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Discussion Starter · #1 ·
My 2007 nnbs Sierra Denali has a 4" stock exhaust. Can't seem to find a muffler to fit. Needs to be 4" inlet, doesn't matter on the outlet, and needs to be offset. Can anybody help me?
 

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GMFS Military Member
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are you sure you have 4" exhaust? Im pretty sure they came from the factory with 2.75" or some crap, 4" seems a little ridiculous. Thats what diesels run.
 

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Discussion Starter · #3 ·
Man I'm an idiot. The old tape I was using is missing like the first 1/2" in markers, so where I thought zero was it wasn't. Got a new tape, it's 3 1/2". Sorry for the bother guys.
 

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HOT AIR BALLOON OWNER
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Yeah... my PSD has a single 3.5" even...
 

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I dont even think the new DMAXs have 4" exhaust. You have 2.75" dude.
 

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TEAM FUEL MOTORSPORTS
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Yeah, the 6.0 HD's have 3.5" single... so with your 6.2 you're right, 3.5".
 

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HOT AIR BALLOON OWNER
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Yeah, the 6.0 HD's have 3.5" single... so with your 6.2 you're right, 3.5".


The new ones? I still don't see the need for that much pipe, 3" supports well over 500rwhp.
 

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GMFS slowest truck :read:
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3.5" is fucking rediculous...

neck down to a 3" single in/out muffler. you will be happier. 3.5 is just stupid on this stuff. my 5000+ rpm spinning 8.1 has a 3" muffler and i GAINED torque.
 

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HOT AIR BALLOON OWNER
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It's that large as it's metric I guess, 90mm is just about 3.5"
 

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Discussion Starter · #13 ·
So yall think I should decrease pipe size? If the factory 405hp ratings are accurate then after all my mods I should be near 450hp at the flywheel. Headers, exhaust, CAI, mass airflow sensor, and tune.
 

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So yall think I should decrease pipe size? If the factory 405hp ratings are accurate then after all my mods I should be near 450hp at the crank. Headers, exhaust, CAI, mass airflow sensor, and tune.
I wouldnt bet that high. If your serious you should dyno the truck stock then after your mods. Im pretty sure the 405HP is a Flywheel HP number too. I think you can pick up a good 15-20 with those mods though...maybe. Not sure about the MAF, and why you need it though.
 

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Discussion Starter · #15 ·
yeah i doubt i make that much stock, everything seems to be overrated these days. Ive already done Volant CAI and mass airflow sensor, aero turbine exhaust goes on this week, then the tune and headers. I'm going with HP Tuners because a good friend of mine does them at his shop. I don't think 50 hp over whatever stock is when all is said and done would be an unfair assumption, but I,ve been wrong before.
 

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I wouldnt bet that high. If your serious you should dyno the truck stock then after your mods. Im pretty sure the 405HP is a Flywheel HP number too. I think you can pick up a good 15-20 with those mods though...maybe. Not sure about the MAF, and why you need it though.
Jameson, Justin told me he typically sees 20-25hp to the wheels on the LQ9 6.0 i have. so i would think that the new 6.2 would be able to pick up that much too with a tune. wouldnt the headers also pick up another 15hp or so?
just curious, i dont think he would pick up 50hp with those mods but maybe around 35 or so.

and agreed with the MAF sensor, just leave your stock one.
 

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TEAM FUEL MOTORSPORTS
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Yeah, my cousins NNBS 6.0 HD has single 3.5". Better than the old NBS 6.0's though, right? They used the same as the 8.1 trucks, dual 3" in/out into a single 3.5" tailpipe.
 
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