header swap vs. my 'green' side.
 

im thinking about installing an uncatted jdl uel header while keeping the rest of the exhaust stock. excited about the potential for a bit of subie rumble and the pickup in midrange and high end grunt but the eco friendly part of me is curious if the stock cat on the front pipe does any decent job of filtering out exhaust pollutants? don't know if anyone has explored that at all or actually tried to bring their similarly setup car through a sniffer test to see.

Go catless and let your grandchildren deal with the pollution. If you keep all exhaust components stock, will be quiet anyway

Not gonna lie, I have thought about the environmental effects of being catless. Some times I think about putting a catted header on too, but I enjoy the sound and power of a catless header too much.

The biggest part of the pollution will be when you first start the car. At cold startup, you're basically polluting about the same as a car from about 20 years ago before OBD-II.

After cold start you should have same tailpipe as a normal car and should pass tailpipe emissions should it be needed.

-alex

so the secondary cat is effective enough to bring emissions down to legal limits when warm? 👍🏻

Put it this way:

Aftermarket header/OP/FP systems with a high-flow catalytic converter emits less tailpipe than stock. Apex'i and HKS are two companies that offer this setup.

-alex

can you quote any measurement data?

Not without modification. The front cat is the primary and the O2 sensors are positioned to manage it, not the secondary. The secondary cat is likely a two-way catalytic converter, as well, so it would need to be replaced with a three-way to see the same benefit.

But as others have stated, the real problem is the warm-up period. Even if you could move the O2 sensors back and replace the secondary with a three-way, it would still take significantly longer to warm up.

I'm not sure about that. I had JDL catted header and catted front pipe (200 cell cats) and my car failed emissions test here in Aus.

Either install a header the car is dieing for or sell it and hug some trees with a Prius!

If you care about the environment and don't want smell just leave at least 1 cat in the car.

In my 2002 Subaru WRX, we have 3 OEM cats. I removed all 3 and just had 1 200Cel cat in my downpipe.

Had no smell and no issues.

For this car I'd suggest Catted Header + Catless Front Pipe.

Well, if you believe in government subsidies and the mess it creates to grow as much corn... which may still be better than gasoline, mind... try E85 for a greener burn.

And keep your eyes out for an available Tesla roadster.

murica. bikinis. beer. football. powar. giggity.

thanks for the constructive input, those with it. i never knew about 2 vs 3 way cats and i guess just having the stock front pipe is something im comfortable with after the research.

Offset the increased emissions by running E85 :party0030: