Congratulations, you’ve settled on a nitrous system.
There are any number of great systems on the market, and choosing a nitrous kit that’s right for your vehicle can be an accomplishment. If you watched our earlier video post, Your Top Nitrous Questions Answered, you know there are specific horsepower guidelines for picking the right system, depending on whether your engine is stock or modified. Hopefully, you followed those guidelines and made the best purchase decision possible.
Now it’s time to tune the nitrous system itself.
Fear not, though, because we’ve got some valuable tuning tips courtesy of Nitrous Oxide Systems (NOS). Read on for some good old-fashioned NOS know-how from the nitrous gurus:
Be Realistic About What Your Engine Will Handle
If you don’t know what’s inside your engine, then the safest route is to assume the components are factory stock and can choose a system based on that. If you’ve added aftermarket components, be conservative in assessing the amount of power they’ve added. If you are unsure about those components, you can call the Summit Racing or NOS tech line, and they’ll be able to help you make a reasonable estimate.
Always Start Conservative
Follow the recommended jet combinations and start with the lowest level if you have an adjustable system. It only takes a few moments to change the jets so don’t take unnecessary risks by starting at the highest level.
You can check out baseline recommendations from NOS in these posts:
Understand the Role of Fuel
Power comes from fuel, and any performance increase is dependent on the amount of additional fuel your system supplies while the nitrous system is operating. If the fuel isn’t there, the power won’t be either and no amount of nitrous or anything else can bring it back.
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. When tuning the nitrous system itself, there are two ways to manipulate the amount of fuel available during system use: the fuel jet size and the fuel pressure.
Monitor Fuel Pressure Correctly
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.
While tuning your nitrous system, take any fuel pressure readings while the system is activated. Some fuel pressure regulators give false readings because the pressure reading will creep up when the system isn’t activated. When this happens, the actual flowing fuel pressure will be much lower than expected and can cause problems. The correct fuel pressure is read while the system is flowing fuel.
Reduce Nitrous Jet Sizing to Avoid Detonation
When problems with misfire or detonation are encountered, always reduce the size of the nitrous jet first! Remember that the power comes from the fuel, not the nitrous, so trying to cool things down by adding fuel simply adds more power and complicates the problem. Carburetors jetted over-rich run cooler and release less power. Nitrous systems jetted over-rich will possibly just release more power, so if you run into problems, reduce the size of the nitrous jet(s) first.
Examine Your Spark Plugs
Hopefully, you’ve chosen the right spark plugs to go with your system. A good plug for nitrous applications typically includes a colder heat range (often one or two steps below your existing plugs), smaller plug gap, and shorter reach.
Your spark plugs can give you clues to how your nitrous system is running and what adjustments need to be made. When you check your spark plugs for signs of how your system is operating, check EVERY spark plug, not just the easiest plug to get to. No two cylinders ever run exactly alike.
Nitrous has the unique characteristic of cleaning the spark plugs very well and leave them looking freshly installed. If there are signs of detonation such as tiny silver or black specks deposited on the porcelain, reduce the nitrous jet size. If the ground strap of the spark plug exhibits a bluish-rainbow coloring, reduce the nitrous jet size. If the ground straps show signs of melting, reduce the nitrous jet size and change to a spark plug with a shorter and thicker ground strap.
Check Your Filters
If your system suddenly develops problems even though you haven’t changed anything, the culprit is most often a clogged nitrous or fuel filter. Check them periodically.
Consider a Bottle Heater
NOS systems are calibrated for optimum performance with a bottle pressure of 900-950 psi, but the actual pressure will change with temperature. Heater kits are thermostatically controlled to keep the bottle at optimum temperature to provide correct pressure. Kits are available for the most popular bottle sizes, with both 12-volt and 10-volt heaters available.
Other things that will affect the performance of your nitrous system include ignition timing and fuel octane. Keep in mind, NOS recommends you retard the ignition timing two degrees for every 50 horsepower added. You can find more information on timing and octane in the Bottle Basics posts mentioned near the beginning of this article.