[ranchman06]

I've done some searching, but have been unable to get a clear answer on which is more restrictive: Muffler or Cat? There are no inspections in Oklahoma and I'm not still under warranty, therefore I can take either off. I don't want to replace the entire system, nor do I want to spend anymore money than just deleting one of these items. Also, I don't mind a little more noise, but I don't want it as loud as a strait pipe.

So which will give me the most air flow?

Thanks

 

[07laramie]

Take the muffler off first,it is the most restrrictive and will give you the best sound! Cats do not restrict much.

 

[dirtbike375]

I have a cat-back straight pipe on mine and it runs great. Makes some noise when you get into it but when crusing on the freeway you cant even hear it. I heard that taking the cat off with a straight pipe makes them 3 times louder

 

[ranchman06]

Anyone else? I'm looking to delete one of them pretty soon.

Thanks for your help

 

[buzzard]

I would keep the cat unless you like drone. Like it was already said, spend 30 bucks and cut the muffler out and you will be amazed at the sound. You have to let someone else drive it while your on the outside to truly appreciate the sound. I never realized how loud my 06 was until my wife blew past me one day.:woot:

 

[awenthol]

If you do a cat delete with stock muffler, you will notice little to no difference.

 

[Mega_Brady]

I put on a 5" cat delete system and it's loud. Yesterday I put the cat back on (dealer trip) and it's still loud. The cat is staying on, no difference noted between cat on and cat off.

 

[runninlean]

Ditch the muffler its the restrictive one the CAT does not hurt much at all.

 

[AH64ID]

I just ditched the muffler, cat is in place... Great sound... It could be a little quieter towing above 2K rpms thou.

 

[ynots57]

i agree, ditch the muffler first

 

[WoodRep]

Glad to see another Okie on here. I dont have the kitty on mine, but wouldn't be disappointed if it was still on there. If you are worried about the drone, just pick up a donaldson muffler from freightliner and sub out the stock restrictive muffler. I punched open the baffle inside the donaldson for better flow. JMO good luck

Wood

 

[4 door fury]

I seen the inside of each one and I say differently. if you want to keep the warranty yes you better keep the cat. if you dont care about warranty it IS restrictive and has 2 screens in it. I have seen lots of mufflers that are straight thru that do not have screens and restrictions in them. I have a diamond eye muffler that is straight thru with nothing to kill the flow of the exhaust. the cat has restrictions in it. when you go with bigger pipe like 5" you will have some drone with or without a muffler from what ive seen

 

[megadually]

I did a cat delete 1st, but I put on a cfm+ at the same time. I noticed my egt's were slightly lower. Later I got talked into putting on a magnaflow 5" turbo back. I didn't notice any benefit with the 5".

 

[AH64ID]

I seen the inside of each one and I say differently. if you want to keep the warranty yes you better keep the cat. if you dont care about warranty it IS restrictive and has 2 screens in it. I have seen lots of mufflers that are straight thru that do not have screens and restrictions in them.

The OEM muffler is far from straight thru, and the cat actually flows very well. Reports are you only gain 2-4 rwhp taking it off.

The only real reason one should need to ditch the cat would be if your truck makes a lot of smoke, I really don't think all that smoke is good for the cat.

I am thinking about adding an Aero 4040XL to my truck, weather or not I ditch the cat depends on how the final version of the SJR turns out, but as of right now I don't make much smoke and will probably keep the cat.. .easier to pass emissions when they implement it.

 

[SootKing]

strait pipe no kitty or muff

 

[Suprcynic]

I took the muffler off mine and kept the cat. I love the way it sounds and it's still quieter than my stock powerstroke was inside the cab

I heard you lose low end when removing the cat.

 

[kgeiger81]

Right after I bought my truck I took of the stock muffler and swapped it out with a Magnaflow. Sounded great with a little bit of noise in the cab. I put gauges on my truck shortly after and my egt's were 1450 with a stock truck with only an intake and muffler swap. I recently ditched the cat and pretty much lost the drone and my egt's went down 150 degrees even with my programmer on the tow setting. Now it barks like it should!

 

[Suprcynic]

Right after I bought my truck I took of the stock muffler and swapped it out with a Magnaflow. Sounded great with a little bit of noise in the cab. I put gauges on my truck shortly after and my egt's were 1450 with a stock truck with only an intake and muffler swap. I recently ditched the cat and pretty much lost the drone and my egt's went down 150 degrees even with my programmer on the tow setting. Now it barks like it should!

I kept the cat lost the muffler completely and my egt's are 700-800 with the pedal down (500 cruising) with an intake and no programmer. I would say your gauges are messed up because if you're running 1300 degrees for any amount of time your turbo is toast

 

[AH64ID]

I kept the cat lost the muffler completely and my egt's are 700-800 with the pedal down (500 cruising) with an intake and no programmer. I would say your gauges are messed up because if you're running 1300 degrees for any amount of time your turbo is toast

I would say that either your pyro is post turbo or you have the bad gauges...

A bone stock 04.5+ 5.9 can hit 1400*+ very easily...

 

[tclappcummins]

does anyone have any sound clips or videos of a 3rd gen with stock exhaust with just a cat delete?