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"THE ULTIMATE EMISSIONS CIRCLE
The following is an explanation of how one emissions gas reacts to tyhe
changing of another. This is true provided the engine is in tip top working
condition.
1) A leaner than normal mixture (air to fuel) means more air is going
into the combustion than there should be. Since this air is taking up
space, the flamefront cannot travel from the spark plug to the fuel fast
enough for a clean burn because the extra air is acting as a "blanket".
Thus, the exhaust will have more hydrocarbons (HC) with a leaner mix due to
incomplete combustion. HC's in the exhaust make eyes watery and smells
somewhat like gasoline.
2) A richer mix means more fuel is going into the combustion than should.
The result in this case can be a number of different things depending on
the severity, from excess HC's, carbon monoxide (CO), both, or anywhere in
between. An overly rich mix can result in the formation and exhausting of
soot, which is simply partially combusted HC's.
3) The above two points have many limits and tolerances, and there is no
such thing as a perfect mix no matter how sophisticated the fuel delivery
system is. But the closer it is to perfect the less of both emissions there
are.
4) If the mixture is right but the air and fuel are not intermixed
properly, HC and possibly CO levels will rise. In one part of the cylinder,
say, at the spark plug, the fuel and air are properly intertwined and will
burn. But if somewhere in the cylinder there are "clumps" of air and/or
fuel they will not burn or will burn with limited air present. Engines are
designed to mix well but they do not do it best with stock injection or
carburetion.
5) NOx (Oxides of Nitrogen--NO, NO2, N2O, etc.) is the most notorious
substance of all. It robs power, decreases efficiency, and, most of all,
constitutes to the rising of the other two gases HC and CO. NOx is formed
when O2 and N2 are subjected together to high heat, maybe pressure, for
prolonged periods of time. NOx is the fusion of O2 and N2, a combustion at
the wrong time. The problem can be many things including ignition timing
and EGR blockage. If it is too far advanced before top dead center (BTDC)
NOx is created instantly as the spark plug fires while the piston moves up.
If the EGR fails to operate or the passages are plugged the intense heat
generated by the slow-burning fuel will generate NOx. Adding about double
EGR never hurts. As NOx levels decrease more O2 is freed up for the
combustion of the gasoline. Under normal circumstances the A/F mix has to
be richened a bit to compensate for the extra air.
6) Ignition timing correction will target the HC and NOx (and maybe CO if
it is extremely retarded). For example, the timing at the factory for a car
is set at 10 degrees BTDC. If it somehow changes to 5 deg. BTDC (retarded 5
deg.), the spark plug would fire later and the fuel starts to burn later.
The result is a loss of power from the engine due to the fact that part of
the fuel charge is burning in the exhaust manifold under little of no
pressure, thus some parts of it cannot burn because it has diffused too
much. This in turn created high HC emissions. If the timing would be 15
deg. BTDC the fuel would burn too early, before the piston rises far enough
on the compression stroke to harness the full effect of the slow burn. As
said earlier, it creates NOx from the added heat of pre-combustion. If the
timing is advanced even further the engine pings and serious damage can
result from backforce (fuel forcing piston in opposite direction).
7) PCV (Positive Crankcase Ventilation) consists of some water, and a lot
of oil vapour, more in the case of older high mileage engines. These are
heave hydrocarbons which cannot burn at the rate of gasoline and is
notorious for fouling up the engine's internals with hydrocarbon soot, and
sometimes even thick residual carbon-like crap.
Depending on the amount of blow by there is, certain measures should be
taken to avoid high emissions of hydrocarbons and/or carbon monoxide. It
will depend on the condition of the oil and the severity of the wear on
engine parts. The older the oil, the more wear the engine has, the more
blow-by is created. If the engine is very old it might be wise to use oil
and some Lucas Oil Stabilizer or MT-10 oil treatment, which tend to be
better than synthetic oils. Friction created heat and worn parts create
more friction than new parts. The more heat generated by such things as
rocker arms or bearings the more oil is vapourized and the more crud will
build up inside the engine. In this case do not go tearing the engine apart
to fix it, just install a PCV catalyst jar. If the problem is extreme
install a surplus silica container before the jar to aid in the breakdown of
the vapours. Also, when using silica units the EGR flow can be increased
because of better cleaner burns.
Somewhere, somehow you will have heard that injecting water into the engine will reduce emissions. This is true only if the water is in its pure
vapour state. If any liquid goes into the combustion of the fuel what
happens is the water and gas will "spatter" much the same as water in
boiling oil does. This creates excessive and unnecessary heat spikes which
in turn result in higher levels of NOx and even exhaust acids. If the water
can aid in dynamic expansion, good...if it reacts with something, change the
vapourizer design or add a heater. Water is also a good tactic to increase
horsepower since the water will expand faster and farther than air.
However, it cannot save gas, as many claim it will, unless the timing is
advanced by one or two degrees and the mixture of air to fuel is leaned out
a tidbit (not much).
Exhaust acidity is the result of combining NOx with water. Usually if
the NOx levels are low so is the acid. If the water is completely
vapourized though it has little if any chance to create such an abomination.
9) A clean engine is a long lasting engine. The combustion chamber stays
cleaner, and spark plugs, valves, oil, exhaust components, and pistons last
longer. The less ping an engine encounters in its lifetime the less
bearings one has to change and the less cylinder wall scratching there will
be, since the detonation breaks loose vast amounts of carbon from chamber
parts. Low acid in the exhaust tends to lengthen the interval between
exhaust system fixes, at least it doesn't rust as much from the inside.
10) If you are crazy enough to set up emissions with your nose remember
this...HC smells almost like gas and tears eyes, CO has no odour and can
make you dizzy and faint, and NOx feels like thorns in your throat, like the
entire desert's worth of cactus needles were just jammed down your throat.
It is advisable though to get an analyzer...at least you can impress people
with such low emissions (and waving the analyzert to them, saying "I got one
and u don't, nyaa nyaa nyaa nyaaaaa nyaaaaaaaa!!). Exhaust acid can be
tested by collecting some water from the exhaust once the engine is warm and
using a pH tester to see how bad it is. This is better to do on a cold
winter day since more water condenses in the tailpipe. All those who have
no cold days, well, too bad--deal with it!!"
