Nissan engine has always been known for its durable skin and few problems, and the MR20 self-priming 2.0L engine developed in 2006 has not been replaced until now, and is still used on the new cars of Qijun and Tianlai, and the Japanese system is very confident in its own engine. If you use a word to describe the Japanese engine, it is "fine", the Japanese engine is said to be dismantled and cannot be restored, and the restoration cannot achieve the original effect? Is this true?
In my opinion, this statement has some exaggerated meaning, indeed the Japanese joint venture brand has entered China for almost 30 years, and its engine durability advantage has been verified by time, but it cannot be restored when it is dismantled, so how does it do maintenance? Is the Japanese engine claiming to be 100,000 kilometers overhauled back to the original factory?
Demolition can not be restored to the situation should refer specifically to some non-professional repair shops, the use of violent means to dismantle. The seamless all-in-one machine of the Japanese engine is really difficult to dismantle, and the average person really has no way to take it, only to use violent means.
Cold shrink fitting of the engine
One of the standard technologies for the assembly of the Japanese seamless all-in-one machine is cold shrinkage assembly, which uses the principle of low temperature shrinkage and normal temperature recovery of metal parts to carry out interference assembly of gearboxes, bearings, engine parts and other objects. Integral parts of cold shrink assemblies are generally defined as fixed connections and assemblies that are not removable.
During the cold shrinkage process, the internal structure of the alloy parts made of medium and high carbon steel will change to a certain extent, and the metallographic structure will be converted from austenite to martensitic (only partially residual austenite), which can increase the strength and hardness of high carbon steel.
The difficulty in realizing this technology lies in the combination of material and size, if the material standard does not meet the requirements, it is easy to cause uneven force on the parts in the shrinkage process to undergo special deformation, resulting in assembly failure. The refined operation of The Japanese manufacturing industry is inseparable from the high standards of the upstream material supply chain.
From the perspective of the engine cold shrink assembly process, everyone should be able to understand why the Japanese engine cannot be restored when dismantled. To be precise, the Nissan engine cannot be completely disassembled at all, and violent dismantling will only cause deformation damage to the parts, and it is difficult to reinstall it.
Similarly, it would be a fool's errand to use only the original method of dismantling and restoration for engine imitation.
Answering the opening question, nissan engines can certainly be repaired, but the cost of repair is higher. The German and American systems may change which parts are broken, and the Japanese system is directly replaced by a large part.
In fact, the cold shrink assembly process is not only used by Japanese car companies, but also used by German, American and domestic car companies, which is just a conventional assembly process. Nissan just pays more attention to this assembly process than other car companies, and the degree of engine integration is higher. Of course, it is precisely because they have done this to the extreme, so the Nissan engine is more solid and not easy to break.
Imagine how desperate you would be if you had glued a model of a pieced block but one day found that one of your places was misspelled. Therefore, the Nissan engine must not be broken often, which is the requirement of the Japanese factory specialization.
Returning to the question of "disassembled and put back but the performance is not as good as the original", there is an important influencing factor is tolerance.
Tolerance formulation
There are tolerances in part production, and tolerances can be understood as acceptable part size errors. An engine is less than a hundred parts, and these acceptable errors are combined, and the structural stability of the engine will be greatly tested. For the engine, this kind of rough use of the fine parts of the collection, that impact is even greater. If nothing else, regular wear is enough to drink a pot.
To solve this problem is also simple to say, that is, to achieve "tolerance fit", let the parts bite each other, achieve positive and negative tolerances to cancel each other out, and achieve the best "tolerance fit". However, it is easier said than done, and to achieve this, countless experimental references are required, and a lot of time and energy is spent to optimize and adjust.
Nissan has been holding a self-priming engine for more than ten years, squeezing its potential again and again, starting from these places, if the tolerance with the Japanese engine has definitely reached the top.
Such a near-perfect engine, the installation of a wrong step in order will destroy the overall tolerance balance, and now in turn to install it again, it will only be more difficult, and it will certainly not achieve the original effect.
At this point, if it is to be imitated, it is even more impossible. After so many years of optimization, even if the same part is produced, you won't get its tolerance ratio data. If you want to study it, at least you have to go the road of Nissan car companies again, so that there is no sense of imitation at all, and it is better to develop it yourself.
Speaking of which, it is necessary to mention that it is still the advantage of the upstream supply chain. In principle, the smaller the tolerance, the better the tolerance fit. Japanese companies control the tolerance of parts is also very strict, and accuracy is their basic need.
"Research on the Relationship between Engine Manufacturing Accuracy and Performance" pointed out that for every ± of parts difference dropped by 0.06 mm, the engine can increase the power of the engine by 0.7% and reduce the fuel consumption by 0.5%.
The characteristics of Japanese engines are fuel-efficient and power-pressed. The reason why they can do this is that the precision of the parts and the tolerance are indispensable. You want to say that the tolerance is cooperative, which car company does not do, are doing, but the time and energy invested are different, and the effect is different.
Many people say that domestic cars will only make a fuss about power, and the durability of the engine cannot be compared with Nissan, which is for sure. Compared to time-consuming and labor-intensive research and development such as improving durability, we definitely focus on research that can directly improve engine performance, and the visualization of high horsepower is undoubtedly more attractive.
Speaking of which, only Japanese cars are willing to do this kind of thing, and other brands are unwilling to do it and can't do it, which is essentially a difference in the concept of car building. To say that these two concepts are better or worse, the market has given the answer, Japanese cars are not dead, American, German, domestic cars are still alive and well, everyone well water does not violate the river water.
The Japanese system is durable, but the engine has not been updated for a long time, self-priming no matter how to play out the flowers, it is still self-priming, and now the Japanese cars have become the representative of the city to walk and buy vegetable cars. In the field of turbocharging, its performance is lackluster, and the CVT gearbox is even more criticized. Nissan's car-making concept has played a self-priming engine out of the flower, but this also limits the development of new machines, fish and bear paws can not be combined.
And domestic car companies are now at a turning point, through joint ventures, imitation or not, we have finally developed our own brand, but the future to go which way to go but began to be confused. We originally wanted to do a big job with other car companies in other countries in the future, but now we have ushered in a good opportunity for electric drives to overtake in such a corner. This has also caused the current situation that domestic fuel vehicles are not high or low. When you encounter such a turning point, how will you choose?
summary
Because of the cold shrinkage assembly process, the Nissan engine is really difficult to dismantle and reinstall, because of tolerances and other reasons, the performance of the reinstalled engine will also be attenuated. Nissan engine's high requirements for materials and assembly make it extremely difficult to imitate it, and if you want to learn the essence of Nissan engine, it is no less than heavy research and development, and the gain is not worth the loss. In fact, domestic car companies do not need to spend time and effort to imitate nissan engines, and now the development of domestic fuel vehicles is suspended, most of the energy is focused on electric drives, and the future is in electric drives.