If anyone is having issues with high NOX readings, lower your Main Spark Advance Table (filled mine with all 10s) and you can seriously reduce it. Spent hours chasing EGR issues and catalytic converter issues that weren't the problem... when all I had to do is burn a chip. Hopefully this saves you time.

1st Test

Failed... Modified Headers

HC 15mph 81(MAX)/65
HC 25mph 58(MAX)/44
CO% 15mph .50(MAX)/.13
CO% 25mph .40(MAX)/.09
NOX 15mph 537(MAX)/1279
NOX 25mph 494(MAX)/1179

2nd Test
Pass... Modified Headers (with sticker from SLP)

HC 15mph 81(MAX)/17
HC 25mph 58(MAX)/10
CO% 15mph .50(MAX)/.03
CO% 25mph .40(MAX)/.02
NOX 15mph 537(MAX)/1291
NOX 25mph 494(MAX)/1243

3rd Test
HC 15mph 81(MAX)/54
HC 25mph 58(MAX)/16
CO% 15mph .50(MAX)/.23
CO% 25mph .40(MAX)/.08
NOX 15mph 537(MAX)/433
NOX 25mph 494(MAX)/456

 

Did you notice any performance gain? Probably not.. California emissions are the hardest to pass and cars have crazy parts that are totally different than Federally regulated cars. Good job on passing that test..

 

" California emissions are the hardest to pass and cars have crazy parts that are totally different than Federally regulated cars."

What are some of these 'crazy' parts? I live in California, bought my Z28 in California, I pass emissions tests in California.

 

I believe it starts with your ECM.. Maybe I am wrong, but CA emissions is different than any other state. Even when I worked in Autozone, I would have to ask if it is Federal Emisions or California Emissions on alot of cars. I would be interested in knowing what ECM and Prom you are using by number

 

from

https://www.thirdgen.org/forums/tpi/...ml#post5477561


Thanks Marc. I have no idea how to burn a chip (have no chip burning equipment either). I need a remedy quickly. I guess I could have someone to burn a chip for me. Any other options on this? By the way how did your car run after that?

 

This is good info. I haven't passed a CA emissions testing since '06.

 

You have not been driving your car since 06'?

In any case I found that my timing was set to 8 BTDC so I dialed it back a little to 6 BTDC and it passed. Try checking your timing and if that's the issue, dial it back some. I know that works for high NOX not sure if it works for anything else.

 

Essentially, all you did to the table is this?

 

that should work, just don't try running with that table on the street. very little power.

 

Wouldn't this damage the engine if you ran it like this on the street?

 

Thanks. Since I know the RPM range where the 15mph and 25mph tests are run, I shouldn't have to change the entire table.

I don't plan on leaving that chip in the car.

 

Far as I know all 50 state cars had the same emissions everything on them.
Ca just regulates its all there more than most

 

hi, I had a question, I’m getting ready for a smog check in California and I’ve read many different tips including back off the timing a bit so I set mine back from 6 btdc to 8 btdc. From your experience this is opposite. I’m just trying to get any helpful info from other peoples trial and errors to help me if you have any input I’d appreciate it thank you!

88 gta 5.7 L98 auto

 

I'm definitely interested to see what the CA folks have to say, but my understanding is that anything that decreases max cylinder TEMPERATURE reduces NOX formation.
Reducing ignition advance is one easy way to reduce cylinder pressure/temperature, but there's lots of others.


Adam