The answer is simple. First you need to understand what a Nitrous motor really is. A true Nitrous motor is a motor utilizing a great deal of nitrous instead of a turbo or supercharger. A nitrous motor is not a motor with a 150hp kit bolted to it. Nitrous motors will typically run a port fogger which starts out around 250HP+.

When your going with a 300HP increase you want to drop your compression ratio just as you would a Turbo motor. I expect you know the reasons for this. One of the main reasons is the lower compression increases the CC volumn which lowers the flame front combustion heat and as you know if you get too close to the thermal capacity of a metal, it will weaken. This is what happens when you deal with pre-ignition and worse, detonation. Pre-ignition is a intake charge that ignites early on leftover heat in the cylinder. The piston will compress the igniting fuel and as a result the heat generated by the burning fuel increase exponentially and if this goes no further then you are slowly destroying your plugs and rings. If preignition gets worse it can and will lead to detonation. Detonation is different, detonation is a more violent ignition of the fuel mixture. One example is preignition leading to Detonation. As i mentioned in preignition the fuel mixture ignites early due to heat. As that is going on imagine the spark plug is getting hotter and hotter. The job of a spark plug is to disipate heat into the head, too hot of a plug will begin to glow if preignition becomes a problem. Now you have fuel buring in the cylinder as a piston compresses it making it hotter. Soon enough the spark plug will get so hot it will ignite the unburnt fuel still in the cylinder (pre-ignition doesnt burn the entire mixture evenly). That flame front is far more of a sudden lighting of the entire mixture. The expanding gasses push so hard against the piston (that is too hot already) and the metal will reach its fatique point and it will either begin to melt small portions or it will entirely cave in. Decreasing the Ratio will keep this under control.
That is only 1 example of hot Detonation occurs, there are several.

Why Cant you just lower timing? Think of Timing as fine tuning the cylinder temps during a burn cycle. Compression ratio would be your course adjustment. IF you are trying to get every tiny bit of power you can from a motor, you first want your timing and plug heat range tuned out. Once you have both of those set in stone, you tune based on heat (EGT's). Every motor will be different. Widebands are good for getting you close and you can use them but if you were to compare heat marks on the spark plugs as you go, you will see the same pattern just not in numbers.

Spark plug heat ranges are another way to tune heat but they also will affect your timing. as you get hotter on the plug, your timing will need to be retarded. I recently toyed with a car on a dyno that when increasing the heat range 1 set up, cuased the timing to be 6* to far advanced. I went from 41* total timing to 35* total. Further tuning will identigy if the heat range choice was better for the motor or stepping down will be warrented. Too rich of a fuel mixture can also make the heat range of a plug look too cool.

Why Nitrous or a Supercharger or Turbo? Becuase you will never be able to get a supercharger or Turbo setup to operate with an intake charge as cool as Nitrogen gets. Nitrous Oxide does 2 things. The Oxygen when introduced into a Flame front increases the Flames heat which is what gives the compressed fuel/air mixture a more aggressive gas expansion during the burn cycle. The Nitrogen is used purely as a cooling medium. Oxygen on its own will melt the pistons/ring before you even get past the 60' mark. Nitrogen gives the mixture some controlability in terms of heat.



A motor with a 150 shot is not considered a Nitrous motor. Thats why its called a cheater kit.

Obviously the downside with Nitrous is the increase maintenance of bottle filling and system cleaning.