There is no lower limit for displacement? Analysis of GM's new 1.0T/1.3T engine

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In 2014, GM introduced a new generation of small-displacement Ecotec engines in China, which are 1.4T, 1.5T and 1.5L respectively. The representative technology is overhead direct injection. Just three years later, GM released an updated small-displacement turbocharged engine, replacing the previous 1.5 liters with 1.0T, replacing 1.4T with 1.3T, and the most eye-catching overhead direct injection was cancelled. Changed to a new generation of dual injection system.

Why does GM want to introduce a smaller displacement engine, and why should it eliminate the overhead direct injection and replace it with double injection?

/01/

Displacement is getting smaller and smaller, not necessarily compromise

GM's new generation of 1.0T and 1.3T Ecotec engines have a maximum output of 92kW/170Nm and 120kW/230Nm, which is 15% higher than the original 1.5L and 1.4T, and in the new intelligent electronic control and Under the supercharged technology, the speed at which the maximum torque is reached is greatly reduced.

For example, a 1.0T engine can output a maximum torque of 170 Nm at 2000 rpm, while a previous 1.5 L engine requires a maximum torque of 141 Nm at 4000 rpm.

At the same time, the direct benefit of reduced displacement is that the size of the entire engine is reduced and the weight is reduced, thereby reducing the fuel consumption of the entire vehicle. The miniaturization of the engine also means that the fewer components involved in friction work, that is, the less energy that is lost by friction during engine operation, which, needless to say, can also reduce fuel consumption.

In addition, GM's new generation of Ecotec 1.0-liter and 1.3-liter supercharged engines have smaller turbo lag and a considerable advantage in low-speed torque, which is why it is possible to achieve low torque.

In fact, not only GM, but Volkswagen, BMW, Volvo, Ford, Peugeot Citroen and other car companies are actively promoting the miniaturization of the engine, which is not entirely a compromise under the pressure of environmental regulations. Nowadays, the small-displacement engine technology is gradually perfected and matured, and the problems of power and smoothness have been gradually overcome. Their advantages in weight, volume and efficiency are the main reasons for the promotion of the three-cylinder machine.

However, unlike many people imagine, these small-displacement engines use a lot of new technology, and their cost is not lower than that of higher-displacement engines. The GM's new generation of turbo engines is even several times more expensive than regular engines. However, when more and more models are equipped with 1.0T and 1.3T, their cost is expected to drop significantly after the scale effect.

/02/

Direct injection and double spray, is it a step backward?

In-cylinder direct injection is a technique that has been relatively hot in recent years. It means that unlike the previous injection of fuel into the intake manifold, the fuel is directly injected into the cylinder and mixed with the air. The advantage is that the higher injection pressure can make the fuel atomization more thorough, accurately control the fuel injection amount, and achieve the fuel consumption reduction under the premise of ensuring power and torque.

However, in-cylinder direct injection is not a perfect technology, it has a problem that is very headache for manufacturers: it is easy to cause fuel wet wall and mixer unevenness in the cylinder, which leads to increased soot emissions. The so-called fuel wet wall is actually that the fuel is not fully mixed with air in the cylinder for combustion, and the fuel consumption is naturally higher.

The Smart Dual Injection (DPI) of the GM's new generation of engines solves this problem. It is different from one injector of a conventional EFI, but two injectors of one cylinder. The principle of reducing the wet wall of the fuel is achieved by co-injection of two injectors to achieve a larger spray coverage area and at the same time increase the atomization rate of the fuel injected.

As a result, the wet wall of the fuel is significantly reduced, and the fuel consumption and emissions are correspondingly reduced. Therefore, the fuel consumption of the new generation of small-displacement supercharged engines is not to be worried. The power, as mentioned above, has not only declined, but has improved. Why is the GM's new generation engine improved in performance and fuel economy?

/03/

How to ensure small displacement performance?

The figure below is a comparison of the parameters of the new 1.0T/1.3T new engine and competing products.

As can be seen from the table, the dynamic performance of these engines is not bad, especially the Peugeot Citroen's 1.2T, the rated maximum power and torque reached 100kW and 230N·m respectively, BMW's 1.5T, the torque is slightly inferior to Peugeot Citroen 1.2T, but at 1250 rpm can already burst out the maximum torque of 220N·m.

To achieve such high performance, different manufacturers have adopted their own skills. From the perspective of parameters, the general 1.3T has greatly surpassed the 1.2T of Peugeot Citroen and Volkswagen Group in performance, and the new 1.0T and Ford and Honda are the same. The displacement models are also in the same grade. How is this performance achieved?

First of all, it is a highly intelligent engine electronic control system.

In addition to autonomous driving and car networking, the intelligentization of the engine's electronic control system is also a key part of the car's intelligent wave. The replacement of the carburetor by EFI technology decades ago is a milestone in engine intelligence, greatly improving fuel efficiency.

Today's engine electronic control system is very complicated, but the target has not changed. It is to judge how much fuel and air the engine needs, and how much oil is needed during operation. Try to provide it in an accurate position and in an accurate amount. The dual-injection system and in-cylinder direct injection technology are all aimed at this purpose, but the paths are different and the effects are slightly different.

In addition, GM's new generation of small displacement machines also use a number of cutting-edge technologies, such as the replacement of traditional mechanical pressure relief valves with electric turbine pressure relief valves, which can more accurately and quickly establish boost pressure and reduce small load pumps. Gas loss.

The central high-angle variable timing valve system directly arranges the solenoid valve on the camshaft, shortens the length of the oil passage, and greatly increases the response speed of the phaser, so that the engine can better "breathe", at both high and low speeds. The ground guarantees the best intake and exhaust effect.

In addition, the new engine has smarter technology and design in thermal management systems, start-stop systems, ignition coils, variable displacement oil pumps and electronic throttles.

The intelligentization of the electronic control system is an electronic measure. In order to improve the efficiency of the engine, it is necessary to make efforts at the mechanical level. The key word in this regard is integration:

When introducing the latest generation of small displacement engines, GM mentioned an interesting concept, "burning single cylinder optimal". What do you mean by this is that when the engine was developed, the manufacturer designed the engine as a whole. When different displacements are required, the method is mainly to change the cylinder diameter and stroke.