Choose the language. Tech Focus Special reed valves: testing on the engine bench. Share the article. Reed valves they are components of reed valve suction engines. When the piston ends its rising phase, the spark plug ignites the spark that ignites the mixture : the combustion generated in this way pushes the piston towards the LDP , the depression in the chamber weakens, thus causing the reed valves to close.
At this point, while the piston continues to descend , the pressure in the pump casing increases , helping the mixture to enter the combustion chamber through the transfer ducts, expelling the combustion gases once the exhaust ports are uncovered. This is why the reed valves must open and close with each cycle, withstanding very high and very stressful oscillation frequencies that sometimes lead to the yielding and deformation of the valves, with harmful effects on the engine.
On the market you can find reed valves of different materials : vetronite, kevlar, carbon In high performance kart engines, the latter is undoubtedly the most used, because it has a low specific weight and consistently high elasticity.
In addition to the materials, reed valves are different based on their thickness and type of fiber intertwining in the case of carbon. The latter can be intertwined at 45 or 90 degrees , also with filaments of different thickness.
The intertwining changes the stiffness and flexibility characteristics of the reed valves. Generally, the intertwining is single frequency , due to the greater simplicity and lower costs; but there are also reed valves with multi-frequency intertwining, which vary depending on the part of the reed valve and can be used in more ways.
A reed valve pack with reed valves, ready to be mounted on an engine. The tuner modifies the reed valves to vary the bending read more. The bending capacity of the reed valves depends on the material they are made of read more. Carbon is the most used material to make reed valves for kart engines read more.
There are reed valves of different thicknesses on the market read more. As previously mentioned, the performance of reed valves depends on their rigidity. More rigid reed valves usually help the engine at high rpm , because they avoid resonance and, by returning more easily to their starting position, they avoid the play of fuel from the crankshaft.
Therefore, the reed valve will tend to deform due to the high operating frequency, no longer able to remain at the end part of the support structure and leaving a small space for the gases to pass through, thus not fulfilling its function as a valve. This reduces the pressure in the crank chamber, preventing the engine from working optimally.
On the contrary, softer reed valves are more suitable for operating at low speeds : in fact, since they require less force to be opened, they allow greater filling of the crankshaft. We have talked about materials, thicknesses and intertwining, but reed valves can also vary in shape.
Also, in this case the aim is to vary flexibility, with the tuner who, depending on the type of flow required, can either use a standard reed valve for the reed valve pack of the engine in question, or cut it directly out of a slab of carbon. Early reed petals were manufactured from stainless steel sheets. Stainless steel reeds are inexpensive, very durable and have good resiliency.
Their main disadvantage is that petal separation usually results in engine damage. This is why in motorsport composite reed petals were introduced. Initially these were glass fiber based. Later, carbon fiber was used as it offers even better parameters — lower mass and higher stiffness at same thickness. Composite, glass of carbon fiber based, reeds are not that durable as metal ones.
However, their significant advantage is that in case of reed petal failure liberated piece will usually not make any damage to the engine. Both these parameters, which correspond to each other, impact performance of a two stroke engine. Typical reed petal thickness available at the market ranges from 0. Carbon fiber based, 0.
Offered sheets have high durability, optimum fiber to reinforcement ratio and narrow thickness tolerance range. High temperature epoxy resin system we use has catalogue temperature capability of degC degF. We use full heat treat cure cycle to ensure the best parameters. All our carbon reeds are intensely tested, including testing by Polish trial and motocross competitors. These are also successfully used on daily basis by hundreds of customers. Based on this cumulative experience and feedback being received we are certain about quality and performance of our product!
CompoTec xmm 3. We are looking forward to cooperation with distributors, shops, two stroke engine service shops as well as individual customers. If a reed is cracked or broken, it will idle horribly, have no hole shot, but run well on top end. Engines with reed valves that are failing can present symptoms of hesitation during acceleration.
The engine may fail to respond to the increased fuel flow and then jump forward as the gas is finally ignited. Reed valves are a type of check valve which restrict the flow of fluids to a single direction, opening and closing under changing pressure on each face. Modern versions often consist of flexible metal or composite materials fiberglass or carbon fiber. There is no need for a reed valve on a 4 stroke cycle engine.
On a 2-stroke they are used at the bottom of the crankcase to let stuff in through the carb as the piston goes up, and block it as the the piston heads down. Because 2-stroke engines are designed to run at a higher RPM, they also tend to wear out faster; a 4-stroke engine is generally more durable. Four-stroke engines have more parts, therefore they are more expensive and repairs cost more.
Two-stroke engines require pre-mixing of oil and fuel, while the 4-strokes do not. Reed valve allows the mixture to move in only one direction — from the carburetor to the crankcase. It prevents the mixture from moving back to the carburetor.
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