CHEMICAL BOOST

EVER THOUGHT ABOUT RUNNING SOME NITROUS OXIDE ON YOUR ENGINE? WE RUN DOWN THE FUNDAMENTAL BASICS SO YOU UNDERSTAND WHAT YOURE DEALING WITH.

We all remember that scene in the original The Fast and the Furious when Brian (may he rest in peace), rocks into The Racers Edge and demands that two of the biggest NOS bottles be installed in his sweet Mitsubishi Eclipse by that evening — then, later that night, his manifold pressure is so high that it somehow blows the passenger floor panel out. Well, we are here to let you know that this will 100-per-cent never happen to you if you decide to go down the nitrous-oxide route. But bad things can happen if you don’t treat the stuff like any other power addition. Think of nitrous like a chemical boost, a facilitator that does exactly the same as a turbo or supercharger, by forcing more air into the combustion chamber, allowing your engine to use more fuel to create a bigger bang and thus more energy (power). The use of nitrous oxide as a power additive can be traced all the way back to World War II, when our allies used it in their higher-altitude planes, at the time before jet engines. However, it wasn’t until the 1970s that it became a popular automotive performance product, thanks to the formation of the company Nitrous Oxide Systems, or ‘NOS’ for short. You’re probably more likely to hear the liquid gas referred to as ‘NOS’, a clear indicator that these guys put the product on the map for us car-loving folk. Here in New Zealand, it’s been a popular drag-racing additive for just as long, but a recent rule rework by MotorSport New Zealand (MSNZ) now allows its use in circuit racing and drifting for the first time, provided the series regs allow for it. This is something that D1NZ has gone for, and it’s aimed at the likes of four-cylinder engines looking to kick it with the big guns. So, what exactly is ‘nitrous oxide’, and how the hell does this magic bottle make so much power?

HOW IT WORKS 

Nitrous oxide is a strongly bonded three-atom molecule consisting of two parts nitrogen and one part oxygen. The nitrogen atoms help to reduce detonation and control the burn of the combustion mix inside the chamber. It’s the oxygen that is the real power additive here, though, due to its weight percentage in the mix compared with the normal atmospheric air your engine usually breathes — 36 per cent oxygen versus 23.6 per cent, which means that you end up with much more air in the combustion chamber to fuel the fire. Stored in a liquid state between 900psi and 950psi, it changes state from a liquid to a gas when released into the intake manifold. During this process, its temperature drops to –88°C, absorbing massive amounts of heat from the intake charge and thus allowing increased oxygen content. As a bonded molecule, nitrous oxide will not burn; the atoms need to be split first. This happens inside the combustion chamber at just over 300°C. Once parted, the two gasses go about their work. But both nitrogen and oxygen are inert gasses, so adding all that extra oxygen is pointless unless you add more combustible fuel to feed off it. So, while many people incorrectly assume the extra power comes from the gas exploding, this is not the case; it simply injects a ton more air into the chamber, just as a turbo or supercharger would.

TYPES OF NITROUS SYSTEM 

There are two types of systems to feed nitrous into your engine, dry and wet, with wet involved in both plate and direct port–style systems. Which type to use depends on exactly what your desired power output and application are. The dry system is the simplest, as it only adds nitrous, relying on the factory fuel system to supply the extra fuel needed. Basically, when the nitrous is added, the factory oxygen sensor picks up the increased oxygen content and adds more fuel to match. The limitations with such a kit are that your injectors and fuel system will probably need upgrading to accommodate the extra strain, and you must have electronic fuel injection (EFI). The dry system is typically used on smaller power systems using under 112kW (150hp) shots. The more common set-up is a wet system. With this, the nitrous is either delivered via a plate system or fed directly into each port. It adds both the nitrous and the extra fuel it needs, so your existing fuel system remains separate and does not need to be upgraded, even if you’re adding a big shot of the giggle gas. The plate style is the easier of the two in terms of installation, as you simply bolt the plate in between the throttle body or carb and the manifold. The plate houses both the nitrous and extra fuel jets/injectors. The direct-port style sees the nitrous and fuel jets/injectors mounted directly on each port runner of the manifold. On the likes of in-line four- and six-cylinder engines, this ensures an even amount of nitrous is supplied to each combustion chamber.

WHAT THE LVVTA SAYS ABOUT THE USE OF
NITROUS IN A STREET CAR

 Nitrous-oxide systems can be LVV certified for use in road cars provided that some fairly basic technical requirements are met. Among these requirements are that hoses need to be routed outside the occupant cell and there needs to be a fail-safe arming switch to prevent unintentional activation. In addition, the bottle must be of an approved type; have a current test mark; be securely mounted, sealed, and vented to the outside of the vehicle if mounted in the occupant cell; and have a pressure safety blow-off valve. The full technical requirements for nitrous-oxide systems can be downloaded for free from LVVTA website (lvvta.org.nz; see LVV Standard 85-40(00) [Engine and Drive-Train Conversions]), or found in section 9.7 of the Engine and Drive-Train chapter of the NZ Hobby Car Technical Manual.

HOW ARE THE FLOW AND TIMING CONTROLLED?
Nitrous does not flow continuously while the engine is running if it did, your supply (generally from a single or perhaps twin bottles) would run out really fast. It is usually used only at wide-open throttle but can be controlled a few different ways. Speed, rpm, boost, and gear selection are all typical ways used to signal the solenoid to get the party started. However, the simplest method is manual control, as in that famous scene we spoke of earlier, via a button typically mounted on the steering wheel. Just how much nitrous and extra fuel get added (with a wet system) is dictated by the predetermined jets inside the injector/nozzle. It is recommended that any system supplying a shot over 112kW be delivered in stages. Nothing good will come from you throwing an extra 300kW at the wheels instantly, unless you plan to break something, with the best-case scenario being traction that you break, but more likely, engine or driveline components.

AGE-OLD PROBLEM

If you are purchasing a secondhand kit, be sure to check the manufacturing date stamped on the top of the bottle. Bottles only have a 10-year life span.

WILL IT BLOW UP MY ENGINE?

As with any boosted engine, the pressure and heat inside the combustion chamber will increase with nitrous oxide. If you’re running a small amount of nitrous, this will be OK (most companies recommend around 45kW [60hp] max for four-cylinder and 75kW [100hp] max for six-cylinder). But, if you plan to introduce more than that, you will need forged pistons and different pistonring clearances. Go over a 186kW (250hp) shot, and you’ll have to add forged rods and a forged crank to the list. Basically, nitrous should be treated just like a turbo or supercharger — you wouldn’t go sticking 30psi into a stock block, so the same applies here.