Nitrous Oxide Systems (NOS)
Some FYI before everyone gets all excited - Nitrous oxide injection is very much like a supercharger or a compression ratio increase in that, during combustion, it can dramatically increase the dynamic cylinder pressure in the engine - too much and you my have just caused serious damage to your engine.
Of course, when you significantly increase the cylinder pressure in the engine, you also increase the engine's tendency to detonate. This is why almost all nitrous motors require retarded spark timing during nitrous oxide operation. The cylinder pressure increase is also why, when misused or improperly installed, operation with nitrous causes problems with head gasket seal and failures of the rings or pistons. I should point out that any number of things that put an engine into severe detonation, such as too much boost from a supercharger, low octane fuel, excessive compression ratio or overly lean air-fuel ratio will also cause the same kinds of damage.
Another challenge with a nitrous oxide system is getting the delivery of nitrous oxide and additional fuel at the correct proportions. If you feed nitrous to the engine without enough extra fuel, the lean air/nitrous to fuel mixture will make the detonation problem even worse. Combustion temperatures will skyrocket and catastrophic failure is certain to occur. If the proportion is such that too much fuel is delivered, the power advantage degrades rapidly.
As you can see, nitrous oxide is like any other power increasing modification in that, when used wisely and installed properly, it works well. Then used foolishly or installed incorrectly it can significantly reduced the reliability/durability of your engine.
Small doses of nitrous oxide can be used in stock engines to gain 25-35% more power. In my opinion, any more than nitrous than that with a stock engine compromises durability too much. This is not only true of nitrous but any modification. Take a stock 82 or 84 engine, up the horsepower to 300hp and do nothing to improve durability and your engine will eventually suffer. Once you pass the 35% power increase mark with nitrous oxide you need to look at things like forged pistons, better connecting rods, better bearings, etc.
Nitrous oxide is also a great value on a dollar-per-unit-power increase when installed and operated properly. The downside, of course, is the fun ends quickly. The power boost lasts as long as the nitrous. The average bottle is a 20 ponder and with a street V8 that might be worth 20 seconds of use.
So, nitrous oxide is not the instant-engine-failure many people think it is. When used properly and when dispensed by a properly designed and installed system nitrous oxide can be responsible for some phenomenal increases in power.