catless header vs catless frontpipe
 

After having determined that the primary cat along with o2 sensors being on the header, I had some questions after some inconclusive results via using the search function...

Having established the above, as long as the header is kept stock or one were to go with a catted aftermarket header, this should keep the CEL at bay and not set it off correct? Regardless of if the frontpipe is with or without a cat?

With all things considered, I imagine deleting the cat in the header would ultimately provide more gains and more sound than deleting the cat in the frontpipe?
getting rid of the cat in the header, it would definitely throw a CEL and there is absolutely no chance of passing an emissions correct?

I've noticed that some people go with a catless header and a catted front pipe, is this to reduce rasp+refine the sound more? and not so much for emission/legal purposes? A catted frontpipe with a catless header will definitely throw a CEL and there is not really a chance to pass emissions no?

Now let's say one were to run an aftermarket catted header, catless frontpipe. this would prevent a CEL, but would it be good enough to pass emissions having a catted header and catless front pipe?

I'm looking to run an invidia headerback (n1 catback, frontpipe, overpipe) to my stock headers for now... just having a bit of trouble on deciding on what to do about the frontpipe cat and the header cat for the future...

I'd like to retain the continuity of manufacturers and keep the same manufacturer through the whole exhaust best I can but I noticed that the berk high flow catted front pipe is most cost efficient while the invidia high flow catted front pipe is almost 2x the cost of the berk. I am leaning more towards a catless frontpipe for this reason...

currently running a berk dual tip muffler delete with everything else stock
i imagine the invidia n1 catback would be quiter than my muffler delete?
now the invidia n1 catback with a catless front pipe or high flow catted front pipe, would this be louder/quieter than my current setup with just the berk dual tip muffler delete?

also not planning any sort of tuning for a while

thoughts?

I think you should read this sticky: http://www.ft86club.com/forums/showthread.php?t=81493

awesome article, but will a car say with a tune and "JDL" headers and stock front pipe with cat pass inspection. that is the only thing i didn't read anywhere or i skipped over it

That's generally correct. A catted header usually will not throw a CEL (but as pointed out in a post below mine, some catted headers still throw a code occasionally).

It seems that way re power. Not sure about sound.

States vary in their inspection procedures. In Texas, newer cars are only OBDII tested. That means they connect to the ECU and make sure all emissions-related systems are reporting "Ready." An active CEL means one system is reporting "not ready" and is an automatic fail. HOWEVER, if you get a tune to go with your catless header, it will disable that CEL code and your systems will report as normal.

Bottom line is catless header + tune = passing emissions (generally).

Most of the power gains are from removing the header cat, so that's the popular choice. Running a catted header + catless FP is only really a good idea if you plan to go without a tune (which is not the best decision). You are correct that leaving a cat in the FP will quiet the exhaust and reduce rasp.

Again, states vary on emissions. In most counties in Texas, eventually our cars will be subject to a sniff test, in which case going 100% catless would mean a failed inspection. In addition, some states do a "visual" inspection of your emissions equipment. An observant inspector might potentially notice that you lack a cat in the FP and fail you. Of course, if your FP or MP has a resonator, that might look enough like a cat to be OK. Or they might not even look. Bottom line is it's a gamble to go 100% catless.

Also, going 100% catless will cause your exhaust to smell like gasoline fumes. Not really pleasant.

Bottom line is it's probably best to leave one cat, and because you get the most power from a catless header, it's probably best to have a catted FP.

Again, it depends on the state. It would probably pass a sniff test. Like I mentioned above, a particularly fastidious inspector might have a problem if he sees a lack of cat in the FP.

You're most likely fine with a catted stock header with a catless FP. Down the line, though, I think the best plan is catless header + catted FP + tune. That way you get the power gains without the gasoline fumes or CEL.

When it comes down to it, the FP is just a pipe. The diameter matters more than who makes it. Just try to match the diameter of the OP and MP.

The N1 will be quieter than a muffler delete, yes. I don't have personal experience, but I know the N1 can be quite loud when paired with other exhaust mods. I'd imagine the N1 + catless FP would rasp and be a little obnoxious. I would suggest going with a catted (and maybe even resonated) FP for now and planning on going with a catless header + tune when you're ready.

That's fine; you don't really need a tune for exhaust. But once you get a header (catted or no), get a tune, even an OFT OTS.


JDL catless header + stock FP would pass an OBDII inspection if you have a proper tune.

ah, visual inspections would be easier to inspect a front pipe as opposed to inspecting the header because of the panels underneath right?

would a high flow catted front pipe no resonator be quieter than a cat delete front pipe with resonator?

do catalytic converters muffle sound more than a resonator does?

I wonder if anyone has compared HF cat real efficiency, as to what actual resulting emissions content is after all these aftermarket cats, wherever in exhaust path they actually might be placed. Is one HF cat enough? If not - are two enough? (for real work cleaning up / burning excesses, not just to be there for visual checks). Are HF cats of specific CPI enough to match stock? Do they still are less resistant for airflow even if of maching efficiency?
Also if stock tune adresses heating up cats for better emissions during cold starts .. maybe there could be made some tune targeting emissions for use during checkups with even underperforming cat configuration? No clue on what principles it should be tuned by. By limiting rpms even at WOT? At some specific richness/leanness? Such 'legal' tune could also limit max noise at that :)

Most HF cats perform just as well as stock cats. I replaced a cat in my ole e30 w/ a hf cat and passed emissions in CA no problem.

As for legality, it's illegal to move any OEM cat. As for enforcement of this law... varies by state.

Warm up... who cares? after driving for a few minutes, you'll be up to temp and good for emissions. No emission testing that I know of checks a true cold-start.

Tunes should all work for emissions. tunes only dump fuel on WOT usually, and emissions are tested (afaik) at set speeds, not under WOT acceleration, and not at high RPMs. Running lean is bad for emissions too.

That's the theory. Of course it's case by case.

Actually, I don't know. I think a cat does more to reduce volume, while a resonator is more to manage rasp and drone. But that's just speculation.

Yes, cat will reduce volume more than a resonator. A resonator is just that, it resonates sound waves and will cancel some out, etc. A cat will completely disrupt the sound waved due to the structure of the cat, so it'll really reduce sound by a lot.

Not always the case people still throw P0420 even with catted header.

http://www.ft86club.com/forums/showt...52835&page=105
http://www.ft86club.com/forums/showt...52835&page=106

only sure way is to disable that CEL code in ECU

Thanks; I edited my response. Didn't know about the CEL with a catted header. Kinda defeats the purpose, doesn't it?

Edit: looks like a lot of the people getting CELs with a catted header were running the OFT OTS stage 2 tunes, which are designed for catless headers. Wonder if that was the problem...?

can't decide between the high flow catted front pipe from Invidia or berk or the resonated front pipe from Invidia...

My Fujitsubo catted header threw a CEL code.

-alex