There’s really no secret to making horsepower with a nitrous system. Nitrous delivers instant power gains by cooling the intake charge, improving fuel atomization, and giving your engine the ability to burn more fuel. But there are four ways you can optimize your nitrous system to ensure you achieve maximum power with your new nitrous system:
1. Go With the (Proper) Flow
The amount of power you gain from your nitrous system is directly proportional to the amount of the fuel you supply to the engine. There are two factors that determine fuel flow with a nitrous system: jet size and fuel pressure.
When it comes to jet size, always follow the recommended jet combinations and settings laid out in the nitrous system instructions. If you have an adjustable system, start conservatively; begin with the lowest jet sizes and work your way up. If you experience detonation or misfire, try easing back on the nitrous by reducing the nitrous jet size. Many times, this will eliminate the problem without sacrificing too much power.
Nitrous systems require a minimum amount of fuel pressure to work properly. NOS systems, for example, require 5.5 to 6 psi of pressure. However, the more fuel you can feed the engine, the more power it can make. You may want to bump the fuel pressure up to a rate that will yield greater power without causing detonation or misfire.
When setting fuel pressure, check the pressure gauge while the system is activated for the best accuracy, then make adjustments accordingly. Fuel pressure readings may creep up when the nitrous system is not activated, causing the gauge to give a reading that’s not valid when the nitrous is actually in use.
On stock or mildly modified engines, the factory fuel system will work just fine. On highly modified engines where horsepower levels are substantially higher, fuel system modifications may be needed. Upgrades could be as simple as a higher flow fuel pump or as complicated as a complete, dedicated fuel system just for use with the nitrous system.
Use this formula to calculate the fuel pump size you’ll need to supply a highly modified engine:
HP/2 = pounds-per-hour
Pounds-per-hour/6 = gallons-per-hour (GPH)
GPH x 1.15 = Minimum GPH
2. Know Your Engine
When it comes to choosing the right level of nitrous, it’s important to know the capabilities, purpose, and limitations of your engine. If you are unsure of the components inside your engine, assume it is stock and lean to the conservative side on jetting and fuel pressure. NOS recommends you stick to the following nitrous levels for stock engines: 40-60 horsepower for four-cylinder engines, 75-100 for six-cylinder engines, up to 140 horsepower for small blocks, and 125-200 horsepower for big blocks.
3. Perfect Timing
Timing on most vehicles is set so that peak cylinder pressure takes place from 10-15 degrees After Top Dead Center (ATDC)–the optimal point in the combustion cycle. To make peak cylinder pressure happen at this point, total advance should be set anywhere from 30-45 degrees Before Top Dead Center (BTDC).
Since nitrous makes the air/fuel mixture denser and begins to burn at a much quicker rate, peak cylinder pressure happens much earlier. As a result, the reciprocating assembly is forced to work against the cylinder pressure and absorb much of the combustion energy. This results in loss of power and torque, and in some cases, engine damage.
To prevent this, nitrous experts and manufacturers recommend retarding ignition timing when using a nitrous system. As a rule of thumb, you should expect to retard ignition timing at a rate of about 1 1/2 degrees to two degrees per every 50 horsepower added by the nitrous system. This will move peak cylinder pressure right back in the 10-15 degree ATDC range. Check your nitrous system instructions for specific ignition settings.
4. The Right Spark
Since a nitrous-injected engine consumes more fuel, you need to make sure you have the right spark plug to ignite the larger air/fuel mixture. There are three factors to consider when choosing a plug for your application: gap, heat range, and reach.
Spark plug gap is the distance between the ground electrode and the center electrode on the plug. When the ignition fires the plug, the spark jumps between these two electrodes and ignites the air/fuel mixture.
In nitrous applications, increased cylinder pressure makes it harder for the spark to jump the plug gap. For this reason, nitrous manufacturers recommend spark plugs with smaller gaps to ensure adequate spark—from .025-.035 inches in most cases. Some capacitive discharge style ignitions may be able to handle slightly larger gaps, but you should check your instructions for manufacturer recommendations. Use of oversized spark plug gaps may cause misfiring and overall power loss.
Heat range refers to the temperature of the ceramic material surrounding the center electrode in relation to how it dissipates heat. Choosing the right heat range for a nitrous application can be like walking a tightrope. If the heat range is too hot, you could run into an overheated or pre-ignition condition. If the heat range is too cold, the plug won’t burn off deposits and can become fouled.
A colder heat range plug works well with the increased cylinder pressures of nitrous applications. Most nitrous system manufacturers recommend moving to a spark plug heat range one to two steps below your existing plugs. Other companies, such as Edelbrock, advise its customers to drop the heat range one step for every 100 horsepower added by the nitrous system.
The final piece of the spark plug equation is reach, or the location of the electrode in the combustion chambers. Always use shorter, non-projected style spark plugs with nitrous systems. Because nitrous helps produce greater combustion heat and pressure, the longer electrodes on projected plugs are more likely to absorb heat, burn up, or cause pre-ignition. In some ultra-high horsepower applications, you may even want to shorten the length of the ground electrode.
Here are a few more, bonus ways to get more bang for your nitrous buck:
- Bottle blanket–– Keeping your nitrous bottle at a constant temperature means more consistent bottle pressure. If bottle pressure falls below 800-900 psi, nitrous flow becomes restricted. That causes a severe drop-off in nitrous system performance. A bottle blanket like this one from NOS will help stabilize bottle temperature and nitrous flow.
- Electric bottle heater–NOS also makes an electric bottle heater that will keep the bottle at a consistent 75 degrees (F)—the temperature required to maintain nitrous pressure above 800 psi.
- Progressive nitrous controller–The controller is timing-based, allowing you to build the flow of giggle gas gradually to full flow. That helps prevent excessive wheel spin off the line from a sudden hit of nitrous and lets you bring in the nitrous when you need it. Properly used, NOS says the controller can knock up to ½-second off your elapsed times.