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Learn About Nitrous
by Joe Evert
Should I Do It?
So, you’re thinking of using nitrous to increase the power of your ride?
You should be. If done properly, nitrous is a safe and effective way
to add instant power and no other power adder equals the bang for
buck nitrous delivers. Using nitrous to give an engine a boost is
nothing new and dates back over 50 years. I’ll spare you the
history lesson and focus on how it is used and why it works in
modern engines.
How It Works
Everyone knows an engine takes in air and fuel, burns it and
converts that energy into horsepower to drive the vehicle. In
general, the more air and fuel the engine can burn, the more power
it’s able to produce. The air to fuel ratio is usually between 12 to
15 parts air to 1 part fuel. Changing the ratio above or below that
ratio usually leads to less power and efficiency. It’s relatively
easy to add more fuel; bigger injectors, higher fuel pressure are
two popular ways to achieve this. But how do you add more air? Once
the throttle is wide open, the engine is pulling in as much air as it
can. In fact, the throttle is what regulates how much air the engine
is allowed to draw in. The vehicle’s on-board computer determines
how much air is entering the engine and controls the fuel flow
accordingly to match the air flow. In order to add more air into
the engine for a given throttle angle, you can do one of two things;
force more air in using a turbocharger or supercharger or inject
nitrous into the air intake stream. Using a turbocharger or
supercharger is referred to as “forced induction”, it’s forcing the
air into the engine under pressure. An engine that does not use
forced induction is referred to as “normally aspirated” because the
engine breaths on its own. The air it takes in is not under any
pressure – it’s being pulled in by vacuum the engine generates.
The air we breathe contains about
21% oxygen. Since oxygen is what is really needed to
burn fuel we’ll focus on that number for a minute.
Remember we can increase the amount of oxygen the engine
takes in by forcing it in by pressurizing the intake
system using a turbocharger or supercharger. Basically,
what that is doing is forcing more of the same 21%
oxygen air we breathe in the same space. This increases
the amount of oxygen and as a result we can add more
fuel which equals more power. But rather than doing
this, what if we could change the oxygen content of the
air the engine was taking in from 21% to say 40%. The
end result would be the same; more oxygen in the engine
right? Sure, and that is exactly what nitrous does. Now
we can add more fuel and gain more power.
It doesn’t sound too safe running
around with a tank of oxygen in your trunk does it?
After all, oxygen supports combustion, a simple fender
bender could turn out to be a major catastrophe. It’s
not safe, but nitrous oxide is not oxygen and that’s the
miracle of nitrous. At room temperature it is a
colorless, non-flammable gas. A nitrous molecule contains
two nitrogen and one oxygen atom (N2O). When nitrous is
exposed to high combustion temperatures, it breaks down
and releases the oxygen which allows additional fuel to
be burned resulting in more power. There's another
advantage too; nitrous is stored as a liquid in the tank,
but when it is released into the intake manifold it
vaporizes into a gas. This reduces the temperature of
the air charge temperature, which reduces detonation and
provides for more air density.
Wet or Dry
Getting more fuel to the engine in addition to adding
nitrous is what makes more power. There are two types of
nitrous systems on the market and you've probably heard
the term "wet" or "dry" systems. This refers to the
method of how the additional fuel is added to the
engine. In a wet system, fuel along with the nitrous is
injected into the air stream or directly into the intake
manifold. When fuel is injected directly into the intake
port just above the intake valve it is referred to as a
"direct port" system. A dry system typically boosts the
fuel system pressure during nitrous engagement to
provide additional fuel flow through the vehicles
existing injectors. Typically, wet systems provide more
horsepower but a dry system may be easier to install
because you won't have to drill the manifold or tap into
the vehicles fuel system. For the average user seeking
50-75 horsepower a dry system might be ideal.
Shots & Pills
The horsepower a nitrous system will make is often
referred to as "shot" size. For instance, a "50 shot" is
equivalent to 50 horsepower. The amount of additional
power is a function of how much nitrous and fuel is
injected into the engine. This is usually controlled by
a jet or "pill" size that is installed in the nitrous
and fuel nozzles. These are essentially a plug with a
precision orifice (hole) drilled into them. The larger the
jets, the more nitrous and fuel and more power.
How Much Is Enough
Most stock engines will easily handle 50-75
additional horsepower without modification. Nitrous is
easy power and as a result, many people have damaged
their engine by pushing it too far without making the
necessary engine modifications. This has given nitrous
an undeserved bad rap. Every engine has it's weakness
and if you push it hard enough it WILL break. Another
issue that can arise that will cause engine damage, is
improper jetting. This usually results in an improper
fuel mixture that is too lean; too much nitrous, not
enough fuel. This causes exceedingly high combustion
temperatures which will melt the ground straps off of
spark plugs, melt the edges of the exhaust valves and if
bad enough, melt the crown of the piston. It's always
better to jet the nitrous system a little on the "rich"
side, which is a little more fuel than what is
necessary. You might not make quite as much power but it
will be a much safer set up.
Progressive
A progressive nitrous controller pulses the fuel and
nitrous solenoid to ramp up the nitrous over a period of
time. This allows the engine to build RPM and allows the
tires to gain traction while the nitrous is introduced.
In theory, this sounds ideal however, in practice there
are some definite down sides. First, nitrous is under
extremely high pressures of over 900 psi. Nitrous
solenoids have to be designed to accommodate these high
pressures. They must positively shut off the nitrous to
prevent leakage. Their sealing surface can be made of
two types of materials; Viton, which is a rubber-like
material or Teflon, a much harder material. Viton
provides a very good seal and will last a lifetime. The
downside is that the Viton does not hold up well to
being switched on and off, rapidly because it will wear
out, it's a softer material and does not take a beating
very well. The other material can be Teflon or Delrin.
Both are similar material and are much harder than Viton.
They do hold up very good to being pulsed on and off but
they don't provide a positive seal like Viton does.
Leakage is not entirely uncommon.
For the average user who is
running 50-100 additional horsepower with nitrous you
can probably skip the progressive control. Using a delay
to allow the tires to "hook-up" prior to
nitrous engagement will do the trick.
If you're going to use a
progressive control scheme make sure you're prepared for
a few solenoid failures down the road (regardless of
manufacturer) and check them frequently to ensure their
still sealing properly.
Summary
Nitrous is like a lot of things; used in moderation it
is safe and fun! Take your time in researching which
system is right for you and take your time doing the
install. Start off easy and go slow, don't add too much
power at once. The temptation of adding more and more
will be great, but will surely end badly. Resist adding
too much power as this will result in engine damage,
ruining your day and providing a bad nitrous experience.
If you have questions or comments
or would just like to provide some feedback feel free to
contact me.
- Joe Evert |
