(historic document) new page www.nitrous.info
Nitrous Oxide Injection F.A.Q.
and as found all over the net....
(From somewhere on the net,
originally, I think, but modified by me)
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Nitrous oxide injection has become one
of the most popular methods of increasing the power output of an internal
combustion engine, and justifiably so. Nitrous oxide (N2O) injection is simple
precisely metered N2O and gasoline are force-fed into the engine, supplementing
the normal air/fuel mixture to release more work-producing heat during the
combustion process. The only equipment required is an N2O storage tank, a pair
of solenoid-actuated valves to control the N2O and gasoline flow, nozzles (or
spray bars) to distribute the N2O and gasoline, and the various hoses, lines and
wiring to connect the system. Engine disassembly is not required for
installation-and the system can be removed for resale or transfer to another car
at any time. The cost of a new professionally prepared system is reasonable
(between $400 and $600 US in most cases), and the power increase is dramatic
(usually in excess of 100 hp for most street systems).
As popular as N2O systems have become (industry estimates are that over 20,000 systems are now in use!), many enthusiasts still think of N2O as some sort of evil black magic. Honest and reliable information about the effects of nitrous oxide, the care and installation of N2O systems and tuning tips regarding N2O use has been practically nonexistent. Instead, the bench racers pass along inflated rumors of unbelievable power gains that rival a Saturn rocket, and incredible horror stories of vehicles supposedly erupting in fireballs that would make a hydrogen bomb seem small.
FALLACY: N2O is explosive and a fire
hazard.
FACT: N2O will not burn, nor is it a fuel. It is merely an oxygen-rich
compound that supports the combustion of additional fuel. That's why additional
fuel is injected along with the N2O on all N2O systems. It is true that if N2O
is added to a combustion process already in progress, the extra oxygen may cause
rapid, uncontrolled combustion, thus raising the peak temperatures produced.
FALLACY: An N2O system will add 200 hp to
a car.
FACT: Although it is possible for the average N2O street system to add
150 + hp to an engine under ideal conditions, most street systems realistically
add 90 to 125 hp to the average engine, but the effect of another 100 hp to most
late model stockers is so dramatic that you'd be easily misled into thinking the
power gain had been far greater. The power increase also varies with N2O tank
pressure, fuel pressure, engine displacement, engine speed, ignition timing, the
normal air/fuel mixture and the N2O system design, so it is impossible to
accurately predict the actual power gain any car might display. As a good rule
of thumb, figure on 110-120 hp, regardless of the advertising claims. There are
special competition N2O systems that typically add another 50-75 hp over what
the street system produces, but forged pistons, special rings, and many other
specialized pieces are recommended to withstand the extra cylinder pressure when
these high-output systems are employed. Without the heavy-duty modification,
engine damage would be likely.
FALLACY: N2O adds octane to the fuel being
used and reduces detonation.
FACT: N2O does not increase the octane of the fuel being used. However,
nitrous oxide injection may suppress detonation due to the intercooling effect
of the depressurizing of the compressed N2O and by the introduction of extra
gasoline. Most N2O systems intentionally add about 10 percent excess fuel as a
safeguard against accidentally leaning the mixture. The extra fuel acts almost
like water injection to cool the mixture and dampen detonation.
FALLACY: Premium fuel must be used with
N2O injection.
FACT: The purpose of N2O injection is to support the combustion of extra
fuel, thereby releasing more work-producing heat in the combustion chambers.
Consequently, maximum cylinder pressures with N2O will be higher than when it
isn't in use. Extra cylinder pressure does tend to cause pre-ignition and
uncontrolled combustion, but as previously described, N2O injection also tends
to suppress detonation. With most street N2O systems, these two opposing forces
tend to cancel each other out, which means you can continue to use the same
octane gas that was acceptable before the N2O was added. Because competition N2O
systems inject a greater quantity of N2O and gasoline than do street N2O
systems, cylinder pressure is frequently raised to the point where a higher
octane fuel (or anti-detonation additives) must be used.
FALLACY: N2O will melt pistons, rings and
valves.
FACT: If the N2O system has been properly designed to supply the correct
amount of gasoline along with the N2O, combustion temperatures will actually be
lower than when N2O isn't being used, so damage from elevated temperatures does
not occur. Since the purpose of N2O injection is to make more heat, this may
sound like a contradiction, but it isn't. With N2O, the total amount of heat
energy released is greater, but the peak combustion temperature is lower. Think
of it this way: A huge oil storage tank burning at an average temperature of
1000 degrees releases a lot more energy than a small acetylene torch with a tip
temperature of 2000 degrees. That's a comparison by extremes, but in an engine
with N2O injection, each cylinder might be burning 25 percent more fuel at a
temperature of 1400 degrees than the engine would without N2O at 1460 degrees.
Claims of engine damage while using N2O are not totally fictitious, however,
since if cylinder pressure does rise above the octane tolerance of the fuel
being used, detonation occurs, and that will damage pistons, rings, etc.
FALLACY: Using N2O on an engine imposes no
special maintenance problems.
FACT: Because N2O injection does increase effective cylinder pressure,
normal blow-by past the piston rings is increased, thereby increasing oil
contamination. Consequently, oil drain and filter replacement intervals should
be decreased by roughly 25 to 33 percent.
FALLACY: Freezing the N2O tank increases
N2O flow and the power output.
FACT: Whenever a pressure vessel is cooled, internal pressure drops. Most
N2O systems are designed to work with tank pressures of 600-800 psi, which is
the approximate pressure of a normal bottle at room temperature (approximately
72 degrees). If the bottle is cooled below room temperature, the pressure
quickly falls, and flow would be reduced to the nozzles. For example, a bottle
that had 800 psi at 75 degrees would fall to 450 psi at 30 degrees, and only 275
psi at O degrees.
On the other side of the coin, heating the bottle increases the pressure, but
heat also tends to make the N2O vaporize in the line between the solenoid valve
and the discharge nozzle, which upsets metering and reduces N2O flow. Ideally,
the bottle and lines should be kept at room temperature. At the drags, some
cooling of the bottle may be required to achieve this while the car sits in the
staging lanes, but a damp cloth or towel wrapped around the bottle will
generally be all that's required. If you really want to pursue additional
cooling, chill the line between the solenoid
valve and the nozzle, and keep that line as short as possible to reduce the
likelihood of vaporization before the discharge nozzles.
FALLACY: N2O injection in the individual
manifold runners, as close as possible to the cylinder head, is more effective
than injection immediately below the carburettor.
FACTT: Although it used to be thought that direct port injection improved
performance by assuring equal distribution, subsequent vehicle and dyno tests
have shown that under-the-carb injection seems to provide a greater power
increase since the gasoline has more time to vaporize as it travels down the
intake runners. Of course, for under the carb injection to work properly, the
nozzles must be designed to provide even distribution to every manifold runner.
FALLACY: As long as there's still pressure
in the N2O bottle, some N2O is left and the system will function properly.
FACT: An N2O system meters and discharges liquid N2O when everything is
working properly. When filled, an N2O bottle is only 68 percent full of liquid.
The remaining space is specified as an expansion area. Additionally, an N2O tank
needs a siphon tube to assure that the pressure head in the expansion area
forces liquid N2O out into the lines, rather than gaseous N2O. When the liquid
N2O is expended, it is not uncommon for the tank to still have 600 psi pressure,
so pressure alone is not an indicator of N2O. Gaseous N2O is clear, whereas
liquid N2O, vaporizing as it leaves the nozzle, will be white in color. This is
a more accurate indication of whether there is still liquid N2O in the bottle.
FALLACY: You need a prescription to buy
N2O.
FACT: A prescription is not required to buy industrial grade nitrous
oxide for automotive use. Nitrous oxide is available at most compressed gas
suppliers, such as welding gas supply houses, but we have heard of isolated
cases where a particular dealer who doesn't want to be bothered servicing hot
rodders will use the excuse that you must have a prescription. If medical grade
N2O (the only difference is the sterilization of the bottles) was being sought,
then a prescription would be required. To make the purchase of N2O even easier,
many speed shops are now refilling N2O bottles. If you live in a really isolated
area or are confronted by an uncooperative dealer, the N2O system manufacturers
will refill your tank, but of course, shipping the bottle back and forth is an
inconvenience.
FALLACYY: N2O requires no special tuning
adjustments.
FACT: Force feeding N2O and extra fuel into the combustion chambers
increases the density of the mixture, which increases the burning rate of the
mixture. Consequently, it is frequently necessary to retard the ignition timing
slightly for optimum results. The greater charge density also imposes a heavier
load on the ignition system, so a good high-energy ignition system, with good
spark plug wires and clean spark plugs is essential. If a competition N2O system
is being used, the plug gap should smaller, and plugs one or two heat ranges
colder than stock are recommended to help dissipate the extra heat of
combustion.
FALLACY: You can build your own N2O system
- YES!!!
FACT: If you're sharp enough, you can.
FALLACY: If tank pressure exceeds 850 psi,
the solenoid valves will leak, flooding the manifold with N2O.
FACT: The solenoid valves used on some systems are rated at 850 psi
working pressure. Other systems have solenoids with even higher ratings. In
truth, the ratings are conservative and even the lowest rated solenoids being
used will work at pressures up to 1500 psi. The working pressure has nothing to
do with the pressure at which the solenoid will leak, since pressure actually
helps close the valve, so the higher the pressure, the more tightly it seals.
The working pressure or rating only refers to the solenoid's ability to open the
valve against the pressure in the system.
FALLACY: N2O will blow up your engine.
FACT If the N2O solenoid valve leaks or malfunctions while the engine is
off, the manifold can become charged with a very lean mixture of N2O and
gasoline. When the ignition is first turned on, a spark impulse may occur in a
cylinder where the intake valve is standing open, igniting the mixture, which
will virtually explode. Carburettors have been blown off manifolds in such
situations. Consequently, it is advisable to turn off the main valve on the N2O
tank whenever the car is going to be parked for several hours. If a leak is ever
suspected, simply remove the coil wire and crank the engine for about 10 seconds
to clear any N2O contamination.
FALLACY: You can smell leaking N2O.
FACT: Nitrous oxide is an odourless, colourless gas.
FALLACY: There's no limit to how much
power you can make with N2O.
FACT: More N2O and more fuel equates to more power, but there's a
definite limit to how much any engine will stand. It all comes down to: How fast
do you want to go? And at what price?