Emergency! Emissions Question!

[Brokechump]

I'm trying to pass emissions in Northern VA. I passed everything except the NOx for the 25mph test, I'm just barely over the line according to the shop guy.

 

My question...will enriching the mixture drop the NOx or increase it? Please please...help!:boohoo: Thanks in advance!

 

-Dan

[Adam N.D.J.]

Cooling your combustion temps will cure this. Check to make sure your EGR is working correctly. That is the function of the EGR (exhaust gas recirculation), it dumps exhaust into your intake, and cools off the combustion temps. If the EGR is working all right, set up a water sprayer to spray a little water into the intake during the test (don't tell anyone I told you this). The water will lower your combustion temps and thus lower your NOx. As far as rich or lean, I'm trying to think here. A leaner mix burns hotter then a fat mixture. If'n you richen it up a bit, then it'll lower the NOx, but don't do it too much or you'll fail the other parts of the test. Hope this helps.

[Nug]

The easiest way to reduce NOX is to retard the ignition timing a few degrees. This is especially good if the HC and CO levels are well within spec, as retarded timing will make them rise.

 

Check your EGR valve for proper operation.

 

If all else fails, add alcohol to the tank. It burns cool, so NOX goes down, and it also dramatically drops HC and CO. You'll want to make it at least around 50%.

 

Get about 8 bottles of DRYGAS, with either isopropyl methyl, or ethyl alcohol. Doesn't really matter.

Don't let the alcohol sit in the tank for weeks on end, it has a tendency to make things corrode. Like after you pass the test, go fill 'er up.

This is one of those things to do when you have around a quarter of a tank of gas in the tank.

 

Don't tell them there is alky in the tank. They won't know if you don't tell them. There is no real harm in putting alky in the tank, but there is no federal tax payed on it, because it isn't considered a motor fuel, and that's where the trouble lies.

 

Lets just say I got a sh*tty 1984 ford van with a carbureted 300 six to blow pure oxygen out its a$$ for a friend in Stafford county.

[Brokechump]

Thanks for the advice! So where might I pick up some of this magic fuel? Do I have to go to WVa to get some grain alcohol??

 

-Dan

[Nug]

Grain alcohol would work, but it seems like a shame that your car enjoy that and not yourself. Isopropyl alcohol works well, it is the ingredient in gas line antifreeze (drygas). On that van, I went to Lowes and picked up a gallon of denatured alcohol (ethanol denatured with methanol, whatever that means) and it worked well.

Since you are trying to control NOX, I'd back the timing off a few degrees, and run around 50% alky to keep CO and HC in check.

 

Let us know your results.

[Brokechump]

This morning was the magic morning....whether or not my tweeking did the trick or the guy didn't want to see my rust bucket again here's what I did to pass emission here in northern VA....Thanks of course to everyone's advice. Unfortunately I didn't go out of my way to find some alky.

 

New air filter and oil change.

Filled near empty tank with 4 gal of 93 oct.

Enrichened mixture with 1/8 turn ccw.

Retarded timing from 8 to 6 degrees.

Pinched off the air hose coming from duty solenoid #1.

Left the car running for the inspector.

 

Dropped my NO number by 1000. Now to finish the rust repair.

 

This was for an 81 Hitachi carbed EA81 GL wagon. Thanks everyone! Now on to rust hole repair!

[Nug]

Glad to see it passed. That was quite a dramatic drop in NOX. I'm impressed.