High-Flow Cat?

[huskyfan23]

Hey, I'm expecting my Borla headers in a week, and am also thinking about getting a High-Flow cat. I've got a Flowmaster system w/ 40 series, so the cat would complete my setup. Anyone know where to get one for a good price?

 

[mattadams]

With a 4.0 and flow 40's, I'm not sure about the gain you'd see. I've heard of some people with 4.6L's on their F-150's putting on free-flow cats and LOOSING power. I put some on my 5.4L and I love it, but I'm not sure what you'd gain in the high end, and if it would make up for the low end loss.

 

[Bashman]

I am getting a muffler put on the truck next monday and I asked about a free flowing cat as well. They suggested they do a flow test on the cat and if the difference is within a pound it's not going to make a difference. Although they said they would be willing to take my money if I insisted on the cat, I decided to go for the test.

 

[Alec]

Unless your stock cats are bad then don't waste your money. Remember that if you open the flow of your exhaust up too much you are going to lose power. The exhaust needs to be carefully matched to the engine to give hp gains while maintaining torque. With headers and catback already, your cats are the only thing keeping your exhaust from beeing too open. If you do have to get an aftermarket cat, you may want to put in a restrictor pipe to restrict flow and you'll also need a resonator (or 2) downstream to keep from sounding like a lawnmower.

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