Well just as the title says, I had a shop install my LG headers with High-Flow Cats .

They installed the Cats before the X-Pipe, I go else where to get it dynoed and was told that isn't the correct way. So they removed them and install the
X-Pipe first then the Cats. ( At my expense) So I email Lg and was told that this method wasn't correct. So my question is, Is anyone else running the cats before the X-pipe and does it really make a difference?

 

As far as I know the cats are always in front of an X pipe. You have O2 sensors in front of the cats and behind the cats and in front of the X pipe.

 

Cats before the X-pipe!!

 

Thanks guys, I'm goin back this weekend to have them reverse what they did.

 

Absolutely cats before the x-pipe. My Dynatech Supermaxx system required O2 wiring extensions but, they were not anywhere near long enough to extend to a position behind the x-pipe.

 

The shop is correct from a pure performance standpoint.
The closer you can put the x-pipe to the headers the more effective it is. Unfortunately, the cats must be as close to the headers as possible
in order to heat up and preform to meet OBDII emissions.

 

Here's a pic of LGM Headers installed by LGM. In this pic of a Z06, the cats are BEHIND the X-pipe. You can see the entire install here: http://www.vetteweb.com/tech/0501vet_lgpipes/

 

123gone, I do not see the after cats sensors. Are they hidden or omitted? If omitted, did they trick the PCM electrically or via a reflash?
BTW looks like LGM did a very nice looking install

Noe

 

OK now I'm really confused?

That's what mine look like, but I'm getting different opinion. So for performance X-Pipe then cats. I've put 100 or so miles without throwing any codes.

So what do I leave them, like the photo above?

 

IMHO yes.

 

LG's old setup had the cats after the xpipe and required longer wires for the o2s if they were not deleted through tunning. Turns out that LG now sells the setup with the cats in front of the xpipe. I suspect that the cats being so far aft were affecting the o2s in a negatitive way. LG will be able to expand on why they changed their setup. My tunner has told me that the cats being so far aft never heated up enough to perform as designed. Again contact LG for the story, they will be happy to explain it to you better.

Mark

 

When I installed my LG's I called Lou and he told me that the x-pipe comes right after the headers and then the cats, so that's the way mine is installed. I had to replace one sensor, but only because I accidentally dented the tip of it during the install. Other than that I've had no problems with it as installed.

 

Magred is right. For best performance the X pipe should be closer to the header collectors. However, it's better for smog control and cheaper to put it after the cats.

 

Agreed. An article in HotRod(i think?) just a month or so ago backs this up.

 

I installed mine after the x-pipe with the rear 02s deleted.

 

If you want to run four O2 sensors like factory (and have them to monitor your cats like factory), the rear O2 has to be in front of the X-pipe and obviously behind the cats. There is a slight power advantage to have the X-pipe up front, but the closer the cats are to the engine the better the cats will work. So, if you want the absolute max power and worried less about emissions then cats in the back. If you want the best emissions or want to run four O2 sensors then put the cats up front. I think the only thing LG changed is they now install bungs for the rear O2s. I think everything else is the same from what I gather from talking with them and reading on the forum. As far as I know you can still install the cats either way you want. It would be good to hear from Lou to know for sure. I installed mine up front because I wanted to run four O2 sensors. I bought the LG system right before they started install the 4 bungs. I bought and installed my own rear stainless bungs. As you can see I also install four extra stainless bungs in front of the cats. I have two extra bungs above the headers so I can run on board wide band O2 sensors. I also added two extra bung facing down so a wide band O2 sensor can easily and quickly be installed for dyno tuning if needed. The extra bungs are plugged until needed. Now if I could just get some O2 extensions cables from LG I could see how the system works! Been trying to get them from LG for over a month and still nothing. They said they would send them but they never did. I don't believe anything they have to say anymore, I'm done trying to deal with them. Anyone know where I can buy some extensions?

 

I have my LG's installed with the R/T Hi Flow cats BEFORE the X-pipe.

I am using all 4 O2 sensors.

Front sensors are connected to the headers themselves (we used extensions cables to get them down there) Then the Cats, Then the X-pipe which is where the rear O2 sensors are connected (to the X-pipe)

Everything is fine.

LG's can be installed EITHER way, Cats then X-pipe or vice versa.

 

Thanks guy's this puts me at ease. Now all I have to do is figure out why I'm getting this slight vibration around 1000 RMP and only for the first 3 of 4 minutes when the car is initially cold . Anyone experince this?

 

SpeedyZ: How do you like those electric cutouts? Any performance changes when they're open? I know it sounds good

 

I love these cutouts, they work great and sound awesome! These are 2.5" McCord cutouts with 100% custom stainless plumbing. I don't expect much performance gains, but I figure with the good flowing factory Ti mufflers and the cutouts it should flow about as good as open 3" exhaust. I have not drove this setup yet, been trying to get O2 extensions from LG for over a month now!