Hada buyer for my car, but the POS failed smog, high NOX... Timing was advanced to 8 or 10.. .dont remember. Will turning it back fix that?

Is there any way to test the EGR valve?


[Modified by Kale, 6:05 PM 5/17/2003]

 

You should always retard timing a few degrees for smog. I know this helps out with keeping HC down, but I can't tell you anything about NOx.

NOx means you're lean right?

The EGR is a pain to test on these cars, cause you can't get to it really. Try hooking up a vacuum pump to it, and pull a vacuum on it to see if the diaphragm moves. Also, it may be sticking and not closing all the way. You'll need a small inspection mirror of some sort to see under there. At idle, if you pull the egr vacuum line, the car should stumble or die. I think that's how they test em at the smog stations anyways.


[Modified by CentralCoaster, 12:39 PM 5/18/2003]

 

I replied in your other thread about the guy possibly buying your car, but I didn't want you to miss this good info..... I had problems with high NOX last October. Read about it here:
http://forums.corvetteforum.com/zerothread?id=402376


There is good info about NOX in there. What it is, how to reduce it, etc.

Replacing the EGR fixed my problem, and also the RPM at which the test is done. Read my reply in your other thread:
http://forums.corvetteforum.com/zero...554#1544044378


here is the link to the EGR info:
http://www.ag.auburn.edu/users/gparmer/efi/egr.txt


Good luck! :thumbs:

 

No, not at all. Running lean will cause a rise in NOx emissions, but running lean is not the reason NOx forms. NOx will form any time the in cylinder temperature is above 1500* F. Once NOx molecules are formed, they are VERY stable and VERY hard to get rid of. The precats on L98 cars are designed to remove NOx from the exhaust. The reason they are so close to the engine is because you have to have a lot of energy (heat) to put into the catalyst reaction to break the NOx apart. If your precats are shot or removed (I'm assuming it's an L98....didn't see any mention of the car's MY), you will have an increase in NOx emissions.

The main way to reduce NOx emissions is to reduce cylinder temperature. If the in-cylinder temp never breaks 1500* F, you will have 0 NOx emissions. Ways to reduce cylinder temperature:
1) put your timing back to the recommended 6* BTDC.
2) try to run the engine cooler (if you have a manual fan switch, turn it on to reduce the coolant temp)
3) It's no use to play with your FPR if it's adjustable, because the ECM should just trim out any extra fuel because it will be running closed loop...
4) Running a colder heat range spark plug may reduce your NOx (but now we're talking about spending money on a car you're trying to sell...)

There are a couple of other things you can do which are slipping my mind right now...if I think of them I'll post them as well...

 

Thanks, ill probably take it down to 4.

 

You don't want to take it down too far, because then you begin reducing the quality of combustion, thus increasing your HC and CO emissions...it's a balancing act.