Hi all,

I just tried to go through the emissions control program here in B.C. Canada (Aircare) and failed twice In the past, my Dad and I have been able to "de-tune" my 1981 Plymouth Caravelle with a 225 2bbl "Super Six" by changing the timing back to about 2-3 BTC. However, just in this past year, some smart people decided to up the Nitrogen Oxides standard from 2500ppm to 1891ppm. My /6 produced over 3000ppm when tuned for regular driving and i've been able to get it down to just under 2000 in the past by changing the timing and leaning it out. My question to you: Is there another way of lowering the high NOx emissions from a slant six? Have any of you had the same problems with extra high NOx due to the /6's high compression?

Ryan

rmuntener@imag.net

What a pain.... looks like you are close, keep reducing the timing and lean it out till it hardly runs. To bad it's a 81 with hydr. lifters, I would loosen the adjustment "lash" on a mechanical set. ( I guess you could try "shimming-up" you rocker shaft a bit to see if that helps)
Keep the idle speed as low as possible for the test. Anything to reduce cylinder pressure will help.
DD

Sometimes leaning out an engine can actually increase NOx emissions due to the higher combustion temps.

If your car is equipped with an EGR valve, make sure it's functioning properly. Introduction of the non-combustible exhaust gas actually reduces the combustion temp without leaning out the mixture. Retarding the timing helps, too, by lowering cylinder pressures.

If you're looking for a "cheat", maybe you could add a hidden line to the manifold which would add a non-combustible gas (CO2, Argon, Helium) to do the same thing (just kidding).



mustang-six@cfl.rr.com

High combustion temperatures is what generates NOX. Leaning the engine will reduce HCs and COs, but may actually increase NOX. Do you have a vacuum advance distributor? If you can temporarily disconnect the vacuum line to the distributor to eliminate your vacuum advance, this will help a lot and may do the trick. If you still have the EGR, make sure it is working.

Mitch


mb589@aol.com

Oxides of Nitrogen, or NOx, is the product of oxygen atoms combining with nitrogen atoms under high temperature conditions. To understand "how" to reduce it, one needs to know that nitrogen has two sources: the fuel (fuel-bound nitrogen) and air (let's call it airborn nitrogen). Oxygen comes from air (of course).

I cannot speak to the content of nitrogen in gasolene, though I suspect there's very little. So I would do anything I could to reduce the "airborn" nitrogen and O2 input by reducing combustion air AND combustion temperature. This means running fuel-rich.

A smog pump reduces NOx, because it recirculates exhaust consisting primarily of CO2, CO, and H2O. Yes there are traces of other stuff, but notice little or no O2 (oxygen) and the NOx has already been generated. This inert air dilutes the combustion air, thus reducing combustion temperature, but more importantly limiting the formation of additional "thermal" NOx (in addition to sending back any unburned hydrocarbons).

Other methods consist of ammonia injection, steam injection, selective and non-selective catalysts, but these methods are not feasible, if not inappropriate for the internal combustion engine.

I don't envy your position 'cause if you run too rich you may not pass the CO and hydrocarbon emission test. SO, you may have to follow the Doc's lean mixture recommendation, cross your fingers, say your prayers, leave $20 bucks (that's about $50 Canadian on the dash and HOPE for the best.

Good Luck,
ToddC


cole020@yahoo.com

Thanks for keeping me honest on the "lean can make more NOx" issue. I guess you have to "dance" the fine line between the NOx and the HC&CO readings

Hate to say that my primary solution to passing emissions has always been to own smog exempt cars!
DD

A few ideas I've had since last night ranging from plausible to borderline hair-brained:

1) Fuel Oxygenates provide a source of oxygen without the air. Remember air is almost 4/5 nitrogen by mass. I believe ethanol accomplishes this. If ethanol or some other "oxygenate" is available as an additive, it will help you tune the engine using less air, ergo less NOx. Note: I don't think you can get the oxygenate MTBE as an additive, and would not recommend that poison even if you could.

2) Try using a lower temp thermostat. This will help to lower the engine temperature and keep the combustion chamber a little cooler where thermal NOx is created.

3) Close off the manifold heat valve/damper. The cooler the fuel/air going in, the cooler the combustion chamber.

4) Find a way to chill your combustion air. Combustion heat will be used up heating the cold air.

5) Chill your gasolene for the same reason.

Would I try these? Maybe for fun, just to screw with the enviro-Nazis. That's why I'm diggin' this topic.

Try ideas 1 to 3 for sure, but I concur with the Doc: buy early exempt years and save yourself the headache. As you have found out with the new NOx restriction, the enviro-Nazis are vigilant, persistent and plentiful, making easy pickins of us oldcar-driving commonsense-environmentalists.

Best of luck
ToddC


cole020@yahoo.com

there are 3 main ways manufacturers combat NOx levels.
1. 3 way catalytic converter
2. EGR system
3.spark delay system

what the main gist is is that the less bang you make, the less heat it will generate and the less NOx will be generated.

try retarding your timing to the $#!+, cooling fuel and air, and introduce non combustable gas into the inlet air

you dont have far to go to pass the test, so it shouldnt be too hard.

Mr_Mopar_Man@hotmail.com

You most likely have a buildup of carbon in the combustion chambers. Try running a cup of water thru the engine when doing a fast idle. This will "steam clean" the combustion chamber and remove the carbon. An alternative is the "Italian tuneup", which is, drop the car into a lower gear and then floor it. This is suppose to remove that same carbon buildup.

Does BC have the two failures then pay the certified mechanic $200 for a fix clause? This might be an escape...



klesteb@aol.com

An alternative is the "Italian

lol, i do the "italian tuneup" all the time on my bushbashers.. never heard it called that! i wouldnt do it on a good car tho, as you really have to rev the rockers off the poor ol engine to do it properly.. which would prob's create other porblems on a slant.. ie ventiated block etc!


Mr_Mopar_Man@hotmail.com