kaidotech

I recently purchased a few pieces to redo the exhaust on my 95 F150 5.0L, and was wondering how many cats do I need to legally pass an emissions test? Im not interested in cutouts, or taking off cats and rewelding them and all that BS. I have a pair of SLP Loudmouth II mufflers, and am looking at a pair of Summitracing high-flow cats to round it out with my summitracing headers. I want something that boosts the sound as much as possible, as well as the power. Im setting up a true dual, with the exhaust exiting behind my doors (single cab flareside) like mine is currently. I like it there, and like the sound.

Anyways! I was thinking one new cat per exhaust side, but do I need more then one? Should I put two cats on each side of the exhaust? I have to pass emissions so I need to figure out how many cats it takes to clean the exhaust of a 302. I'm also going to be adding an H pipe and was debating where to add that too.

Currently my exhaust goes: manifolds, tubes, Y pipe, cat, cat, Y pipe back out to two, muffler on each side and exit.

I'm debating: headers, pipes, h-pipe, cat, pipe, muffler, exit pipe (on each side) (and I've deleted my front tank so clearance isnt an issue)

burnthelight88

I think you'd be fine with one on each side. In PA my '92 is allowed to pollute 1.2% at idle and at 2500rpm (that's the two tests for tailpipe). With two cats on mine I polluted 0% at idle and only .23% at 2500rpm...Mine is a 4.9L though. Does your engine show signs of wear? What were your emissions results last year?

On a side note...'95...don't you have OBDII? If you do, you can just buy MIL eliminators and trick the computer, because if you have OBDII they don't do the tailpipe test, they just do an emissions code read.

kaidotech

95 with OBD1 only, they do an exhaust test on the rolling road. My engine has 245,000 miles but still runs very strong.

burnthelight88

What state are you in? How do they test emissions while they are moving? That's wild! If you could find your results from last year that would give you a pretty good idea what you can do...if your state even gives results printouts. Its really hard to answer emissions questions across different states.

ymeski56

In California (the toughest state), you are allowed to use a single hi-capacity Cat in replacement for dual Cats. Just make sure they increase diameter at the Y. If it flies in my state, it'll fly anywhere!

ymeski56

Think Dyno. In Ca., they test at idle, 15mph & 25mph. They used to use Monkeys to push the machine behind the vehicles, but they finally ran out of monkeys. It was fun while it lasted!

kaidotech

I live in Texas, if that makes any difference.

ymeski56

That's a cake walk compared to Ca. It' a Fed law variance that allows the 2 for 1 hi-capacity anyway, so state shouldn't make a difference. This is specific to F-150's. Don't know about other vehicles.