DISCLAIMER:the following info was taken directly from my head and may not be very coherent at times and i apologize if you noticed anything i left out please feel free to correct me as i have not used this info for a while. this is also focused to a N/A engine as forced inducted engines work differently.
basically a supercharged engine is anything that operates at over 100% volumetric efficiency(VE). a typical stock application is around 72-78%VE. adding a camshaft and cylinder heads will increase VE sometimes to the point of reaching over 100% VE, thus becoming supercharged. to get to this point is not easy and there are several points that must be optimized.
first of all, the throttle blade(s) open and allow air into the intake manifold which is directed to the intake valve in the cylinder head, this air hits the valve and is redirected into the inlet tract until the incoming air is strong enough to overcome the reverted air. this new incoming column of air is directed to the intake valve once again, and in a few cases, is entered into the combustion chamber INERTIALLY FILLING the cylinder. this is known as the second wave pulse. if this air does not enter into the combustion chamber and bounces off the valve it is reverted again into the intake manifold until it is overcome again by the incoming charge. this is a third wave pulse. as you can guess by now, with each successive wave pulse the inertial filling becomes less effective as the motion of the air is wasted on bouncing off the reverted air. very few engines operate solely on a second pulse tune-mostly two stroke engines-but the ones that do are very effective, read LS1. stock engines, such as our beloved 5.0, are based on a 3rd pulse tune.
this wave pulse tune can be altered by cam timing, intake runner length and cylinder head burn characteristics, which is why a matched combo is so important. first we will take into consideration the intake runner length(we will assume intake volume is suffficient). this is important as the optimum length is usually very different at varying rpm's. at lower rpm's the piston is moving at a much lower speed which means the actual time between firing events is lengthened. so a short runner intake at lower rpm's(piston speed) will needlessly shift your wave pulse to 4 or maybe five as the time for the air to reach the valve is shortened, and it will continually bounce off the valve. adversly a long intake runner may take to long to supply the engine with air at higher rpm's as the time to reach the combustion chamber is increased. a matched runner length to our combo will supply the incoming air charge at an acceptable wave pulse at our peak efficiency range.
the next component in line is the cylinder head, the head has many functions and is often considered the most critical. the head must first be able to supply the engine with enough air to meet the demands of engine output. second the head must have a well shaped combustion chamber that is capable of reducing burn time as much as possible. the reduced burn time allows the enigne to reduce time between firing events.
the most important of this combo is one single event, the point at which the intake valve closes. considering you have a suitable cylinder head the cylinder is able to fill even after the piston is at BDC, up to a certain point. it is nessacary to determine this point by using a very eloborate chart of cylinder head flow data, this results in finding out at what point the intake valve needs to close. close to early and you don't get an optimized fill, close to late and the piston will push air back into the intake manifold and reduce the inertia that is already present.
with all of these items working in conjunction with each other, it is possible to have an engine that is capable of operating in a second wave pulse tune and inertially supercharge your engine to over 100% VE.
edit: broke it into paragraphs
basically a supercharged engine is anything that operates at over 100% volumetric efficiency(VE). a typical stock application is around 72-78%VE. adding a camshaft and cylinder heads will increase VE sometimes to the point of reaching over 100% VE, thus becoming supercharged. to get to this point is not easy and there are several points that must be optimized.
first of all, the throttle blade(s) open and allow air into the intake manifold which is directed to the intake valve in the cylinder head, this air hits the valve and is redirected into the inlet tract until the incoming air is strong enough to overcome the reverted air. this new incoming column of air is directed to the intake valve once again, and in a few cases, is entered into the combustion chamber INERTIALLY FILLING the cylinder. this is known as the second wave pulse. if this air does not enter into the combustion chamber and bounces off the valve it is reverted again into the intake manifold until it is overcome again by the incoming charge. this is a third wave pulse. as you can guess by now, with each successive wave pulse the inertial filling becomes less effective as the motion of the air is wasted on bouncing off the reverted air. very few engines operate solely on a second pulse tune-mostly two stroke engines-but the ones that do are very effective, read LS1. stock engines, such as our beloved 5.0, are based on a 3rd pulse tune.
this wave pulse tune can be altered by cam timing, intake runner length and cylinder head burn characteristics, which is why a matched combo is so important. first we will take into consideration the intake runner length(we will assume intake volume is suffficient). this is important as the optimum length is usually very different at varying rpm's. at lower rpm's the piston is moving at a much lower speed which means the actual time between firing events is lengthened. so a short runner intake at lower rpm's(piston speed) will needlessly shift your wave pulse to 4 or maybe five as the time for the air to reach the valve is shortened, and it will continually bounce off the valve. adversly a long intake runner may take to long to supply the engine with air at higher rpm's as the time to reach the combustion chamber is increased. a matched runner length to our combo will supply the incoming air charge at an acceptable wave pulse at our peak efficiency range.
the next component in line is the cylinder head, the head has many functions and is often considered the most critical. the head must first be able to supply the engine with enough air to meet the demands of engine output. second the head must have a well shaped combustion chamber that is capable of reducing burn time as much as possible. the reduced burn time allows the enigne to reduce time between firing events.
the most important of this combo is one single event, the point at which the intake valve closes. considering you have a suitable cylinder head the cylinder is able to fill even after the piston is at BDC, up to a certain point. it is nessacary to determine this point by using a very eloborate chart of cylinder head flow data, this results in finding out at what point the intake valve needs to close. close to early and you don't get an optimized fill, close to late and the piston will push air back into the intake manifold and reduce the inertia that is already present.
with all of these items working in conjunction with each other, it is possible to have an engine that is capable of operating in a second wave pulse tune and inertially supercharge your engine to over 100% VE.
edit: broke it into paragraphs
