I was looking on SLR today and noticed that they have headers for the xterra...anyone have these or know aobut them? are they worth the money or is any of that stuff worth it (ie. throttle body etc...) any input would be appreciated.

Last I heard about those was that someone bought them and found out they had some extra holes in them (not the kind you want) and returned them.

I have not heard of anyone else getting them.

I'm sure everybody knows about those headers being "offroad use only"... Also, the headers take away the pre-cats, which hasn't been factually proven (not that I know off) as a necessary part to keep emissions down, but most probably is. I noticed how alot of VG33E owners are a little skeptical about emissions when it comes to those headers, mainly due to the lose of the pre-cats. But I got a question for you emission guys out there...

If you used the headers, could you buy a cat that would do the pre-cats job, and the cat's job?

Essentially just running an exhaust system with

- headers
to
- (2)catalytic converter's (one that could act as a pre-cat and normal cat, enabling you to pass emissions)
to
- dual exhaust

I'm sure the power gains would be tremendous, all we need to do (as a community of truck owners) is push some company to produce headers that actually work, and research high-flow catalytic converters that would work with the headers.

I never seem to understand why so little people are willing to bump the hp on the Xterra. We allready have a online website devoted to this truck, we might as well give it our all in every aspect eh?

It is against federal law to remove the factory cats, unless they are not working, and then only to replace them. That is one of the reasons headers that force you to remove / relocate the factory cats are scarce to nonexistant. Other trucks / cars that the cats are mounted differently can use headers, as there is room for them without messing with the factory cats.

The cats that are displaced by the SLR headers are NOT the pre-cats, they are the PRIMARY cats. The 2000 model year had 4-cat (California-emissions) and 2-cat (Federal emissions) versions, and the 2-cat ones had the same upper/primary cats and were missing the secondary/lower cats.
There is a Frontier owner in PA that has them and has no problems. That is the only other owner that I know of that has him other than the one here that had problems with his.

So the guy with the Froniter in PA uses the SLR headers, and has no problem with emissions? So with the headers he replaced the PRIMARY cats, but the secondary/lower cats were enough to pass federal emissions... Wow, so were all running at California emissions?

Then putting on the SLR headers should be alot bigger power increase cause were also removing 2 cat's. I'm stating the obvious because I'm confused as to why more people aren't getting these headers? Other than the uneeded holes (which can be fixed), what else is stopping us from using this?

Nothing...except the snot to be one of the first known guinea pigs to spend the money and try them out...

I don't know what sort of emissions testing (if any) they have in PA. If it's just a sniffer test, it may well be possible for a properly-running engine to pass the test without cats in the first place, and he's getting by. However, if they do any visual inspection, he'd be up a creek.

The secondary/lower cats have nothing to do with passing any sort of emissions. Nissan now builds all their vehicles to the California emissions specs.
I don't know if he kept them in place on his truck or not, but it's a 2001 or newer and would have had all 4 cats before the headers were installed.

SLR changed the supplier/builder of the headers after the one that the member here (perna as I recall) bought and found to be defective.

Would a vehicle inspector know that a Nissan would have 4 cat's though? I'd think that a vehicle inspector would simply look at the exhaust for 2 cat's, and find them, not try to search for additional cats in the headers.

Is their any other things I'm missing out on? I feel like I'm beating on a dead horse for raising this header subject, but I simply don't understand why were not taking advantage of this situation to add some roar to the engine, and some horses to the wheels. That's the whole point of this section...

I would prefer not a harsh response, but a long drawn methodical use of words from a source on this site that holds the rank for this kinda of response.

I have a 2000 but I'm not sure how many cats I have. I will crawl under there today and take a peak.

They just started doing emission testing last year in upstate NY and I don't remember them doing anything other than a sniff test. I don't think a non-Nissan mechanic has any idea how many cats are under there.

OK, just so everyone knows, Federal emissions Xterras don't have 4 cats.

If you crawl under the X and look at the exhaust, up by the exhaust manifolds, you'll see 4 parts.

The first part (1 on each side, bolted to the manifold) is the actual cat. It is the only cat (1 per side). Verified by the fact that the O2 sensor that you can see from underneath is the rear O2 sensor. That sensor is for diagnostics of the cat only, and does not control fuel mixture like the first one does (the one you can see from inside the engine bay).

The other big piece of metal that you see (sure looks like a cat) isn't a cat, but is in fact a pre-muffler for the exhaust.

That's all it is. You can take that piece off and put in a straight pipe (I'd reccomend going to the size of the exit hole for the cat) and it will not affect your emissions or throw a code!

The Law for the cats is meant to state (in layperson's terms) that removal of the cat for the purpose to run the vehicle on public streets is unlawful. If relocation of the cat is the purpose, and the primary function of the cat is not circumvented, then relocation is acceptable. But remember, you'll have to relocate the rear O2 sensors to behind the relocated cats in order to maintane the function of the diagnostics of the X. You'll have to leave the front O2 sensors where they are, as they need a lot of heat to function. Their placement is critical.

If you do relocate the cats (or go to a big one, like on the older Chevy trucks [3" in and 3" out!]) then you may have to add an air pump to the system to get the cat up to operating temp and keep it there. Just like the old Chevy trucks.

Relocating a cat isn't something that you 'just do' one day. It's a process and you should know what you're doing. Not taking the extra steps into consideration can lead to emissions failure due to a lack of follow-through.

But if you're willing to perform the necessary tasks, then by all means, you should see some performance gains from a set of headers, opening up the exhaust system with a nice exhaust system and bettering the intake. Especially the S/C guys.

So you're saying this is not a cat of any sort?


( Link to Ebay listing if the photo doesn\'t work )

So all that the California (and MD, ME, and a few other Northeast states) in 2000 got was a "pre-muffler" that would do nothing to affect emissions?

Here are 3 photos from the 2000 service manual showing the exhaust system from the manifolds back:

http://mywebpages.comcast.net/xterra/tech/EngineCats.gif
http://mywebpages.comcast.net/xterra/tech/FedExhaust.gif
http://mywebpages.comcast.net/xterra/tech/CalExhaust.gif

I do note that they don't refer to the part in question as a catalyst, just a "front tube" for both Fed and Cal versions, but if it doesn't do something for emissions, I don't understand its purpose.

Either way, the SLR headers displace the important part, the "secondary" cats or whatever they are can be done away with no problem, but that doesn't get us anywhere.

Brent

Xterrible, that pic is of the front tube, which is basically a muffler (expansion chamber). It does nothing for the emissions, as in, it's not a cat.

We don't get many California Emissions vehicles here in Colorado, so I can't say with 100% certainty that this part isn't a cat in the Cali trucks.

But everyone that has a Federal Emissions vehicle, can yank 'em. Just be sure to weld a bung for the sensor at the front there, just like in your pic.

wow, thanks Cyclemut for the response, it really did clear up alot of things in my mind. So essentially, the quick and easy way to upgrade the exhaust system is simply to remove those "cat's" (pre-muffler's), and just make it straight pipes. Would I need to incorporate those O2 sensors after the actual cat?

Removing/replacing that portion still doesn't take care of the problem with the SLR headers displacing the primary cats.
Even if the part shown above is actually a secondary cat on the California/etc. 2000 and all 2001+ models, removing them would be inconsequential, the engine and emissions system would be oblivious.
The rear 02 sensors that go into them are also useless, they're only there to detect if the primary cats fail. You can buy "dummy" rear 02 sensors to connect in place of the ones that go into the part shown above and not have to worry about ensuring whatever replaces that portion of the exhaust has bungs for the rear 02 sensors.

Anyway, we're no closer to making an emissions-compliant installation of the SLR headers happen...

Brent

Actually Brent, we are.

If someone wanted to put on the extra cat later on downstream in the system, and wire in the sensors, then it would be perfectly legal.

Yes, you would need to put in an O2 sensor bung about the same place as the one shown in the picture above to get the rear O2 sensors to read correctly.

Nissans don't like the O2 sensor simulators, as Nissan has a logic built into the programming that the sims can't duplicate. What happens when the sims are acting like the vehicle is fully warmed up and it's still on cold idle? The computer throws a code. Or when the evap system decides to purge and the cats react to it? Sims can't and won't duplicate the real thing.

We've seen so many sims on the SpecV Sentras and 3.5 Alty's fail to correctly simulate that it's not even funny any more.

Hmm, interesting about the sims.

Moving the cats further downstream is always an option, but they would have to be aftermarket.

I am reviving this thread because i can't take reading 30 threads to get one piece of information.



So, it took two pages to decide what enthusiasts for all other major car brands have been doing for ages. Thank you to Cyclemut for clarifying what each of the parts is for and telling us all what needs to be done. The Corvettes (LT1 cars) had a very similar problem and you could only (until recently) put shorty headers on them because of this. It is not rocket science here and i truly believe that headers will make a huge power gains coupled with exhaust and intake on my 2003 supercharged. So, in short, i need to keep the primary o2 sensor on the header, install the cat immediately after this, then have a custom exhaust shop fabricate the rest(since the aftermarket pre-fabs won't bolt up any longer) and weld in a bung for the secondary o2 sensor which is to remain stock as the sims don't work well. sheesh....