With the current gas prices going up like a ****, i was just wondering what would be worse for getting crappy gas mileage. Having a blown aftermarket carcound cat with possible bad o2 sensors because of it OR a testpipe? Getting like 170 miles on a full tank these days. I'm using the caround cat but i think her time as came and gone haha so i was thinkin of just getting a test pipe. I'm runnin the smsp header and exhaust. need feedback plzz

 

I didn't notice any difference in gas milage when I put on my test pipe vs. my cat.

 

Test pipe user here and I can get 35 mpg on the hiway if I can keep it between 75-80mph. but the rest of my exhuast is free flowing too. oem 4-1 and BCIII, which I'm sure helps a bunch.

 

still waiting for my mugen twin loop and test pipe...stock exhaust for me Mark...although the white deposits coming outta your exhaust the last time I saw it wasn't so good as well! lol get a test pipe made mang

 

a cat can clog, which creates more pumping losses for your engine and reduces efficiency. for it to work, the ecu runs in a lean-rich cycle. with a test pipe, tuning is more flexible, since you don't have to worry about frying out the cat (hence having to run the rich cycle to cool it back down), and you don't have the restriction.

 

90K mi on original cat and I just calculated to 36.36 mpg @ 80mph highway with A/C radio and headlights on for quite a distance.

I believe you'd get better mileage without the cat though, I dont think I'll be doing that anytime soon.