First mounted on Chuanqi GS5 GAC 1.5T GDI engine.

　　[car home Engine Disassembly] It’s human nature to like new things, and you won’t miss an important new car like brand-new (|). But I’m sorry, the new car hasn’t come on the market yet, and even the test drive report hasn’t been seen yet, but it doesn’t matter. Let’s take a look at the new 1.5T GDI engine on the new GS5 first.

● Basic information of engine

　　We noticed that the cylinder diameter/stroke ratio of GAC, a brand-new 1.5T GDI engine, has become smaller. This change of long stroke is helpful to improve the engine torque and make the engine respond better at low speed.

　　However, by comparing the power parameters of the three engines in the above table, we can intuitively see that the same 1.5T engine has different tuning and the maximum power/torque is different. Take the maximum horsepower as follows: Honda 177Ps＞ > Chuanqi 171Ps＞ > Great Wall 169Ps, but the maximum torque is reversed: Great Wall 285N·m＞ > Chuanqi 265ps. Chuanqi’s self-positioning in this "challenge" is quite clear. The setting of power parameters is not blindly adjusted upwards, but on the premise of ensuring power and torque, the output speed of maximum power is lowered and the output speed range of peak torque is widened.

　　Of course, Chuanqi 1.5T GDI engine, as one of the "three big parts" of the whole vehicle, is an important factor that many consumers consider before buying a car. This disassembly is more to help consumers clarify the advantages and disadvantages of Chuguangqi 1.5T GDI engine. AB: What is the difference (highlight) between Chuanqi GS5 1.5TG DI and GS4 1.5T engine in 2019? What gains can these highlights bring?

● What are the highlights of GAC’s 1.5T GDI compared with the previous 1.5T?

Highlight 1: change from manifold injection to in-cylinder direct injection

　　First of all, the biggest difference between this 1.5T GDI and GS4 1.5T engine lies in its name-GDI (in-cylinder direct injection). The most direct benefit of changing the fuel injection system from manifold injection to in-cylinder direct injection is that the engine power performance is improved and the harmful gases in the exhaust gas are relatively reduced. Moreover, we know that the first-tier cities in China will soon implement the more stringent national six emission standards. As a car company, GAC must be ahead of the policy, so this engine adopts in-cylinder direct injection technology to achieve the national six emission standards.

　　It is worth mentioning that "National VI" refers to a national policy standard for automobile exhaust emission. After the implementation of the "National VI" emission standard, it will be divided into two stages: "National VI A" and "National VI B", which will be implemented on July 1, 2020 and July 1, 2023 respectively. In some emission standards, "National VI B" is more than twice as strict as "National VI A" )

　　It is worth mentioning that with the help of turbocharger, a higher compression ratio means that the engine is more efficient, can improve more power performance, and saves more fuel, etc. After all, the working feature of direct injection engine is to directly inject fuel into the cylinder, and use the air flow in the cylinder and the fuel on the piston surface to achieve better atomization effect.

　　Direct injection engine has a good performance in working uniformity and performance under full load, and even the problem of working instability of cold car has been significantly improved. Of course, things are two-sided. While the engine enjoys the power improvement brought by high compression ratio, it is also a test for the fixation of high-pressure fuel rail and the fuel pump pressure of the fuel supply system.

　　The "dadada" sound of direct injection engine during fuel injection has always been a headache for engine NVH engineers. We can see their solutions on GAC 1.5T GDI this time:

　　When the engine is running in the compression stroke, the pressure in the cylinder is very large. For in-cylinder direct injection engines, ordinary fuel pumps can’t meet the demand. Another important feature of in-cylinder direct injection engine is that the fuel supply pressure of fuel pump is very high, so that gasoline can be effectively injected into the high-pressure combustion chamber.

　　Because of the combustion characteristics of gasoline, the compression ratio of ordinary engines can’t be designed too high, otherwise it is easy to knock, so most direct injection engines will divide the fuel injection process into two stages, that is, two injections. The GAC 1.5T GDI engine made a small breakthrough in fuel injection-The strategy of "three injections per cycle" is adopted under the specific working condition of "high load and low speed"(It can be understood that the fuel is injected three times per cycle only when the vehicle starts, and it is injected twice in other working conditions): The first-stage pre-injection (which occurs in the intake stroke and the crank angle is about 360°~180°CA) can take away a lot of heat in the cylinder under the action of gasoline volatilization, and reduce the cylinder temperature, so as to achieve a lower ignition angle, and to effectively suppress the probability of knocking and ensure stable combustion. The second and third main fuel injection (which occurs at the end of compression stroke and before power stroke, and the crank angle is about 0°CA) can bring higher exhaust temperature and accelerate the light-off of three-way catalyst.The advantage isTo achieve a rapid start, reduce engine emissions, meet the national six B emission standards, and reduce fuel consumption.

Highlight 2: Switch to exhaust gas turbocharger with lower inertia.

　　Although turbocharging technology is not a brand-new technology, it is the mainstream development direction to apply turbocharging technology to small displacement engines. Thanks to the ingenious design of turbine blades, the low inertia exhaust gas turbocharger provided by Borgwarner can take into account both high speed and high power and low speed and high torque.

Highlight 3: The three-way catalytic converter has added more precious metals.

　　Engineers have made a lot of efforts to purify the exhaust gas in order to make the exhaust gas from the 1.5T GDI engine meet the national sixth B emission regulations. The biggest highlight is the adoption of a brand-new three-way catalytic converter and the addition of more precious metals in the catalytic converter, thus reducing the light-off temperature to 270℃. What is the concept of 270℃? Let me give you an example for your reference: the light-off temperature of the three-way catalytic converter in the general national standard is 400℃, and the difference between them is 130℃.

　　The author jokingly said here: the exhaust gas discharged by an engine that can meet the national six B emission regulations should be cleaner than the air in many cities, right? Is that engine like a walking "air purifier"?