I was wondering. Im looking to get an O/R H-Pipe but my grandpa said not having the cats on there could hurt the car. is there any truth to this for a daily driver?
I doubt it would hurt the car, but it will cause you to fail emissions testing if your County / State requires it. Here in TN, if I install on O/R X pipe, I immediately fail the visual inspection.
If you don't tune out the rear O2 sensors or install MIL eliminators, your check engine light will come on too.
High flow 2 1/2" cats are so good now that you might get an extra 3-5 whp if you ran long tube headers and no cats, so why bother, just get a better flowing 2 1/2" X or H pipe IMO.
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"Ignore that whistle, it's just a vacuum leak."
2000 Mustang GT:
Saleen Series IV Twin Screw, Chicane I/C, AFCO Extreme H/E, 2.8" pulley, FMS 42# injectors, Dual Catted 2 1/2" UPR X Pipe, UPR LCAs/UCAs, 2 1/2" Flowmaster American Thunder kit, 90mm LMAF, 112" Goodyear Gatorback, Kenne Bell BAP, Mosaleen idler, T-56, Detroit TrueTrac w/ 373s, Demolet 100mm CAI, SCT XCal2 with JDM Engineering 93 Octane "Race" tune.
I run with a Pypes brand 2.5" o/r x- pipe and I have no trouble at all just smells a little rich sometimes but not having cats will do that but in MI where i am I don't have to worry about any smog testing. also the x-pipe also toned down the sound from my flomasters over the h-pipe. I like the sound oh the H better but get a tad better throttle response with the X. Just my opinion though
I run with a Pypes brand 2.5" o/r x- pipe and I have no trouble at all just smells a little rich sometimes but not having cats will do that but in MI where i am I don't have to worry about any smog testing. also the x-pipe also toned down the sound from my flomasters over the h-pipe. I like the sound oh the H better but get a tad better throttle response with the X. Just my opinion though
well x gives better flow than h so u will get more horsepower. im actually looking at a H-pipe. high flow cats bc KS has 700$ per cat fine if you get caught. but about hurting it, no it shouldn't but if your county/state does have tests, i wouldn't risk it, just go w/ high flow cats. you might lose 2-3hp w/ the cats over the no cats, so not to bad over all! good luck with anything you do!
He's talking about a lack of back pressure. On these cars, so long as you run with mufflers, I'm sure you'll be fine. What catback do you run? o/r h sounds pretty gnarly.
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well x gives better flow than h so u will get more horsepower. im actually looking at a H-pipe. high flow cats bc KS has 700$ per cat fine if you get caught. but about hurting it, no it shouldn't but if your county/state does have tests, i wouldn't risk it, just go w/ high flow cats. you might lose 2-3hp w/ the cats over the no cats, so not to bad over all! good luck with anything you do!
-Joe
I don't know about most, but for me, the reason I run without cats is for the sound. Cats just flat limit the sound of a car.
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99' Rio Red Mustang GT:
Summit O/R H, MAC Flowpaths Turndowns, BBK Shorty Headers, Steeda UDP, K&N FIPK2 intake, Diablosport Delta chip, BBK 75mm throttle body, Trickflow upper plenum, Intake spacer, H&R SS springs, Cross drilled & slotted rotors, "Functional" hood scoop
Can O/R H-Pipe hurt 
