What are the ventilation losses of automobile engines?

The negative pressure in the cylinder causes qigong absorption loss, the early opening of the exhaust valve causes expansion work loss, and the forced exhaust of the piston causes success loss.

Therefore, ventilation loss includes intake loss and exhaust loss, but exhaust loss is greater.

Working principle of pumping loss

When you lightly step on the accelerator, the throttle valve only slightly opens, but at the same time, the piston moves down, trying to suck air from the intake pipe that is close to closing. At this time, a vacuum will be formed between the throttle and the piston, and the atmospheric pressure outside the crankcase will form a great resistance to the vacuum suction of the piston, which will greatly consume energy (pumping loss).

In addition, the high-speed airflow in the narrow gap of the throttle will cause intake friction. The lower the engine speed, the tighter the throttle, and the greater the energy loss.