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Digital Subscriptions > Vroom International > n. 206 August 2018 > THE TURBO OF 2-STROKES


Walter Kaaden, one of the greatest technicians in the history of motorcycling competitions, invented the expansion exhaust: with it the 2-stroke; up to then relegated to the role of an engine for utility vehicles, it outclassed the 4-stroke. Here are the working principles of this extraordinary condensate of physics principles which, in fact, is a turbo system in waves.



For a moment, let’s leave aside the concept that we young folks have about 2-stroke engines and go back over 60 years. The “mixed-fuel” engines, at those times, were mounted on contraptions that defining as “motorcycles” is a blasphemy worthy of the rack. Whoever tried to make them go faster than they ought would end with something that, put simply, did not work. With equal displacement, the more noble and sophisticated 4-stroke was the most unattainable of chimera. In these poor engines, the exhaust pipe had exclusively the function of silencing the huge noise produced by the evacuation of gas exploded by the cylinder. Then, with time, the exhaust system revealed one of the most important parts in characterizing the behavior of a 2-stroke engine. It is the geometry of what we call “expansion” to determine in what way the pressure waves, which expand in its interior, go to interact with the exchange phase of the motor fluid (so-called wash), a phase that is translated in the capacity of the engine to “fill itself.”

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In this issue: So and so In the second and decisive round of the KZ and KZ2 Continental races, the first Championship titles of the CIK FIA season were awarded to Holland's Jorrit Pex (Crg / Tm) and France's Adrien Renaudin (Sodi / Tm). Debatable, the ten-second penalty inflicted on De Conto, winner of the KZ final. FOCUS WEIGHT REDUCTION Racing CIK-FIA EUROPEAN CHAMPIONSHIP KZ-KZ2 EASYKART EURO TROPHY IAME X30 EURO SERIES ROTAX ASIA MAX CHALLENGE TECHNICAL SIDE The exhaust system in high performance 2-stroke engines - Part I EMOTIONS EXPERIENCED BY MARCO AMBIVERI VINTAGE SILVERCAR CLOSE UP PORTUGAL AND SPANISH KARTING CHAMPIONSHIP ROTAX MAX CHALLENGE US GRAND NATIONALS