Lb7 Duramax Exhaust

[yukon25008.1]

im under the understanding that a diesel doesnt need the backpressure a gas engine does, and i dont remember the previous dmax,s i had what ran, so with 188,000 miles is there a chance its getting clogged.. so should i remove the cat and let it breathe/exhaust freely.

also does it have to be 4 or 5" whats better, i think you would lose some torque with no backpressure at all.

i figured id eliminate the cat and go with 3 or 4" pipe and a decebt muffler

all sugestions are appriciated, thanks guys

[ChevyTech77]

im under the understanding that a diesel doesnt need the backpressure a gas engine does, and i dont remember the previous dmax,s i had what ran, so with 188,000 miles is there a chance its getting clogged.. so should i remove the cat and let it breathe/exhaust freely.

also does it have to be 4 or 5" whats better, i think you would lose some torque with no backpressure at all.

i figured id eliminate the cat and go with 3 or 4" pipe and a decebt muffler

all sugestions are appriciated, thanks guys

 

4" isn't much of an improvement over stock and the cat on the LB7 doesn't work like a cat on a gas engine. It won't

get plugged.

 

If you plan on more mods in the future go 5". The reduction in exhaust temps alone is worth it. I prefer MBRP's

systems myself.

[Prokopchuk_9]

if you go with a straight pipe your egt's will be way lower, and no the less back pressure the better. i used to have a cummins, i ran 5 inch on it..i just did it for the sound and egt's. if you get this thing, put a 4 oor 5 inch exhaust on it, cold air intake on a diesel is a waste of money. just get a better filter. beware if you take that muffler off and run straight pipe, like a turbo-back 5 inch. that truck will be very obnoxious sounding, you might get annoyed. i know i got annoyed sometimes with the noisy old 5.9 litre cummins. if you do that, you gotta buy the DSP5 switch from EFI Live, you can run 5 custom tunes from EFI on a switch in your truck. very handy for a diesel. lots of other cheap mods with lb7 too, fuel rail shim mod, fuel line porting, turbo horn porting...lots more....whatever you do like i said before be veeeery careful with the 5 speed allison.

[yukon25008.1]

if you go with a straight pipe your egt's will be way lower, and no the less back pressure the better. i used to have a cummins, i ran 5 inch on it..i just did it for the sound and egt's. if you get this thing, put a 4 oor 5 inch exhaust on it, cold air intake on a diesel is a waste of money. just get a better filter. beware if you take that muffler off and run straight pipe, like a turbo-back 5 inch. that truck will be very obnoxious sounding, you might get annoyed. i know i got annoyed sometimes with the noisy old 5.9 litre cummins. if you do that, you gotta buy the DSP5 switch from EFI Live, you can run 5 custom tunes from EFI on a switch in your truck. very handy for a diesel. lots of other cheap mods with lb7 too, fuel rail shim mod, fuel line porting, turbo horn porting...lots more....whatever you do like i said before be veeeery careful with the 5 speed allison.

 

 

Ok, so 5 inch is the way to go with the pipe, as far as the cat i should get rid of it correct..if i want the least ammount of back pressure?

i will put a muffler of some kind so it isnt to loud, what do you reccomend, i never tried bully dog.

Also im very interested in the tuning..i was gona go with banks. but whats the story with this efi live?

[yukon25008.1]

so is it better for exhaust temps and performance to have no muffler..and just go 5" pipe from the turbo back?

[Prokopchuk_9]

if you go with a straight pipe your egt's will be way lower, and no the less back pressure the better. i used to have a cummins, i ran 5 inch on it..i just did it for the sound and egt's. if you get this thing, put a 4 oor 5 inch exhaust on it, cold air intake on a diesel is a waste of money. just get a better filter. beware if you take that muffler off and run straight pipe, like a turbo-back 5 inch. that truck will be very obnoxious sounding, you might get annoyed. i know i got annoyed sometimes with the noisy old 5.9 litre cummins. if you do that, you gotta buy the DSP5 switch from EFI Live, you can run 5 custom tunes from EFI on a switch in your truck. very handy for a diesel. lots of other cheap mods with lb7 too, fuel rail shim mod, fuel line porting, turbo horn porting...lots more....whatever you do like i said before be veeeery careful with the 5 speed allison.

 

 

Ok, so 5 inch is the way to go with the pipe, as far as the cat i should get rid of it correct..if i want the least ammount of back pressure?

i will put a muffler of some kind so it isnt to loud, what do you reccomend, i never tried bully dog.

Also im very interested in the tuning..i was gona go with banks. but whats the story with this efi live?

 

 

man...you gotta join duramaxforum.com, find "idahorob" he is a good one for tuning. thats pretty much the best site. my buddy is a hardcore duramax enthusiast, he has about $100K invested in a dirty-max...we have done all the work ourselves. ive helped him almost every step of the way...his is an LMM, Sun coast stage 5 tranny, industrial injection twins, dual cp3, 5 inch turbo-back, air dog lift pump, reso-plug, fuel rail shim, afe up-pipe.blah blah blah...a whole laundry list of goodies. it goes on and on and on. the first thing i would do is put a 4 inch or 5 inch turbo back straight pipe. if you dont want it too loud you could go with banks (very pricy tho) or a magnaflow pipe (cant go wrong with maggies). 4 or 5 wont make much difference, the only thing is read up tail pipe EGT's on the different mufflers. ive heard MBRP is the worst, highest temps. and yes dump the cat(if you can in your area, here you can) , your fuel mileage will go up....EFI Live is tuning software, same thing justin uses at blackbear...its complicated and you should find a good guy on that forum. they will have better anwsers than me dude...hope i helped.

[yukon25008.1]

if you go with a straight pipe your egt's will be way lower, and no the less back pressure the better. i used to have a cummins, i ran 5 inch on it..i just did it for the sound and egt's. if you get this thing, put a 4 oor 5 inch exhaust on it, cold air intake on a diesel is a waste of money. just get a better filter. beware if you take that muffler off and run straight pipe, like a turbo-back 5 inch. that truck will be very obnoxious sounding, you might get annoyed. i know i got annoyed sometimes with the noisy old 5.9 litre cummins. if you do that, you gotta buy the DSP5 switch from EFI Live, you can run 5 custom tunes from EFI on a switch in your truck. very handy for a diesel. lots of other cheap mods with lb7 too, fuel rail shim mod, fuel line porting, turbo horn porting...lots more....whatever you do like i said before be veeeery careful with the 5 speed allison.

 

 

Ok, so 5 inch is the way to go with the pipe, as far as the cat i should get rid of it correct..if i want the least ammount of back pressure?

i will put a muffler of some kind so it isnt to loud, what do you reccomend, i never tried bully dog.

Also im very interested in the tuning..i was gona go with banks. but whats the story with this efi live?

 

 

man...you gotta join duramaxforum.com, find "idahorob" he is a good one for tuning. thats pretty much the best site. my buddy is a hardcore duramax enthusiast, he has about $100K invested in a dirty-max...we have done all the work ourselves. ive helped him almost every step of the way...his is an LMM, Sun coast stage 5 tranny, industrial injection twins, dual cp3, 5 inch turbo-back, air dog lift pump, reso-plug, fuel rail shim, afe up-pipe.blah blah blah...a whole laundry list of goodies. it goes on and on and on. the first thing i would do is put a 4 inch or 5 inch turbo back straight pipe. if you dont want it too loud you could go with banks (very pricy tho) or a magnaflow pipe (cant go wrong with maggies). 4 or 5 wont make much difference, the only thing is read up tail pipe EGT's on the different mufflers. ive heard MBRP is the worst, highest temps. and yes dump the cat(if you can in your area, here you can) , your fuel mileage will go up....EFI Live is tuning software, same thing justin uses at blackbear...its complicated and you should find a good guy on that forum. they will have better anwsers than me dude...hope i helped.

 

 

Thanks and yes lots of help..i appriciate your time, we;ll have to talk one day, but yea now i cant wait to start toying with it,

im gonna do a 5" turbo back with no muffler, i dont mind the loud.. if the kids are in the truck ill just turn up the radio/dvd.

does the brand reaaly mater then? ive seen some 5" turbo back on ebay with no muffler from $277 to 800..

as far as intake you really dont think i need an aftermarket intake? i would like to get more air in if im getting more air out/faster.

ill talk to justin, he tuned my 8.1 yukon. THANKS

[Prokopchuk_9]

if you go with a straight pipe your egt's will be way lower, and no the less back pressure the better. i used to have a cummins, i ran 5 inch on it..i just did it for the sound and egt's. if you get this thing, put a 4 oor 5 inch exhaust on it, cold air intake on a diesel is a waste of money. just get a better filter. beware if you take that muffler off and run straight pipe, like a turbo-back 5 inch. that truck will be very obnoxious sounding, you might get annoyed. i know i got annoyed sometimes with the noisy old 5.9 litre cummins. if you do that, you gotta buy the DSP5 switch from EFI Live, you can run 5 custom tunes from EFI on a switch in your truck. very handy for a diesel. lots of other cheap mods with lb7 too, fuel rail shim mod, fuel line porting, turbo horn porting...lots more....whatever you do like i said before be veeeery careful with the 5 speed allison.

 

 

Ok, so 5 inch is the way to go with the pipe, as far as the cat i should get rid of it correct..if i want the least ammount of back pressure?

i will put a muffler of some kind so it isnt to loud, what do you reccomend, i never tried bully dog.

Also im very interested in the tuning..i was gona go with banks. but whats the story with this efi live?

 

 

man...you gotta join duramaxforum.com, find "idahorob" he is a good one for tuning. thats pretty much the best site. my buddy is a hardcore duramax enthusiast, he has about $100K invested in a dirty-max...we have done all the work ourselves. ive helped him almost every step of the way...his is an LMM, Sun coast stage 5 tranny, industrial injection twins, dual cp3, 5 inch turbo-back, air dog lift pump, reso-plug, fuel rail shim, afe up-pipe.blah blah blah...a whole laundry list of goodies. it goes on and on and on. the first thing i would do is put a 4 inch or 5 inch turbo back straight pipe. if you dont want it too loud you could go with banks (very pricy tho) or a magnaflow pipe (cant go wrong with maggies). 4 or 5 wont make much difference, the only thing is read up tail pipe EGT's on the different mufflers. ive heard MBRP is the worst, highest temps. and yes dump the cat(if you can in your area, here you can) , your fuel mileage will go up....EFI Live is tuning software, same thing justin uses at blackbear...its complicated and you should find a good guy on that forum. they will have better anwsers than me dude...hope i helped.

 

 

Thanks and yes lots of help..i appriciate your time, we;ll have to talk one day, but yea now i cant wait to start toying with it,

im gonna do a 5" turbo back with no muffler, i dont mind the loud.. if the kids are in the truck ill just turn up the radio/dvd.

does the brand reaaly mater then? ive seen some 5" turbo back on ebay with no muffler from $277 to 800..

as far as intake you really dont think i need an aftermarket intake? i would like to get more air in if im getting more air out/faster.

ill talk to justin, he tuned my 8.1 yukon. THANKS

 

 

im not sure if justin tunes diesels....i know of other tuners that would probly be better suited to use rather than him. that idahorob guy has one of the fastest duramaxes on the planet. i just dont know if he tunes diesels too??? i just dont know maybe he does, if he did i wouldnt be scared to use him. me and my buddy have our own EFI Live software, we built a tune for my truck and his. it takes time and practise, we still got pointers from reputable tuners too its hard. the air intake is for looks man, just as it is on a gasser. youll get like 10 horse maaaaybe LOL. nothing compared to the 150 you can tune into a diesel....

[yukon25008.1]

im curious about the efi live..if you use it and know it works..thats enough for me. like i said i want to make some power and have fun but not abuse the truck. its funny the younger guys or kids think that all that black smoke is cool, but dont understand that its just waisted fuel flying out of the exhaust...ill do like you said with the airbox, ive done that plenty of times in the past. and your suggesting just a good replacement filter? ive seen alot of 5" exhaust out there just not sure what direction to go in. i think im gonna do a 5" turbo back with no muffler or cat..thanks again for your help.once i get my hands on the truck we'll have to talk.

[jro909]

forced induction engines don't need back pressure

[yukon25008.1]

so what differences am i going to see going from stock setup.. to 5" turbo back with no muffler or cat?

[Prokopchuk_9]

you wont notice much, just if you had an EGT gauge you would. 5 inch will sound alot more raspy than 4 inch also...fair warning. idling will be noisy, no noisier than a cummins tho LOL. EFI Live is tuning software, not just a hand held unit, you need to bring your laptop right in the truck...(dont need too but i do for data logging). you need to read up on alot of things before you try to do any tuning yourself, you can fry a diesel engine in a hurry if you dont know wut ur doin. you also you shouldnt change anything with shift points or anything with the tranny, you can but its not wise...(duramax makes all the power down real low anyways, no need to change around shift points) leave the TCM alone or else you will pay. you could try a shift de-fueling tune too to save the tranny. but like i said if you dont have a shift kit, or anything done with the trans, i would NOT put any more than 50-75HP to it. you will just keep limping it and before you know it you wont have any gears left. everybody thinks the allison is so tough, its tough if you just leave everything alone but you cant put very much power to it...theyll fry. a good clean 70HP tune will do you good....we tried PPE too, without supporting mods with PPE your EGT's will skyrocket...too smokey. any other questions? just join duramaxforum.com...guys on there are pretty hardcore. and most know what they are talkin about...youll get good opinions there too...the diesel section here is pretty tame most times ive noticed

[jro909]

the thing i've seen atleast on newer the newer ditymaxes is the exhaust almost shrieks not so much drone...the last one i saw had the msbp(spelling may be way off) and it sounded bad at idle...i like the cummins drone though lol

[yukon25008.1]

yea i would never try playin with the tune without knowing what im doing.. as far as the exhaust, i dont mind it sounding like a diesel either, but do not want it to sound bad.. would the 4" be better than for the qaulity sound. or does it really not matter

[rmkleman]

Hi there, i currently have an 03 lb7 with a 5" exhaust, no muffler, no cat. I know the only 03 lb7's that came with a cat from the factory were the california trucks. Not certain on the 04 but i think it's the same thing? I have a cheapo alum. intake from ebay (get alum, the turbo whistles a LOT more vs. plastic) Any way, you probably don't "need" 5" unless you plan on adding over 450HP to the truck and when you get into that range you need to get your tranny built somewhere to the tune of 3+ grand due to the weak cp3 clutch packs of the allison. I have heard my buddy's lb7 with the 4" and all my friends prefer the exhaust note of my 5". Warning, diesel addiction gets EXPENSIVE after the first mod any questions pm me, i'd be glad to help you out. Also, i don't think it's woth it to spring for a fancy exhaust system... i got a cheapo one off ebay and when i did the install, it was easier then doing my friends expensive mbrp kit. Guess i'd say go with a cheap ebay aluminized exhaust 4" downtube from the turbo and 5" straight pipe all the way back. Drone is almost anoying to me running from 70-80 on the highway, but the truck is loud enough to terrify small children when i get on it