How do headers affect smog results?

[yipiokayyay]

Been trying to find the answer online for a while with no luck. Aside from just a regulation thing. Why do headers even affect smog results?

Any help appreciated.

 

[B2FiNiTY]

In a nut shell, headers will affect your cars a/f ratio which results in different exhaust temperatures which coincide with your catalytic converters efficiency. I can't say exactly how better or worse they will affect your results. Every car is going to be different.

As long as your cats are in good shape and you give them time to heat up, you shouldn't have too much trouble passing smog. Assuming everything else is working properly.

 

[darock]

The biggest issue I had with different stainless tube headers is to get heat into the cats. Especially if the cat is already 10+ years old it needs even more heat to work properly. The stainless headers transfer more heat from the exhaust gases to the outside. We have emission testing every year here with kinda strict limits but standstill, so no rolling road like cali. You need to drive the car hard before doing the smog. 5 Minutes are enough to cool down the cat enough to get in trouble. Most older mechanics here know that and send you for a spin around the block

Bernhard

 

[Rope]

Ceramic coating your headers makes a noticeable difference in engine bay temps so that means all of the heat is retained in the exhaust gases. That should remedy the issue of the cats cooling off or not having enough heat in them.

 

[mochanges]

My old DC Headers prevented me from passing smog because they had the O2 sensors in a poor location.

 

[Jinks]

I have the new version of dc sport headers. No issues passing smog test in California. The headers from from what I have read, have different collectors which in turn flow faster. Usually , "from my own experience, " the bigger the collector, the more epa issues you will have. If you are in California, buy a set of new style dc's or ct engineering and none other. If not, love fab or sos.

 

[koeech]

My old DC Headers prevented me from passing smog because they had the O2 sensors in a poor location.

Realize this post is about 10 years old, but curious to know how you remedied this? Did you somehow relocate the O2 sensors?

Asking as my relatively new-to-me ‘93 came with DC headers and has trouble passing Calif smog check. I’m considering replacing with OEM exhaust manifolds.

 

[docjohn]

Cali can be tough on smog...look at old posts about little tricks guys do to pass, but it may come to getting your cats to proper temp, or replacing them. The oem manifold is a HP killer, keep the headers you have or replace with another brand including the oem 97-up

 

[mochanges]

Unfortunately my solution was pretty expensive. I replaced them with CT engineering headers which, iirc, have a different design I think in the collector, which allowed them to pass.

 

[koeech]

Cali can be tough on smog...look at old posts about little tricks guys do to pass, but it may come to getting your cats to proper temp, or replacing them. The oem manifold is a HP killer, keep the headers you have or replace with another brand including the oem 97-up

Thanks for the suggestions! I've also heard about OEM manifolds sucking HPs. But, I'm an older guy and just enjoy occasional pulls on the highway and twisties in 2nd & 3rd - I don't go to the track - so not too concerned about loss of HPs by reverting to OEMs - *IF* it helps with passing smog here in Cali.

My smog guy (a fellow NA1 owner) knows to get the temps up before testing but even with the high temp I barely passed HC this most recent check. That's why I'm exploring what else I can adjust - including getting a fresh(er) set of cats.

 

[koeech]

Unfortunately my solution was pretty expensive. I replaced them with CT engineering headers which, iirc, have a different design I think in the collector, which allowed them to pass.

Thanks for sharing, good to know the available options!