
if you look in the very first post I have the Brand, part number and who I ordered it from. its a 4" pipe, no left over stock LB7 one.

"I ordered this frontpipe from Mark Craig at DPPI and the part number is GMS9401 and is an MBRP product."

I read that part...it was more of a curiosity question as to if it was an aftermarket part bar none or similar to the LB7 stocker. I've never owned a diesel before and this will be my first one.

I read that part...it was more of a curiosity question as to if it was an aftermarket part bar none or similar to the LB7 stocker. I've never owned a diesel before and this will be my first one.
oh ok..usually most never read the entire thread.. lol

yes its an aftermarket pipe, 4" and fits LB7 and LLY, its stainless and bolts to the stock 4 bolt flange or to an aftermarket 4 bolt flange.

the stock pipe is 3 or 3.5" in diameter not to mention is much lighter without the cat on it.

hope this helps.

I always read the whole post lol. Ok with this pipe....it removes the cat, is this the only cat or does our trucks run multiple cats? You think this is something a dealer would even notice during regular servicing?

duramax's have only one huge cat under the passenger floor board area and YES this is somethign the dealer may notice depending on what service you are going in for. keep the old pipe just in case

Just killed :eek: my kitty with dmaxalliTech's help!!!

And the dealership will know when they hook-up the Tech II for any updates or code checks. If going cat-less doesn't through the SES light, it will still show hidden codes.

Pssssssssst.... and it's ILLEGAL !!!!!!!!!!! but I won't tell.;)

Legal/Illegal, Tomato/Tomato lol. I guess that throws my idea of welding up a dummy looking cat over the new pipe if it is still going to throw codes...

fyi..the hidden codes still show up with a scanner, just don't trip the SES... so far I have scanned mine every 2 days... no codes yet. When I did the complete system months back, I had codes 1 day after doing it.

as long as you go to the dealer WITH the cat on their should'nt be any issues.

some have still not thrown any codes with just the front pipe changed out. they left the original muffler on and there was enough back pressure. but if you get codes, just get a finger stick and it will clear the codes.

I just purchased a 2005 duramax in Jan. and while surfing the net I found this forum.
You guys and gals are awesome. I already have a predator, catless down pipe, and afe stage 2 filter. My wife says no more ha ha. I have one question which has less back pressure the cat or stock muffler, I want to eliminate the cat and keep the stock cat back is this the way. I don't want a turbo back system because of dealer issues.

Thanks, JDE650

yes it could be the way. or you can gut the cat and put it back as if it was there, gutless kitty (***** cat for some) and all. I have mine with the MBRP 4" pipe and it works well. the rest is still stock for now. I will be changing the rest in the near future though. i am nearing the end of my warranty period anyhow.

I just purchased a 2005 duramax in Jan. and while surfing the net I found this forum.
You guys and gals are awesome. I already have a predator, catless down pipe, and afe stage 2 filter. My wife says no more ha ha. I have one question which has less back pressure the cat or stock muffler, I want to eliminate the cat and keep the stock cat back is this the way. I don't want a turbo back system because of dealer issues.

Thanks, JDE650
if I am reading this correctly you already have eliminated the cat with a catless pipe and have stock cat-back.. thats pretty much what I have.

Thanks,
I just wanted to make sure I was on the right track. I am going to eventualy go with the cat back. This is my first diesel and sure is an expensive forum to vist. But I like it.

By the way briano thanks for the pictures and explantion on how to proceed, helped
immensely.

I also was thinking about gutting the cat and bolting it back up. Unless the tech was smart enough to tap on it to hear that it was gutted, it would pass the visual inspection which IMO is the most important part. My service manager already told me he doesn't give two hoots about lift kits, intakes, or cat back systems....he did however say that the cat better be on there for any related warranty work. Now if I can finger out a way to gut the cat without any cutting or welding I'd be GTG.

Take it out and punch a screw driver through the cat with a hammer. It is just a ceramic comb with a few different precious metals coating it. they are actually quite brittle.

btw it is easier to get the cat in and out if you drop the tranny crossmember.

Looking through the threads, I didn't see anything about a possible mileage increase, just lower egt temps. Does it help the mileage? Or just give it more turbo whine?I'm so close to having to have it, just need a good reason to buy it! :lol:

since installing this, EGT's are lower, turbo whine is louder of course, and my mileage seems to slowly keep increasing. Every truck is different though. I think its worth the money for no EGR issues/codes and lower EGT's. Those both equate to longevity of the turbo and system.

Just my $.02

BlkSilverado, lower EGT's should be good enough reason if you are looking for a reason. Lower EGT's means less heat getting to the turbo and longer turbo life.:cool:



Looking through the threads, I didn't see anything about a possible mileage increase, just lower egt temps. Does it help the mileage? Or just give it more turbo whine?I'm so close to having to have it, just need a good reason to buy it! :lol:

I just unbolted the flange after the cat, pushed the exhaust out of the way and used a piece of rebar to punch holes in the material. I did it in a circle as far to the outside as I could and the knocked the middle into pieces. Then started the truck let it warm up a little and rev it up to blow the junk out. I checked it a couple weeks later and it looked like the rest of the stuff I couldn't get to burned out because it was completely empty. I also put a straight pipe in for the muffler.:grd:

I just put on my MBRP 4 inch front pipe this weekend and can't believe the difference! The truck sounds like a freaking f-14 jet taking off! There is a noticeable increase in throttle response, better spool times, and an amazing turbo whine. I LOVE IT!!!!!


The only noticeable bad part about doing this is .... man does it stink now! -:t WIndows must go up at the stop light now or I will gag at the smell. Its worht it though!!!!:D

Oh ... forgot to mention ... unplugged EGR and installed the front pipe with no SES light to speak of.

you may be still throwing codes but not the SES light. When i blocked my EGR i threw 2 codes but the SES did not come on. You can check them with your Predator. I think they were 0401 and 0404 IIRC.

Codes do no harm as long as you have a Predator to clear them before the dealer.

you may be still throwing codes but not the SES light. When i blocked my EGR i threw 2 codes but the SES did not come on. You can check them with your Predator. I think they were 0401 and 0404 IIRC.Those codes are correct ss, I also have those two codes w/no SES light 'cause I am using the plate w/o the finger stick - for now.

Has anyone found any decrease in performance or other detrimental effects from the codes being there long term?

on edit:
looks like you already answered my ? zoobs! I just thought I read on here somewhere someone complaining about a lack of power and some hesitation. Anyone else recall that?

Codes do no harm as long as you have a Predator to clear them before the dealer.

Are you sure? How do you know what the truck is programmed to do to compensate when it sees a reduction in air flow at the MAF or EGR?? This is still one of those "up-in-the-air" topics as it relates to the EGR mod. Truck could be telling itself to cut back on fuel flow to match the air flow that it thinks it's getting.

Are you sure? How do you know what the truck is programmed to do to compensate when it sees a reduction in air flow at the MAF or EGR?? This is still one of those "up-in-the-air" topics as it relates to the EGR mod. Truck could be telling itself to cut back on fuel flow to match the air flow that it thinks it's getting.
If that were the case there would be a decrease in power or some other tell tale. This thing runs like a scalded dog. Just my assumption.

Just put the finger stick on and I noticed the exhaust did not smell as bad as it did without the stick. It also seems to be a little more responsive. MPG is about the same.

it all depends on the codes you get. If you have a failed part that throws a code and SES light then yes it will probably decrease performance because it failed..BUT the known codes with exhaust are EGR and they only light up the SES after many many times being tripped, otherwise are hidden, but still in the computer.

basically..it depends on what the codes are for. by no means am I a diesel mechanic, but it just makes sense to me.

Got the 4" front pipe on order today from Diesel Performance Parts. Thanks for the info, and the great description and photo's..

Got the pipe Friday, and installed it today, Not the funnest job, but didn't take long at all. Does have a nice sound. I'll find out if it changes anything when I tow next weekend. Acceleration feels real good, but unloaded it alway's has. Thanks again Briano for the info.. ):h

Got the pipe Friday, and installed it today, Not the funnest job, but didn't take long at all. Does have a nice sound. I'll find out if it changes anything when I tow next weekend. Acceleration feels real good, but unloaded it alway's has. Thanks again Briano for the info.. ):h
cool, glad the info helped someone. You'll like it..best part is ..no codes!!

Thanks for all the information guys on the exhaust upgrades. Have a few questions need help with. Two weeks ago traded in my Cummins for a 2005 Duramax 2500HD. Very impressed so far. This evening I installed an aftermarket exhaust system off a 2003 Duramax on my new truck and reinstalled my complete stock system (including cat) on the 2003 model. Looking at the systems I thought all the models came with the cats I thought the aftermarket system replaced the cat with zero issues. I thought the stock 2003 pipe was aftermarket and replaced my cat. Bolted in with zero problems. My friend who owns the 2003 is trading the truck in on a new SUV ,so he swapped the exhaust no charge if I installed my stock stuff on his trade in. Pretty sweet deal. Had no problems making the swap but think I should have left the cat on and went cat back only. Like so far the improvements but only been a couple of hours. Sorry so long but needed to explain my dilema.
-Will I have any issues or future problems w/out the cat on my 2005?
-Will my buddys 2003 have any problems with the cat installed?
-What is this "finger thing" mentioned above?
-Do I need to block of my EGR and why?
-Will hidden codes cause any problems or make truck do funny things?
-What periodic updates would my dealer do to the trucks ECM and will I be notified of these?
I have been in the low tech Dodge diesel world many years and did not realize how high tech my truck is. Just though better exhaust flow was the right thing to do! Not to mention the exhaust system was free. Just cost labor.
My buddy is a service manager at a local Chevy store in Dallas so I don't suspect I will have any warranty issues. I will stop with these questions so far.:help:
Jeff H.
Rowlett,Tx
2005 Chevy Crew Cab

Jeff, if you install only the straight front pipe replacing the Cat then you will have no issues on the 05. the issues begin when you install an aftermarket free flowing exhaust system and it messes with the EGR not detecting back pressure and you get loss of power, smoke, fuel smell, etc... not to mention EGR codes popping up. To fix the codes someone made the Finger Sticks. For the EGR someone made a block off plate to disable it basically.

So.. if you in essence have the exact same exhaust on both trucks, but yours now does not have a cat then you should be fine. if you change cat back and get a different muffler other than stock then you will need to get teh sticks and plate.

good luck

He will have warranty issues if the dealership notes his 05 does not have the cat. They can and will if needed, void his new vehicle warranty.:(


or am I mistaken?????

He will have warranty issues if the dealership notes his 05 does not have the cat. They can and will if needed, void his new vehicle warranty.:(

or am I mistaken?????
True..forgot about that.. I kept my cat just in case I needed to go to the dealer. They won't void the warranty, just won't cover or look at it until it comes back with the cat on and exibits the issue as well. Just like the stock tires..don't go in for drivetrain issues if you have upgraded your tires size. borrow some stock ones.

Jeff, if you install only the straight front pipe replacing the Cat then you will have no issues on the 05. the issues begin when you install an aftermarket free flowing exhaust system and it messes with the EGR not detecting back pressure and you get loss of power, smoke, fuel smell, etc... not to mention EGR codes popping up. To fix the codes someone made the Finger Sticks. For the EGR someone made a block off plate to disable it basically.

So.. if you in essence have the exact same exhaust on both trucks, but yours now does not have a cat then you should be fine. if you change cat back and get a different muffler other than stock then you will need to get teh sticks and plate.

good luckThanks Briano for replying.
I do have an aftermarket exhaust installed. Today everthing seems good but curious about the sticks and EGR block. Concerned about longivity of my Duramax with those type of mods. Any info would be great.

Thanks,
Jeff
2005 Duramax

My wife just bought a Mbrp 304 single with muffler. Am I reading right that if the stock is change with this system it will throw codes? If so, should she just keep the stock muffler on this exhaust system? There is no front pipe. Sorry for this, but it gets very confusing. I just thought if you took the cat off it would throw codes.
Doug

the whole codes thing is the EGR not detecting enough back pressure. You can do one of a few things here..

1. remove cat and keep stock muffler = no codes (what I did)
2. keep cat with aftermarket muffler(catback) = no codes
3. full aftermarket free-flowing exhaust = codes
4 full aftermarket exhaust + Finger sticks for codes+ EGR blocker plate = no codes

Just replacing the front pipe will lower your temps about 50-100 degrees and replacing the entire exhaust system with an aftermarket one will drop temps at least 200 degrees.

Keep in mind you may have to visit the dealer at some point so keep the Cat pipe handy.

for specific Fingers and blocker plate answers just do a search for that stuff, its all over.

This may may be a dumb question but what exactly are we gaining by reducing the EGT's by 50 or so degrees at idle by removing the CAT? Are the EGT's lowered exponentially at speed or under load??

the degree drop is just at idle, the benefit is while towing they are lower and when the temps get high they actually drop faster versus the cat. this is just the cat pipe. with a full exhaust its a 200 degree drop across the board. I don't have exact numbers since every truck is different

briano,

:cool: If I recall, even if you change the Cat out with a LB7 or equal downpipe, you will still be getting codes. The SES light won't come on BUT, there are hidden codes that show up even on the Federal trucks. I'm Cat-less but still have the codes show on the tech II per dmaxalliTech's check when we changed out the cat. Now if I install the Fingerstick, I won't have any codes show. This is what We've learned on my truck. I do have the stock exhaust from the bolted flange back(stock muffler).

this must be on a truck to truck basis... I have had this LB7 catless pipe on for over a month now, checked for codes every 3 days and still have nothing. I have the stock muffler in place which to me provides enough back pressure for no EGR issues.

True, the SES light won't come on until the code has been tripped a number of times maxing out the buffer. I have been checking and no codes to date.

Now, when I installed the complete exhaust months ago..I got codes the next day.

<TABLE class=tborder cellSpacing=1 cellPadding=6 width="100%" align=center border=0><TBODY><TR><TD class=thead colSpan=2>Today 08:26 AM</TD></TR><TR title="Post 552516" vAlign=top><TD class=alt1 align=middle width=125>MiDmax</TD><TD class=alt2>briano,

:cool: If I recall, even if you change the Cat out with a LB7 or equal downpipe, you will still be getting codes. The SES light won't come on BUT, there are hidden codes that show up even on the Federal trucks. I'm Cat-less but still have the codes show on the tech II per dmaxalliTech's check when we changed out the cat. Now if I install the Fingerstick, I won't have any codes show. This is what We've learned on my truck. I do have the stock exhaust from the bolted flange back(stock muffler).</TD></TR></TBODY></TABLE>


What codes are you getting for the removal of the Cat? I also put this pipe on (about a week ago) and the only codes I have are the 401 and 403 caused by my EGR blocker plate since I do not have the stick. I have had no other codes since the install of the catless pipe.

D/A power, You Sir, are absolutely right:) . I have the same set-up as you. I guess I didn't make it clear.

Thanks for setting it(me) straight.......;) :Nothing_f

Just installed a 4" MBRP stainless front pipe last nite. Took about 1 hour. Cat pipe came out pretty easy. Already did the Finger stick and EGR plate prior to the front pipe. The sound is slighty more whistle and seems to have quicker spool up. Not any louder at all. No lights either. Straight pipe or remaining exhaust is next.

I've read about the EGT temp drop with the cat gone and the stock muffler in place, but how about with the stock muffler gone (straight piped) and the cat in place? After my last fiasco with Dodge and getting my warranty soposedly canceled because I removed the cat from my 2003 non-cali Cummins truck (non-cali 2003's didn't have cats), I'm a bit gun shy about taking mine off. I already lost the muffler and the service manager said he didn't have a problem with that. He did say that the cat better be on there for any related warranty work. In his words "it's illegal to tamper with federal emission devices.":eek:

I've read about the EGT temp drop with the cat gone and the stock muffler in place, but how about with the stock muffler gone (straight piped) and the cat in place? After my last fiasco with Dodge and getting my warranty soposedly canceled because I removed the cat from my 2003 non-cali Cummins truck (non-cali 2003's didn't have cats), I'm a bit gun shy about taking mine off. I already lost the muffler and the service manager said he didn't have a problem with that. He did say that the cat better be on there for any related warranty work. In his words "it's illegal to tamper with federal emission devices.":eek: I was thinking about the same thing.:exactly:

Did anyone put that hanger & bracket back in with the new downpipe? The pipe seems to be very tight in there w/o that bracket thingy.

Did anyone put that hanger & bracket back in with the new downpipe? The pipe seems to be very tight in there w/o that bracket thingy.
Are you talking about the bracket on the tranny? I did put it back in because I wanted to avoid any vibration/resonance that some are experiencing where they have to put counterweights on the downpipe.

Yes, I am referring to the tranny bracket. I have had if off for a week now, no extra noise or vibration.