This technical information is to be used as an aid in helping to tune our nitrous oxide systems. Before addressing the nitrous variables, be sure that you have properly tuned your engine and that it's working at peak efficiency without nitrous. Our goal is to provide reliable horsepower gains without sacrificing dependability or reliability. To achieve the gains that we did, you need to eliminate variables that could cause less-than-ideal operation.
BOTTLE PRESSURE Bottle pressure is one of the most important factors in tuning a nitrous oxide system. Many people feel that if a bottle is full then the pressure must be right, however, that isn't always true. Pressure has a direct relationship to temperature. A full bottle can vary from 750 to 1200 psi. All Edelbrock nitrous systems are tuned utilizing liquid nitrous, which is denser than gaseous nitrous and more stable. Nitrous becomes a liquid at a temperature of -127°F at atmospheric pressure. Since this temperature is nearly impossible to sustain and there would be no pressure to carry the nitrous where it needs to go, we use the alternate method to change the phase to a liquid by pressurizing it to a level of 735 psi or greater, ideally 950 psi. At 950 psi nitrous has a density of 5.44 lb/gal., bottle pressure is more stable and can easily be sustained with the use of a bottle heater. A common misconception is that running bottle pressure greater than 950 psi will generate a much higher flow of nitrous, however, this is not the case. At excessive bottle pressures as bottle volume decreases the rate of pressure drop increases and it becomes harder to maintain a stable pressure. A consistent bottle pressure provides a consistent amount of nitrous delivery during a given period of time. It's also good practice to top off the bottle when it reaches a volume of less than 40%.
FUEL PRESSURE A commonly overlooked problem is insufficient fuel pressure. To maintain consistent fuel pressure and delivery we must determine if it is adequate for the task. Most modifications will be fine on factory fuel delivery systems. On highly modified engines that horsepower levels exceed 40% over the manufacturer rated hp level, modifications like the addition of an in-line booster pump or dedicated fuel system is recommended. The purpose of a booster pump is to work in conjunction with the stock pump and maintain a more consistent fuel pressure. The booster pump allows the factory pump to provide its maximum volume capacity; the booster pump then increases the fuel pressure. In racecar applications with a direct port nitrous system or wet nitrous system, a dedicated fuel system is recommended. A dedicated fuel system consists of a fuel pump, fuel pressure regulator and feed line to the fuel solenoid. The purpose of a dedicated fuel system is to provide fuel enrichment for the nitrous system independent of the primary fuel system. A dedicated fuel system offers a greater degree of tune-ability and eliminates problems that might arise from sharing a fuel pump with the engine.
TIMING When we set the timing on a car we are actually finding the point in which the engine will initiate the burn so that at about 15° After Top Dead Center (ATDC) peak cylinder pressure can occur. Depending on combustion chamber design and cylinder filling, this point can be anywhere between 30° and 45° Before Top Dead Center (BTDC). The reason we retard timing with nitrous injection is that the air charge becomes more oxygen dense, causing the air/fuel mixture to burn at a much higher rate. In other words, accelerated combustion occurs. This acceleration in combustion causes peak cylinder pressure to happen much earlier. The problem with this is that instead of using the energy generated by combustion to give the piston momentum we are transferring that heat energy onto the rotating and reciprocating assemblies, and possibly hurting them. In the process we are losing torque and horsepower. To prevent this, we recommend that you retard the ignition timing 1-1/2° to 2° for every 50 hp added through the nitrous system. This will ensure that peak cylinder pressure occurs at the same point it did before the nitrous was injected into an engine. Also keep in mind that retarding too much timing will also hurt you. If you retard more than the recommended amount, peak cylinder pressure can occur much later in the combustion cycle and that energy will be wasted. In most cases, avoid aftermarket chips or computers that are not designed for use with nitrous. They typically add more ignition timing, which could lead to power loss and engine damage.
SPARK PLUGS The last frequently misunderstood factor in adapting a nitrous system to your engine is the spark plug. Three important aspects of spark plugs must be looked at: their heat range, reach and gap. We advise lowering the heat range of your spark plugs 1 step for every 100 hp added with nitrous. The other aspects of a plug that must be looked at are the reach and gap. It is best to use a non-projected type plug. Projected plugs allow a greater portion of the electrode to be exposed to combustion gases and possibly cause pre-ignition. The spark plug gap also plays a large roll in nitrous engine performance, because increased cylinder pressure from the additional nitrous and fuel makes it harder for the spark to jump the gap. The same gap that worked for a non-nitrous set-up may be too much for nitrous, leading to excessive misfires and loss of power. Also, we recommend that you do not use platinum plugs. The platinum tips can get extremely hot and will cause detonation. Plus, there is a chance the tip may break off in even cases of mild detonation and can severely damage the engine.
Ideally a gap between .025" and .035" should be used on high horsepower applications where an inductive style ignition system is utilized. Engines equipped with capacitive discharge ignition systems may use gaps larger than .035". It's very important to learn how to read the plugs after a pass. A plug can tell you a lot of what is happening in the combustion chamber. CLICK HERE to view spark plug heat ratings.
Edelbrock suggest an NGK Spark Plug with a heat range of -9 to -11 depending on the nitrous power level being tuned. When in doubt, always go to the next colder heat range plug.
NITROUS TECH TIPS Engine configuration tips for Edelbrock Direct Port Systems
TECH TIP 1 When using an Edelbrock Direct Port Nitrous System, extra fuel is required to make the additional horsepower. Call the Edelbrock Tech Line at 1-800-416-8628 from 7am to 5pm PST Monday-Friday for more information regarding Edelbrock fuel pumps.
TECH TIP 2 In extreme horsepower applications, such as with our Victor Jr., Victor & Super Victor Series Nitrous Systems, extremely high cylinder pressures can be generated. We recommend high-strength internal engine components such as forged pistons and crankshaft, high performance connecting rods, etc. Please contact the Edelbrock Tech Line for more information regarding your engine configuration for the power gains you are looking to achieve.
TECH TIP 3 For race engine applications, there are cams specifically designed for use with nitrous. Typically, these cams will feature a wider-than-normal lobe separation angle, usually around 112° to 114° to keep the nitrous-enhanced intake charge from being purged out through the exhaust valve. Cam changes such as these are only to be performed on racing engines, not stock or near stock applications.
TECH TIP 4 For race engine applications, many standard ignition systems experience misfires at high cylinder pressures and/or high RPM. We recommend using a high-quality performance ignition system for such racing applications.
NITROUS JET MAPS Click Here to view the nitrous jet maps.
INSTALLATION INSTRUCTIONS Click Here to view the installation instructions.
NITROUS WIRING DIAGRAMS The following diagrams illustrate how to wire up various nitrous kits and components. Please click on image to download pdf.
Click here to download The Nitrous Catalog PDF (you will need Acrobat Reader® in order to view this PDF). If you do not have this installed you can download it by clicking the icon.