Awesome thread! Thanks for the info

 

great info thanks

 

Quick question, I am prepping to swap my stock downpipe for a TurboXS catted downpipe and wanted to know if the o2 sensor wire reach or if I need to buy on o2 wire extender. I don't think I do but wanted to confirm before I started this small project.

 

Don't know for sure but my ZZP dp was fine. If your txs pipe has the short tube coming off of it to mount the O2 sensor in you will be fine.

 

Thanks. It has an angled o2 tube coming off of it. I guess I'll just try and see what happens!

 

It will reach, you should be fine

 

I'm comparing the ZZP downpipes currently. Which one do you guys think would be best? Is a catless downpipe better flowing than a catted one? Any HP gain differences with or without a cat?

Catless
400 cell cat
catless w/ 02 bung
catless w/ angled 02 bung

SOO MANY CHOICES?!?!

 

Get a high flow cat. No fuel smell and it'll barely affect performance.

 

I went with the zzp dp with high flow cat. The amount of hp/tq difference isn't worth the headache from the fumes and having to change it out every year for inspection. Held up for 2 NY winters so far too! But catless does sound sexy..

 

ZZP is 3". is that same as stock?

 

I think stock was 2.5", but it bolts right up. I've got the mpx 3" with angled bung. No cels, and passes Illinois emissions.

 

Yeah I am debating on catted DP and a catback. I just don't want the car to drone while im commuting everyday.

 

Catless isn't really that loud until you put your foot in it. It's louder than stock, but not terrible.

 

Get the downpipe before a cat back. It's great for daily driving. Almost stock quiet until you get on it. Cold start/ cat warm up drones for a minute but goes away.

Personally I'd get a catted dp if I did it again. Catless throws off my class in SCCA autocross.

 

I need a cat to please NJ visual

 

Yes u do. I had a hollowed out cat welded into my catless DP for NJ inspection.

 

I might just leave the cat in, less gas smell and less sound. If I wanna go ballztothewall I'll get one without a cat haha

 

Stock SS/TC downpipe is def not 2.5"...

It's closer to 3", if not 3". The restriction is it has two cats and a dimple at the o2 sensor.

Even the stock SS/SC downpipe is 2.75". That's why it boggles my mind when people put a 2.5" downpipe on them.

 

This. There is also the stamped hole for the secondary o2 senor that makes an odd shape of the pipe on both cars.

 

Seems like this is an ok thread to ask this.... since LHU and LNF are so close....

So over on the Regal Forums, the guys think the second cat (the unmonitored one), is the primary cat, and the monitored cat in the o2 housing (1st cat) is just a "light off" cat. I'm dying to correct them, but I just wanted to make sure I'm right that the unmonitored cat (2nd cat) is only there for clean up duty and most likely strict California emissions. Makes no sense that the primary cat wouldn't have o2 sensors monitoring it.

 

Your thinking is correct, the first deals with some NOx, the hydrocarbons, and CO. iirc the second one helps with further conversion of NOx to N2 (strict Cali emissions). Although the o2 sensor only can check for hydrocarbon removal performance, not NOx conversion. So depending on what they claim is the main pollutant would depend on which they call the primary or secondary (nomenclature cluster **** is what is sounds like)

 

Question, if I get a catless downpipe I know I'll shoot the check engine light. But if I keep my stock downpipe and put it back for emissions come testing time. Will it remove the check engine light? The price for carted dp is so much lol

 

You will need to drive the car a bit to make sure the CEL doesn't come back, but yes, many people switch back to stock to pass emissions.