Car Customization - NOS
Many of the serious drag racers would seriously think about adding NOS to their vehicle. But what is NOS? and how does it work? I was able to find out this article for people who are intersted in getting their own NOS system. There's also a huge bunch of scientific terms about chemicals and compounds and whatever the hell they're talking about so feel free to read through them and learn more about speeding up your ride.
Chemical Properties : A nitrous oxide molecule is made up of 2 atoms of nitrogen and 1 atom of oxygen. By weight it is 36% oxygen (air is only 23.6% oxygen). At 70° F it takes 760 PSI of vapour pressure to hold nitrous in liquid form. The critical temperature is 97.7° F; at this temp the vapour pressure can no longer hold the nitrous in liquid form. At this point the nitrous turns gaseous and will be at 1069 PSI. As temperature rises further, so will pressure, but it will remain in gaseous form. If you intend to siphon liquid nitrous, it is important to keep the temperature below 97.7°. When liquid nitrous is released, it will go from 760 PSI to 14.7 PSI (normal atmospheric pressure). It will then begin to boil and rapidly expand; the pressure drop will cause the temperature to decrease. Nitrous boils at 129.1°F below zero.
How Nitrous Oxide Injection Creates Torque :
Torque is the force that turns the crankshaft and creates acceleration. People are consumed with hp numbers, but hp is not what creates acceleration for winning drag races. Hp does create top end speed which is fine for land speed records or long distance endurance racing where acceleration rate / torque is not what determines the winner. To get the best out of nitrous, you need to utilize the massive torque it provides and concentrate on getting the highest torque across the whole rpm range.
Nitrous oxide systems make large amounts of torque by allowing an engine to burn more fuel at a lower rpm range than normal. Burning more fuel this way creates a longer burn period (and slightly higher cylinder pressures, if the timing is not corrected), that will push down on the pistons with greater average force. When the nitrous is injected into an engine and the initial combustion takes place, it creates enough heat to separate the nitrous oxide into its two components, nitrogen and oxygen. Once separated, the additional oxygen is then free to allow combustion of the additional fuel, while the released nitrogen acts as a buffer against detonation and damps mechanical loads.
To run nitrous successfully and safely, you have to introduce precise amounts of additional fuel with precise amounts of nitrous oxide. All of the extra oxygen provided by the nitrous oxide must have fuel with which to burn or you may damage your engine severely. When the amount of nitrous and the amount of supplemental fuel is controlled precisely, your engine can safely and reliably generate exceptional power increases.
Combustion : Nitrous oxide does not burn, it is an oxidiser. It provides more oxygen, so more fuel can be burned, and the result is more power. The atoms in a nitrous oxide molecule are bonded together. The oxygen is not free, but fortunately the bond breaks down as temperature rises. At 565° F, the bond is broken and the oxygen is then free. Combustion temperatures are much more than 565°, so it's not a problem. By adding nitrous oxide to an engine, the total amount of oxygen is increased while the volume of nitrogen is decreased (as a percentage of the whole). This speeds the burn rate and requires less timing advance for peak output. It is hard for many people to grasp gaining power with less timing, but it's a fact. Peak cylinder pressure must occur at approximately 20°ATDC to make peak power. If you speed the burn rate, peak cylinder pressure will occur too soon. It is easy to run too much ignition advance with nitrous, but too much will not only hurt power, it can quickly bring a nitrous engine into detonation and destroy it.
Detonation : Large power increases achieved by using nitrous oxide can increase the chance of detonation. To keep the engine out of detonation, you must control the extra heat that nitrous can make. The easiest way to do this is to add more fuel. All nitrous systems come with rich jetting to give you a safe starting point. The extra fuel takes away heat and raises the detonation limit. If you don't try to over do it, and keep the hp levels within reason, running slightly richer should be all you'll need to control detonation. Running richer will reduce the power output, but raising the detonation limit will allow more nitrous to be used to get more power.
Nitrous-to-fuel Ratios : The chemically correct nitrous to petrol ratio is 9.649:1. If a nitrous engine runs lean, it can destroy the engine in a matter of seconds. There must be enough fuel to maintain this correct ratio, if there isn't, temperatures rise rapidly. The oxygen that was left over from burning the limited amount of fuel will result is a lean burn situation raising cylinder temperatures and melting components. So don't run lean.
Cooling Effects : Cooler intake air is denser and contains more oxygen atoms per cubic foot. So cooler air will allow more fuel to be burned and in turn, make more power. A 10 degree drop in temperature can add 1 to 1.5% power to an engine. Nitrous oxide boils at -129°F and it will begin to boil as soon as it is injected. This can cause an 80° or so drop in manifold air temperature. Now if we are dealing with say a 400 hp engine, we can see a gain of well over 30 hp from the cooling effect alone. This cooling effect also helps the engine deal with detonation.
Average Power : If you were to build a 350 hp 3.5 Rover V8, it would have to rev to 7000+ rpm to make that kind of power and only make power over a narrow rpm range. A nitrous injected 3.5 Rover V8 making 350 hp would make that power at a much lower rpm with a higher average horsepower. So the nitrous engine will out perform the normally aspirated engine by a healthy margin. The reason is that nitrous flow remains constant no matter what rpm the engine is running at. At lower speeds there is more time for the nitrous to fill the cylinders, so you get more nitrous in the cylinders per power stroke at lower rpm. This will boost torque and consequently power more at low rpm. As rpm increases, you will get less nitrous per power stroke, but the engine will start making more normally aspirated power. This really flattens out the torque curve and widens the power band.
So Why Not Pure Oxygen ? : Air has only 23.6% oxygen by weight, the rest is made up largely of nitrogen. That nitrogen does not aid in combustion at all, but it does absorb and carry heat away. When you add nitrous, it has 36% oxygen with the rest being nitrogen. So the more nitrous oxide you add, the less percentage of nitrogen is available to absorb heat. That is why nitrous increases engine heat very rapidly. If we were to add pure oxygen (which has been tried), the percentage of nitrogen would fall even lower as more oxygen was added. We would not be able to add much oxygen before heat was a problem to control. Also compressed oxygen is in a gaseous form, so adding oxygen takes up more room and reduces normally aspirated power, and the amount of nitrogen from it. To put it simply, using nitrous oxide, we can get more oxygen atoms in the engine and have a lot more nitrogen as well. Nitrous can make much more power before heat is uncontrollable.
The Difference between Wet & Dry Systems :
A fuel injected dry manifold system uses a nitrous ONLY injector to deliver only nitrous oxide to the intake. A wet manifold system introduces fuel and nitrous into the intake manifold usually through a combined fuel and nitrous injector. With a dry manifold system, the additional fuel is supplied by increasing fuel delivery through the original fuel injectors when the nitrous system is activated. It is called a dry manifold system because there isn't any fuel present in the intake manifold.
Chemical Properties : A nitrous oxide molecule is made up of 2 atoms of nitrogen and 1 atom of oxygen. By weight it is 36% oxygen (air is only 23.6% oxygen). At 70° F it takes 760 PSI of vapour pressure to hold nitrous in liquid form. The critical temperature is 97.7° F; at this temp the vapour pressure can no longer hold the nitrous in liquid form. At this point the nitrous turns gaseous and will be at 1069 PSI. As temperature rises further, so will pressure, but it will remain in gaseous form. If you intend to siphon liquid nitrous, it is important to keep the temperature below 97.7°. When liquid nitrous is released, it will go from 760 PSI to 14.7 PSI (normal atmospheric pressure). It will then begin to boil and rapidly expand; the pressure drop will cause the temperature to decrease. Nitrous boils at 129.1°F below zero.
How Nitrous Oxide Injection Creates Torque :
Torque is the force that turns the crankshaft and creates acceleration. People are consumed with hp numbers, but hp is not what creates acceleration for winning drag races. Hp does create top end speed which is fine for land speed records or long distance endurance racing where acceleration rate / torque is not what determines the winner. To get the best out of nitrous, you need to utilize the massive torque it provides and concentrate on getting the highest torque across the whole rpm range.
Nitrous oxide systems make large amounts of torque by allowing an engine to burn more fuel at a lower rpm range than normal. Burning more fuel this way creates a longer burn period (and slightly higher cylinder pressures, if the timing is not corrected), that will push down on the pistons with greater average force. When the nitrous is injected into an engine and the initial combustion takes place, it creates enough heat to separate the nitrous oxide into its two components, nitrogen and oxygen. Once separated, the additional oxygen is then free to allow combustion of the additional fuel, while the released nitrogen acts as a buffer against detonation and damps mechanical loads.
To run nitrous successfully and safely, you have to introduce precise amounts of additional fuel with precise amounts of nitrous oxide. All of the extra oxygen provided by the nitrous oxide must have fuel with which to burn or you may damage your engine severely. When the amount of nitrous and the amount of supplemental fuel is controlled precisely, your engine can safely and reliably generate exceptional power increases.
Combustion : Nitrous oxide does not burn, it is an oxidiser. It provides more oxygen, so more fuel can be burned, and the result is more power. The atoms in a nitrous oxide molecule are bonded together. The oxygen is not free, but fortunately the bond breaks down as temperature rises. At 565° F, the bond is broken and the oxygen is then free. Combustion temperatures are much more than 565°, so it's not a problem. By adding nitrous oxide to an engine, the total amount of oxygen is increased while the volume of nitrogen is decreased (as a percentage of the whole). This speeds the burn rate and requires less timing advance for peak output. It is hard for many people to grasp gaining power with less timing, but it's a fact. Peak cylinder pressure must occur at approximately 20°ATDC to make peak power. If you speed the burn rate, peak cylinder pressure will occur too soon. It is easy to run too much ignition advance with nitrous, but too much will not only hurt power, it can quickly bring a nitrous engine into detonation and destroy it.
Detonation : Large power increases achieved by using nitrous oxide can increase the chance of detonation. To keep the engine out of detonation, you must control the extra heat that nitrous can make. The easiest way to do this is to add more fuel. All nitrous systems come with rich jetting to give you a safe starting point. The extra fuel takes away heat and raises the detonation limit. If you don't try to over do it, and keep the hp levels within reason, running slightly richer should be all you'll need to control detonation. Running richer will reduce the power output, but raising the detonation limit will allow more nitrous to be used to get more power.
Nitrous-to-fuel Ratios : The chemically correct nitrous to petrol ratio is 9.649:1. If a nitrous engine runs lean, it can destroy the engine in a matter of seconds. There must be enough fuel to maintain this correct ratio, if there isn't, temperatures rise rapidly. The oxygen that was left over from burning the limited amount of fuel will result is a lean burn situation raising cylinder temperatures and melting components. So don't run lean.
Cooling Effects : Cooler intake air is denser and contains more oxygen atoms per cubic foot. So cooler air will allow more fuel to be burned and in turn, make more power. A 10 degree drop in temperature can add 1 to 1.5% power to an engine. Nitrous oxide boils at -129°F and it will begin to boil as soon as it is injected. This can cause an 80° or so drop in manifold air temperature. Now if we are dealing with say a 400 hp engine, we can see a gain of well over 30 hp from the cooling effect alone. This cooling effect also helps the engine deal with detonation.
Average Power : If you were to build a 350 hp 3.5 Rover V8, it would have to rev to 7000+ rpm to make that kind of power and only make power over a narrow rpm range. A nitrous injected 3.5 Rover V8 making 350 hp would make that power at a much lower rpm with a higher average horsepower. So the nitrous engine will out perform the normally aspirated engine by a healthy margin. The reason is that nitrous flow remains constant no matter what rpm the engine is running at. At lower speeds there is more time for the nitrous to fill the cylinders, so you get more nitrous in the cylinders per power stroke at lower rpm. This will boost torque and consequently power more at low rpm. As rpm increases, you will get less nitrous per power stroke, but the engine will start making more normally aspirated power. This really flattens out the torque curve and widens the power band.
So Why Not Pure Oxygen ? : Air has only 23.6% oxygen by weight, the rest is made up largely of nitrogen. That nitrogen does not aid in combustion at all, but it does absorb and carry heat away. When you add nitrous, it has 36% oxygen with the rest being nitrogen. So the more nitrous oxide you add, the less percentage of nitrogen is available to absorb heat. That is why nitrous increases engine heat very rapidly. If we were to add pure oxygen (which has been tried), the percentage of nitrogen would fall even lower as more oxygen was added. We would not be able to add much oxygen before heat was a problem to control. Also compressed oxygen is in a gaseous form, so adding oxygen takes up more room and reduces normally aspirated power, and the amount of nitrogen from it. To put it simply, using nitrous oxide, we can get more oxygen atoms in the engine and have a lot more nitrogen as well. Nitrous can make much more power before heat is uncontrollable.
The Difference between Wet & Dry Systems :
A fuel injected dry manifold system uses a nitrous ONLY injector to deliver only nitrous oxide to the intake. A wet manifold system introduces fuel and nitrous into the intake manifold usually through a combined fuel and nitrous injector. With a dry manifold system, the additional fuel is supplied by increasing fuel delivery through the original fuel injectors when the nitrous system is activated. It is called a dry manifold system because there isn't any fuel present in the intake manifold.
posted by ,. @ 10:03 PM
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