Hello, This is going to be a question for a member with vast knowledge of aftermarket parts and how they make these cars run. So having said that, I have a hollowed out cat by the radiator due to failure and a hollowed cat in the ypipe. Instead of fixing with new cats or headers i am considering just having the cat by the firewall hollowed out and getting one installed in ypipe and extending the o2 sensors just like there were headers...... Will this basically be the equivalent of adding headers? Is there some obvious downside to this compared to the op that i am missing? Maybe someone out there has some experience in this dept. as i am always learning. Thanks in advance.
Jay

P.S. Also just wanted to make sure is there 4 or 5 o2 sensors in our system. and by the way i have an 04 se.

 

It will most likely flow more air due to less restriction from hollowing out the cats. Extending the rear o2 sensors past an aftermarket cat in the y-pipe should work. Our car has 4 sensors... two primary air/fuel sensors in the header manifolds, and 2 secondary o2 sensors.

Only thing that may be of concern is running rich/lean codes (typically P1273/1274 and P1283/84) because of the extra air flowing over the primary a/f sensors. I really don't think you'd have any issues since you still have the stock 2.25" diameter piping in your headers. A few of us here have been dealing with above codes with aftermarket headers, and there doesn't seem to be any solution.

 

What diameter is the tubing on the headers? do you think i will see the same gains as with headers? Will i need an ecu reflash and what is the proper way to extend the o2 sensors as far as the wiring and finding bungs for the 02's? Sorry for so many questions at once? Will this route add more performance to my car vs. the ceramic oem cats?

 

The OEM cats are cast iron. Heavy suckers. Stock diameter is 2.25". Aftermarket exhaust parts for our car are typically 2.5". I doubt you'd see gains like you would with aftermarkets.

No ECU reflash. Just disconnect your negative battery terminal for 10-15 minutes and that should reset things.

You'd only have to worry about extending your rear o2 sensors if you get aftermaket headers/y-pipe. It's pretty easy, and any competent mechanic should be able to do it.

You need 18 gauge electrical copper wire. Solder the extension wire onto the harness somewhere in the middle, and not onto the o2 sensor itself.

I had success with this stuff:

http://www.radioshack.com/product/in...ductId=2049741

Any muffler shop should be able to weld bungs in the correct location... a few inches past the cat on your y-pipe.

 

Does anyone else have any input on this setup? I would like to avhieve more performance and not have to worry about failure(cat breakup) by hollowing out the cat by the firewall, as the one by the radiator already is. I am then entertaining the idea of treating the rest of the installl like a header install by extending the o2 sensors and installing a high flow cat om the ypipe. Do you guys think that this is a good way to approach this problem? All headers do is flow more. Hollowed out precats should do about the same thing. Theoretically. Is there anyone with experience in this field? Thoughts?

 

So you have a stock Y-pipe and one of your precats is hollowed out? The tricky part is going to be getting all of that cat material out of the rear cat, I thought about the same thing before I went with headers.

Are you going to remove the cat before you bore it out? If you don't get all the ceramic out of the cat it could still potentially get sucked back in to your engine and ruin it. Be 100% sure on this.

I think you will see some gains but not as big as headers just because the header design is more free flowing.

I don't even think you will have to extend any sensors. I'd try it without extending anything unless you have to.

If you are not getting any codes now with one cat bored out....... I am suprised. Perhaps my issue with codes is more related to the fact we had to extend the front 02 sensors, which are highly sensitive. I'll be real curious to see if you get any codes after boring out the 2nd cat.

Good luck

 

Apollos,
Thanks for your input, I already have the cat in the ypipe hollowed out because the one by the radiator went out and clogged the one in the ypipe. I am now just entertaining the idea of paying a guy labor to take the one by the firewall off, Cleaning it out, reinstall it, extending o2 sensors and installing highflow cat back in y-pipe. Basically I think it would be about like adding headers.......I think (pretty redneck method headers). hahaha
Anyway just trying to gather some peoples knowledge who know more than me or who can think of things that i have not. I have not done this I am just trying to see if it will work. Thanks,
Jay

 

It won't be exactly like adding headers. In the same way hollowing out the Y-pipe cat isnt the same as adding an aftermarket Y-pipe. I hollowed out the stock Y cat and went straight to the track, it made zero difference. The flow of the aftermarket cat is just way better.

I'm not saying its a bad idea, and I think it will be better than stock. Oh yeah I guess you could extend the rear sensors but I would do that last.

Check this out. See the difference?
CATTMAN Y


STOCK vs CE Y (now out of business)

 

Nice pics!

 

Very nice pics Thanks. You guys out there with headers, do you all have an ecu reflash or tune? Also is it nesecary to do so or will you just lose low end torque without it? Or is it more so the cold air intake that is prone lag a little in the low end? Im trying to figure how my car will run if do hollow both precats and install a high flow cat in ypipe.

 

Car should run fine.

I don't have a tune. Never got one. Car still runs awesome!

What year is your Max? If it's an '04 with a Gen. 1 ECU, you won't be able to get a tune with UpRev's Osiris software. Early '04s (mine) have the older ECU. Only way to really find out is to take it to a tuner that uses the software:

http://uprev.com/dealers.php

Honestly, unless you're tracking your car, there'd be no need for a tune. You will feel the gains with every reputable aftermarket upgrade.

 

Yeah the car will run fine. I think you will feel more power with the cats hollowed out and a high flow cat, plus it will still pass emissions. Mine did.

 

I wonder if anyone has ever tried this route? What brand cat did you put in the ypipe(universal)? Where did you bet your O2 bungs and plugs for sensors or are these pretty common exhaust shop supplies? I know this next question is a little off topic but is there a lightweight pulley available that is not underdrive for our cars? thanks

 

People hollow out their cats all the time. Rarely any problems. Any muffler shop will have bungs, but I'd go to some place you can trust to extend you rear o2 sensors.

Unorthodox makes a stock diameter lightweight pulley.

 

No one that I know has hollowed out their pre-cats. I have a lightweight crank pulley, you can get the cat for your Y-pipe from Cattman. If I were you, I would wait on the pulley and by a Y-pipe from Cattman with one of his fast cats already installed. You will be happier with the perf results.

 

Dont you think i can achieve almost the same thing by welding in a high flow cat and also the bungs for less money. I guess except for the less dramatic bends that the cattman ypipe provides. essentially the same I think.

 

Would you be doing this to the stock y-pipe? Gotta keep in mind it only has a 2.25" diameter. You may get 1-2hp with an HFC, if that.

It all depends on what you are going for.

 

Yes (just entertaining the idea) I was thinking I would just keep the stock y-pipe. what kind of gains if any do you think i would achieve?

 

With an HFC, you'd probably see 5ish. But that's just an educated guess. All oem cats are quite restrictive.

I may have some o2 spacers for you... if they ever get delivered. It's been a week already. But we can talk about that via PM.

Good luck!