cat or no cat??
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New User
Joined: Dec 2008
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cat or no cat??
I just bought a 97 class rv witha v-10. I want to cut the cat off it ,but my muff shop said it could hurt my power and mpg. I bought a large 3 chamber muffler and dont know what to do on the cat,what do you think?
Posting Guru
Joined: Aug 2006
Posts: 1,199
Likes: 0
From: High Point, NC
No cat for me please... I'm a dog person 
Sorry, I couldn't help it.
I would leave the cat on - it provides needed back pressure on the exhust system. There have been folks that have removed them and regretted it (esp when towing).
Sorry, I couldn't help it.I would leave the cat on - it provides needed back pressure on the exhust system. There have been folks that have removed them and regretted it (esp when towing).
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
The engine does not need any backpressure. You need to maintain exhaust velocity. Many confuse backpressure with velocity and its not the same.
I don't really like cats and if it wasn't for the law I wouldn't have one on my truck. I don't forsee you losing any power by removing the cat actually you'll probably gain power and very slight mpg. You could always find a happy medium and replace the cat with a properly sized higher flow aftermarket cat. Or you could get sneaky and gut the cat and put a piece of exhaust pipe through it. You don't want to just empty out the cat and run it hollow, it will kill velocity and hurt performance. Removing the cat altogether will throw up a red flag if anyone ever looks underneath your rig.
I don't really like cats and if it wasn't for the law I wouldn't have one on my truck. I don't forsee you losing any power by removing the cat actually you'll probably gain power and very slight mpg. You could always find a happy medium and replace the cat with a properly sized higher flow aftermarket cat. Or you could get sneaky and gut the cat and put a piece of exhaust pipe through it. You don't want to just empty out the cat and run it hollow, it will kill velocity and hurt performance. Removing the cat altogether will throw up a red flag if anyone ever looks underneath your rig.
Postmaster
Joined: Jun 2008
Posts: 2,564
Likes: 11
From: Wayyy NoCal, USA
Unlike the 70's and 80's mistakes, modern monolithic honeycomb style cats are very well designed and sized, so it may gain you all of 2 hp to remove off of a stock engine. The ones in these trucks are fantastic.
Personally, I can't stand the smell of exaust without the cat - and I grew up with pre-cat cars. I am planning a fun street machine to use a nice engine I have, and I plan to install cats even though they aren't required.
And of course, there is the environmental impact.
Personally, I can't stand the smell of exaust without the cat - and I grew up with pre-cat cars. I am planning a fun street machine to use a nice engine I have, and I plan to install cats even though they aren't required.
And of course, there is the environmental impact.
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
The stock cats on 99'-04' are huge and kill sound and they have restriction to them. If your stock cat is working properly replacing or removing it isn't going to give you much gains in either department. Seems a lot of guys sniff their exhaust, stop it.....its not good for you even if you have a cat.
I have no problem with a motor running through open non restricted pipes like god intended.
I have no problem with a motor running through open non restricted pipes like god intended.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 421
From: Long Island USA
Keep the cat - depending on your state, and if you ever get stopped by state troopers, you might be in for a heck of a fine.
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Elder User
Joined: May 2007
Posts: 699
Likes: 1
especially if its on an RV, I'm not sure how it works in other states with emissions testing but I'm sure if you get stopped in states that check you could get screwed.
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