Performance Catalytic Converters

[BassQuake9000]

I have a 1998 Ford Expedition and I'm looking to replace all of my catalytic converters with new performance ones. I heard there were four of them, so I want to know if they are all exactly alike, or if they are different types. Basically, I just want to order all four at the same time if I can, and just get everything taken care of on the same day. I'm going for 3" outlets also, instead of the 2.25" outlets of the stock converters. I want more power, and a more agressive sound. I have a flowmaster Super 40 Series muffler with a downspout right now, but I'll have to switch that also since its inlet and outlet are only 2.25".

 

[BassQuake9000]

Does anyone know if there are 2 or 4 catalytic converters on the 1998 Ford Expedition with the 4.6 liter V8?

 

[green03]

If it's not a straight piece of pipe it is a Cat they also have a heat shield on them. I recently replaced my 4 converters with 2 high flow units from dynomax. Carsound (magnaflow) also make good converters. I don't know how legal it is to remove 2 of the cats, but on mine the front 2 were the only ones being monitored by the computer. There is a front and rear oxygen sensor on each bank, the front sensor is what the computer used to monitor the mixture. The rear 02 sensor is just there to monitor the cat's performance and will let you know when there is too much unburnt fuel making through the cat (cat failure). I pulled off my pipes and chopped off everything from the first cat back and put in my own pipes and 2 cats. My factory piping was 2.5 inches. It is also much louder now with the new cats in place meaning that my factory cats were really choking off the motor......
Matt

 

[BassQuake9000]

Cool. Actually I just received 2 magnaflow cats today, and yesterday I bought a new Flowmaster Super 40 series muffler with 2 outlets, so I'm going to put 2 downpipes on it. Hopefully it will sound really good.

 

[green03]

That is going to be loud!!!!!!!!! You might end up adding resonators to the setup like I am thinking about doing since mine is now louder than I like after replacing my cats. It sounds really good at WOT, but at part throttle and crusing it is a little bit too loud now.
They make resonators for larger pipes for the turbo import crowd and I think it would be just the ticket to take the deep resonance out of my exhaust while still being a straight-through exhaust flow.
As soon as I get back from NY (here for a month) this will be my next mod.
Matt

 

[BassQuake9000]

I got everything installed earlier today. All four stock cats were removed, the two performance ones were put in, 3" pipe was added where the Y pipe meets, and the new muffler was added with downspouts. Its really loud now! It sounds great. I know what you're saying though, at any amount of throttle its pretty loud, so no matter what, I'll be really loud going any speed unless I temporarily let off the gas entirely. This may sound weird, but when I get into the neighborhood, I try to keep it as quiet as possible because I don't like disturbing everyone. Everyone else my age stomps on the gas whenever they get in here.

Video of new exhaust!

 

[green03]

It's all user preference when it comes to mufflers and yes the factory cats are very restrictive. I like the magnaflow mufflers because they are straight through (the good ones not the cheaper ones) and stainless steel. If you go with the flowmaster get the 50 series SUV mufflers unless you really like it loud then go with the 40 series or super 40 series. Both will sound good at WOT but the 50 series SUV will be quieter during cruise. Also be sure to have the muffler shop install a crossover pipe where the stock y pipe was located if possible. If you are using 2.5 inch tubing for the exhaust, use 2 inch pipe for the crossover portion. This will increase low end torque and give the exhaust a smoother quieter tone.
Matt

 

[firemann32]

Originally posted by BassQuake9000
I got everything installed earlier today. All four stock cats were removed, the two performance ones were put in, 3" pipe was added where the Y pipe meets, and the new muffler was added with downspouts. Its really loud now! It sounds great. I know what you're saying though, at any amount of throttle its pretty loud, so no matter what, I'll be really loud going any speed unless I temporarily let off the gas entirely. This may sound weird, but when I get into the neighborhood, I try to keep it as quiet as possible because I don't like disturbing everyone. Everyone else my age stomps on the gas whenever they get in here.

Video of new exhaust!

Where did you get the new cats at and what about th O2 sensors? I've been wanting to do headers and remove/replace the cats. I already have a 3" catback system.

 

[BassQuake9000]

I bought the two cats on ebay for about $60 a piece, I haven't changed the O2 sensors though. I have JBA shorty headers, that definitely makes a difference on how my exhaust sounds.

 

[green03]

I watched your video and you are right is sounds awesome. Sounds more like a mustang than a truck. I was thinking about installing a race single chamber flowmaster in front of my current muffler to give it that flowmaster sound and quiet it down even more than it is now instead of the resonator I was talking about earlier. It's hard to beat the way a flowmaster sounds, but the droning inside the cab is why I took them off my mustang and have been using magnaflow ever since.
Sounds really nice! Good job.
Matt

 

[BassQuake9000]

Thanks for the compliment! I'm going to take a couple more videos, a drive by, and starting the car and take off.

 

[BassQuake9000]

Here's my newest video with the new exhaust. I revved it a couple times then floored it.


http://www.youtube.com/watch?v=G51ZlfMzzSQ

 

[firemann32]

Bringing back a dead thread, anyone have anymore information.

 

[99 Expy]

Haha, I didn't even realize how old this thread was until i saw comments on your video lol. I think it sounds great BassQuake. It could just be the video, but I think mine sounds a little deeper with the 4.6, but I still have stock cats w/ no muffler

 

[huklebuk]

Do any of you guys go through emmisions? I have to here in NC and I want to put in the magnaflows and chop the front two off. What exactly do the front two do that two high flow magnaflows can't?

 

[DR3W]

Sweet ass sound dude! haha