This is a method to determine the indicated power of a cylinder in a multi-cylinder engine. In this method, the engine is first run at the required speed and the output is measured. One cylinder is then cut out by short circuiting the spark plug or by disconnecting the injector, as the case may be. The output is measured by keeping the speed constant at its original value. The difference in the output is a measure of the indicated power of the cutout cylinder. Thus for each cylinder the IP is obtain and is added together to find the total IP of the engine.
IP of n cylinders, IPn = BPn + FPn
IP of (n − 1) cylinders IPn−1 = BPn−1 + FPn
IP of nth cylinder, (IP)nth = BPn − BPn−1 = IPn − IPn−1
Total IP of engine, IPn = ∑(IP)nth
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