Nitrous Information
A Bit of Nitrous History
The use of nitrous oxide (N20) as a performance enhancement has been traced back to World War II, where it was employed first by the German Luftwaffe to give their fighter aircraft “emergency” boosts in both airspeed and altitude capabilities. The primary aircraft utizing nitrous oxide injection was the Messerschmitt BF-109 outfitted with the "GM-1" system. Nitrous was used by the Allies as well on various aircraft in response, notably on the American P40 and some British aircraft. However, with the advent of jet propulsion toward the end of WWII, and the resultant phasing out of piston-driven fighter aircraft, nitrous oxide R&D was shelved.
There were sporadic attempts at using nitrous oxide in race cars over the next couple of decades, but for the most part it was a clandestine, closely-guarded secret, and not too many people were aware of its existence. NASCAR legend Smokey Yunick was rumored to have experimented with nitrous oxide in the 1950's, but not many other "known" racers even knew about it. Early attempts at using nitrous on racing engines led to some discoveries, both good and bad (the bad leading to some of the rumors and misinformation about nitrous use today).
Around the 1970s, nitrous use started to pick up. Astute racers such as Mike Thermos, Dale Vaznaian and Marvin Miller saw the potential for nitrous use in race and street cars. Enthusiast publications of the day, (Hot Rod, Car Craft and Popular Hot Rodding to name a few), started running tech articles about the safe use of nitrous oxide, and interest started to take off. Savvy racers (drag and street racers alike) saw how easy it was to make "horsepower on demand".
Perhaps the single greatest boost to the popularity of nitrous oxide was the advent of drag racing’s Pro Modified class. Early pioneers in Top Sportsman racing (the forerunner to Pro Mod) such as Charles Carpenter, Bill Kuhlmann and Rob Vandergriff captured the imagination of race fans with their impressive performances with stock-bodied cars. These early cars evolved into todays low 6-second "bottle rockets" seen at IHRA and NHRA events.
Today, nitrous is used in a lot of applications, from Pro Mod racers to serious street cars. Other uses of nitrous include motorcycles, Powersports, and even RC applications!
An Overview Of Wet, Dry And Direct Port Systems
These are three basic types of nitrous systems: dry, wet, and direct port. There are differing schools of thought on "wet vs dry" systems, each have their pros and cons. Direct port systems are considered "wet" systems.
Dry Systems
typical dry system shown (Courtesy of Nitrous Supply)
A “dry” nitrous system is a system that injects nitrous "by itself" into the intake tract with a nozzle. What this means is that the fuel required to make additional power with nitrous will be introduced through the fuel injectors (remember, fuel makes power, nitrous simply lets you burn more of it). This keeps the upper intake dry of fuel. This is accomplished by changing what the engine computer "sees" coming into the throttle body (more "air"), basically "tricking" it into adding the required fuel. along with the nitrous to generate additional power.
The main advantage to a dry system is simplified plumbing and less of a chance of a "nitrous backfire" due to fuel puddling. The main drawback is the reliance on the engine computer to increase injector pulse width to add additional fuel. Without a supplemental fuel supply, the dry system user stands a very real chance of a lean condition developing and subsequent engine damage. Dry systems in particular can cause severe engine damage when used with factory rev limiters.
Wet Systems
typical wet system - single nozzle show (Courtesy Nitrous Supply)
The second type of nitrous kit is the “wet” style of kit. These kits include carburetor and throttle body plate systems as well as single and double nozzle EFI systems. These systems add nitrous and fuel at the same time and place (normally 3-4” ahead of the throttle body for fuel injected nozzle applications or just under the carb/behind the throttle body as with plate systems). This type of system requires tapping into the vehicle's fuel system for the additional fuel needed. They also will make the upper intake wet with fuel during use. These systems are used as stand-alone systems, but they can also be used in turbo/supercharged applications.
The main advantage of a wet system is no reliance on the engine computer (in EFI applications) to supplement fuel, using instead a fuel solenoid to add the required additional fuel. This eliminates the possibility of a dangerous lean condition. The main drawback for wet systems is the increased possibility of nitrous backfires due to fuel puddling over dry systems.
In both cases (dry or wet), nitrous systems and rev limiters (especially factory rev limiters that cut fuel) do not mix!
Direct Port
The last type of system is the direct port system. Just as it’s name implies, it introduces the nitrous and fuel directly into each intake port on an engine. These systems will normally add the nitrous and fuel together through a fogger nozzle or a "sandwich" type of nozzle sold by NOS as the NOSzle™. Both types of nozzle mix and meter the nitrous and fuel delivered to each cylinder. This is the most powerful and one of the most accurate type of nitrous system used today. This is due to the placement of the nozzle in each runner, as well as the ability to use multiple and higher capacity solenoid valves. A direct port system will typically have a distribution block and solenoid assembly which delivers the nitrous and fuel to the nozzles by way of connecting tubes. Because each cylinder has a specific nozzle and jetting (both nitrous and fuel), it is possible to control the nitrous/fuel ratio for one cylinder without changing that of the other cylinders. These systems are also one of the
more complicated systems when installation is considered, as the intake must be drilled, tapped, and the “plumbing” made to clear any existing obstructions. Because of this and the high output of these systems, they are most often used on racing vehicles built for the strain of such high horsepower levels, but are also used in "serious" street vehicles. These are not for the novice user!
What Nitrous Oxide Is and What Nitrous Oxide Isn’t
What is Nitrous Oxide?
Nitrous Oxide is an oxidizer that is used as a carrier for oxygen. Mixed with the right ratio of fuel, it provides additional combustible material into the cylinders, creating more power. To simplify, think of nitrous oxide as "chemical supercharging".
To your engine, nitrous oxide is a more convenient form of normal air. Since we are only interested in the oxygen the air contains, nitrous oxide provides a simple tool for manipulating how much oxygen will be present when you add additional fuel in an attempt to release more power. The power always comes from the fuel source. Nitrous oxide is not a fuel. Nitrous oxide by itself is non-flammable. As stated previously, nitrous oxide is a convenient way to add the additional oxygen required to burn more fuel. If you add only nitrous oxide and do not add additional fuel, you would just speed up the rate at which your engine is burning the fuel that it normally uses. This, more often than not, leads to destructive detonation and subsequent engine damage. The energy comes from the fuel, not the nitrous itself. Nitrous oxide simply allows you to burn a greater quantity of fuel in the same time period; thus the overall effect is a tremendous increase in the total amount of energy, or power, released from the fuel and available for accelerating your vehicle.
There is no "voodoo" or "black magic" involved in nitrous oxide. In effect, using nitrous is no different from using a bigger carburetor or fuel injectors, a better manifold, a supercharger, or a turbocharger. Understand that the air you and your engine breathe is made up, at sea level, of 78% nitrogen, 21% oxygen, and just 1% other gases. Nitrous oxide (N2O) is made by simply taking the 2 major components of earth’s atmosphere (in this case 2 molecules of nitrogen and 1 molecule of oxygen) and attaching them together with a chemical bond. When the nitrous oxide goes into your engine the heat of combustion breaks the chemical bond to provide your engine more oxygen with which to burn fuel.
All high-performance and race engines operate under the same principle: More air (better breathing, supercharging, turbocharging, or nitrous) plus more fuel in a denser vapor equals more power.
Nitrous Oxide vs. Other Performance Products
Dollar for dollar, nitrous oxide offers the most performance a consumer can buy. You could spend thousands of dollars on different carburetion, intake manifolds, valve train components, exhaust, pistons, porting, supercharging, or turbocharging to get the same amount of extra horsepower that a nitrous system would provide for just a few hundred dollars. But this doesn’t mean you won’t benefit if you also install other performance parts. Once you have installed a nitrous system, all those other performance parts just increase the nitrous power. If you have a limited budget and want lots of extra power, the best choice is a nitrous system.
Only nitrous oxide is a part time power increaser. All of the standard performance parts put additional stress on the engine and burn more fuel all the time; not to mention what a pain it is to ride around town with a lumpy idle from a camshaft that is barely streetable. Power on demand is one of the great things about a nitrous system; it only works when the driver wants it. The rest of the time, the engine operates normally; no extra stress, no extra fuel use, and no driveline problems and/or driveability issues associated with other power adding modifications.
Nitrous Oxide and Emissions
Use of nitrous oxide (N20) doesn’t necessarily increase the oxides of nitrogen (NOX) that pollute the air, Of course, there are “race only” systems that are not legal for use on pollution controlled engines. However, many nitrous systems have received certification for 50-state emissions legal use in the United States. The approvals for use on emissions controlled vehicles were obtained by independent laboratory testing which proved that these systems do not increase tailpipe emissions in normal driving conditions.
Spark Plugs and Nitrous Oxide:
What Works, What Doesn’t, and Why
Over the years there seems to have been a great amount of technical material written about the simple operation of a spark plug and what they can do in relation to the way an engine runs. There are a few basic characteristics about spark plugs that you need to know to make an intelligent choice about the correct spark plug for your application.
First, and most important; a spark plug must be of the correct design to operate within the environment of your engine not the other way around. This means that the spark plug has virtually no influence on how the engine burns fuel or runs in general. The correct spark plug will simply survive the conditions present in your engine. A spark plug must maintain a certain temperature to keep itself clean. The wrong heat range can cause an overheated plug or a fouled plug. The heat range refers to the temperature of the ceramic material surrounding the center electrode.
Lean air/fuel ratios are more difficult to light because there are less fuel molecules in the area of the plug gap when the plug is scheduled to fire; thus, protected nose plugs were designed for late-model lean-burn engines. Modern high-energy ignition also allowed larger plug gaps. All the while this was happening, something else happened. Something that no one seems to have really noticed as the real culprit when the issue of factory type plugs being used with nitrous comes up. We’d like to clue you in...
Quite often, a factory type, wide-gap projected plug will produce a misfire condition after only a few seconds of nitrous use. The misfire is not due to the heat range. The misfire occurs because the ground strap of the spark plug becomes a glowing ember because it is too long to dissipate the extra heat produced by a nitrous-accelerated burn condition. The correct fix for this phenomenon is to replace the plugs with one that has a shorter ground strap. By doing this, you will shorten the path for the heat being absorbed by the ground strap. You can use the same heat range, you just have to find a non-protected nose plus with a shorter and preferably thicker ground strop.
If you only change the heat range of the spark plug to a colder heat range, you may very well still have the misfire problem. Since the length of the ground strap is the cause the misfire, a colder spark plug may have the same length of ground strap as the hotter plug you replaced it with.
Spark plug gaps should generally be .030” to .035”. Never try to gap a plug designed for an .060” gap down to .035’. Find the correct non-projected nose plug designed for an .035” gap.
Common Sense Usage of Nitrous Oxide
Nitrous oxide is used only at wide open throttle (WOT), and should not be engaged below 3000 RPM in most cases. Manual transmission equipped vehicles should have an RPM "window switch" installed to prevent the possibility of hitting the rev limiter while the nitrous system is engaged. Manual and automatic equipped vehicles should also use a window switch for another reason, explained below. Another good safety item is a fuel pressure safety switch (FPSS). We'll list details on these specific items below.
Window Switch:
An RPM operated electrical device that provides a closed circuit to the solenoids based on the engine being between two RPM values (the RPM "window") that allows system operation within a specific RPM range for two very different reasons.
• At low RPM, the system is spraying nitrous into the intake at a constant flow. Inside the engine, the nitrous and fuel mixture is being sucked into the cylinders during every stroke. The net result is that at very low RPM, the engine is getting far more of the mixture into the cylinders than at high RPMs. At 3000 RPM, for example, the engine's getting twice the amount than it would at 6000 RPM. So, you can imagine that running nitrous at, say 1000 RPM, is far more stressful on the motor as at 3000 RPM, and typically causes a "nitrous backfire" - meaning that the nitrous/fuel mixture can explode in the intake manifold, rather than burn in the cylinders - a very bad thing. This is why nitrous in not triggered below 3000 RPM.
• At high RPM, the situation is easier to explain. Given the discussion of rev limiters earlier, the user will want the nitrous system to shut off before hitting that rev limit. If you're running a stock ignition, you certainly want a window switch. If you're running an aftermarket ignition, it's a little safer for the motor to run nitrous during the rev limit (that cuts spark, NOT fuel), but still not recommended. It's not particularly easy on your transmission or clutch to have all that power during the shift either, which may be a reason to keep the window switch set a bit before you shift. With manual transmissions, missed shifts can cause you to hit the rev limiter, so a window switch should be considered a mandatory item.
• Typical settings would be - on at 3000RPM, off at 5800-6000 RPM. This is a guideline only, as individual setups vary.
Fuel Pressure Safety Switch (FPSS):
A switch that's plumbed into the fuel system, and provides an open or closed circuit based on availability of fuel pressure. It can be used in the triggering circuit to make sure the system does not engage in the event of a fuel system problem. Typically, a FPSS is used it to switch off the nitrous solenoid, rather than both solenoids. Turning off the fuel solenoid in addition to the nitrous solenoid can start a cycle of "pulsing" both solenoids on and off while the pressure raises and drops in the fuel system. Allow the pressure build up in the fuel lines when you open the fuel solenoid, and when it's high enough, the nitrous solenoid will open. The switch can be used whether you've got a wet or a dry system. You can adjust the pressure at which it triggers by using an allen wrench on the back of the switch (loosen the screw lowers the pressure threshold).
Typically, the FPSS is set to shut off the nitrous if fuel pressure drops around 10psi below optimal. On a typical wet EFI system, this will be
around 33psi, and on a dry system around 45psi.
