Why 4 cats
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Junior User
Joined: Jan 2001
Posts: 84
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From: Morgantown, WV
Why 4 cats
Looking at replacing my exhaust system, but have a few questions to find out about Fords logic.....
2007 F150 SCrew, 5.4, 5.5 bed, 4x4, auto, 3.55 LSD,
1. Why 4 cats?
2. Does replacing exhaust system void warranty?
3. What about the Ford Performance exhaust systems?
I was thinking about going with two high flow cats (any brand suggestions), and true dual exhaust (any brand suggestions) with a 'mag' muffler. I understand that I would need to make sure the the sensors are replaced before and after the cats.
Not needing a lot of 'loud growl', just want to open up the exhaust for better breathing.
Don't want to void the warranty, so .....
2007 F150 SCrew, 5.4, 5.5 bed, 4x4, auto, 3.55 LSD,
1. Why 4 cats?
2. Does replacing exhaust system void warranty?
3. What about the Ford Performance exhaust systems?
I was thinking about going with two high flow cats (any brand suggestions), and true dual exhaust (any brand suggestions) with a 'mag' muffler. I understand that I would need to make sure the the sensors are replaced before and after the cats.
Not needing a lot of 'loud growl', just want to open up the exhaust for better breathing.
Don't want to void the warranty, so .....
Logistics Pro
Joined: Feb 2000
Posts: 3,955
Likes: 50
From: Mesa
There are 4 because that is what is needed to pass the federal emissions regs. If you want sound then just do a cat-back or muffler swap. That shouldn't void the warranty. I would not touch the cats.
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Junior User
Joined: Jan 2001
Posts: 84
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From: Morgantown, WV
Why 4 cats
Does the mustang (same engine) have 4 cats also?
Sounds like 'engineers' could design it with one or two cats, like most everyone else that has vehicles. Doesn't the headers eventually go into one pipe? How many mufflers do 5.4 trucks have?
Does anyone have the factory schematic (picture) on the exhaust system from the headers back on the 5.4 trucks?
Sorry for all the questions, I will be receiving my truck in a few weeks.
Sounds like 'engineers' could design it with one or two cats, like most everyone else that has vehicles. Doesn't the headers eventually go into one pipe? How many mufflers do 5.4 trucks have?
Does anyone have the factory schematic (picture) on the exhaust system from the headers back on the 5.4 trucks?
Sorry for all the questions, I will be receiving my truck in a few weeks.
Senior User
Joined: Feb 2007
Posts: 283
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From: South Jersey
the reason for the 4 cats is, I bringing this from memory of something I read last year.
When the engine is 1st started, the primary ones convert the gasses right away. There is a emission law that states the cats must be operational within the 1st 3 seconds of engine running. The secondary cats do not heat as fast, therefore, are not operating correctly.
And the mustangs also have 4 cats. My 2003 4.6 stang had 4 cats, I swapped out the mid pipe for a H that only has 2 High flow cats. It runs fine with no codes and with the Magnaflow catback, it sounds real sweet.
When the engine is 1st started, the primary ones convert the gasses right away. There is a emission law that states the cats must be operational within the 1st 3 seconds of engine running. The secondary cats do not heat as fast, therefore, are not operating correctly.
And the mustangs also have 4 cats. My 2003 4.6 stang had 4 cats, I swapped out the mid pipe for a H that only has 2 High flow cats. It runs fine with no codes and with the Magnaflow catback, it sounds real sweet.
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Junior User
Joined: Jan 2001
Posts: 84
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From: Morgantown, WV
Why 4 cats
Thanks for all the info.
Not doubting anyone. I am learning here.
Can't wait till they go with 6 cats. HaHaHa
I guess that a cat(s) back system may be best. Is the cats on the F150 5.4 considered 'high(er) flow' cats? Reason I am asking, if we really open up with a cat back exhaust system, but the restriction is in the cats, don't see much improvement in exhaust flow.
I have heard that some on this board have used a cat back system but removed 2 of the cats and replaced the sensors.
Not doubting anyone. I am learning here.
Can't wait till they go with 6 cats. HaHaHa
I guess that a cat(s) back system may be best. Is the cats on the F150 5.4 considered 'high(er) flow' cats? Reason I am asking, if we really open up with a cat back exhaust system, but the restriction is in the cats, don't see much improvement in exhaust flow.
I have heard that some on this board have used a cat back system but removed 2 of the cats and replaced the sensors.
Senior User
Joined: Feb 2007
Posts: 283
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From: South Jersey
there's all kinds of stuff that you can do. Replacing the Cats is one of them, but it is expensive. My Mid Pipe cost me $550. Plus $250 for the cat back. As far as restriction, the stock mufflers hold back quite a bit. I can see daylight through the MagnaFlows.
I added the Cat Back 1st then a year later changed the mid pipe. I didn't get that much of a horsepower increase when I changed out the Mid Pipe, maybe 10rwhp at the most.
So just go with the catback for now and in 100,000 miles when the Cats go bad you can change out them for a straight pipe.
I added the Cat Back 1st then a year later changed the mid pipe. I didn't get that much of a horsepower increase when I changed out the Mid Pipe, maybe 10rwhp at the most.
So just go with the catback for now and in 100,000 miles when the Cats go bad you can change out them for a straight pipe.
New User
Joined: Apr 2007
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Iam asking the same questions about exhaust, but still can't find out,
WHAT IS THE BEST CAT BACK EXHAUST OUT THERE????
bORLA, ROUSH(OFF ROAD), MAGNAFLOW
WHAT IS THE BEST CAT BACK EXHAUST OUT THERE????
bORLA, ROUSH(OFF ROAD), MAGNAFLOW
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Senior User
Joined: Feb 2007
Posts: 283
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From: South Jersey
All of the cat backs are within a few hp of each other, so basically it comes down to sound preferance.
I like the old type muscle car sound, so I went with a H-pipe and Magnaflow mufflers.
So if you hear a truck that you like, ask what he has for exhaust.
here's a good site for exhaust sounds.
http://www.mustangexhaust.com/forums/soundclips.php
I like the old type muscle car sound, so I went with a H-pipe and Magnaflow mufflers.
So if you hear a truck that you like, ask what he has for exhaust.
here's a good site for exhaust sounds.
http://www.mustangexhaust.com/forums/soundclips.php
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Elder User
Joined: Aug 2005
Posts: 831
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From: Katy, Texas
must work within 3 seconds, whats lets say 10 seconds of non cat'd emission gunna do to the flippin air! Freaking rediculous to have 4 cats on the truck. Seems like a loss of HP, worse gas mileage, meaning more fuel consumption, more fuel consumption depleats our earths "Natural Resources" These EPA cooks need to decide on what they want to save, global warming or the depleating oil supply due to their strict regulations on emission control. Sure the numbers are minute but hell we all want more HP and global warming just means we gunna have a little more sun and a lot more water, who gives a flyin flip!
Senior User
Joined: Feb 2007
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From: South Jersey
I kept the original Cast Iron Manifolds, then got a MRT 2.5" Stainless Steel H-pipe (AKA Mid Pipe) with Cats and then the Cat Back is Magnaflow 2.5" Pipes and Mufflers al the way back. But yes it is true duals, all the way back.
So the Stang definitely runs better, but I had to get the engine tuned cause it was running lean with the exhaust and K&N Air Filter. Once that was done, It was night & day. Total cost - Tune $500, Exhaust $800, Intake $200. But it didn't stop there!!! That is why my SuperDuty is stock, I AIN'T GOT NO MONEY LEFT!!!!!!!!!
So the Stang definitely runs better, but I had to get the engine tuned cause it was running lean with the exhaust and K&N Air Filter. Once that was done, It was night & day. Total cost - Tune $500, Exhaust $800, Intake $200. But it didn't stop there!!! That is why my SuperDuty is stock, I AIN'T GOT NO MONEY LEFT!!!!!!!!!
Last edited by JJPMach1; Apr 11, 2007 at 08:46 PM.
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
Does West Virginia do the "Sniffer Test" like California requires? Or do they do a visual inspection like here in PA? If they just do a visual insp. (Are the Cats there) you could get away with just having 2. No doubt ford put 4 cats on some models so they pass emmisions in all 50 states, even if your state of residence doesn't use calif. emmisions.
Elder User
Joined: Aug 2005
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From: Katy, Texas
See it is a lot different here in Texas. The State doesn't mandate the "sniffer test" it goes by county. I live on the tri county line of Harris, Ft. Bend, and Waller counties Unfortuneately I am in harris which requires the "sniffer test" as well as Ft. Bend. Waller on the other hand, a predominantly rural county, does not require the sniffer test. I think here, if you live in a rural area with lots of farming they don't require it or something. Not exactly sure but thats how it works here.
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Junior User
Joined: Jan 2001
Posts: 84
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From: Morgantown, WV
Why 4 cats
Here in West Virginia NO sniffer test.
It has been my experience (in WV) that if the vehicle is fairly new, they don't even do a lot of 'inspecting' cause it is so new.
I have never seen anyone look at my exhaust system to inspect. My exhaust systems are mostly stock, and nothing loud, so this may be the gauge they are using.
It has been my experience (in WV) that if the vehicle is fairly new, they don't even do a lot of 'inspecting' cause it is so new.
I have never seen anyone look at my exhaust system to inspect. My exhaust systems are mostly stock, and nothing loud, so this may be the gauge they are using.
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