98 Subaru header questions

[That New guy]

Will a un equal header cause a check engine light and a fail for smog testing ? Also would a un equal header with a catted downpipe from the header cause a cel or fail on smog test? Even if I have 1 cat still ? Im thinking about purchasing these I want my car to be not so quiet and have a nice subie sound.

 

http://www.cntracing.com/mobile/Product.aspx?id=37365

[matt167]

your in California, so yup it will fail.. Even if no light, which there shouldn't be, its not gonna pass visual missing a cat. They wont even try to pass it

[Bushwick]

Seeing as how the cat will be included in the kit, I'm not sure what Matt was talking about? Worse case, keep the factory cats and manifolds and just swap that back if it won't pass. Can even ask a tester directly if there will be an issue or not beforehand (must state the factory cats are junk and ruined and you are fixing the car, but they might request some documentation so be warned). If there is, just swap it out for testing (but obviously keep this to yourself and don't discuss it; EPA doesn't have the funds to directly go after everyone, but why risk it?). If you ever sell the car and it's not passable, you'll need to revert it for the sale as the new owner could sue you (exception being maybe a car with historical plates or a race-only vehicle, etc. but need to double-check this as I'm guessing.)

 

Those are actually Equal length headers. Unequal length are what most factory engines have as it saves space and lowers complexity of the cost to make it. Equal length means every exhaust port travels the same distance to the collector, which can improve performance. Unequal headers are like runners on a race track where everyone has a different stopping location and can reach their finish line faster than others. On a daily driver it's acceptable but not optimal. Just like how an X pipe crossover is better than an H pipe which is better than a Y pipe and all will get the car down the road, but the X pipe will offer best performance and free up a few hp more over the H pipe.

 

Also, don't do this for the "sound" as it won't be justifiable. The benefit will be a better, smoother powerband.   

 

 

Buy a tube of anti-seize and coat each bolt with it from header studs to collector bolts, etc. every time you swap it and it'll be a 30 minute affair to switch over assuming the exhaust studs are NOT hard to get at with the equal length headers. If they are, consider converting to ARP studs instead. It'll be easier to just stick header up and set it on the studs than trying to fish a bolt through the flange while working around the piping getting threaded into the head. Studs can also make alignment issues go away as all you have to do hang it on the stud then start hand-threading a nut. Once both sides are aligned and all nuts are hand-snug, you can just wrench them down. Much easier this way. And having anti-seize on all threads will make future removals a breeze.

 

Oh yeah, try and get the headers with the smaller runner if they offer them. I once went from a 1 5/8" unequal to a 1 3/4" equal on one of my 306 Mustangs and I regretted it as it lost some velocity. That car had 10:1 compression, 4:10's, small carb, 5 speed conversion and posi, and weighed about 2800 pounds with me in it and could run a 13 flat on street tires. It felt like it lost some early torque. On a car with over half as little HP weighing hundreds of pounds more and a ton less torque, having 15 hp more on the top end won't be justified if you loose 20 tq early on.

Edited October 27, 2015 by Bushwick

[Durania]

I may be wrong but won't the testing station look to see if that header is C.A.R.B compliant? If not, they may fail you.  It also looks like the kit uses a hell of an angled extension piece to get the rear oxygen sensor out of the exhaust stream. That used to be a way to keep from getting the P0420 code on my RS. The idea is to pull it further out of the exhaust stream so the CEL would go off. Didn't work for me though.

Edited October 27, 2015 by Durania

[matt167]

simple.. Factory cat converter setup uses 2 cats.. The header eliminates a cat.. California emissions will not certify that. Its plain and simple

[Bushwick]

We don't have that nonsense in Ohio. They aren't even allowed to pop the hood nor are they trained to do anything other than sweep under the car with a mirror to visually confirm a cat is in place. As long as it's not throwing a CEL when it comes or after restarting, they'll test it. If for some reason their device can't communicate with the OBD II port, they'll idle test it with a probe at high rev. They used to do a roller test on a dyno device, but that seems to have fallen out of favor.

 

 

Just swap back and forth. While not technically legal, as long as it's running a cat it's not going to hurt anything, unlike mowers and motorcycles that still run catless and dump a ton of pollutants. Kinda funny how that works. While a pain to swap, if you are using anti-seize it won't be so bad. Don't forget to dab the threads of the O2 sensors but don't allow it to get on the actual sensor openings. This will make future removal of them easy. If you want more tangible performance, get a turbo car or a more powerful 6 or 8 cylinder car.