Nissan XTerra Forum banner
1 - 20 of 20 Posts

·
Premium Member
Joined
·
306 Posts
Discussion Starter · #1 ·
I suspect variations of this question have been asked in the past, but I ran a search and didn’t find anything with anyone using the downstream CEL eliminator contraptions to eliminate the Check engine light coming on. Was wondering if any of the more modded users here have used them, and if so what side-effects (if any) were noticed. The upstream ones are in my opinion, the more important ones and you dont want to mess with the input the ECU gets from them since that is directly affecting the air/fuel mix. Unless things have changed in ECU inputs, the downstreams were mostly just for emissions purposes and gauging how effective your cat converters were doing their job. I have seen many people mentioning they were running gutted converters or straight piping after the headers. I’m referring to Gen2 models if there is any difference than the Gen1. So long way of asking, those with gutted converters, are here any adverse side-effects to your performance?
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,928 Posts
I am but on a Gen 1 truck and the 2000 model was different than later Gen 1 trucks as it only had 2 cats.

Excuse the 10+ year old bad drawing but this is the OEM exhaust on my truck.




Long tube headers once installed are the length of the Ex manifold and Cat combined. So in order to run long tube headers the Cats need to be eliminated or relocated, I eliminated. Note that the first O2 sensors are installed at the inlet to the Cat, pre Cat, and the second set of sensors are in the down tubes, post Cat.

First O2 sensors location in the inlet to the Cat. Left side of pic is forward facing.


So Ex manifold and Cats are gone replaced by long tube header. I have a set of emulators installed in the factory location for the second set of O2 sensors. Runs fine, no codes and no CEL. Is the AFR correct? No it’s not and on a Gen1 truck no real way to fix it. Basically the emulators pull the second set of O2 sensors so far out of the Ex stream that they think the Cats are still there doing there job.

The emulators I used from AC


Emulators installed in factory down tubes
 

·
Premium Member
Joined
·
306 Posts
Discussion Starter · #3 ·
Thanks! And your drawing is leagues better than mine would be :p

Have you hooked up an A/F meter to gauge it? I thought that the A/F mix was dependent on the pre-cat O2 sensors (front ones) for attempting to meet stoichiometry, and the rears only measured whether or not the cats were functional and efficient? Do you think you are just dumping a lot of extra fuel into the engine? I mean otherwise does the X run the same, better or worse. I did read another post here where someone was pretty vocal about being against straight piping for environmental reasons, and I respect everyone opinions or their reasons….. however honestly you do you and let me do me :) I am simply exploring the mechanical and performance benefits or detriment to making such a modification. If my locale cared so much about it, they would have us doing emissions which they do not, and removing cats in my opinion is one less thing to go bad on my X and one less thing I have to spend money on, and if I can get a few ponies out of it all the better!
 

·
Registered
2004 Xterra XE 4WD Auto 3.3L NA V6
Joined
·
1,658 Posts
I've been giving this same subject some thought lately, so I appreciate you asking the question.

If my cats fail, my current thoughts are to find equal-length headers and try to find new cats just so I don't have to wonder if I'm dumping too much gas into the exhaust. This kills 2 birds with one stone by getting rid of the less efficient log-style manifold and tuning the exhaust for better flow. I'm still not fully in that camp yet, but I'm also not digging in my heels to resist it, either.

I'll keep following this thread as it seems to have promise of good info to come.
 

·
Premium Member
Joined
·
306 Posts
Discussion Starter · #5 ·
I mean if by eliminating the cats creates a running-like-butt-sauce condition then I’ll replace the cats lol but I’m just going on my former track days and removing cats and using some sort of device to trick the downstreams would create more power albeit destroying gas mileage…. But who gives a crap about gas mileage anyway :p
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,928 Posts
Have you hooked up an A/F meter to gauge it? I thought that the A/F mix was dependent on the pre-cat O2 sensors (front ones) for attempting to meet stoichiometry, and the rears only measured whether or not the cats were functional and efficient? Do you think you are just dumping a lot of extra fuel into the engine?
I have not hooked up a wide band, I have one just never hooked it up. IIRC I think I can see the A/F on my scan gauge and I want to say 14.5 maybe? Of course I have no clue what the target A/F the ECU is trying to maintain.

I mean otherwise does the X run the same, better or worse.
My truck went from stock to headers, no Cats, emulators, and a Nismo Cat/back system in one step and yes it ran much better. Slightly better mid range and much better top end. Fuel economy was better as well.
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,928 Posts
I've been giving this same subject some thought lately, so I appreciate you asking the question.

If my cats fail, my current thoughts are to find equal-length headers and try to find new cats just so I don't have to wonder if I'm dumping too much gas into the exhaust. This kills 2 birds with one stone by getting rid of the less efficient log-style manifold and tuning the exhaust for better flow. I'm still not fully in that camp yet, but I'm also not digging in my heels to resist it, either.

I'll keep following this thread as it seems to have promise of good info to come.
My main reason for headers was to replace fractured OEM Ex manifolds. The kicker with the Gen1 manifolds is once you replace the broken ones the replacements will eventually crack as well. No thanks headers it is.
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,928 Posts
I mean if by eliminating the cats creates a running-like-butt-sauce condition then I’ll replace the cats lol but I’m just going on my former track days and removing cats and using some sort of device to trick the downstreams would create more power albeit destroying gas mileage…. But who gives a crap about gas mileage anyway :p
Runs fine with the above set up. Runs even better now with the addition of cams, HD springs, porting, and a proper 3 angle valve job. However it is still not 100% correct as there is no way to re-map a Gen1 ECU short of MoTeC, Magneti Marelli, Mega Squirt, or one of the other stand alone engine management systems. 15 to 18 MPG, better power all through the RPM range, and no CEL. It’s a 5500 pound offroad rig in my case not a tuner car so a stand alone ECU I just can’t justify at this time when it runs good with these mods.
 

·
Registered
2004 Xterra XE 4WD Auto 3.3L NA V6
Joined
·
1,658 Posts
My main reason for headers was to replace fractured OEM Ex manifolds. The kicker with the Gen1 manifolds is once you replace the broken ones the replacements will eventually crack as well. No thanks headers it is.
I've read on here about the stock manifolds cracking, so if I were to replace the cats, I'd just whack it all at one time and be done with it.

I have not hooked up a wide band, I have one just never hooked it up. IIRC I think I can see the A/F on my scan gauge and I want to say 14.5 maybe? Of course I have no clue what the target A/F the ECU is trying to maintain.

My truck went from stock to headers, no Cats, emulators, and a Nismo Cat/back system in one step and yes it ran much better. Slightly better mid range and much better top end. Fuel economy was better as well.
Would you be able to share any suggestions on where to acquire the headers and cat/back? Mine is the 2004 VG33E, so all of the parts are likely the same. Is there room for cats if that's what I wanted to do, or are the headers so long that the cats would be forced to hang too low and be at risk of damage when off-roading?

@RacerXXL, thanks for your input, I really appreciate it.

@DickyDck, thanks for letting me jump in. If you'd rather I started my own thread, just say so.
 

·
Premium Member
Joined
·
306 Posts
Discussion Starter · #10 ·
I have not hooked up a wide band, I have one just never hooked it up. IIRC I think I can see the A/F on my scan gauge and I want to say 14.5 maybe? Of course I have no clue what the target A/F the ECU is trying to maintain.



My truck went from stock to headers, no Cats, emulators, and a Nismo Cat/back system in one step and yes it ran much better. Slightly better mid range and much better top end. Fuel economy was better as well.
your headers, custom made or does someone actually mass produce them?
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,928 Posts
Would you be able to share any suggestions on where to acquire the headers and cat/back? Mine is the 2004 VG33E, so all of the parts are likely the same. Is there room for cats if that's what I wanted to do, or are the headers so long that the cats would be forced to hang too low and be at risk of damage when off-roading?
I have the following parts installed for my headers
4x4 Parts - Xterra Headers PPAC0004XHD3.0NSC - Your #1 Source for Nissan Aftermarket Parts!

4x4 Parts - Check Engine Light Eliminator PPACCELELIMX - Your #1 Source for Nissan Aftermarket Parts!

They also carry the Doug Thorley headers that were not an option when I purchased mine. The Thorleys are a bit nicer finish than the ones I went with.

Is there room for the cats? Certainly cut up and installed in the downtubes I would think plenty of room there. Just going to have to extend O2 sensor leads.

Catback system you got me. 11 years ago this guy shows up on eBay with a stack of Xterra and Fronty SS catback exhaust systems. IIRC he wanted $300 each for them really good price he finally gets pics up and it turns out they were NISMO, Nissans motorsports division, systems. Hi quality, hi performance, well designed, and pricey. So for $300 they went quick. Turned out he had bought them in a lot from a warehouse fire and the packaging had been water damaged but actual NISMO systems they were. NISMO no longer produces these systems


your headers, custom made or does someone actually mass produce them?
See link above or search for Doug Thorley headers.
 

·
Registered
2004 Xterra XE 4WD Auto 3.3L NA V6
Joined
·
1,658 Posts
Thank you, sir!

I took a gander at the link and was a bit disappointed that the first headers were listed as "Sold", but at least the Doug Thorley headers are still available. Based on their comments, it'd probably be easier and better to run without cats on them.
 

·
Registered
Joined
·
152 Posts
MeToo, you've seen my 04 in person, with the long tube headers, etc installed. It runs quite nicely, and, after choking on $300 worth of upstream O2 sensors (both were crap), my mileage in that beast has increased from about 11 mpg to not quite 16, at Interstate speeds. My son is already looking at getting the same for his "just acquired" 01 Xterra, since the passenger side manifold is, indeed, cracked.
 

·
Registered
Joined
·
12 Posts
I suspect variations of this question have been asked in the past, but I ran a search and didn’t find anything with anyone using the downstream CEL eliminator contraptions to eliminate the Check engine light coming on. Was wondering if any of the more modded users here have used them, and if so what side-effects (if any) were noticed. The upstream ones are in my opinion, the more important ones and you dont want to mess with the input the ECU gets from them since that is directly affecting the air/fuel mix. Unless things have changed in ECU inputs, the downstreams were mostly just for emissions purposes and gauging how effective your cat converters were doing their job. I have seen many people mentioning they were running gutted converters or straight piping after the headers. I’m referring to Gen2 models if there is any difference than the Gen1. So long way of asking, those with gutted converters, are here any adverse side-effects to your performance?
Yeah you have four catalytic converters on the exterior your front and rears I took off my rear caps and unplug the sensors too cuz all they are just verifying the fronts doing the same and you got more horsepower as loud little bit sounds a little tougher as long as you put some flex pipe where you cut the beers off but leave the fronts
 

·
Premium Member
Joined
·
306 Posts
Discussion Starter · #16 ·
Stopped by the shop that is working my transmission, seems someone robbed my cats and they are ordering new ones…. Wish they would have called me since I would have just gotten straight pipes instead.
 

·
Administrator
2000 Xterra XE 4x4 3.3L AT
Joined
·
9,928 Posts
Stopped by the shop that is working my transmission, seems someone robbed my cats and they are ordering new ones…. Wish they would have called me since I would have just gotten straight pipes instead.
Man the cat theft is out of control. They hit all four of our service vehicles at work last weekend.
 
1 - 20 of 20 Posts
Top