so i just order a 02 sensor defouler from modernperformance, here is the link to it.
http://www.modernperformance.com/vib...or-p-2094.html

and now i'm experimenting this defouler with the stock downpipe, and i'm going to gut out the first cat as you can see from the pictures. when i get this done, i will let you all know if it will throw cel or any problem, stay tuned, thanks.

 

wierd

 

i know, just want to try it out, if no dyno performance gain, then i will just get some real catless downpipe.

 

I did something similar with a spark plug defouler for my 2nd o2 sensor on my L61 almost a year ago. Its still running around to this day without a cat or CEL.

 

^cool, but i did this for performance gain and just to be a first one to test this product for the community.

 

ok, the defouler should be here tomorrow. so stay tuned.

 

...whats the point in keeping the cat after the o2 sensor? you should just get a catless dp that is 3" smooth flow instead of all wonkey with a gutted stock one. The fowler shown is just like any of the dp's available with a angled bung or zzp's which is almost the same. Theres still a chance of a cel with full catless. You may see a tiny gain but again I'm confused as to why you would keep the rear cat....

 

yeah...for real, if ur gutting the first half, why not the whole thing??? why would u want the restriction after everything is opened up....it's like when there's road construction and everyone is suddenly trying to merge down to one lane at the last minute

I used a sparkplug fowler on my AP2 s2000 test pipe and NEVER had a CEL...same deal with my evo8 cat...i gutted it instead of buying a test pipe and had to use a fowler...no problems and should be the same with the product ur buying....I SAY GUT THE WHOLE DAMN THING THO!!!!!

wouldn't it be funny if gains were only slighly less than an aftermarket DP....you saved like $200-$300 and gave everyone who bought a DP a sore a$$

 

The only issue I have with the stock pipe being gutted is the gutted cat sections are going to throw some funky ass air flow and how the pipe is pressed where the o2 bung threads.. a 3" piece aftermarket will be a nice smooth flow and have a angled bung.. but it would be interesting to see this done.

 

^^AGREED...there would be lots of "turbulance"

would still be interesting tho, but by the time $ is spent on the fowler and a dyno run "just to see," a person could be half way to buying an official 3" DP...don't we all wish we had a friend who allowed free dyno runs

 

I started to type then I read this ......

 

The CEL eliminator works... I've been using a similar one in an LSJ since the winter of 2006 and have never thrown a CEL. (Note that I haven't tuned off the codes in HPT, as to avoid the 'issues' it creates).

With respect to gutting the cat... as others have mentioned, don't do it. It creates a very bad flow system in the 'cat' area due to the neck up / neck down sections no longer serving a purpose, and because of the rough pattern of the substrate. I've seen many people do this on cars, trucks, bikes, etc and they all have negative side effects.

If you want a cheap-o DP, my suggestion would be to buy a properly sized mandrel bend and replace the first cat and pressed O2 bung.

 

i've already gutted the rear o2 sensor, lol. sorry for misinformation for everyone. but my plan is to have the whole dp gutted, with the o2 defouler install, and dyno it when i have time. like i said, its just a test. even for people who put a real catless dp, then they have to dyno it to see the gain anyway. so if this "modified stock" dp push out close to a catless dp on a dyno, would be fun and interesting to see. stay tuned, and my o2 defouler should be here tomorrow.

 

Even if you do gut the stock downpipe it won't flow as well as any true catless downpipe simply because of that dip down for the O2 Sensor the downpipe goes from 3" to about 2.25" back to 3". Don't waste your time or money just get a catless DP they can be had for cheap now days.

 

I installed a oxygen sensor defouler last night onto our 09 Cobalt SS project car because every 75-100 miles or so we would get a check engine light on our downpipe.

This should eliminate all check engine lights from popping up in the future.



After installing the oxygen sensor defouler

 

Why would you gut out 1 of your cats on your stock dp? that will probably do absolutly nothing

Just bite the bullet and buy a dp from whatever vendor w/ angled 02 and call it a day

 

So I installed that same defouler that you sent me, and instead of P0420, now I get P013E, also cat related.

 

updated:

so i put the defouler on, no cel. everything seems to be good, a little bit more pop, and a little raspy. but the bad news is the one of the nuts that bolts down the downpipe to o2 housing is stripped. like the nut is on the o2 housing screw just free spinning, and won't come off or screw on, just free spinning on the o2 housing screw. any help please?

 

anyone? i'm thinking just gonna try impact gun and try to force that nut on, but any input would be helpful, thanks.

 

Are you sure you didn't just loosen the stud? Don't just impact it on without knowing what's going on.

 

did you use pentatrating oil to do its job when you first took off your downpipe and the o2 sensor?

 

no i did not use any oil, and the stud is on it not moving at all. the nut just spins, won't tighten or loosen.

 

ya penetrating/nut buster oil would help greatly.

 

people, please understand that the nut is not round off, it is on the o2 housing stud. its freely spinning on the housing stud. like it won't losen or tighten.
p.s. the nut is NOT round off, it just spin, won't come off and won't tighten.

 

Sounds like you completely ruined the threads. Now you have to cut the stud off and weld a new o2 bung in.