Model Engine Company of America
Instructions on

Working principle of the tuned pipe... When the engine is operated with a standard silencer or without silencer, losses of unburnt mixture during the exhaust stroke occur. Therefore, the ensuing working stroke can use only the remaining part of the mixture to produce power. In the tuned pipe, cyclic pressure waves develop due to reflection of the exhaust gases by a baffle. During this "supercharging" process, unburnt mixture normally lost through the exhaust is returned into the combustion chamber thus improving the volumetric efficiency of the engine.

The HP TUNED PIPE SILENCER yields this effect even without being matched to the operating conditions. For obtaining the full potential power gain, however, it is necessary to tune the ENGINE-TUNED PIPE SILENCER system precisely to existing operating conditions This is easily achieved by adjusting the manifold length. The HP manifolds are delivered with excessive length, and have to be shortened to suit the operating conditions.

The HP TUNED PIPE SILENCER offers good exhaust muffling combined with considerable power increase to satisfy both environment protection considerations and the modelers demand for more power. In the 12.000-16.000 R.P.M. range, the HP TUNED PIPE SILENCER gains up to 1700 R.P.M. for your HP engine when compared to the standard silencer and up to 1000 R.P.M. when compared to the engine without silencer. The power increase is achieved by making better use of the combustible mixture.
 For tuning, a precision tachometer and two props of the same type with identical diameter, but with pitch differing by about one inch, are needed, for example.

For .61 engines --- 11x6 and 11x7 or 11x7 and 11x7.75
For .40 engines --- 10x5 and 10x6

In flight, the engine's speed is higher by about 1000 R.P.M. (depending on the model's velocity) when compared to a static R.P.M. with identical prop. For exact tuning on the bench, a prop should be used which has static R.P.M. coinciding with flight R.P.M. of the prop to be used on the model (for example, if 11 x 7 is the flight prop, use an 11 x 6 for tuning). When cutting down the manifold outlet (in 1/4" steps), R.P.M. will go up gradually. When no additional R.P.M. increase occurs, the length of the system is correct. Any further shortening of the manifold will decrease R.P.M.

Small deviations from the correct length can be compensated by adjusting the silicone tube, which also depends on the type and brand of propeller. The graph shows the principal form of the power curve.



The above information is provided as a guide. Since MECOA/K&B has no way of determining the ability of the individual using and understanding this information, we assume absolutely NO RESPONSIBILITY for any damage to person or property from the use of this information.

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