# of Cats on Fox Body H-Pipe

HISSIN50 · Sep 8, 2005

95GTAODE said:
Ah Hissin, you're killing me!

Don't take this as gospel, but I've read that the "pre" cats are one ways and that the second is a two way. The pre's are there because they heat up faster and reduce emissions while the car is cold. After market pipes use 2 3-way cats.

Thanks for the reply bud - I was not trying to be a pain. I recently had to jump through hoops with the EPA over this stuff because I have an aftermarket catted pipe (2 total) instead of the stock 4 on one of the stangs.

I have read so many sources of info and I never saw anything definitive. When dealing with this stuff, I had wanted to know exactly what was inside each cat. I thought the same as you, but then one decent source mentioned that the second cat was a 3-way, which surprised me and made me wonder why the first cat was needed (I also thought it was a one way and a two way, as tech was not as good back in the day).

I do appreciate your info.

ALMOST STOCK · Sep 8, 2005

Unless I wrong IHCScoutMan asked

how many catalytic converters come on an OEM H-pipe on a '92 fox body. Or any fox body for that matter.

And I see 4 in that pic....be it pre or af,............... it's just 4... RIGHT?

Lyncher · Sep 8, 2005

jstang209 said:
Pre= before

StreetStang302 · Sep 9, 2005

So the "precats" are 2 out of the 4 cats? right?

StreetStang302 · Sep 9, 2005

Anyone willing to answer my question if the "precats" are 2 out of the 4 cats? Well, are they?

HISSIN50 · Sep 9, 2005

StreetStang302 said:
Anyone willing to answer my question if the "precats" are 2 out of the 4 cats? Well, are they?

I can tell you with 50% certainty.

That is just what we were debating and I really dont know or I would tell ya bud. I want to know too.

Mustang5L5 · Sep 9, 2005

95GTAODE said:
To clear it all up: The above picture is correct (with minor differences) for all '86-'2004 'stangs with a factory H-pipe. The pre cats are the 2 small ones right after the header flanges(1 on each side).

96-98 4.6L Mustangs came with 6 cats.

For the '99 model year Ford went back to 4-cat pipes but used up remaining supplies on early '99's.

So some '99 Mustangs have the 6-cat h-pipe while later '99-04's had a 4-cat pipe.

Click to expand...

ALMOST STOCK · Sep 10, 2005

Ok... so on the 96-98 4.6L Mustangs with 6 cats, that would that be 4 precats and 2 cats then right?

MyCARneedsHelp · Sep 10, 2005

there were 4 cats on my 88 GT and my 87 GT. They both were simular to the pic ALMOSTSTOCK posted....

89Red5.0 · Sep 10, 2005

my 89GT has four. two forward, two aft. kinda crappy b/c i had a custom built cat-back and the fwd stock ones couldnt b replaced/removed w/o a ton more work.

RacEoHolic330 · Sep 10, 2005

The first 2 cats near near the header flanges are the pre cats, and as stated before they are there to reduce emissions when the engine isn't running at operating temp.

Those of you with aftermarket catted x or h pipes, you've probably noticed that when you start your car up when the engine is cold the exhaust fumes are really strong for a few minutes. That's because the cats haven't had time to heat up yet and do their job. The pre cats on a stock h-pipe are closer to the engine so they heat up much quicker and, in turn, recuce emissions when the engine is cold.

4G-KDMP · Sep 10, 2005

now i understand.

StreetStang302 · Sep 12, 2005

So to clear everything up, when I put my Off-Road H-Pipe on in 2 weeks, there will be no "precats" and no cats at all, right? and for the final question, will someone that honestly 100% knows, answer the following question, the "precats" on my '89 are 2 out of the 4 cats on my stock H-Pipe, right?

Mustang5L5 · Sep 12, 2005

Yes, the first 2 closest to the engine are precats and the other 2 are the main converters.

Their function is to control emmissions on cold startup. Cat's work better hot, so by being close to the headers, they warm up faily quickly and begin converting gases right away.

The Main cats take a bit longer to warm up so that is why Ford uses pre-cats.

You can pass emmissions with a aftermarket H-pipe with 2 cats. Just make sure you drive around for a while and get the car faily hot before heading to the inspection station.

2-cat h-pipes will pass inspection. Various states have passed around notices that a Mustang with 2-cats will pass visual if it passes emmissions.

HISSIN50 · Sep 12, 2005

So what is inside a 'pre cat'? It sounds like atleast one matrix (it is at least a one-way cat).

FWIW, I just flunked the visual inspection with an aftermarket catted (two 3-way cats) H-pipe. There is nothing steadfast with emissions testing IMHO (other locals with the same pipe pass all the time). Kind of a luck-of- the-draw thing.

StreetStang302 · Sep 12, 2005

Mustang5L5 said:
Yes, the first 2 closest to the engine are precats and the other 2 are the main converters.

Their function is to control emmissions on cold startup. Cat's work better hot, so by being close to the headers, they warm up faily quickly and begin converting gases right away.

The Main cats take a bit longer to warm up so that is why Ford uses pre-cats.

You can pass emmissions with a aftermarket H-pipe with 2 cats. Just make sure you drive around for a while and get the car faily hot before heading to the inspection station.

2-cat h-pipes will pass inspection. Various states have passed around notices that a Mustang with 2-cats will pass visual if it passes emmissions.

Thanx for clearing everything up. Later, Jeff.

ALMOST STOCK · Sep 12, 2005

HISSIN50 said:
So what is inside a 'pre cat'? It sounds like atleast one matrix (it is at least a one-way cat).

What I saw when I took this pic of the 'per cat', as I looked down through the pipe I saw a honey comb or very fine looking mess of some sort.

View attachment 504121

HISSIN50 · Sep 12, 2005

Almost Stock, Thank you sir. That looks more like a one-way cat than something that is not a cat (the name 'pre-cat' suggests something other than a cat, to me).

ALMOST STOCK · Sep 12, 2005

HISSIN50 said:
(the name 'pre-cat' suggests something other than a cat, to me).

That is my thought also.

# of Cats on Fox Body H-Pipe

HISSIN50

"How long does it take to get help in here?

ALMOST STOCK

Lyncher

New Member

StreetStang302

New Member

StreetStang302

New Member

HISSIN50

"How long does it take to get help in here?

Mustang5L5

That is…until I whipped out my Bissell

ALMOST STOCK

MyCARneedsHelp

89Red5.0

New Member

RacEoHolic330

I like to dress like a pretty girl

4G-KDMP

StreetStang302

New Member

Mustang5L5

That is…until I whipped out my Bissell

HISSIN50

"How long does it take to get help in here?

StreetStang302

New Member

ALMOST STOCK

HISSIN50

"How long does it take to get help in here?

ALMOST STOCK

Similar threads

# of Cats on Fox Body H-Pipe

"How long does it take to get help in here?

New Member

New Member

New Member

"How long does it take to get help in here?

That is…until I whipped out my Bissell

New Member

I like to dress like a pretty girl

New Member

That is…until I whipped out my Bissell

"How long does it take to get help in here?

New Member

"How long does it take to get help in here?

Similar threads

Privacy & Transparency

Privacy & Transparency