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Gentlemen,

I was just pondering this very issue last night so I thought that I would pose the question the those concerned.

"Why would we expect a 6M to not pass emissions?" I understand that it does not come equipped with an EGR system, but do we really expect that the EGR system makes that big a difference?

I tell you why I ask! The gas that is recirculated by the EGR system is a small amount of gas which passes from the #6 cylinder exhaust runner. The passage is about 1/2" in diameter and is positioned perpendicular to the flow. Also, the EGR system is only operable under certain conditions. Based on the fact that it only involves one cylinder, it is not exposed to more than 17% of the engine emissions. And of this 17% it will only recirculate a small amount...

Now what are some of the things that should we expect from a normal internal combustion engine? First, NOx will generally tend to increase with increases in air/fuel usage and resultant increases in temperature. Because NOx production results from the burning of atmospheric nitrogen, we will naturally see this increase.

CO is generally a product of incomplete combustion and lower operating temperatures. As temperatures increase (a sign of improved combustion), CO numbers usually go down. (the carbon (C) results from unburned fuel).

As for the catalytic convertor, it will help emissions by converting some of the NOx to N2, the CO to CO2, and the HC,s to H2O. This system has limits however and is dependent upon a healthy running engine for starters.

This can be a tricky endeavor, because as combustion improves (and thereby improving CO emissions), too lean a fuel mixture may trigger an increase in NOx emissions, and too rich a fuel mixture and the HC emissions will increase.

Therefore, it looks as if we need to pay very specific attention to the tune of our vehicles. Also, as internal tolerences begin to increase we may see an increase in overall emissions.

P.S. Just curious to see if we could collectively identify the solution to fail-proof emissions testing...

Regards,

Carlos
 

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Gentlemen,

When I have an opportunity I will report my findings regarding improved auto emissions. Of course some of the actions are obvious:

Clean/fresh Air filter,
Fresh Spark plugs,
Good condition wires (and ignition system),
Clean and operable EGR system,
Good working Catalytic Convertor,
Fresh Oil change (I am seeing this recommended more and more),
High Quality fuel (some brands like Chevron include emissions reducing additives),
O2 Sensor in good working order,
Properly warmed vehicle and Catalytic Convertor (it has been recommended that you keep your car running prior to testing since heat is mainly responsible for conversion),
but, test during the evening or on cool day so to keep engine "cooler" so to reduce NOx emissions,

Additional action not yet confirmed:

Retard Timing a couple of degrees,
Various lash adjustment settings (not applicable).

It appears that the established emissions limits are set very near the operating thresholds of the internal combustion engine. Perhaps this is why the smallest improvement is sometimes enough...

Regards,

Carlos
 

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Djgoop,

What year is your car or more specifically, what year is your engine? That may not do it either, so, does your throttle body have a mixture adjustment screw on it (should). Try making a slight adjustment to the TB once the car is at operating temperature. If you are infact running rich, make about a 1/4 turn counter-clockwise to the adjustment screw and see if the idle smooths out a little (P.S. Mark the original position of the screw before beginning).

You should see a slight increase in RPM as a result of the increased O2 (very slight), but it really helps to fine tune the fuel mixture. Despite the fact that many believe this to be a none adjustment for certain years, I have always had great success with this adjustment on my 86 5MGE.

Regards,

Carlos
 
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