What is total pressure in cylinders of an automobile engine? The operating state of engine primarily depends on pressure in the engine cylinder. As a rule, a gasoline engine has a power of about 1000 kPa, and a diesel engine has a power of about 2000 kPa.
The cylinder pressure of most EFI engines is 1200~1400kPa, and cylinder pressure of some high compression engines is over 1700kPa. The pressure in cylinder of original design of engine mainly depends on volume of combustion chamber, compression ratio of engine and presence of a pressurization mechanism; main factors affecting pressure of each cylinder of an engine in real operation are amount of carbon deposits in combustion chamber, as well as absence of seal and exhaust obstructions, etc.
What is total pressure in cylinders of an automobile engine? An introduction to reasons why cylinder pressure is too high or too low
Introduction to why tank pressure is too high or too low
Cylinder pressure results may show that cylinder pressure is too high, within standard, and cylinder pressure is too low. If measured value of cylinder pressure exceeds standard value specified by original factory, cylinder pressure is too high; if measured cylinder pressure is below 80-85% of standard value specified by original factory, cylinder pressure is too low.
What is total pressure in cylinders of an automobile engine? An introduction to reasons why cylinder pressure is too high or too low
Cause of too high cylinder pressure
The cause of high cylinder pressure is mainly due to excessive carbon deposits in combustion chamber or excessive grinding of mating surface of cylinder block and cylinder head during repair, which leads to a decrease in volume of combustion chamber. and too high a compression ratio.
What is total pressure in cylinders of an automobile engine? An introduction to reasons why cylinder pressure is too high or too low
Cause of too low cylinder pressure
The cause of too low cylinder pressure is more complex. To determine specific cause, you can perform an in-depth diagnosis according to following steps.
①Inject 20-30 ml of lubricating oil into spark plug (or fuel injector) hole of cylinder, and then measure cylinder pressure again with cylinder pressure gauge. If re-tested cylinder pressure is significantly higher than first time, it indicates that cylinder, piston ring, piston wear is too great, or piston ring is aligned, stuck, broken, and cylinder wall is under tension, causing cylinder to be perforated.
②If cylinder pressure is same as first test, it indicates that intake and exhaust valves or cylinder liner are not sealed.
You can additionally check following:
a. Shake cylinder to compression top dead center, lower transmission and apply parking brake.
b. Apply high pressure air to cylinder through spark plug (or fuel injector) opening and listen for sound of air leaking.
c. If you hear sound of air leaking from exhaust pipe, this means that exhaust valve is not closed tightly; if you hear sound of air leaking from air filter port, it means that intake valve is not closed. tight; sound of air leakage indicates that the cylinder head gasket is not tight.