First of all, let's talk about the background of this engine: this 1.2T engine is a member of the Toyota ESTEC engine family. ESTEC is the abbreviation of economy with superior thermal efficiency combustion, which means excellent high-efficiency power of thermal efficiency combustion system. It feels awkward. The combustion system is based on Atkinson cycle.
At present, there are two kinds of ESTEC engines, 8AR-FTS and 8NR-FTS, of which 8AR-FTS is the 2.0T used by Highlander. A few weeks ago, I sent an analysis of this engine. If you are interested, you can have a look, and 8NR-FTS is what we are going to talk about today.
This 1.2T is also called D-4T in Toyota, which is the abbreviation of direct injection four-stroke turbine engine and also a direct injection four-stroke supercharged engine.
Toyota 1.2T engine performance is not outstanding, only 85kw, 185Nm. But this does not mean that this engine is not advanced. The following is a brief analysis of the main technical scheme adopted by the engine.
1. Atkinson cycle combustion system
Toyota 1.2T engine adopts Atkinson cycle. The topic of Atkinson cycle has been said many times recently and it is a hot topic. To put it simply: Atkinson uses the method of closing the intake valve late to press the air entering the cylinder back to a part of the intake pipe, so that the acceleration stroke of the piston is longer than the stroke actually used for compression, that is, the expansion ratio is greater than the compression ratio. So it will be more efficient.
In order to reduce the fuel consumption caused by Atkinson cycle, Toyota 1.2T engine adopts VVT with medium oil pressure control valve and medium lock technology. Although no electric VVT is used, this configuration is the most advanced in the traditional hydraulic control VVT. Compared with the traditional indirect drive, the single-side locking VVT technology can adjust VVT faster. At the same time, because the direction can be adjusted in advance and later, the degree of freedom of adjustment is also greater. By optimizing the VVT control strategy to balance the pumping loss and the efficiency optimization brought by high expansion ratio, the maximum thermal efficiency of the engine finally reached 36.2%, which is quite good.
Atkinson's disadvantage is that it will affect the performance, which is also a reason why the performance of this engine is not outstanding.
2. The cylinder head is integrated with the exhaust pipe with water jacket cooling.
In this design, the exhaust pipe is integrated on the cylinder head, and the cooling water of the cylinder head is used to reduce the temperature of the exhaust gas, so as to avoid the over-temperature protection of the exhaust gas by the supercharger, thus meeting the emission requirements under the actual road driving conditions in Europe 6B RDE. The integrated exhaust pipe of Toyota 1.2T engine adopts the way of layered cooling from top to bottom, which improves the cooling efficiency. At the same time, the length of the exhaust passage is lengthened as much as possible to further reduce the mutual interference of the exhaust energy of the four cylinders and improve the efficiency of the supercharger. Due to the adoption of integrated exhaust pipe, Toyota 1.2T engine can maintain the ideal condition of air excess coefficient = 1 under almost all engine working conditions, and the whole vehicle has high cost performance. At the speed of 190km/h, the excess air coefficient can be maintained at 1, which is very beneficial to RDE emission. At the same time, the strategy of not enriching also affects the maximum power of the engine. Here is a picture showing Toyota's integrated exhaust pipe and stratified cooling.
3. Independent cryogenic cooling system.
That is to say, in addition to the ordinary engine cooling water circulation, an independent low-temperature water circulation is prepared for intercooler and supercharger cooling. Independent electronic water pump is used for control. In this way, the intercooler can be water cooled.
Toyota 1.2T adopts external water-cooled intercooler. In fact, the 2.0T and 1.2T of Toyota ESTEC engine all adopt external water-cooled intercoolers, instead of the water-cooled intercoolers with integrated air intake pipes like Volkswagen EAEAEA211.4t. The spatial layout of the external water-cooled intercoolers is easier, and the space and material requirements of the air intake pipes are also reduced, which is a better design scheme. In fact, Volkswagen's latest EA211.5tevo engine has also been changed to an external water-cooled intercooler. In this regard, it can be said that the public referred to Toyota's design scheme. Compared with the air-cooled intercooler, the water-cooled intercooler has higher cooling efficiency, and because of the large heat capacity of water, it is also helpful to the transient performance of the engine. Therefore, the water-cooled intercooler is a common design on the newly designed turbocharged direct injection engine, especially the water-cooled intercooler with small displacement has almost become the standard design scheme.
4. Optimize the design of combustion system and multi-injection strategy.
Toyota 1.2T adopts the scheme of single direct injection injector, unlike the dual injection scheme of direct injection and port injection in 2.0T ..
For 1.2T Toyota, the fuel beam design and injection strategy of the fuel injector are specially optimized, which greatly reduces the possibility of oil dilution caused by gasoline entering the engine oil. Oil dilution is an important development content of injector, piston top design, port including odd angle design and injection strategy formulation. That is, the oil dilution mentioned in the figure. Finally, the oil dilution of Toyota 1.2T engine is controlled at about 2%, which is a good result, and the general development requirement is less than 5%.
In this regard, Honda should reflect on how to avoid dilution of 1.5T engine oil during development.
Toyota 1.2T has formulated a complex multi-injection strategy, which mainly considers the cold start performance, even using four injections in the cold start situation. At the same time, emission optimization and prevention of super knock caused by pre-ignition are considered. The following two diagrams are schematic diagrams about the multiple injection strategy of Toyota 1.2T engine.
Super detonation is another important subject to be considered in the development of direct injection supercharged engine. Super detonation is a spontaneous combustion phenomenon caused by hot spots in the combustion chamber before ignition (ordinary detonation occurs after ignition and can be controlled by delaying ignition). This kind of super detonation will cause ultra-high explosion pressure and shock wave, easily penetrate the piston and cause serious damage to the engine, so it must be avoided as much as possible in the development process.
Supercharged direct injection engines are more prone to super-knocking, because supercharged direct injection engines can often output the maximum torque at low speed, resulting in higher in-cylinder pressure and temperature than non-supercharged direct injection engines, and at the same time, the residual exhaust gas will be difficult to control under heavy load. In addition, direct injection engine will lead to more oil dilution, which is another important factor causing super knock.
5. Reduce turbine lag through optimized VVT control strategy.
Another important problem of supercharged engine is turbine lag. The main problem is that it will take some time for the turbine to start to overcome its own inertia.
Toyota uses the central oil pressure control valve with double VVT for quick response, and adopts the opening of the atmospheric valve at low speed, heavy load and rapid acceleration, so that more air can pass through the turbine, and the supercharger can be started quickly to improve the turbine lag. Figure 8 below shows the improvement effect of this strategy on dynamic response.
6. Comparison between Toyota 1.2t and Volkswagen1.2t..
The comparison between the two engines has always been a concern. Generally speaking, the main technical configurations of the two engines are relatively close, such as direct injection, supercharging, water-cooled intercooler, integrated exhaust pipe and other technologies, all of which are equipped, and the level is relatively close. Generally speaking, my opinion is that Toyota's 1.2T is more advanced, mainly in the following aspects:
Toyota 1.2T was developed later, and some newer technologies were adopted.
For example, Toyota 1.2T adopts Atkinson cycle technology, and Volkswagen 1.2T still adopts Otto cycle. Until the latest generation EA2111.5 Evo, there was no similar Miller cycle technology.
In addition, Toyota's technology of not enriching the full-load area has taken into account the regulations of Euro 6b on RDE's actual road driving emissions, and Volkswagen 1.2T will not be considered until the latest generation.
Another factor is that Volkswagen's 1.2T is a model developed on the basis of 1.4T, and the main structure and most parts are of universal design. This kind of expansion and development often need to make some compromises in performance and weight index. Toyota 1.2T is independently developed and optimized, and the overall effect may be better.
Figure 9 shows the results of Toyota's own accelerated comparison study. Compared with Volkswagen 1.2T CVT, Toyota has a slight advantage at the beginning. The main reason for Toyota's analysis is that it takes time for the clutch of DCT to be fully combined, and the acceleration of DCT will catch up, but in the end the acceleration achieved by the two is almost the same.
The above information is for your reference, welcome to discuss, and the professional interpretation of engine technology will be issued every week. Welcome to forward your attention, thank you!
The dynamic parameters of Toyota 1.2T engine are not bright. At present, it is mainly assembled on Corolla and Lei Ling. Before talking about this engine, let's briefly compare several common 1.2T engines.
Among the four engines, Peugeot's 1.2T engine adopts a three-cylinder design, which has the highest maximum power and torque, that is, the best power performance. Volkswagen's EA2 1 1 (the one on the new golf) has the same power as Corolla's 1.2T, but the torque is relatively large, and the maximum torque corresponds to the rotation speed of 2000-3500rpm, which requires higher gasoline, requiring #95. Corolla's 1.2T engine parameters are not too outstanding, but the low torque output is good. The maximum torque is185n m, which can be output at 1500rpm, and can last up to 4000rpm.
In fact, this engine can be regarded as a miniature version of the Toyota 2.0T engine, because many technologies are similar. So, what's special about this engine?
1, the thermal efficiency of the engine reaches 36%, and now the thermal efficiency of Chery's 1.5T engine exceeds 37% (not yet on the market);
2. Using VVT-iW ultra-wide angle variable valve timing technology, the seamless switching between Otto cycle and Atkinson cycle can be realized;
3. Multi-injection, optimized spray shape and strong tumble effect make the mixing more sufficient, thus realizing high-efficiency and high-speed combustion;
4. Lightweight and low inertia turbine with fast response speed can improve the torque performance at low speed;
5. Water-cooled intercooler and integrated exhaust manifold improve the cooling efficiency of waste.
All in all, this engine has many technical highlights. Whether to burn engine oil, carbon deposit, etc. I won't discuss it here. Those who like to debate can say it themselves in the message area!
The engine has high thermal efficiency and good dynamic performance, which can bring strong acceleration performance. By adding supercharging technology to the development technology of hybrid engine and conventional engine, a supercharged engine with world-class high thermal efficiency is realized. By combining the exhaust manifold with a water-cooled cylinder head and a single scroll turbocharger to optimize the exhaust gas temperature, excellent turbocharging efficiency can be achieved. By using the compact water-cooled intercooler, regardless of the thermal load of the engine, the cooling effect of the intake air can be displayed according to the working conditions. Real-time response to accelerator operation and maximum torque generation in a wide rotation range are realized.
In addition, the powerful vertical rotating vortex in the cylinder and the advanced direct injection technology D-4T form an ideal air-fuel mixture, which realizes efficient and high-speed combustion. In addition, by pursuing the improvement of combustion and loss, such as the stepless gas timing mechanism VVT-iW which controls the valve opening and closing timing according to the load, the Atkinson cycle (intake side) is realized, and the thermal efficiency of supercharged gasoline as an engine can reach up to 36%.
8NR-FTS uses supercharging instead of high compression ratio. It seems that the birth of the engine benefited from the accumulation of Toyota engine technology.
1) 1.2T？ 8AR-FTS adopts variable valve timing mechanism VVT-iW. Compared with the traditional type, the variable range is expanded, which makes the Atkinson cycle operation more radical, and the middle lock mechanism ensures the startability.
2) The key of turbine engine is to suppress knocking. The head integrated with water-cooled exhaust manifold, piston-cooled fuel injection control mechanism and water jacket gasket improves the output by 10% or more.
3) The intercooler is water-cooled, and Toyota claims that its cooling efficiency is higher than that of other companies. The installation position is the upper part of the engine, and the airflow path will be shorter.
4) In the direct injection turbocharger, air and fuel must be mixed quickly and evenly with uniform tumble flow, and burn quickly. By designing the shape of the air inlet, the shape of the tumbling combustion chamber is maintained, and various fuels are injected.
Summary: The performance of this engine is basically the same as that of Volkswagen 1.2T engine, but the compression ratio of Volkswagen is 0.5 higher than that of Toyota. Volkswagen uses 95# fuel and Toyota uses 92# fuel, so the extra compression ratio is not difficult to understand.
I don't know much about the technical level. Tell me how I feel.
Especially suitable for city shuttle, the response is very fast at 40- 100, and the high-speed dynamic response below 140 is also very fast, which is still in the absence of motion mode.
Toyota home configuration is not high. The core cost of this car is this engine. It feels comfortable to drive, and there is a lot of space, which is enough. After all, the price is here.
Toyota 1.2T engine also needs our overall grasp. Analyzing this automobile process, the fuel consumption has different forms, which is also a way to grasp the automobile driving process. It needs independent thinking, and it is also a time process. It needs our own comprehensive analysis to improve our driving process.
It is also the problem of engine fuel consumption, which needs our own comprehensive grasp, a time process, and the overall grasp. Fuel consumption is also determined by the engine and needs to be fully understood by yourself. The performance of the engine is also a cognitive process that needs to be improved by ourselves and analyzed by ourselves. It is also a time process, which requires our own efforts to change the process and fully grasp it. It is also a time process that we need to grasp the direction ourselves, and it is also a process of promotion. It also needs a process, which requires us to grasp it comprehensively, and it is also a time process to improve ourselves.
Fuel consumption is also a time process. Grasp the dynamics, have good quality, have new harvest, but also need to comprehensively choose technology, automobile performance, new ways. It is also a time process of self-improvement, which requires us to fully grasp and improve ourselves as a whole. It is also the time to fully grasp the application, the needs of automobile driving, and the overall grasp.
It is necessary for us to master the driving process in an all-round way, and it is also a process that requires us to master the fuel consumption in an all-round way. Good quality is also helpful to fuel consumption, and it is also a time process that requires our own overall analysis and comprehensive improvement. We need comprehensive analysis and grasp, which is also a process of overall grasp. We need to grasp the overall performance of the car according to the fuel consumption, and there are also new considerations.
What's special: this is a self-priming engine!