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Discussion Starter · #1 ·
Looking for opinions on MBRP 4" Stainless vs 5" Aluminized.

Currently running Triple Dog with Oulook with an AFE CAI and stock exhust on a '05 LLY. Wanting both higher mpg and lower egts. I pull an unltralight 5'er weighing in at less than 9k lbs.

I have heard good things about MBRP, but see that they only offer downpipe back system stating that the turbo pipe is short and a booger to replace.

I am not sure what kind of performance increase to expect from only going up to a 4" exhaust since the stock exhaust is 3.5".

Am I missing something in the math or physics of airflow that make 1/2" increase susbstantial?

Lay some knowledge on me.
 

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I read somewhere that 1/2 an inch in diameter of a pipe can almost double the cfm flow of the same pipe! As for the 5" i really dont think its nessary, its more of a i have a bigger pipe thing! From what ive heard also the 5" has a bit more droan to it also!!!
 

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heres some food for thought but i noticed when i had the 5" on my LLY and then switch to the 4" my EGT's dropped a little and the only thing i could come up with is that with the bigger pipe it would loose volasity and then kinda roll around in the pipe leaving more heat in instead of shooting out the back(hope that made sense)so i would highly recommend the Silverline or MBRP 4" SS 304 is the best but if you only drive in some salt go with the 409SS..
 

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As for the 5" i really dont think its nessary, its more of a i have a bigger pipe thing! From what ive heard also the 5" has a bit more droan to it also!!!
Mine had the 5" MBRP on when I bought it. So I can not compare before and after. Mine does not have a drone. Fairly quiet inside when the windows are up. Not too bad when they are down.
 

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I run a 4" silverline 409 ss no muffler turbo back on my early 07 and i like it alot. Its quit we you need it to be but when you put the hammer down its loud as hell. Egt's are low and not much drone inside. My late model 07 lbz I just put on the magnaflow 5" system and had to keep the muffler on cause it was to loud even for me , but they both have there ups and downs.
 

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ss vs aluminized

i dont know where you live but anywhere that gets snow (salt) the aluminized is going to fall apart and look bad much sooner than ss. i got 409ss instead of 304ss to save some money and kinda regret not getting the 304ss.
 

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i would go with a 4 in if you are towing because with a trailer the 4 can even be a little loud at times and i am a part of the loud and proud people
 
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