Nitrous oxide injection
Nitrous oxide injection is a method for increasing the performance of internal combustion engines with the help of the oxygen carrier nitrous oxide (laughing gas).
history
The injection of nitrous oxide to increase the performance of internal combustion engines was already investigated by the physical chemist Walther Nernst in his private car around 1900. During the Second World War , this technology was further developed in Germany in order to increase the high-altitude performance of aircraft engines (see GM-1 ).
The technology was applied to both gasoline direct injection engines and diesel engines. Originally, liquefied laughing gas was injected into the intake tract of the loader; later, cold liquefied laughing gas was used as it did not require heavy pressure vessels. In addition to the oxidizing effect, the charge air cooling also made a notable contribution to the increase in performance.
technology
The injection of nitrous oxide is possible in almost all types of internal combustion engines. However, an engine that has had its compression increased or its ignition timing changed is not an optimal starting point. These engines can also be equipped with a nitrous oxide system, but then require additional modifications and a fuel with an octane number greater than RON 95.
Laughing gas (nitrous oxide, N 2 O) has the property at 575 ° C in two nitrogen atoms and an oxygen atom to disintegrate. Therefore, if more oxygen per cylinder filling is available for the combustion at corresponding temperatures in the cylinder , more fuel can and must be correspondingly burned per cylinder filling. If there is an excess of oxygen, overheating and destruction of the motor are to be expected.
The ratio of nitrous oxide to fuel is strongly to the disadvantage of nitrous oxide. In relation to the mass, you need significantly more nitrous oxide to burn a certain additional amount of fuel. The ratio depends on the type of fuel (gasoline, kerosene, heating oil, ethanol, methane, biogas, LNG, propane, wood gas).
The underlying reaction equation is:
3 molecules of n-octane , 25 molecules of oxygen and 25 molecules of nitrous oxide react exothermically to form 24 molecules of carbon dioxide, 27 molecules of water and 25 molecules of nitrogen.
However, two real chemical reactions are summarized in this summed reaction equation. On the one hand, this is the splitting of laughing gas into nitrogen and oxygen. On the other hand, this is the combustion of n-octane with oxygen. Both reactions are exothermic.
This means that instead of a nitrous oxide injection, an injection of oxygen or an injection of air are also conceivable.
Laughing gas has a boiling temperature of −88.48 ° C at a pressure of 101.325 kPa.
Therefore the intake air temperature drops by around 20 ° C. This is an essential property of nitrous oxide injection, because this cooled gas flow reduces the thermal load on the engine. This cooling also significantly increases the amount of fuel and oxygen molecules per volume, so that a higher amount of energy is available per volume and thus the performance of the engine by up to 55% and, with corresponding (strong) changes, even by several hundred % can be increased.
Basic variants of nitrous oxide injection
“Dry System” Here only nitrous oxide is injected; the additional fuel required must be supplied by the fuel injection system or carburetor (s) of the engine. This variant is the less secure one, as there is no uniform mixture for each cylinder and the maximum efficiency of standard injection nozzles / carburettors is quickly achieved. From this point on, the fuel is no longer sufficient for the nitrous oxide supplied and the engine becomes lean, which means that it receives too little fuel and too much oxygen, which can result in what is known as knocking combustion, which in turn can cause damage to the engine (burned down Spark plugs, valves, pistons).
“Wet System” Here laughing gas is injected together with gasoline through one or more mixing nozzles that are part of the system. The advantage is that a finished mixture is injected and all cylinders have the same mixing ratio. The maximum flow rate is also much higher with such nozzles, i.e. H. you can inject more fuel. Modern mixing nozzles have a passage for max. approx. 20 hp per nozzle. Special nozzles develop a potential of up to 40 HP per nozzle.
So-called direct port systems have at least one injection nozzle per cylinder instead of just one injection nozzle for the entire engine. Since an injection nozzle max. 20 hp, an eight-cylinder engine can theoretically achieve up to 160 hp more power. However, these systems are sometimes also required when a relatively low output is desired, for example in the case of open individual throttle valve systems. Direct port systems can be “wet” or “dry”.
Operating time and operating costs
With a moderate increase in power (series engines can usually handle up to 20 HP more power per cylinder), you could empty a 10 lb bottle (standard size for American systems) in one go. However, this should only be possible with great difficulty, as the final speed is reached long beforehand and it is then no longer sensible to supply the additional power. Laughing gas currently costs around 5–8 euros per lb, depending on the provider, a 10 lb cylinder is sufficient for around 4–5 minutes of operation time with 50 HP more power, the actual use time is strongly dependent on the cylinder pressure. The fuel consumption increases in relation to the additional power, but this is not particularly significant with additional power up to 150 hp because of the relatively short duration of use.
The great advantage of increasing performance by means of laughing gas is the high performance yield at comparatively low costs, which is then only possible for a relatively short time and is therefore only optimal for acceleration and sprint races. A laughing gas system is not well suited for circuit races etc.
The nitrous oxide injection must not be confused with a nitro injection . In these systems, nitromethane is also injected. As a result, the power output is even higher, but at the expense of the motor, since the thermal and mechanical overloading of the motor is enormous.
Operating permit in Germany
In Germany, laughing gas kits are subject to approval if you want to use them within the framework of the StVZO.
Such approval can only be given by approved examiners. The approval can be obtained through an operating permit # General Operating Permit for Vehicles (ABE), but it is also possible through other test procedures with greater effort. If you are not afraid of cost or effort, you can have a fully functional system that does not have a ABE entered in the vehicle documents after it has passed the test.
The main limitation here, similar to turbo or compressor conversions, lies in the maximum engine power, which is often caused by certain safety-relevant components such as B. the brake system, which has to be stronger than the engine, but is ultimately limited by the body load capacity. Therefore, it is often the case that, for example, only 30 HP more power for cars are registered or approved, which i. d. R. far below.
The last provider of laughing gas kits with ABE was NOS1. Other systems, e.g. B. NOS, Nitrous Express (NX), ZEX or Venom are also registrable, but have no ABE and must be checked and approved according to other procedures. The bottles in these USA systems are usually DOT approved. This type of test is accepted by the German TÜV, which is a basic requirement for successful acceptance.
The bottles (pressure vessels), regardless of whether they are of German or American origin, must be subjected to a regular inspection that meets the legal requirements.
See also
Individual evidence
- ↑ ABE 91065
- ↑ Untitled document