HIGH NOx failed emmisions any suggestions??

[REDS197]

HIGH NOx failed emmissions any suggestions??

As title states I just failed emmissions because of NOx being to high.
Colorado has a sniffer test with a loaded dyno to simulate normal driving.

I have a whipple blower with detroit rocker blower cams and longtubes with high flow cats.
What causes high NOx and are there any tips you can give me to help lower the NOx!!

 

[jcwatson.doc]

NOx stands for Nitrogen oxides. It is the by-product that comes out of your tail pipes. This is what the EPA is trying to keep at a reasonable level when they implemented emmisions testing. The only thing that they want to see coming out of your tail pipe is H2o. You know, that little bit of water condensation, that's normal.

This is what the catalytic converters are supposed to do for the vehicle. Since you were running cats at the time of the test, all I can say is that those cats are not efficient enough for your engine. Or, at least not efficient enough for Colorado's sniffer test.

This might mean that you are going to have to ditch the long tubes and high flow cats in favor of the stockers, just for testing purposes. Throw the manifolds back on, along with the stock cross over pipe and call it good. There is just no real way around that damn sniffer. Good luck, man.

 

[RRRoamer]

IF my memory is correct, NOX is caused by high combustion temperatures. That was the reason cars originally used exhaust gas recirculation, to cool the combustion event by including gasses that would not burn (aka: exhaust) in each combustion cycle. Our cars do NOT have EGR as they used the VCT to achieve the same result, but I do not remember exactly how this was implemented.

So, given that, I would look to your tuner and see if they have reduced or deleted the VCT range and if he knows any way to cool off the combustion temperatures.

Good luck! Hopefully some folks with more direct knowledge will post shortly with more detailed info for you.

 

[RRRoamer]

I did a bit of digging. jcwatson.doc has a good point: You might need to look at your high flow cats. Only a 3-way cat can reduce NOx and it can only do it well in an oxygen starved zone (aka: engine running a tad rich). Put a high flow cat (which almost NEVER clean as well as a stock cat) together with a slightly lean condition and you are hosed on NOx. The really pissy part is if you get the tune adjusted to allow NOx reduction to occur properly, you might then start to fail for CO and HC limits!

 

[REDS197]

I understand what both of you are saying. Thanks for the input. If i retard the timing a couple degrees and raise the AFR a little will this help? I also am going to a 5psi pulley from 10psi to reduce the heat. One last thing i took the test on 95 degree day and I am curious what happens if let the car cool before the test on a cool morning.
.

 

[5spdGT]

running it cold is not a good idea, the cats work best when they are hot, so running it cold could get your nox higher. when i did new york state inspections back home we used to have to run the cars at 2500 for 5min before the dyno test so they would pass. make sure there is an extra fan blowing on your radiator when on the dyno to keep it cool.

 

[REDS197]

I know that i have to find a balance between a hot cat and a cool engine. We will see tomorrow if I can pass.

 

[mustangdave]

I would think the cam overlap is playing a big part in letting the nasties through. I've never known anyone to pass a Sniffer test with cams that have alot of overlap. Maybe a tuner could offer up some help.