Are tests for efficiency of the IC piston engine accurate !

[prospero]

I was reading an article the other day to the effect that the methods used to test the efficiency of an IC piston engine might not be very dependable. The argument goes like this:
The efficiency of the IC piston engine, is mainly affected by the very short crank throw and the angle which the connecting rod makes with the crankshaft as it travels down the cylinder. The contention is that even taking into account piston speed etc., the efficiency of the IC piston engine is very low b’cos of these two factors. As an example taking actual figures given by an automobile manufacturer of a maximum 39.5 bhp at 5500 rpm and max. torque of 79 N-m at 2500 rpm. Bore: 6.82 cm, Stroke 7.2 cm : The argument is that pressure on piston head after combustion equals 35 Kg/cm^^2 (figures quoted from text book on automobile engineering) area of piston head equals 36.5 cm^^2 approx. Therefore initial pressure on piston head equals 1277.5 kgf. If this force had been applied at right angles on a lever that was 30 cms (1 ft. long) (quoting Archimedes) it would have resulted in a torque of 383.25 kgm (3755.85 N-m ) being generated. Yet the manufacturers figure of 79 N-m maximum torque means that the torque generated is always much lower than this. The fact IS that power is a function of torque and engine speed. So torque does matter.
This mean that compared to possible output the IC piston engine has only (79/3755.8) x 100 = 2.1% efficiency. Does this denote in effect that the use engineers have been making of Carnots heat engine theory is flawedand calorific value of fuel to measure power in power out is worng? Could this be right, is there something truly wrong with the IC piston engine around which much of our world revolves ?