Deeper technical questions about headers

[Buellracer]

So I've read many exhaust and header threads now and I've been shopping for headers. I've seen many threads where people talk of the Kook's headers as being more of a mid length system compared to SW or ARH. It's obvious looking at pics that the primaries are shorter BUT their bends also look much more equal length than the other systems.
I have no loyalty to any of these three brands but I want to know which would theoretically flow better, what exactly does primary length change in power or sound wise, and how important is it to have equal length headers (seems like it'd make it run smoother)?
Any input is appreciated.

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[dev1360]

Shorter primaries generally move the power a little higher in the curve. But honestly, the space restrictions of a modern factory vehicle make all headers very similar in power production.

That said, I prefer the longer primaries for more of a balanced power output. ARH would be my pick of those brands. I went with Stainless Power because they fit the budget much better for me.

 

[Dragster]

One other thing to keep in mind is emissions testing, if any, in your state. I see you're in Houston, and I would assume that Texas is probably pretty easy going on that stuff, but I'm not sure. We have an OBD test for emissions in my state that starts after 3 years. I went with Kooks green catted headers because they can work with an "emissions compliant" tune (i.e., you don't have to turn off the O2 sensors, which would cause a failure of the emissions test). I didn't want to have to take off the headers and retune the car every year for testing.

 

[stang77]

One other thing to keep in mind is emissions testing, if any, in your state. I see you're in Houston, and I would assume that Texas is probably pretty easy going on that stuff, but I'm not sure. We have an OBD test for emissions in my state that starts after 3 years. I went with Kooks green catted headers because they can work with an "emissions compliant" tune (i.e., you don't have to turn off the O2 sensors, which would cause a failure of the emissions test). I didn't want to have to take off the headers and retune the car every year for testing.

Emissions is the one thing that has me on the fence about headers. Kooks headers are pricy for me. SW headers are cheaper but I was told that the catt on those are lower quality that may not pass emissions. Dam laws :frusty:

 

[Jeff_oddo]

One other thing to keep in mind is emissions testing, if any, in your state. I see you're in Houston, and I would assume that Texas is probably pretty easy going on that stuff, but I'm not sure. We have an OBD test for emissions in my state that starts after 3 years. I went with Kooks green catted headers because they can work with an "emissions compliant" tune (i.e., you don't have to turn off the O2 sensors, which would cause a failure of the emissions test). I didn't want to have to take off the headers and retune the car every year for testing.

I threw the P0420 and P0430 CELs with my Green Cats. Had my tuner disable those codes in the tune and all my readiness codes have finally set to ready! But yes, turning off the rear O2 sensors will in fact not allow your CAT, HO2 and O2 readiness codes to set properly.

 

[dev1360]

My past 3 cars have passed OBD2 emissions tests no problem with the rear O2s turned off and no cats.

 

[Buellracer]

Hmmm good to know

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