# 2005 Duramax modification



## subsea78 (Sep 12, 2007)

Here is my question and what I have. I am looking to get more power and better mileage. I currently have a superchip and AFE cold air intake. I want to remove my cat on my 05 Duramax. I have already removed my muffler and it didn't make it much louder which I am happy with. I was told that my truck would get better mileage if I removed my cat is this true? If I do remove my cat will it make my truck any louder? Also if I remove my cat will I have to buy any kind of device to send a false signal to anything to keep my truck running right? I am getting 21-22mpg on the highway and 16-17 in the city now so if I can get better than I will be happy. But if you think I am maxed out then I don't mind not removing the cat. I have also been told to buy a (mouth piece from AFE) it will give me like 27hp. Has anyone done this modification to there Durmax. Any feedback will be great. I am not looking to make a speed machine just make my truck run better.



Thanks for any info..
Greg


----------



## DSL_PWR (Jul 22, 2009)

From my standpoint having owned a couple of dmax trucks, you are about capped out on mileage. You won't see much better than what you are getting now.

The mouthpiece is a toss up, some say it works and others don't but can't hurt to try. Increasing air flow and it being more unrestricted can help but I don't think you will see a significant improvement.

Yes you can remove the cat, yes it will make your truck a lot louder. A complete straight pipe system does sound pretty cool though.

If you want better mileage dump the superchips and get with BD, PPE or EFI live. Check out www.dieselplace.com and I think you will find ample reading material.

I used to own a couple of dmax's. I had both straight piped and pushing some massive HP all while getting great mileage. I have run just about everything out there for the dmax and I think you would find the ease of use with the PPE or even Bully Dog but if you want to stay with superchips that is up to you.


----------



## bcavnar (Jul 23, 2010)

call my buddie jason over at murff racing or check out his web sight http://murffracing.com/


----------



## BIG PAPPA (Apr 1, 2008)

*YOU'RE ABOUT MAXED OUT FO SHO*

But the EFI live is a real Screamer..smoke the tires at 30 mph when rolling.
But they're pricey as well.


----------



## Tin Can (Dec 12, 2008)

Your truck will get a lot louder and you will be able to hear the turbo wistle a lot more but your truck will definitly be bale to breath better.


----------



## subsea78 (Sep 12, 2007)

Thanks for the input guys, uncertain still on if I am going to remove my cat. It sounds like the main thing I will gain out of doing it will be sound and little better air flow. For what you guys a re saying also I am topped out on my fuel mileage. Oh well wouldn't be nice to get better!!!!! 


Greg


----------



## rockyraider (Feb 1, 2006)

Be careful if you remove emissions equipment. If you have a shop that will inspect it I probably wouldn't worry but if not you could have issues. A turbo used to qualify as a muffling device but I believe the law has changed. Also, its technically illegal to remove any part of the emissions system and not replace it with a like component. You could technically be cited for it and I have heard of some Troopers who will check diesels to see if it has been straight piped. I have done all my research on Cummins and I have typically read about 1 or so mpg increases from straight piping. Most say that a quality hi flow aftermarket muffler will perform just as good without all of the excess noise. For what its worth, I've thought about straight piping my '00 Cummins but I'm afraid it might be too loud.


----------

