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.
turbo vs. CAT back exhausts
Anyone have a preference???........I'd like to eventually take this step but want to research it as much as I can before deciding which way to go......I occasionally pull a 4 horse gooseneck that may get to 10,000 pounds.......Mostly used as a grocery getter......We do intend on eventually pulling more frequently when time allows...... I by no means work the truck hard compared to what I've seen some guys do but I would like to try to make it a little snappier and save a little on fuel if possible.......There are so many choices by so many different companies that it can be difficult to decide.
21 - 36 of 36 Posts
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.
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.
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.
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".:fart :gearjaminyou 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..
the magnaflow is a great kit too.... and don't be tight, just get the stainless the first time!! 
STAINLESS STEEL man you can see yourself:cool
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
i know i wouldn't run anything but stainless steel,
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.
I cant think of ANY shops in the Denver area that can mandrel bend 5 inch stainless, match factory mount locations and have a no-drill installation.... definitely going to disagree with you on the price too... you are not only paying for Joe Schmo to build ONE system (at +/-$90/hr) when MBRP builds hundreds a day to precision standards with full warranty.... are you drunk?? And who wants to pay someone to put an exhaust system on? its a simple bolt-on, and if you don't want kats bat enough, thats a do-it-yourself thing too...
they are a few here in ohio that will custom bend up to 5" exhaust but will not eliminate the cats
To a business, tampering with required smog hardware is a $10,000 fine, a federal clean air act violation.
The DIY'er is exposed also. $2500 IIRC
The DIY'er is exposed also. $2500 IIRC
no wonder!!with that kind fine i wouldn't do it either
why would you pay someone to do a simple bolt on in the driveway?? isn't that half the fun of mods to a truck? I'm still curious what shops will do mandrel bending on command... an "off road" bolt on kit from companies like MBRP would be so much faster, easier, and just as custom.... that post about having a shop make your exhaust kit is just mind boggling to me! there is now way that could be cheaper unless you owned your own shop and still built the kit yourself.
working 6 days a week its hard for me to install all of my axcessories,allthough i try to,but sometimes its just easier to pay someone
21 - 36 of 36 Posts
- This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Chevy and GMC Duramax Diesel Forum
A forum community dedicated to Chevy and GMC Duramax diesel owners and enthusiasts. Come join the discussion about modifications, towing, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
Top Contributors this Month
View All
Piper One
152 Replies
Ron Nielson
147 Replies
Huntinrig
134 Replies
Recommended Communities
