Here you go... On my truck, it looks like I have this 'pre-cat' but not on the passengers side.

Drivers side


Passengers side without...


The drivers side cat


Passengers side...

Does anyone have the description from the ESM?

I just took a look in the ESM for the 2000s. I swear to god I don't see any cats anywhere in the exploded exhaust diagrams except on the 4 cylinder model. It looks like the O2 sensors screw right into what is just a plain old exhaust pipe.

Obviously, we do have cats so I conclude that I am missing something important here.

The ESM doesn't seem to ahve anything helpful...I looked too.

Stormy, you're photos are good, but show what are the only cats for 2000 owners (except California). We don't have the ones down lower at all. Also, you indicate that there isn't one on the right side but it is shown very clearly in your picture. The main thing is that for 2000 we only have cats attached right at the manifold and nothing downstream. The cats at the manifold are displaced by the headers. So it looks like we would either need to go to the 2001+ setup or come up with another solution.

I was talking about the pre-cat. This is a picture of the passengers side. It is pointing to a 2-1/4 (give or take) pipe. That is just a heat shield.

But the cat is under the shield just like on the other side. In the upper right of your photo I can see the first oxygen sensor and then the pipe widens there and becomes the cat. Just like on my truck it sits in very close to the engine. It does appear that it might be slightly smaller than mine though? Damnit; now I'm gonna have to go look again! :rolleyes:

Anyway, the cat is in there, just covered a bit.

Some of us back east have "California" emission equipment too. I have upper and lower cats on both sides. The uppers are cylindrical and only a bit larger than the pipe they're inline with. The lowers are where the exhaust system makes the bend to run along the bottom of the truck.

The O2 sensors are fore and aft of the small upper cats, meaning that they are the main ones.

I just checked my ESM and under my hood (2002). What is shown on page FE-12 of the ESM is two TWC (Three Way Catalytic Converters), one on each side. They each have an O2 sensor plugged into them. So much for adding headers on California 02 Xterras.

-Doug

Ok, I've got it now. On my 2002 there are two canisters up close to the engine block. They appear to be about 5" in diameter. These must be the "pre catalytic converters". Then there are two more more traditional looking units down underneath the vehicle on each side of the front drive shaft. These are the must be the "secondary catalytic converters". From reading the SLR information, the headers replace the manifold and pre cats back to the flange just in front of the secondary cats.

That seems like a reasonable setup to me. Whether or not it'll pass emissions is another question. I'd think it would pass fine, but can not be positive.

At $475 and ceramic coated, these headers are a good deal. The ones for my 3.4L V6 Tacoma were nearly $700 plus about $1000 to install them. I never did bite the bullet on those.

One thing someone with an ECM will want to look at...where does the air conditioner drain drip the condensation? If it will drip on these headers, that might be a problem. Several and by several I mean about 25% of the guys I knew who bought the Tacoma headers had them crack after the first year. Many believed this to be due to the a/c dripping on them. The whole "hot cold hot cold" thing. They always cracked right where the condesation would drip on them.

I'd love to get these headers. $475 is a good price. I think SLR needs to get CARB approved for this to be successful. Also, with them being stated as "off road use only" that probably means they also have NO WARRANTY. That's something else to explore AND get in writing should you decide to buy.

Who's up for being a guinea pig??

Wouldn't exhaust wrap or tape help that? It would keep the pipe cooler.

It might have. It was basically a design flaw. They had the collector placed directly under the a/c drain. The pipes would get hot from exhaust, then the a/c would drip cold water on them. Over time this cracked them right at the collector.

That clear it up?
Brent

Yep. Too bad they don't label what those secondary "cat looking" things are. I wonder now if they're even cats? They might be sound dampeners or resonators.

No, they are secondary cats. I'm not really sure why they are necessary, but they are there. Normally, a secondary cat is suppose to clean whatever is remaining after the main cats, but the function of the main cats is to clean up small amounts left after combustion. If the other emission controls are functioning properly and the engine is maintained there should not be much even hitting the primary cats so really the secondaries shouldn't be doing anything at all.

What i'm still unsure of is how much workload the secondary cats can take. If their normal duty is to clean up remains then what happens if they are the first line of defense? Can they handle that?

The bottom picture is showing no lower cat. does that mean I have a CA emmissions truck

Every 2001 and newer Xterra has all 4 cats.

All 2001's and newer have the lower cats and meet the same requirements.

A very good question. Someone will need to be the guinea pig. $475 is a STEAL for a set of headers!

They updated their web page, and SLR is saying that the 2nd set of cats are the main ones, and the first set are pre-cats. They also updated with some other info and say installation directions are coming soon.

I bought my X a couple of months after it came out in Missouri so it probably has (2) cats. So what you guys are saying is I would need a custom job to fit the cats further downstream? How much would it cost to do all of this?

SLR is still wrong...

I bought them. I tried installing them today but it didnt go very well, couldnt get the bolts off the cats or manifold no matter what I tried. am going to buy an impact wrench tommorow. It was asked if it is a DIY job, well depends if you want to take alot of things off you truck. Took me 5 hours to get to where I could even get to begin to take off the manifold and cats. You have to put your truck on jack stands take off the front tires, remove the rubber mat and get in the engine compartment through the wheel wells. have to remove heat shields to get to all the cat nuts and manifold nuts, out of all the nuts I broke 1 loose by hand and my truck was made in Aug., but hopefully an impact wrench will fix that.

http://members.tripod.com/~Perna/pics.html

Soak down all the nuts liberally with WD-40 for 24 hours prior to removing the exhaust system nuts and bolts. It will make it a much easier job.

try sticking a metal pipe at the end of your wrench, it'll give you the extra leverage. btw, does look like a bolt-on project or do you have cut & weld?

perna,

Try Axle's tip before you take an impact wrench to the exhaust and manifold bolts. A good soaking with a penetrant does wonders. There is nothing worse than snapping off a fastener; especially a stud. As a last resort I've used a small propane torch (AKA "Heat Wrench") to free really bad fastners on the suspension, frame and exhaust. Use extreme caution and common sense when applying this technique!!!!!!!!!! Darwin is always watching!! I only do this outside with fire extingishers close-by and after checking the area in relation to any systems and their corresponding lines;ie: fuel, electrical, etc...