Yup. The "1/3-rd of mechanical power" is an empirical rule.
However, it seems reasonable once you think about it.
The mechanical power of a car is about 25-30% of the total heat generated. So a 150hp car actually generates about 450hp of heat energy. Most of that power is indeed lost in exhaust. The 1/3 of 150hp is 50hp, around 10% of the total.
However, it seems reasonable once you think about it.
The mechanical power of a car is about 25-30% of the total heat generated. So a 150hp car actually generates about 450hp of heat energy. Most of that power is indeed lost in exhaust. The 1/3 of 150hp is 50hp, around 10% of the total.