What are the main differences between nitrous and boost in the sense of the activity that takes place in the combustion chamber? I ask because I was researching different pistons and i noticed that the pistons designed for boost applications were designed for low compression while the nitrous pistons were designed for high compression. Don't nitrous and superchargers/turbos work off the same fundamental principle of more air and fuel=more power?

 

Nitrous adds a greater % of oxygen while maintaining one atmosphere of pressure. Boost adds more oxygen solely by increasing pressure. Both increase O2, but N2O doesn't multiply compression until after the fuel starts to burn. I understand the involved physics much better, but I don't know how to properly explain them much better.

 

Maybe this will help. Air is a mixture of gases that consists of about 21 % Oxygen and 78% Nitrogen and about 1 % other gases. So of a given volume of air going into the combustion chamber at one atmosphere of pressure (sea level pressures of 14.7 PSI or 1 bar or several other ways of measuring the same pressure) only 21 % of that air is available to combine with the fuel to produce combustion. With a supercharger or turbocharger running at two atmospheres (2 bar) then the air is still 21 % oxygen, however the density is doubled (assuming that the temperature is the same, perhaps via an intercooler) so a given volume of air at 2 bar has twice the number of molecules of Oxygen that can combine with the fuel to produce combustion.

Nitrous Oxide is a chemical compound (N2O) where during the combustion process, the oxygen and nitrogen molecules separate into their elemental states and the oxygen is available for combining with fuel to boost the power level. At the same time, the chemical reaction separating the nitrogen and oxygen produces additional heat which produces additional pressure in the cylinder during the power stroke.

The super/turbochargers are just trying to cram in more air to combust in a normal way and unless the pistons are dished or the combustion chamber is huge to reduce the compression ratio, there will be extreme detonation problems under high levels of boost. The magic of NOS occurs once combustion begins in the cylinders. The blend of air and NOS is still coming into the induction system at about 1 bar. Because of this, the static compression ratio can be about the same as a normally aspirated engine with no NOS. However, NOS engines with a very big shot need sturdy pistons, rods, etc. because of the extreme cylinder pressures, heat, etc.

This may help and it may confuse and it may do some of both.

All my best,

Steve

 

Steve also worth noting that in a FI setup you still have the same raito of Nitrogen in the charge as you do with a NA engine. this means there the "correct" about of exhaust gasses to get rid of the heat.

i a N2O setup you can find the engine getting hot. this is becasue there is less exhaust gas volume for the same power as the FI setup. so the heat is transfered to the block, heads, etc more.

think thats right. lol

CHris.