VW Vortex - Volkswagen Forum banner
1 - 20 of 54 Posts

·
Registered
Joined
·
2,199 Posts
Discussion Starter · #1 ·
I just got back from a test and had a 1.8582 on NOx Values. I need a 1.5 to pass so I guess I'm not too far off. From what searching I've done people suggest something as simple as changing the oil. I'm on about 4k Miles on my current change 040w Mobil 1 so I could try that to see if it helps. I usually change every 5k miles. I also have pretty new plugs gapped at .28, air filter is clean and was running 91 octane 7-11 Gas. I have an aftermarket TB exhaust/high flow cat.

Some other suggestions were to check the EGR, run a little bit of E85 (don't like this idea), run higher octane. I have a full APR program load 91,93,100. Not sure how to check the EGR but don't think I shouldn't have to since I'm failing my just a little. Other suggestions included getting the car heated up pretty good before the test. Any other ideas?

Also note>

I've been having an issue where my car throws a Oxygen Sensor Code P0420 code for over a year now. It used to only come on when it was really cold with wet roads. Now the code will randomly come on in any weather. I usually just clear it but it's coming on to often now. I don't notice any performance issues or gas mileage problems. I have an aftermarket exhaust/high flow cat. I wasn't throwing this code when test was done. I think if you have a CEL on they fail you anyway.
 

·
Registered
Joined
·
2,010 Posts
I have an aftermarket exhaust/high flow cat.
This is most likely the cause of the high NOx readings. In addition, the P0420 is a cat efficiency code. Basically, the computer is saying that the cat isn't really changing the exhaust stream chemistry that much.

Re-install the factory downpipe for the emissions test and then go back to the high-flow part after you pass. If you don't have the factory DP consider getting a good quality cat, cut the ****ty one out and weld-in the new.
 

·
Registered
Joined
·
614 Posts
I just got back from a test and had a 1.8582 on NOx Values. I need a 1.5 to pass so I guess I'm not too far off. From what searching I've done people suggest something as simple as changing the oil. I'm on about 4k Miles on my current change 040w Mobil 1 so I could try that to see if it helps. I usually change every 5k miles. I also have pretty new plugs gapped at .28, air filter is clean and was running 91 octane 7-11 Gas. I have an aftermarket TB exhaust/high flow cat.

Some other suggestions were to check the EGR, run a little bit of E85 (don't like this idea), run higher octane. I have a full APR program load 91,93,100. Not sure how to check the EGR but don't think I shouldn't have to since I'm failing my just a little. Other suggestions included getting the car heated up pretty good before the test. Any other ideas?

Also note>

I've been having an issue where my car throws a Oxygen Sensor Code P0420 code for over a year now. It used to only come on when it was really cold with wet roads. Now the code will randomly come on in any weather. I usually just clear it but it's coming on to often now. I don't notice any performance issues or gas mileage problems. I have an aftermarket exhaust/high flow cat. I wasn't throwing this code when test was done. I think if you have a CEL on they fail you anyway.
Get the car heated up really good? That's stupid advice. NOX forms due to high cylinder temperatures. By the way, I don't see that you are failing "just a little". My math says you're 23% higher than the limit and you are probably worlds higher than a normally functioning car.

Deal with the oxygen sensor codes. Figure out what the problem is there. If you're running lean, that would explain the high cylinder temps, and would put on track to solving the issue.

And don't rule things out, until they've been ruled out for a reason.
 

·
Registered
Joined
·
2,199 Posts
Discussion Starter · #4 ·
TheBossQ,

Ok, I guess I'm failing by 24%. It just seem didn't that bad looking at the numbers. I just talked to a friend that works at a Dealership and he mentioned that that their is a potential software update the might fix the P0420 code my engine throws. Apparently their is a TSB out that has to do with a cold engine misfire causing the computer to mis-throw a P0420 code. He said the dealer can't do the update since it might mess up the ECU programming. He knows that I have a TBE and thinks I should talk to the shop that did my APR programming to see if they're aware of this software update that might have to do with this Catalytic converter error code.

Also, what's strange is the guy ran my car for twice the normal time. It says on the video that the test can last upto 4 minutes. Well, he went at least 8 minutes on my test. I know because the people that came in after me finisher first in the other row. Seemed kinda strange. I talked to my friend that recently failed on his older truck and he thought the guy doing my test noticed I failed so tried a second run? Not sure since the guy that ran the car was different than the guy that gave me my paperwork saying I failed. Sounds like you're saying the cooler my car is the lower my Nitrous Oxide (N0x) levels will be. Right?

Either way, I'll probably talk with the shop that did my tune to see what they suggest about a potential update that won't affect my current software load. Hopefully that might fix my occasional P0420 code and lower N0x levels. I'd like to get the car VAG-com scanned also.

Blackfin

I don't want to remove the factory downpipe or mess with the exhaust or anything unless absolutely necessary. I've had this exhaust on for years and I passed the Drive-By monitoring test they have on the sides of the highways the last few years. I didn't pass enough of those drive-by testers this time I had to go in for the test. The only other mod I've done since I passed last year was a Turbo Inlet Pipe. This couldn't of caused that big of a change in N0x levels.

Thx you both for these Ideas/tips.
 

·
Registered
Joined
·
897 Posts
NoX is NOT Nitrous Oxide it's Nitrogen Oxides, what contributes to acid rain or more commonly called SMOG. It's true that it is caused by excessive temperatures, around 1300 degrees and up. What's causing it in your car is a combination of a small leak pre 02 sensor, most likely at the manifold to turbo connection or turbo to cat, and the presence of a high flow cat. Oxygen is pulled in through the small leak and mixes with the exhaust stream causing the temps to climb in the cat and thus causing NoX. The high flow cat is not converting the unburnt (and now diluted) exhaust mixture efficiently enough (because it is designed to not impede flow over catalyst efficiency by design) and the introduction of oxygen into the flow is causing the NoX. I would imagine if you fix the leak you would probably pass as you did before but the cat that's in your car now will not have enough catalyst material to last for a very long time. Usually a couple of years to maybe three is it, at least as far as my own experiences have shown.
 

·
Registered
Joined
·
2,199 Posts
Discussion Starter · #6 · (Edited)
NoX is NOT Nitrous Oxide it's Nitrogen Oxides, what contributes to acid rain or more commonly called SMOG. It's true that it is caused by excessive temperatures, around 1300 degrees and up. What's causing it in your car is a combination of a small leak pre 02 sensor, most likely at the manifold to turbo connection or turbo to cat, and the presence of a high flow cat. Oxygen is pulled in through the small leak and mixes with the exhaust stream causing the temps to climb in the cat and thus causing NoX. The high flow cat is not converting the unburnt (and now diluted) exhaust mixture efficiently enough (because it is designed to not impede flow over catalyst efficiency by design) and the introduction of oxygen into the flow is causing the NoX. I would imagine if you fix the leak you would probably pass as you did before but the cat that's in your car now will not have enough catalyst material to last for a very long time. Usually a couple of years to maybe three is it, at least as far as my own experiences have shown.
Yeah, I was reading this website and it was saying Nitrous Oxide levels. N0x Levels.
http://www.smogtips.com/failed-high-NO-nitrous-oxide.cfm On the sheet they gave me it just says NOx Readings. I just noticed on the sheet they gave me it says High NOx reading are the result of High Combustion Temperatures AND/OR High Combustion Pressure. I'm guessing this leads to higher EGT's and thus higher NOx readings. Like I mentioned the guy that did my car ran it for twice as long as other peoples in other lanes. This might of caused higher readings also. I'm thinking if I put my car in Limp Mode so that makes no boost it would lower the Combustion Temperatures AND/OR High Combustion Pressure quite a bit.

Appreciate your insight into what you think is causing my high levels. Sounds like your pretty accurate about this issue. I haven't really noticed any drop in boost pressure or noticed any exhaust leak. In the long run, I'm hoping I don't have to go through replacing to much to pass the test. From what you've mentioned I'm really thinking the High Flow Cat is the issue. I just checked my order on ECS website for Fully polished down pipe with high flow catalytic converter and that was back on 6/29/2009. So, I've had this pipe on for about 3 years. Do you think if I just replaced that with a new high flow catalytic converter it would lower my NOx levels? Imagine it would since a new high flow catalytic converter comes with enough catalyst material to pass again right? Again, I'm thinking if I turn off boost I'll greatly lower my readings. Any ideas if a VAG-com scan would show leak issues around my O2's? I can tell you the O2 by the cat looks nice and tight since I was recently doing some work on my car. Not sure about the one by the turbo. Thx
 

·
Registered
Joined
·
4,807 Posts

·
Registered
Joined
·
614 Posts
It's true that it is caused by excessive temperatures, around 1300 degrees and up.
At 1300, it should be noted you are referring to Celsius, not Fahrenheit.

Second thing to think about is that aftermarket catalytic converters come in different flavors. Most these days (even the high flow) are three way cats, but if your aftermarket cat is not a three way cat, it's going to do roughly jack for NOX. There are a number of Magnaflow race cats that aren't three way cats.
 

·
Registered
Joined
·
4,807 Posts
Hey, I've been throwing the P0420 code now for about 1 year. I haven't swapped out any of the O2's but was thinking I'd swap out the Rear one by the Cat to see if that helps with this issue. Any suggestions?

I haven't ever heard of this "cat balls" before but I have a very annoying rattle that has had me stumped for over a year now. I thought it might of had to do with the repairs that were done when someone hit me from behind but the body shop that did my work said it has nothing to do with the repairs they did. I'd like to believe them since they did good work. It seems to come from the Rear passenger side so it might not have to do with my CAT since it's on the drivers side. Hard to pinpoint driving down the road. Do you think if I had someone VAG-com my car I would be able to see which O2 sensor is throwing the P0420 code and potentially causing "Cat-Balls"? LOL. I have an aftermarket Milltek Cat-Back exhaust so I hope it's not the issue causing my rattle. I also had the exhaust shop double check my exhaust system and it's secure. This is the first time I've come across this cat balls. Also, what do you mean by the cell broke off? Thx for any/all info.

BTW, I just failed my Emissions test with slightly High N0x values so I'm hoping to get that fixed with the 02 issue(s).


Taken from another thread,

Its your cat, Replace it.


And please, post all issues with the car when trying to figure out one of them, it REALLY Helps. :wave:
 

·
Registered
Joined
·
2,199 Posts
Discussion Starter · #10 ·
http://forums.vwvortex.com/showthread.php?5479896-E-Test...-Exhaust-leak-Really

This may help... :)

I tossed so many spare parts that i had lying around from my swap into the beater, but i was finally able to get it to pass.

NOx is high temps, it can be caused by running lean, bad injector, bad cat/etc.

Good luck!
Nice/nice. Thanks for this info. You're situation was a little worse than mine but that's some good info. I'm betting that if I replace my High Flow cat that I'll pass. I'll probably just end up doing an oil change and then drop the boost and re-test. I'm guessing that I'm not running boost the N0x levels will get reduced quite a bit. I'm not trying to ruin the environment or anything so I'd like to get my levels lowered for good. But, I only have 10 days to get a re-test for free so I'll try the cheap route first. If necessary, I'll get the Cat replaced and have some sort of exhaust pressure test done or something. Someone local might assist with a VAG-com scan as well. Thx :thumbup:
 

·
Registered
Joined
·
2,199 Posts
Discussion Starter · #12 ·
No need for lowering the boost, most of the high flow cats are only good for so long.... And it's usually short time.
Yeah, you're probably right but this is my logic (found with google search):

NOx emissions levels are directly related to EGT's. Any increase in EGT will cause NOx levels to increase and the opposite if EGT's are lowered.

So, I'm going to contact ECS today about a new Cat but I only have 10days to re-test so I'll probably lower boost and give it a try after a fresh oil change. Besides, I think the guy that ran my car ran it for twice as long as he was supposed to and had the fan like 10 feet away from the car. Yeah, I think he was intentionally trying to fail me! :mad:
 

·
Registered
Joined
·
4,807 Posts
Yeah, you're probably right but this is my logic (found with google search):

NOx emissions levels are directly related to EGT's. Any increase in EGT will cause NOx levels to increase and the opposite if EGT's are lowered.

So, I'm going to contact ECS today about a new Cat but I only have 10days to re-test so I'll probably lower boost and give it a try after a fresh oil change. Besides, I think the guy that ran my car ran it for twice as long as he was supposed to and had the fan like 10 feet away from the car. Yeah, I think he was intentionally trying to fail me! :mad:
its up to the machine how long it takes, and the fan really wouldnt have that much of an issue being that far away... your car is designed to keep its self cool.

Find a local place that sells the cats, they can be had around me for $60, and get an exhaust shop to weld it in.

Done and doner.
 

·
Registered
Joined
·
3,049 Posts
its up to the machine how long it takes, and the fan really wouldnt have that much of an issue being that far away... your car is designed to keep its self cool.

Find a local place that sells the cats, they can be had around me for $60, and get an exhaust shop to weld it in.

Done and doner.
Or save yourself the money and buy an O2 spacer... :screwy: so you can keep the performance of your high flow cat. High flow cats are nowhere near as large or as dense as a stock cat, your not going to get the performance emissions wise out of them. Again don't waste your money buying a new cat when your solution is a spacer.
 

·
Registered
Joined
·
4,807 Posts
Well, i guess he could space his rear 0/2 out and get rid of the P0420 code...


it would do nothing for the main issue of him not being able to pass emissions, But his CEL wouldnt be on!
 

·
Registered
Joined
·
3,049 Posts
Well, i guess he could space his rear 0/2 out and get rid of the P0420 code...


it would do nothing for the main issue of him not being able to pass emissions, But his CEL wouldnt be on!
Here's my logic and please bare with me. NOx levels directly reflect EGT levels. EGT levels directly reflect A/F ratios. A/F ratios are controlled by the precat o2 sensor. However NOx levels are then picked up by the post cat o2 sensor for emissions testing as well as deficiency testing as the cat is suppose to burn up any harmful gases exiting the exhaust. If you pull this sensor further away from the exhaust the amount of harmful gases picked up by the sensor lessen thus removing any codes thrown including readiness monitors failing. The spacer will also give the benefit of lengthening the life of your post cat o2 sensor.

I've ran a spacer for years with no cat and I've had absolutely no problem passing emissions testing. So to say a spacer will not allow you to pass emissions testing is far fetched and very untrue. Now if his state is using tailpipe sniffers (as in not using obd2 hookup to pull the readings and rather their own o2 sensors) it would be a different story. I'd be moving if that's the case or blaming it on their 20+ year old technology and sniffers.
 

·
Registered
Joined
·
4,807 Posts
That's all fine and good, and what your stating would accomplish is getting rid of the p0420 code...

The p0420 code has nothing to do with emissions, or the fuel mixture that the engine is running, that is the job of the primary and primary alone.

As I have in my posted thread, I don't have rear o/2's in two of my cars, and both passed legit tail pipe sniffing without an issue.

Moreover, in the quote that I posted he complained about an accident that he was in, and he has a rattle in the exhaust that he can't track down.... What would happen if the cat element came apart from the housing?

The element would get way more exhaust flow then it was intended and super heat... The remainder of fuel flowing would get high NOx...

If you want to, take the cat off, punch out all of the element ( make sure to get it all ) change the oil and go for a test, same as four locals have done here and passed without an issue.
 
1 - 20 of 54 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top