Nitrous oxide is an oxygen-bearing compound. Its chemical
designator is N2O, so we know each nitrous oxygen molecule
has two nitrogen atoms and one oxygen atom. Nitrous oxide
is sometimes incorrectly known as "NOS". That is
an acronym for the company, Nitrous Oxide Systems, which is
the largest marketer of nitrous oxide injections system for
automotive use.
Injection
of nitrous oxide into the combustion chambers of an internal
combustion engine as a way to increase power output was discovered
by the German aircraft industry early in the Second World
War. Thousands of German fighter and reconnaissance aircrafts
were equipped with the so-called "GM-1" system,
which added nitrous oxide to the intake charge to compensate
for reduced air density and less oxygen high altitude. The
British Royal Air Force also used aircraft engines with performance
enhanced by nitrous oxide. Interestingly, there was no use
of nitrous oxide injection by the American military air forces
other than very limited experimental use. It is interesting
to ask oneself that, if nitrous oxide injection was so dangerous
to an engine's reliability, why would so many airplanes have
used it?
In this country
during 1950s the famed stock car racer Smokey Yunick rediscovered
nitrous oxide injection as one of his many schemes for winning
races until discovered and outlawed by NASCAR. Nevertheless,
there have been several nitrous oxide cheating scandals in
NASCAR over the years and it is probably still used today
by the slowest of back markers. In the late-70s/early-80s
nitrous oxide was "rediscovered" by drag racers
and hot rodders.
Today nitrous
oxide injection, like many other modifications such as more
aggressive camshafts, bigger carburetors, higher compression
ratios, more free flowing intake and exhaust systems, can
be a practical way to more horsepower. And, like any other
modification, perhaps even more so because it so easily lends
itself to misuse, there can be a reliability and durability
price to pay.
Nitrous oxide
is a colourless, non-flammable gas. It has a slightly sweet
taste and odour. It is non-toxic and non-irritating and when
inhaled in small quantities can produce mild hysteria and
giggling or laughter. This is where the nickname "laughing
gas" comes from. When inhaled in pure form it will cause
death by asphyxiation because at atmospheric temperatures
and pressure, the oxygen in nitrous oxide is not available
to the body.
A property of
nitrous oxide is that at about 565 degrees F, it breaks down
into nitrogen and oxygen. When it is introduced into the intake
tract of an internal combustion engine, it is sucked into
the combustion chamber and, on the compression stroke, when
the charge air temperature reaches 565 deg., a very oxygen-rich
mixture results. If we add extra fuel during nitrous oxide
injection, the effect is like a super charger or increasing
the compression ratio of the engine. Automotive nitrous systems
work like the automotive equivalent of a jet's "afterburner"
and is used for short duration extra bursts of power.
Nitrous oxide
has this effect because it has a higher percentage of oxygen
content than does the air in the atmosphere. Nitrous has 36%
oxygen by weight and the atmosphere has 23%. Additionally,
nitrous oxide is 50% more dense than air at the same pressure.
Thus, a cubic foot of nitrous oxide contains 2.3 times as
much oxygen as a cubic foot of air. Just do a bit of math
in your head and you can see if we substitute some nitrous
oxide for some of the air going into an engine then add the
appropriate amount of additional fuel, the engine is going
to put out more power.
Simply stated,
nitrous oxide injection is very much like a supercharger or
a compression ratio increase in that, during combustion, it
can dramatically increase the dynamic cylinder pressure in
the engine.
Of course, when
we significantly increase the cylinder pressure in the engine,
we also increase the engine's tendency to detonate. This is
why almost all nitrous motors require retarded spark timing
during nitrous oxide operation. The cylinder pressure increase
is also why, when misused or improperly installed, operation
with nitrous causes problems with head gasket seal and failures
of the rings or pistons. I should point out that any number
of things that put an engine into severe detonation, such
as too much boost from a supercharger, low octane fuel, excessive
compression ratio or overly lean air-fuel ratio will also
cause the same kinds of damage.
Another challenge
with a nitrous oxide system is getting the delivery of nitrous
oxide and additional fuel at the correct proportions. If you
feed nitrous to the engine without enough extra fuel, the
lean air/nitrous to fuel mixture will make the detonation
problem even worse. Combustion temperatures will skyrocket
and catastrophic failure is certain to occur. If the proportion
is such that too much fuel is delivered, the power advantage
degrades rapidly.
As you can see,
nitrous oxide is like any other power increasing modification
in that, when used wisely and installed properly, it works
well. When used foolishly or installed incorrectly it can
significantly reduce the reliability and longevity of your
engine.
Small doses of nitrous oxide
can be used in stock engines to gain 25-35% more power. In
my opinion, any more nitrous than that with a stock engine
compromises durability too much. This is not only true of
nitrous but any modification. If you were to take a stock
100hp engine, up the output to 300hp and do nothing to improve
durability, your engine will eventually suffer. Once you pass
the 35% power increase mark with nitrous oxide you need to
consider things like forged pistons, stronger connecting rods,
beefier bearings, etc.
Nitrous oxide is also a great
value on a dollar-per-unit-power increase when installed and
operated properly. The downside, of course, is the fun ends
quickly. The power boost lasts as long as the nitrous. The
average bottle is a 20 pounder and with a street V8 that might
be worth 20 seconds of use.
Nitrous oxide is not the instant-engine-failure
many people think it is. When dispensed by a properly designed
and installed system, nitrous oxide systems can be responsible
for some phenomenal increases in power.
See an example
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- Author Unknown
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