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Go Back   Chevy and GMC Duramax Diesel Forum > Chevy / GMC Duramax 04.5-05 LLY Forum > 04.5-05 LLY Performance Parts Discussion

04.5-05 LLY Performance Parts Discussion Discussion of Performance Parts For the 04.5-05 LLY Duramax Trucks No Advertising

 

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Old 01-16-2007, 11:59 AM   eBay Motors  #21 (permalink)
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Go ahead and elminate it. I think that cats don't restrict flow as much as a muffler does, but they do help completely free up airflow.
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Old 02-16-2007, 06:49 AM   eBay Motors  #22 (permalink)
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The Cat is worse than the muffler, especially aged Cats, on second generation diesels.

There is no point in an intake. The only thing you stand a chance of gaining is MAF problems. The stock intake is the best combination of filtration efficiency, freedom, and code free operation that exists. The aftermarket intakes are a complete waste of money, unless you need to run over 70 lb/hr airflow. That is over 32 psi at 3400 rpm. And no box tuner does that really. Eliminating heat soak in the intake is another matter. That is the worst offense, not restriction. Airbox temps of over 200 degrees. And AFE/KN does not help with that.

A V-clamp back exhaust is definately an improvement, or splicing as mentioned earlier, and improvement to egt. The downpipe restriction is significant, but these restrictions are in series, eliminating a lesser restriction does not negate its benefit, just because there is another restriction that is even more. The garden hose idea mentioned proves this. 2 equal length hoses, a 1/2" and 3/4" hose. Put a 1/2 id" washer in each one, and the 3/4" hose still flows more, with less total pressure drop, a fact.
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Old 02-16-2007, 07:19 AM   eBay Motors  #23 (permalink)
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i agree about the cats,i noticed a big difference in the performance of my trucks when i put a straight pipe on it,i use to have the stock pipe with no muffler and no cats with a 4" tip.i didn't gain much better performance by putting in an after market air intake,i also gained 2 miles a gallon by doing the straight pipe and air intake.
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Old 02-16-2007, 10:06 AM   eBay Motors  #24 (permalink)
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you have to go turbo back... cat back systems are more for looks and sound, if you want a true change in performance, X the cats and get a 4 or 5 inch mandrel bent kit... MBRP is one of the easiest to install... looking at about an hour tops in the driveway..
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Old 02-16-2007, 12:00 PM   eBay Motors  #25 (permalink)
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Quote:
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you have to go turbo back... cat back systems are more for looks and sound, if you want a true change in performance, X the cats and get a 4 or 5 inch mandrel bent kit... MBRP is one of the easiest to install... looking at about an hour tops in the driveway..
i agree with what bnkrupt said about the turbo back exhuast,i ran 5" magnaflow on my 06 lbz and i wouldn't switch back to the 4".
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Old 02-16-2007, 12:04 PM   eBay Motors  #26 (permalink)
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the magnaflow is a great kit too.... and don't be tight, just get the stainless the first time!!
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Old 02-16-2007, 12:32 PM   eBay Motors  #27 (permalink)
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STAINLESS STEEL man you can see yourself:cool
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Old 02-16-2007, 12:52 PM   eBay Motors  #28 (permalink)
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if you live in CO and the roads have for chloride than cement on them from the ice melt, the "aluminized" just wont cut the mustard
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Old 02-16-2007, 12:56 PM   eBay Motors  #29 (permalink)
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i know i wouldn't run anything but stainless steel,
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Old 02-16-2007, 01:49 PM   eBay Motors  #30 (permalink)
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You don't have to limit yourself to store bought kits, you can find a good muffler shop that will insatall a much better exhaust and place it anyway you like for 100's less. Your only problem is some will not bend the law and remove the cat. So you might have to look at more than one place.
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