Don't believe that the timing chain is maintenance-free for life, be careful of the "ten thousand yuan overhaul"

I wrote an article about engine oil knowledge last month, which mentioned a few timing chains. So, some riders asked me questions in this regard. The rider "Qiuqiu" asked: Does the 2016 Camry 2.0G use "belt timing" or "chain timing", and which of these two types of timing is better.

So after consulting, I determined that the engine of this car uses a timing chain (the engine of this car is 6AR-FSE, the entire 6AR family is chain timing). As for the belt and chain which is better, in fact, these are just two ways of engine timing. We must say who is good and who is bad, this is really hard to say. Because they have different characteristics. There are three different timing methods for

engines:

: gears, chains, and belts. There are actually three timing methods for

engines. The first is called "gear timing". This formal method, as the name suggests, is "the gear meshes with the gear and transmits the timing signal." This timing method has the highest precision, highest reliability, and basically unlimited life. No matter what it is, it is the best.

However, the formal gear method is not without its drawbacks: high cost (especially for "overhead camshaft engines", the crankshaft is far away from the camshaft, requiring multiple gears to transmit power, which is surprisingly expensive)! Because it's too expensive, civilian cars won't be used at all. Only top racing cars (and classic cars) will consider adopting this timing method. Let's not study it.

Belt Timing: Quiet, soft, and no noise

The second timing method is called "belt timing". The structure of this timing is also very simple: a "wide gear" is placed on the crankshaft and a "wide gear" is placed on the camshaft. "Wide gears", connected with a "toothed belt" is the end. Therefore, the biggest advantage of the belt structure is its simple structure! And there is no need for lubrication at all (even if it is directly exposed to the air)! The advantage of the simple structure of

is low cost. In addition, the belt itself is made of high temperature resistant rubber, which is wrapped with a "cord skeleton" made of glass fiber, so it is as soft as a tire. Therefore, the timing belt is very quiet when it is running, without any metal-to-metal noise. The

belt also has disadvantages: short life

needs regular replacement of

belt timing seems to have a lot of benefits, so does it have any disadvantages? Of course there is! That is the belt life is too short. Like tires, rubber belts are also afraid of high temperatures. The result of long-term high temperature baking is belt aging, loss of elasticity and toughness. When the rubber material of the belt is completely aging, it may suddenly break off one day, causing the engine to be scrapped instantly.

Therefore, each automobile manufacturer usually stipulates that the timing belt needs to be inspected and replaced every 80,000 kilometers. In this way, it can fundamentally avoid the sudden loss of control during the operation of the engine caused by the belt tension, and the collision of the piston and the valve stem will cause the engine to damage. (In fact, the high probability of such a serious failure is the "belt overdue service", Big Tiger You has experienced it once before) The

chain has obvious advantages: it will not break

. For family cars, it is almost maintenance-free. The last engine of

This kind of timing method is now the timing of the "full street" chain. Like the "belt system", the crankshaft and camshaft are still covered with metal gears, but the belt is replaced by a metal chain. Moreover, the metal chain is immersed in the engine oil and is protected by the engine oil all the time.

metal chains are different from belts, and there is no possibility of chain breaking. So 80,000 kilometers, 100,000 kilometers, and 120,000 kilometers are just used. Because it will not break, many riders have such an impression of it: the chain is used for life and does not need to be replaced.

In fact, this is true in a sense. For example, the replacement cycle of most domestic cars in my country is even shorter than 8 years or 150,000 kilometers (in fact, family cars with a mileage of 20,000 kilometers or more per year Rarely). Under this premise, there is a high probability that the timing chain does not need to be replaced or maintained. The

chain is not without its shortcomings: elongation is the culprit once the tensioner

is adjustedTo the limit, the chain is abolished

. But for a car over 8 years or 150,000 kilometers, can the chain really be left alone for life? Not necessarily! The timing chain is made of steel and will be elongated for a long time under the action of tension. Once the chain is elongated, the precision of the transmission is reduced. Fortunately, all cars now have a VVT system that can correct errors in real time. This is one of them.

Second, after the chain is stretched, there will be a tendency to "detach from the gear". So there is a magical component "tensioner" on the car. The function of this component is to "tighten" the chain. However, the tensioner has an adjustment range. Once the adjustment margin is all used up, it means that the chain has been pulled to the longest, and the "chain + tensioner" should be replaced together at this time. If no matter what, once the chain "jumps" one day, the result of the engine is basically not far from the overhaul.

In fact, a few years ago, the Volkswagen 888 family had a congenital defect in the design of the tensioner. A certain screw was not locked tightly, which caused the tension to fail and "jump teeth". How many engines were finally overhauled as a result? Players who are familiar with Volkswagen engines should remember this deeply. Although

chains and belts have their own advantages

under the "maintenance-free" thinking, the chain has become the mainstream

, so the timing chain must be more "advanced" than the belt. This statement is not strict. Chains are as good as chains, but they are not without their shortcomings. For example, loud noise (the loudest of the three timing methods) is also an obvious disadvantage. Although the belt life is short, it will be fine as long as it is changed regularly as required.

If so, why are there fewer belts now? It's simple: Nowadays, "maintenance-free" is emphasized everywhere, which is a big trend. In addition to the timing method, there is also a battery. In addition to the battery, there is a "shaft head". Everyone who plays off-road or truck drivers knows that many "axle heads" of previous cars were reserved for grease nozzles. Nowadays, the "axle heads" of cars are almost all maintenance-free, and if it breaks, just replace it with another one. Maybe this is the general trend!