Re: How many good power bands is it supposed to have ?

Rebel Moby /
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If you have the right compression ratio to the number of transfer ports then you will have the capacity to create many power bands on your engine. As you add compressions it creats a apoliginshia effect to make the extra vacuum pulses in the piston crown assemblies. This extreme cylinder vacuum causes the intake ports to open, because the intake ports are maintained at atmospheric pressure while the transfer ports have now spent the energy stored which causes a differential. The exhaust ports, however, stay closed because of a vacuum which has developed in the headers. The cause of this vacuum is several fold: First, a rarefaction was caused during the intake stroke when hot exhaust gases were sucked into the cylinders. Second, the heat sinking effect of the long mufflers (whose job it is to cool the exhaust in order to most efficiently extract spent implosion products) has caused the exhaust to cool during the intake/compression cycle. Third, the acoustical resonance of the pipes reinforces the vacuum pulses at certain frequencies. This is how proper performance bikes have multiple "powerbands".

When the intake ports open, fresh mixture rushes into the cylinders, immediately neutralizing the vacuum due to implosion. This allows the pistons to move full speed to the bottoms of the cylinders where they again rebound off the connecting rods and begin traveling upwards. The gas is squeezed and pressure rises, creating a superheated condition in the spent gases. The pressure is relieved by the piston rings and vented into the crankcase, where the gases are safely relieved to the exhaust pipe by the crankcase breather and exhaust gas recirculation system. This is called the "exhaust stroke" because this will exhaust all of the stored energy. When the kill switch is pressed on a engine this is where the engine will always stop. To get more power from a 2 stroke engine you need to add on an expansion chamber to the exhaust system. An expansion chamber allows the exhause recirculation system to go through a pressure inversion because the pipe is always bigger then the engine itself. The inversion will make the piston become sucked down faster by the power stroke vacuum which will spin the wrist pin faster and generate more power. As the sides of the expansion chamber expand and contract it sets up a harmonic frequency which further strengthens the acoustical resonance of the intake/compression cycles.

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