This is what happens when u fit NOS to a pocket bike

[Cactus Jack]

Nitrous oxide would be best injected (along with carefully metered additional fuel) via a solenoid activated spray bar between the carb and the inlet manifold ! Since it works by increasing the density of the air BEFORE it enters the engine , the closer to the carby it is , the better it will work . You want to get the air cold and dense before it passes the reeds or inlet valve - then once it's in there - it's trapped and is forced to do its' job of boosting cylinder pressure when burnt !

The engine will still draw in the same volume of air/fuel mix as normal - only the colder charge will be denser and will expand to a greater volume when heated by combustion than it would if it was at normal temperature . Mechanical blowers work by pumping a greater volume of air/fuel mix into an engine at boosted pressure levels and at normal temperature ! Nitrous oxide injection compacts the fuel /air mix by chemically reducing its' temperature which in turn increases it's density at normal atmospheric pressure .

A reed valve is simply a one way valve - the intake charge opens the reed petals in the direction of flow but forces them closed if the flow tries to reverse - so once the denser charge passes the reeds , it doesn't matter if it starts expanding in the cases because the increased pressure would still make it to the cylinder .

You have to remember that everything is happening thousands of times per minute so there isn't much time for the charge to start heating up before it reaches the cylinder and is ignited ! IF the oil did happen to increase viscosity due to lowered temperature - that would actually be a bonus because the increased film strength would help to keep metal parts such as the bearing rollers wedged away from the crank pin and the piston away from the cylinder wall - reducing wear and friction !

2 strokes are poorly lubricated as it is - so you have to ensure that they don't run too rich because the fuel "washes" the oil off the parts - weakening it's ability to keep them away from each other ! In a well tuned 2 stroke engine the fuel turns into a gas and the oil falls out of suspension - adhering to the working components . The spinning crank keeps everything churned up in the cases .

It would be safe to say that the use of nitrous oxide in a 2 stroke engine would require a fine balancing act as far as tuning goes ~ there'd be a fine line between life and death of the engine !

 

[mech_eng_matty]

Mechanical blowers work by pumping a greater volume of air/fuel mix into an engine at boosted pressure levels and at normal temperature !

I will only add one thing to this jack. A mechanical blower, or a turbo for that matter will actually increase the air temperature by a certain amount. This happens because when air is increased in pressure, the temperature increases with it (due to a change in enthalpy).

I'm not gonna go into a bit thermodynamic calculation to prove it but you can chose to reguard it or disreguard it.

This phenomenom is the reason that intercoolers are used. The air temp increases after passing through the compressor hence making a smaller temperature differential inside the combustion chamber and reducing the effectiveness of the boosting. By passing the compressed air through an intercooler, the compressed air gets reduced in temp again before entering the combustion chamber. This essentially gets it back to a similar point as where it would be after using nitrous.

Also, the main advantage of using Nitrous is not as much the cooling of the air, but the fact that the air/fuel mixture gets bombarded with extra oxygen from the nitrous oxide (give its chemical composition of 1 nitrogen molecule to 2 oxygen molecules....NO2) which allows you to burn more fuel for the same amount of air going into the combustion chamber.
An internal combustion engine's major limitation is how much air it can get into its combustion chamber...hence why turbos, superchargers and nitrous are used, they all in a manner of speaking, increase the amount of air (and oxygen molecules) in the engine.

 

[THUMPY125]

i'm with mech_eng_matty, they are not really nos they used to sell them on ebay for $400, you would proabbly find that its a nitro fuel from what some of you guys run your rc cars on.

 

[Cactus Jack]

I will only add one thing to this jack. A mechanical blower, or a turbo for that matter will actually increase the air temperature by a certain amount. This happens because when air is increased in pressure, the temperature increases with it (due to a change in enthalpy).

I'm not gonna go into a bit thermodynamic calculation to prove it but you can chose to reguard it or disreguard it.

This phenomenom is the reason that intercoolers are used. The air temp increases after passing through the compressor hence making a smaller temperature differential inside the combustion chamber and reducing the effectiveness of the boosting. By passing the compressed air through an intercooler, the compressed air gets reduced in temp again before entering the combustion chamber. This essentially gets it back to a similar point as where it would be after using nitrous.

Also, the main advantage of using Nitrous is not as much the cooling of the air, but the fact that the air/fuel mixture gets bombarded with extra oxygen from the nitrous oxide (give its chemical composition of 1 nitrogen molecule to 2 oxygen molecules....NO2) which allows you to burn more fuel for the same amount of air going into the combustion chamber.
An internal combustion engine's major limitation is how much air it can get into its combustion chamber...hence why turbos, superchargers and nitrous are used, they all in a manner of speaking, increase the amount of air (and oxygen molecules) in the engine.

I already knew all about the heating effect of mechanical super and turbochargers and what inter coolers do plus the HP lost in driving a blower and how nitromethane produces its' own oxygen etc etc - been into drag racing for over 30 years ! But I had never looked into the chemical side of nitrous oxide other than its' cooling effect on intake air !

Here's some info from wikipedia:

When you heat nitrous oxide to about 570 degrees F (~300 C), it splits into oxygen and nitrogen. So the injection of nitrous oxide into an engine means that more oxygen is available during combustion. Because you have more oxygen, you can also inject more fuel, allowing the same engine to produce more power. Nitrous oxide is one of the simplest ways to provide a significant horsepower boost to any gasoline engine.

Nitrous oxide has another effect that improves performance even more. When it vaporizes, nitrous oxide provides a significant cooling effect on the intake air. When you reduce the intake air temperature, you increase the air's density, and this provides even more oxygen inside the cylinder.

The only problem with nitrous oxide is that it is fairly bulky, and the engine needs a lot of it. Like any gas, it takes up a fair amount of space even when compressed into a liquid. A 5-liter engine running at 4,000 rotations per minute (rpm) consumes about 10,000 liters of air every minute (compared to about 0.2 liters of gasoline), so it would take a tremendous amount of nitrous oxide to run a car continuously. Therefore, a car normally carries only a few minutes of nitrous oxide, and the driver uses it very selectively by pushing a button.

Howstuffworks

Nitrous Oxide - Chempedia

In this link , they talk about nitrous use in a 2 stroke engine :

Nitrous oxide vapor delivery system for engine power enhancement - Patent 7210472

 

[pegleg]

Matty,
here we go, I will try to repeat what my better half just told me about modifiers in motor oils.
eg:10W-40, the 10 is as you said the cold temp viscosity, and the 40 is the hot temp. The W indicates there is a viscosity modifier in the oil, it is part of the classification system within the industry. The modifiers work by the use of a polymer, it is curled up like a coil, when heat is applied the coil opens up thus thickening the oil, the same polymer works for cold temperatures also in that it's presence, still curled up prevents the wax in the oil "dropping out" and causing it to solidify.
Using an engine oil that has a VI modifier in a 2 stroke is pointless as the fuel dilutes the oil so much it doesn't do anything. Due to this dilution the oil stays fairly thin, dependent on the ratio of fuel/oil/NO2 it shouldn't have a significant effect on the viscosity of the oil, the amount of gas and therefore the cooling down of the oil would be negligible,she thinks.
I hope this explains it somewhat.
Cheers
--
Steve

 

[pascal125]

whoa, this is gettin pretty technical ocnsidering it is just a video of a minibike, lol.