Morse Test: Used for multi cylinder engines
The engine is run at the required speed and the torque is measured.
One cylinder is cut out by shorting the plug if an S.I. engine is under test.
The speed falls because of the lass of power with one cylinder cut out but is restored by reducing the load.
The torque is measured again when the speed has reached its original value.
If the value of I.P. measured simultaneously for each cylinder In this method the BP of whole engine is first of all measured at a certain speed and load with the help of dynamometer. Then from total number of cylinders of the engine one of the cylinders is cut out by short circuiting the spark plug. The output is measured by keeping the speed constant. The difference in the outputs is measure of the indicated power of disconnecting cylinders. Thus for each cylinder the IP is obtained and then is added together to find the total IP of the engine.
Where BP= Brake power
IP= Indicated power
FP = Frictional power
Let F.P. of cylinder 1,2,3,4 be F1, F2, F3, F4 respectively.
Then total FP of engine = F1+F2+F3+F4
Let IP of cylinder 1 2 3 and 4 be I1, I2 I3& I4 respectively.
The total IP of engine is given by,
IP= I1 +,I2+ I3 + I4
The total BP of engine when all cylinders are working
BP= Total IP – Total FP
B = (I1 +,I2+ I3 + I4)–(F1+F2+F3+F4)----------1
When cylinder 1 is cut off, the BP developed by the remaining three cylinders,
B1= (0+,I2+ I3 + I4)–(F1+F2+F3+F4)------------2
Subtracting (2) from (1) we get
B- B1 = I1
Therefore, IP of cylinder 1, I1 = B-B1
IP of cylinder 2, I2 = B-B2
IP of cylinder 3, I3= B-B3
IP of cylinder 4, I4 = B-B4
Total IP of Engine = I1+I2+I3+I4
Friction Power F.P. = I.P – B.P