4" in/out catalytic converter?
Thread Starter
Joined: Oct 2006
Posts: 2,608
Likes: 0
From: Webb City, MO...out in the garage
4" in/out catalytic converter? i'm thinking about actually having legal exhaust on my car 
....but obviously don't want to choke it down either. i know magnaflow makes a 4" cat, but its for diesels, if that even matters, that's just how they advertise it. i figure most diesel trucks are 6.0L or bigger and force inducted, so that cat might not choke down a NA 454 TOO badly. if nothing else, i'll gut it, but i want it to at least look legal. we don't do a sniffer in missouri, just visual inspection. a lot of cars with resonators and no cats will pass around here from what i'm told.
Just for reference, my exhaust consists of 2" Kooks headers with 3.5" collectors. i'm going to run the 3.5" pipes off the headers to a Flowmaster Y-merge that is dual 3.5" in/4" single out and then have a 4" bullet (or something) dumped off of it. i figured i could probably put the cat between the muffler and the merge.
any thoughts? ideas?
....but obviously don't want to choke it down either. i know magnaflow makes a 4" cat, but its for diesels, if that even matters, that's just how they advertise it. i figure most diesel trucks are 6.0L or bigger and force inducted, so that cat might not choke down a NA 454 TOO badly. if nothing else, i'll gut it, but i want it to at least look legal. we don't do a sniffer in missouri, just visual inspection. a lot of cars with resonators and no cats will pass around here from what i'm told.Just for reference, my exhaust consists of 2" Kooks headers with 3.5" collectors. i'm going to run the 3.5" pipes off the headers to a Flowmaster Y-merge that is dual 3.5" in/4" single out and then have a 4" bullet (or something) dumped off of it. i figured i could probably put the cat between the muffler and the merge.
any thoughts? ideas?
I've been thinking about doing something similar as well. The reasons: hopefully stay out of trouble and not smell like I've been on a riding lawnmower for 16 hours after a simple 10 minute cruise in the car....
What I have been considering is a removable cat/muffler system I can leave in place while on the street, but pull fairly easily at the track. I currently only have the 3.5" out on the y-pipe, but even if I move up to the 4", i will probably step down to a 3.5 cat/muffler for the street anyways. The damn car never hooks on the street anyways...
What I have been considering is a removable cat/muffler system I can leave in place while on the street, but pull fairly easily at the track. I currently only have the 3.5" out on the y-pipe, but even if I move up to the 4", i will probably step down to a 3.5 cat/muffler for the street anyways. The damn car never hooks on the street anyways...
4" cat If the Cat was mounted between the merge and the muffler, it would loose it's functionality. Cats need the heat from the exhaust, that's why there always right after the headers.
It might pass a visual inspection as it would be in the exhaust stream.
I've read that usually with Hi flow cats, you'll loose anywhere from 4 > 10hp depending on engine size n such.
It might pass a visual inspection as it would be in the exhaust stream.
I've read that usually with Hi flow cats, you'll loose anywhere from 4 > 10hp depending on engine size n such.
Thread Starter
Joined: Oct 2006
Posts: 2,608
Likes: 0
From: Webb City, MO...out in the garage
The car never had cats before. I only became concerned when I found out it could be up to or over $5000 and one year in a federal prison...wtf, right? I just want it to look legal and not lose any flow if possible. Its going on my 454 if that matters.
You will be fine mounting the cat after the y-pipe. The cats were mounted like this for years on the 3rd gens, as well as many other vehicles.
The only difference is that you will not have the "AIR" setup running to the cat like the older vehicles did on the cats after the y pipe. So the cat will not heat up as fast, meaning its not going to be doing it's job as quickly on cold start ups. But for what you're looking to do, that won't matter.
The only difference is that you will not have the "AIR" setup running to the cat like the older vehicles did on the cats after the y pipe. So the cat will not heat up as fast, meaning its not going to be doing it's job as quickly on cold start ups. But for what you're looking to do, that won't matter.
