cat
- Thread starter loweuro77
- Start date
well i did it and the mazda tech was wrong.i noticed a pretty good sized power gain and my engine light never came on. i also took out the resonator and the sound difference is huge ,it now has a nice deep tone and isnt too loud. if anyone else has done this and has had problems let me know. this forum rocks.
If you gut the second cat, you probably won't get a CEL. If you gut the first one, you will. There is a second O2 sensor right after the first cat that checks for efficiency. If it doesn't see a certain amount of difference between the readings for the 1st and 2nd O2 sensor, it throughs a CEL to have the cat checked.
Gutting cats doesn't usually gain you anything. It acts like a large diameter resonator. The exhaust gas expands into the larger area, and then has to be compressed back down to go out of the outlet. The stock catalyst directs the flow through in a straight line. I've seen several of them actually cause a loss in power due to the flow restriction created. Just think of exhaust like water trying to flow through a pipe. The best way to disable a cat is to simply weld in a pipe that goes straight through it. It will still look like a cat is there, but it's functionally a test pipe. This is the way to get around visual testing.
Gutting cats doesn't usually gain you anything. It acts like a large diameter resonator. The exhaust gas expands into the larger area, and then has to be compressed back down to go out of the outlet. The stock catalyst directs the flow through in a straight line. I've seen several of them actually cause a loss in power due to the flow restriction created. Just think of exhaust like water trying to flow through a pipe. The best way to disable a cat is to simply weld in a pipe that goes straight through it. It will still look like a cat is there, but it's functionally a test pipe. This is the way to get around visual testing.
loweuro77 said:
screech!!!!!
dont weld anything. Mazda is all bolt-on. Someone, (DG motorsports, maybe?) makes a cat replacement pipe. It's just a pipe the same diameter as the rest of the exhaust, bolts in and out where the second cat is. best of all, you can switch it in like 5 minutes when it's cold. And because we're using this puny 2.0l (i love it, dont worry) we cant just "take off" our exhaust like the big turbocharged V*s can. we need the exhaust backflow to pull air out, and you can get that backflow only with an exhaust. It might sound better, but you will be losing low to mid range torque on our N/A cars if you take off the exhaust, or open it up at the cat.
(drinks) to all the wonderful folks on this site.
okay, the gopher has been busy. I have several things regarding test pipes for our car.
First of all, I wonder why anyone would put a test pipe on an otherwise stock car. If you replace just the 2nd cat with a test pipe, we're talking 1 or 2 hp, literally. Sure, you get a great sound.....If you replace everything from the block back (headers, 1 and 2 cats, muffler and all piping), we're still talking, oh hell, i dunno, about 7-12 hp, and that's being generous. For the test pipe to really shine, you have to get more air coming into the motor, or increase exhaust (e.g. through forced induction, or a serious N/A tuneup (cams, compression, etc) like some folks have here). On an otherwise stock car, yer just getting sound.
Second, test pipes are illegal in all fifty states, and probably Canada. It can be a ticket in some states.
Third, changing out the cat for any reason other than malfunction in the first 50,000 miles of a car voids the warranty, and may constitute an "instant fail" at emissions if they find out.
That said, my job is to get info, so I got it.
Know first of all that there are high flow cats that offer the same gains (at least on a "normal" car) as the test pipe:
go to driver fx and search for our car and catalytic converter, there's a bunch of cats there.
IF you just really want to kill the environment and void your warranty, then check out Bosal. They offer a true test pipe with their "federal" line of exhausts. Someone here has one on, I believe. Again, until you get the turbo or tuned engine to go along with it, it's just gonna sound good. here's the page w/ the part # its 112-210 or 112-213, i believe
btw, if you are buying a bosal exhaust (not the whole set), these guys are selling them for HALF OFF!
well, I'm sure I've forgotten some info, but oh well. If you have any other questions, just ask or pm me
First of all, I wonder why anyone would put a test pipe on an otherwise stock car. If you replace just the 2nd cat with a test pipe, we're talking 1 or 2 hp, literally. Sure, you get a great sound.....If you replace everything from the block back (headers, 1 and 2 cats, muffler and all piping), we're still talking, oh hell, i dunno, about 7-12 hp, and that's being generous. For the test pipe to really shine, you have to get more air coming into the motor, or increase exhaust (e.g. through forced induction, or a serious N/A tuneup (cams, compression, etc) like some folks have here). On an otherwise stock car, yer just getting sound.
Second, test pipes are illegal in all fifty states, and probably Canada. It can be a ticket in some states.
Third, changing out the cat for any reason other than malfunction in the first 50,000 miles of a car voids the warranty, and may constitute an "instant fail" at emissions if they find out.
That said, my job is to get info, so I got it.
Know first of all that there are high flow cats that offer the same gains (at least on a "normal" car) as the test pipe:
go to driver fx and search for our car and catalytic converter, there's a bunch of cats there.
IF you just really want to kill the environment and void your warranty, then check out Bosal. They offer a true test pipe with their "federal" line of exhausts. Someone here has one on, I believe. Again, until you get the turbo or tuned engine to go along with it, it's just gonna sound good. here's the page w/ the part # its 112-210 or 112-213, i believe
btw, if you are buying a bosal exhaust (not the whole set), these guys are selling them for HALF OFF!
well, I'm sure I've forgotten some info, but oh well. If you have any other questions, just ask or pm me
here's the one i forgot. testpipe.com sells pipes for just about all cars, and if they dont have it, they'll get it.
save up for a turbo, IMHO.
save up for a turbo, IMHO.
sheeeit, me again. I spaced it, and completely forgot thesystem that flyin miata is putting on our turbo p5 as they test the BEGI turbo. That has a high-flow cat (actually, it might just be a resonator) combined with mandrel bend piping and a performance muffler.
Okay, that's it, im done, i swear.
Okay, that's it, im done, i swear.
