Weird Exhaust question

6.6

New member
Dec 18, 2011
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I looked at an 06 6.6 that at one time had exhaust stacks through the bed. The dealership took them out an put in "stock exhaust". From the cat back, they put in a smaller pipe (by 1/2") than the pipe coming out of the cat. They put it inside the cat pipe and welded it in place. I was told that they did this because the truck had very little power. I was told that they replaced the exhaust and had to change the MAF as well. It seems strange to me that actually going smaller with the exhaust could be good for the engine, but I don't know alot about this. Any input?
 

whitetrash21

put on da damn helmet day
Apr 29, 2008
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Vegas
uh huh... ^^^^^^ what these 2 said

When they plug in a tech2 ( if they can figure that one out), stand back with a dumbass look on their face(surprise), and then start scratching their ass while making grunting sounds...... Get yo shit and leave before they f*** it up even worse!!!
 

Texas Chevy

Active member
Feb 14, 2011
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Vista, Ca
The exhaust was probably cause when the dealership got it the piping was bigger than stock so they just welded the stock size on the cat back
 

6.6

New member
Dec 18, 2011
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0
The exhaust was probably cause when the dealership got it the piping was bigger than stock so they just welded the stock size on the cat back

I'd be fine with stock, but this appears to be smaller than stock. The cat outlet piping is one size and the tailpipe is 1/2" diameter smaller.
Is this going to cause engine damage? If I go up to the original size will I have to retune or anything?
 

MadMaxx61

Devilmaxx
Oct 13, 2008
5,458
1
36
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Windsor, Ont, Canada
I would call them out on this crap on a diesel you want as much flow as you can get.

Remember you have a turbo giving you back pressure you could take off the exhaust from the turbo and be fine well if it would not burn up the firewall and make a mess.

Now if it was gas and that is how must dealers think yes sometimes it can be too big.
 

LWATSON

future trans limpers
Jul 30, 2008
2,587
1
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Scotland Neck NC
I had a stock 02 duramax that had more power with the stock 3 1/2" exhaust than it did with a banks 4" exhaust. On a completely stock truck slowing the exhaust velocity can hurt power, I went through this and the only solution was to put the stock exhaust back on. If my truck had been tuned results would have been different I'm sure but there were not many tuning options back then. The dealer may be full of crap, but this is what I experienced a while back.