The effect of an empty CC

[morebiodiesel]

Long winded introduction to my question follows...

The Banks monster exhaust is 4" but necks down to 3.5" to mate up with the stock CAT (after cutting 7" off the stock CAT flange). That's how it's currently installed on my truck. But I'd like to try it without the CAT (off road only of course).

Banks sells a CAT test pipe (nice name eh?) that I was going to try but the dimensions of the pipe didn't make sense. It was a 26" x 4" pipe. The CAT (after modifying for fitment to the Monster exhaust is only 21" long and has 3.5" end pipes).

Turns out that the BANKS test pipe doesn't mate up with the existing Monster exhaust since it necks down to 3.5" for the CAT. So the Banks sales guy called me today and said he went back and asked the engineer how it was supposed to be used and the engineer told him that the pipe is intended to slip OVER the 4" portion of the Monster exhaust past the 3.5" reduced sections and that I should cut off the 3.5" neck down sections of the Monster exhaust that the CAT mates up with...

Well at that point there'd be no going back to the CAT at all so it's not much of a "TEST PIPE".

Soooo here's finally my question: I have a used CAT that I purchased locally and I was going to try and use IT as a test pipe by putting it on a weight loss plan, but I'm concerned that the resulting hollow bell would create damaging resonance in the exhaust flow.

Has anyone actually run their truck for an extended period of time with an empty CAT in-line without problems? Did it drone, and more importantly did it result in any cavitation in the exhaust flow?

Please refrain from Banks bashing. I know there are many who don't like their products but I've got to live with my choice at this time and can't afford a different exhaust. Just reply to the question if you have an answer.

Thanks

[symbols]

I'm pretty sure that 90% of the guys on here tossed their cat the first week of ownership. We only use these trucks offroad of course.

[Saber123316]

If I were you and my state permitting just ditch the cat... the affect that has on your engine can be best described as this.

find a cat (an actual kitty cat that meows) remove some hair from said cat make a hair ball with this hair shove that hair ball down your throat and then using your hand to muffle the sound try and breathe. thats what your engine goes through every day with the stock exhaust.

It would be in your trucks best interest to just cut it off and forget about it.

[morebiodiesel]

Originally Posted by Saber123316

If I were you and my state permitting just ditch the cat... the affect that has on your engine can be best described as this.

find a cat (an actual kitty cat that meows) remove some hair from said cat make a hair ball with this hair shove that hair ball down your throat and then using your hand to muffle the sound try and breathe. thats what your engine goes through every day with the stock exhaust.

It would be in your trucks best interest to just cut it off and forget about it.

I reside in a county that has strict inspections. For diesels they do an OBD-II test and a visual to make sure all the equipment is there. I've watched the inspector shine a flashlight under my truck to check for the CAT so a straight pipe is not an option.

[symbols]

I didn't know they even did that. What if you just gut it and stick it back on?

[Saber123316]

Originally Posted by morebiodiesel

I reside in a county that has strict inspections. For diesels they do an OBD-II test and a visual to make sure all the equipment is there. I've watched the inspector shine a flashlight under my truck to check for the CAT so a straight pipe is not an option.

ok well I dunno if there is one but I heard of a highflow cat for diesels.

(It may have been a rumor.) but I would look into that also.

I do not beleive a hollowed cat will do any damage to your engine. in my opinion I don't see how it could be worse than stock.

[gabelnj]

Do you have to use state operated inspection stations or do maintenance shops have state inspection certified mechanics working in them. If that is the case just go down to your local garage and pay the mechanic a little extra for your inspection and ditch the Kitty all together.

[morebiodiesel]

I've considered that but have checked around and haven't heard of a mod friendly inspector in my county. I'd like to try the empty cat but was concerned about strange harmonics. It's a pretty large open chamber and harmonics can do some strange stuff.

I've already paid for the extra cat to play with and don't want to cut the exhaust for the BANKS "test pipe" since there'd be no going back if I was forced to put the fat cat back on. Just trying to find someone who's done this without problems.

[symbols]

I don't know anybody that's done it to a diesel but I've done it to several cars and it's just made it louder. Never any "strange" noise.

[tech10002]

Why don't you just buy a piece of 3.5 inch stainless pipe and make your own? Jegs sells it in 3 foot lengths. I've been thinking of doing this myself as I have the same exhaust as you. My truck is also registered where they do emissions, so I have to be able to reinstall the cat. It really pissed me off when I found out how the Banks cat delete pipe is made.

I also considered having some flanges welded on the 4" section and the cat assembly so I could switch out a 4" flanged test pipe and the cat so I could run 4" all the way back, but I really don't think the little length of 3.5" pipe makes much difference since the downpipe is 3.5" anyway.