Light the Fire
Increased combustion pressures often require a more powerful ignition system than that on a non-nitrous engine. This is especially true on kits for late-model, fuel-injected production cars. Since many ignition systems are only powerful enough to operate under the conditions they were designed for, increased combustion pressures may exceed the limits of the original ignition system. A lack of spark can cause drastic reductions in power and allows the unburned, highly atomized air/fuel mixture to enter the exhaust system, which can lead to explosive backfires.
Timing also plays a key role in the performance of a nitrous kit. Due to the increased cylinder pressures, it's unnecessary and inadvisable to advance the timing as much as a normally aspirated engine. Overly advanced timing leads to detonation and can cause severe damage to the engine's internals. As with jetting, start conservatively and gradually progress to optimum performance. The following adjustments will serve as a general rule of thumb:
After the kit is installed and plumbed, but before the bottle is installed, the first step is to check the operation of the solenoids. Arm the system and press the button. An audible click should be heard from both solenoids.
Next, run the vehicle and check for fuel leaks. Now, with the fuel system pressurized and the car idling, raise the engine speed, arm the system, and tap the button momentarily. The engine speed should drop as soon as the button is pushed, indicating the extra the fuel was injected.
Now install the bottle. With the engine off, open the bottle valve and check for leaks. If there are no leaks, you are now set to go to the drag strip to try your system.
It is best to initially activate your nitrous system at wide-open throttle (WOT). Using nitrous at too low of an engine speed can cause detonation, so it is best to be careful. Never activate the nitrous system with the engine not running. If you do, an explosive backfire could occur on start up. If you accidentally activate the system with the engine off, pull the coil wire off or disconnect the power to the coil, and crank the engine over for 30 seconds to clear the nitrous from the cylinders.
As previously stated, nitrous oxide is stored as a liquid under high pressure in the bottle. Bottle pressure will vary with temperature. If heat were continually applied to the bottle without a safety release, the bottle would explode. The explosion would be so violent that it could destroy the car that the bottle was mounted in. While each bottle is equipped with a 3,000-psi pressure relief to prevent explosions, care should be taken not to allow the bottle to be overheated.
The fitting on the valve in the upright position is the pressure relief. Should the cylinder exceed 3,000 psi, this relief fitting is where the cylinder will empty. If the car is to be used in IHRA competition, the rules dictate this relief fitting be vented to the outside of the car, a good idea in any situation. Relief valves with a threaded housing that accepts an -8 AN hose end are available.
Bottle pressure is also a key to nitrous system performance. Nitrous kits are usually jetted for optimal performance at a bottle pressure of between 950 and 1,000 psi. If the bottle pressure is higher, the mixture could be too lean, and if the bottle pressure is lower, the mixture is too rich. This is why nitrous racers are always concerned about bottle pressure.