Why is the turbocharger the most malfunctioning assembly on the Cummins engine?
Because the rated working speed of the turbocharger is above 130,000 revolutions per minute, and it is at the outlet of the exhaust manifold, the temperature is extremely high (above 800℃), and the inlet and exhaust pressures are also high, that is, high temperature, high pressure, and high speed. , So the requirements for the lubrication, cooling, and sealing of the turbocharger are relatively high. In order to ensure the service life of the supercharger, the design should ensure the lubrication and cooling of the supercharger’s floating bearing. At the same time, it is required to do the following during use:
① After starting the engine, it should be idling for 3-5 minutes. Do not add load immediately to ensure good lubrication of the turbocharger. The main reason is that the supercharger is located on the top of the engine. If the supercharger starts to run at a high speed immediately after the engine is started, the oil pressure will not increase in time to supply the supercharger, causing damage to the supercharger due to lack of oil or even burning. Broken the entire supercharger.
②The idling time should not be too long, generally no more than 10 minutes. If the idling time is too long, it is easy to cause oil leakage at the compressor end.
③ Do did not turn off the engine immediately before stopping. It should be idling for 3-5 minutes to reduce the speed of the turbocharger and the temperature of the exhaust system to prevent the occurrence of heat recovery-engine oil coking-bearing burnout and other faults. Frequent incorrect use will damage the supercharger.
④ For engines that have not been used for a long time (usually more than 7 days), or engines with new turbochargers, the oil should be filled into the oil inlet of the turbocharger before use, otherwise, it will reduce the life or damage the turbocharger due to poor lubrication…
⑤ Regularly check whether there is loose air leakage/oil leakage at each connection part and whether the oil return pipe is unobstructed, if any, remove it in time.
⑥ Ensure that the air filter is clean and replace it regularly as required.
⑦ Change the oil/oil filter regularly.
⑧ Regularly check the radial and axial clearance of the turbocharger shaft. The axial clearance should not be greater than 0.15 mm. The radial clearance is: the clearance between the impeller and the pressure shell is not less than 0.10 mm, otherwise, it should be repaired by professionals to avoid enlarged losses.
Why is the life of the newly replaced supercharger often shortly after the supercharger on some Cummins engine is damaged?
①The lubricating oil is not clean.
②There are impurities in the oil passage.
③There is foreign matter in the intake and exhaust pipes.
⑵Diagnosis and treatment methods
① Check whether the lubricating oil is clean. Because the speed of the turbocharger is very high, the matching accuracy between the bearings is also very high, if the lubricating oil is not clean, the shaft of the new turbocharger will be damaged quickly, so when replacing the new turbocharger, replace the lubricating oil and engine oil The filter is very important.
② If the lubricating oil and oil filter are replaced when the turbocharger is replaced, the service life of the turbocharger is still very short, it is caused by too many impurities in the oil passage, and the oil passage needs to be cleaned. Please refer to the following cleaning methods :
⒈Remove the broken turbocharger and drain the oil when the engine is warming up.
⒉Add a certain amount of mixed oil (30% engine oil + 70% diesel).
⒊Put the oil inlet pipe of the turbocharger into the oil return pipe or seal the outlet of the oil inlet pipe.
⒋Start the engine, stop after idling for 1 to 2 minutes, drain the mixed oil (if it is dirty, it is better to clean it twice), and the above work is carried out when the car is hot.
⒌Clean or replace the turbocharger oil inlet pipe, clean the oil pan and replace the machine filter and air filter.
⒍Install a new turbocharger, and add lubricating oil to the oil inlet of the turbocharger, then install it into the oil pipe, fill the filter with oil and install it, and finally install other pipes.
⒎Start the engine, increase the speed after idling for 3 to 5 minutes and check whether there is any leakage of oil or gas.