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
Today nitrous oxide injection, like many other modifications
such as more aggressive camshafts, bigger carburettors,
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 were the nickname "laughing gas" comes
form. 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 than 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
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
As you can see, nos kits is like any other power
increasing modification in that, when used wisely and
installed properly, it works well. Then used foolishly
or installed incorrectly it can significantly reduced
the reliability/durability 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 than
nitrous than that with a stock engine compromises durability
too much. This is not only true of nitrous but any modification.
Take a stock 82 or 84 engine, up the horsepower to 300hp
and do nothing to improve durability and your engine
will eventually suffer. Once you pass the 35% power
increase mark with nitrous oxide you need to look at
things like forged pistons, better connecting rods,
better 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.
So, nitrous oxide is not the instant-engine-failure
many people think it is. When used properly and when
dispensed by a properly designed and installed, nitrous
oxide systems can be responsible for some phenomenal
increases in power.
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