Is Nitrous Oxide?
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.
A nitrous oxide molecule is made up of 2 atoms of nitrogen
and 1 atom of oxygen. By weight it is 36% oxygen (air
is only 23.6% oxygen). At 70° F it takes 760 PSI of
vapour pressure to hold nitrous in liquid form. The critical
temperature is 97.7° F; at this temp the vapour pressure
can no longer hold the nitrous in liquid form. At this
point the nitrous turns gaseous and will be at 1069 PSI.
As temperature rises further, so will pressure, but it
will remain in gaseous form. If you intend to siphon liquid
nitrous, it is important to keep the temperature below
97.7°. When liquid nitrous is released, it will go
from 760 PSI to 14.7 PSI (normal atmospheric pressure).
It will then begin to boil and rapidly expand; the pressure
drop will cause the temperature to decrease. Nitrous boils
at 129.1°F below zero.
Nitrous oxide systems make large amounts of torque by
allowing an engine to burn more fuel at a lower rpm range
than normal. Burning more fuel this way creates a longer
burn period (and slightly higher cylinder pressures, if
the timing is not corrected), that will push down on the
pistons with greater average force. When the nitrous is
injected into an engine and the initial combustion takes
place, it creates enough heat to separate the nitrous
oxide into its two components, nitrogen and oxygen. Once
separated, the additional oxygen is then free to allow
combustion of the additional fuel, while the released
nitrogen acts as a buffer against detonation and damps
run nitrous successfully and safely, you have to introduce
precise amounts of additional fuel with precise amounts
of nitrous oxide. All of the extra oxygen provided by
the nitrous oxide must have fuel with which to burn
or you may damage your engine severely. When the amount
of nitrous and the amount of supplemental fuel is controlled
precisely, your engine can safely and reliably generate
exceptional power increases.
Nitrous oxide does not burn, it is an oxidiser. It provides
more oxygen, so more fuel can be burned, and the result
is more power. The atoms in a nitrous oxide molecule
are bonded together. The oxygen is not free, but fortunately
the bond breaks down as temperature rises. At 565°
F, the bond is broken and the oxygen is then free. Combustion
temperatures are much more than 565°, so it's not
a problem. By adding nitrous oxide to an engine, the
total amount of oxygen is increased while the volume
of nitrogen is decreased (as a percentage of the whole).
This speeds the burn rate and requires less timing advance
for peak output. It is hard for many people to grasp
gaining power with less timing, but it's a fact. Peak
cylinder pressure must occur at approximately 20°ATDC
to make peak power. If you speed the burn rate, peak
cylinder pressure will occur too soon. It is easy to
run too much ignition advance with nitrous, but too
much will not only hurt power, it can quickly bring
a nitrous engine into detonation and destroy it.
Large power increases achieved by using nitrous oxide
can increase the chance of detonation. To keep the engine
out of detonation, you must control the extra heat that
nitrous can make. The easiest way to do this is to add
more fuel. All nitrous systems come with rich jetting
to give you a safe starting point. The extra fuel takes
away heat and raises the detonation limit. If you don't
try to over do it, and keep the hp levels within reason,
running slightly richer should be all you'll need to
control detonation. Running richer will reduce the power
output, but raising the detonation limit will allow
more nitrous to be used to get more power.
The chemically correct nitrous to petrol ratio is 9.649:1.
If a nitrous engine runs lean, it can destroy the engine
in a matter of seconds. There must be enough fuel to
maintain this correct ratio, if there isn't, temperatures
rise rapidly. The oxygen that was left over from burning
the limited amount of fuel will result is a lean burn
situation raising cylinder temperatures and melting
components. So don't run lean.
Cooler intake air is denser and contains more oxygen
atoms per cubic foot. So cooler air will allow more
fuel to be burned and in turn, make more power. A 10
degree drop in temperature can add 1 to 1.5% power to
an engine. Nitrous oxide boils at -129°F and it
will begin to boil as soon as it is injected. This can
cause an 80° or so drop in manifold air temperature.
Now if we are dealing with say a 400 hp engine, we can
see a gain of well over 30 hp from the cooling effect
alone. This cooling effect also helps the engine deal
If you were to build a 350 hp 3.5 Rover V8, it would
have to rev to 7000+ rpm to make that kind of power
and only make power over a narrow rpm range. A nitrous
injected 3.5 Rover V8 making 350 hp would make that
power at a much lower rpm with a higher average horsepower.
So the nitrous engine will out perform the normally
aspirated engine by a healthy margin. The reason is
that nitrous flow remains constant no matter what rpm
the engine is running at. At lower speeds there is more
time for the nitrous to fill the cylinders, so you get
more nitrous in the cylinders per power stroke at lower
rpm. This will boost torque and consequently power more
at low rpm. As rpm increases, you will get less nitrous
per power stroke, but the engine will start making more
normally aspirated power. This really flattens out the
torque curve and widens the power band.
Thanks To Trev And Highpower
for all the Info above,