If you want to go faster with Nitrous Oxide you probably should know a few things before you blow your engine up. I’ll go through a few different types of kits, how to set them up, and what other changes you will need to make to keep the pistons inside the engine.
#1 Dry Kit
Dry nitrous kits spray Nitrous Oxide into the air intake or intake manifold of the engine, this improves the oxygen content of the intake air chemically and air density by its cooling effect. Because this type of system does not add additional fuel, you will need to either jet your carb larger or use larger fuel injectors with software changes to your engine computer. If you don’t really know what you’re doing I don’t advise using a dry kit since the probability of going to lean and destroying your engine is higher.
I used a dry kit on the Janky Cycle because it didn’t have a fuel pump and also the shot size was very small. It was annoying to change the carb jet every time I wanted to use nitrous, but without a fuel pump there was nothing to force fuel into the intake except the single barrel carb with the gravity fed tank. Propane injection may come in the future which would change it over to a wet kit.
#2 Wet Kit
Wet kits are basically the same thing as a dry kit, but with the addition of a secondary fuel delivery system. This system compensates for all the extra oxygen entering your engine by also adding the appropriate amount of extra fuel, keeping your air to fuel ratio (AFR) the same as if it was operating without the nitrous kit. This type of kit is what I use for a car that I want to drive around normally without nitrous and then flip a switch to activate the nitrous system without having to modify any fuel system components. On a fuel injection car you can take the scrader valve out of the fuel pressure test port and attach a small hose with a solenoid on it for your extra fuel. For a carburated system you can place a tee if your fuel line and run a line from there to your solenoid.
I used a wet kit on both my 89 IROC Camaro and the 99 ls1 Camaro, both of which were daily drivers equipped with nitrous for the track.
#3 Timing retard
If you’re only running a small shot size you can probably get away without changing your ignition timing, but since you want to go fast you are going to change out those small jets after like 15 minutes. The “general rule” is 2 degrees of timing for every 50hp of nitrous for a v8, so obviously if you have a go kart you might have to do something different. You can change your timing either by turning your distributor if you have one, tuning your ECU if you have a coil over plug engine or you can add a timing retard computer that is an additional device that only retards timing when the nitrous system is activated. Some small engines like have a fixed ignition timing so you may need to use a timing retard box.
On the 99 Camaro I retarded all of the ignition timing in the range that I use nitrous with HPtuners by 6 degrees (and then did some smoothing) before I spray. It has a 150 horsepower shot wet kit installed.
#4 Spark Plugs
Depending on how much horsepower you are adding you might need to change your spark plug(s) to a colder heat range. Adding horsepower to an engine means there is more heat in the combustion chamber. Spark plugs are designed to operate at a certain temperature so they are hot enough to burn off fuel deposits and not foul, but not too hot to ignite the fuel mixture before the spark. A colder heat range spark plug dissipates heat faster to maintain that ideal operating temperature when the combustion chamber is hotter. Idle and low rpm drivability can be negatively affected by going with too cold of a spark plug.
Another consideration is non-projected tip spark plugs. For combustion efficiency manufactures used spark plugs that extend the tip and the ground strap of the spark plug farther into the combustion chamber to make it easier to ignite leaner fuel mixtures. If you’re running nitrous that longer ground strap metal can heat up and ignite the mixture in the cylinder before the spark the same way running too hot of a heat range will. Cutting off some of the ground strap or running non-projected tip spark plugs can solve this issue.
On the ’99 Camaro 150 shot I’m currently running NGK TR6 plugs which are 1 step colder than stock. I recently found out about this projected tip thing so I’ll be changing them to either NGK BR6EF or BR7EF plugs.
#5 Piston Ring Gap
As you add more power to the engine all the metal components are going to expand even more than normal. If the piston ring gap fully closes, the metal will have nowhere else to go and will apply pressure to the top and bottom of the ring grove in the piston until the piston breaks. This is probably the most common engine failure with nitrous unless you have detonation caused by lean conditions, too much timing or too hot of spark plug.
With a file or ring gap tool you can open up the ring gap to adjust for this depending on how much extra power you are adding and for how long. It is recommended to open one of the piston rings (top or bottom) a few thousandths larger than the other ring so pressure doesn’t build up between the rings and break the piston.