[YesAuto Engine Technology] Mazda has always insisted on its own Chuangchi Blue Sky naturally aspirated engine, which has advantages over small-displacement turbocharged engines in terms of fuel economy and power balance. Mr. Jian Mitsuo, who is known as the father of Chuangchi Blue Sky, held a press conference more than once to confirm the above point of view with various technical data. The models launched by Mazda in China have always been equipped with naturally aspirated engines, and at the same time, they have always promoted the company's insistence on naturally aspirated engines. But not long ago, Mazda launched its new 2.5T turbocharged gasoline engine, which belongs to the Chuangchi Blue Sky product series. Why did Mazda give up its past persistence and step into the turbocharged engine camp after a turn? As the father of Chuangchi Blue Sky, what kind of “black technology” did Mitsuo apply to this 2.5T engine? This article will reveal the secrets for you one by one.

● The first Chuangchi Blue Sky turbocharged gasoline engine

Mazda's new 2.5T engine is accompanied by the new CX-9 model. This new engine replaces the 3.7L V6 naturally aspirated engine on the old CX-9. While optimizing the power output performance, it has made great progress in fuel economy.

The reason why Mazda has not launched a turbocharged engine for a long time is more because it has not yet achieved key technological breakthroughs, and the product has not yet reached the target performance in the research and development stage, and there is still doubt whether it can be mass-produced. Boasting Haikou is obviously not the style of Mazda, a Japanese company. Uncertain things can't be publicized. The product “bounces” and the company's face can't bear it! After several years of research and development, Mazda finally put this first turbocharged gasoline engine belonging to the Blue Sky product series to the market. It is not clear how many ripples it can cause in the market, but the birth process of this engine is certainly not an overnight success.

How did the Mazda 2.5T engine achieve the above goals? This article will provide you with an in-depth analysis. But before analyzing this 2.5T engine, let’s go back to 30 years ago to understand what Mazda did on turbocharged engines at that time.

● Mazda's exploration of engine miniaturization 30 years ago

Thirty years ago, Renjian Mitsuo studied the subject of miniaturization of engines through turbocharging technology, but the technology at the time (variable valve timing technology and direct injection technology have not yet emerged) could not achieve power and performance. The balance of fuel economy. The mechanical supercharging technology can achieve a certain degree of engine miniaturization. Compared with turbocharging technology, it can better balance the power performance and fuel economy, and became the engine miniaturization program recommended by the people at that time.

The Mazda KJ-ZEM engine uses the Miller cycle, which has a higher thermal efficiency than the traditional Otto cycle, to improve engine fuel economy. At the same time, the engine is equipped with supercharger technology, which uses the crankshaft pulley to drive the supercharger through the belt to compress the air before introducing it into the cylinder to increase the engine's low-rotation torque output and make up for the weak output of the Miller cycle engine. So that the engine has better power and fuel economy in the entire speed range.

Mazda KJ-ZEM and Honda J30A1 parameter comparison
engine model Mazda KJ-ZEM Honda J30A1
Displacement/structure 2.3L/V6 3.0L/V6
Intake form Supercharged inhale naturally
Maximum power 220 horsepower/5500rpm 204 horsepower/5500rpm
Peak torque 294 N·m/3500rpm 264 N·m/4800rpm

Mazda's KJ-ZEM engine adopts a supercharger, and on the basis of realizing the miniaturization of the engine, the power output exceeds that of the 3.0L naturally aspirated engine at that time.

Thirty years ago, variable valve timing (VVT) and in-cylinder direct injection technology had not yet emerged, which created a lot of resistance on the road to miniaturization of engines using turbocharging technology. Mr. Renjian is a pragmatist and tends to develop engines that are more efficient in actual use, so he chose to develop a supercharged engine using the Miller cycle at that time, and did not go down the road of a turbocharged engine.

● Everyone sees the reason why Mitsuo admires the self-priming engine with high compression ratio

At the beginning of the 21st century, as the upgrading of emission regulations is pressing for manufacturers, engineers from various manufacturers have racked their brains to study energy-saving and emission-reduction methods. The mainstream technology route at that time was the route of a small-displacement turbocharged engine. By reducing the engine displacement and the number of cylinders, the engine volume was reduced, the weight of the engine and its running resistance were reduced, and the turbocharger was used to increase the power of the small-displacement engine. To the level of a larger displacement engine, the power performance and fuel economy are finally improved.

With the maturity of direct injection technology, although fuel-rich injection can reduce cylinder temperature (gasoline evaporation heat absorption) to suppress knocking and increase the compression ratio to a certain extent, the gasoline used for cooling is wasted, and some working conditions Lower fuel economy is poor. This is also an important reason why the fuel economy of the small-displacement turbocharged engine in the medium and high load/torque output conditions is not as good as that of the Chuangchi Blue Sky naturally aspirated engine. It is also an important reason why Mr. Ren Jian has been advocating a high compression ratio naturally aspirated engine in recent years. One of the reasons.

● 2.5T turned out — market competition has spawned technological upgrades

The Mazda's 3.7L V6 naturally aspirated engine on the 2013 Mazda CX-9 is already outdated in terms of fuel economy. Before the introduction of the 2.5T engine, there was a lack of a gasoline engine product with an output of more than 200 horsepower in the Chuangchi Blue Sky product line. This means that Mazda's product strength is insufficient in the medium-to-large car/medium-to-large SUV market.

Fortunately, today, 30 years later, the mechanical structure of the engine can be optimized through the analysis of the engine structure to improve the structural strength and NVH performance of the engine; the combustion chamber simulation technology can optimize the design of the combustion chamber structure to a higher level at the design stage. High level, speed up research and development and reduce research and development costs. Variable valve timing technology, turbocharging technology, in-cylinder direct injection technology, and various electronic control technologies that replace mechanical control all make it possible to improve engine performance indicators. Mazda has achieved the design goal of a turbocharged engine with a high compression ratio through the integration of the above-mentioned various technologies.

● Black technology of Mazda 2.5T engine

Compared with the previous generation CX-9 using a 3.7L V6 naturally aspirated engine, the new Chuangchi Blue Sky 2.5T engine has improved performance and emissions, and the downsizing of the engine has brought about 20% fuel economy. Promote. In addition, compared with the 3.7L V6 engine, this 2.5T inline four-cylinder engine has a reduction in cylinder volume/weight due to the reduction in the number of cylinders, as well as the number of variable valve timing regulators, camshafts, fuel injection rails, pistons, and connecting rods. The reduction also greatly reduces manufacturing costs.

Comparison of new and old Mazda CX-9 engine parameters
Model 2016 US version of Mazda CX-9 2013 US version of Mazda CX-9
engine capacity 2.5L 3.7L
Intake form Turbocharged inhale naturally
Compression ratio 10.5:1 10.3:1
Maximum power 253 horsepower/5000rpm 277 horsepower/6250rpm
Peak torque 420 N·m/2000rpm 366 Nm/4250rpm
U.S. EPA
Fuel consumption test data
21MPG (city)/27MPG (high speed)/23MPG (comprehensive) 16MPG (city)/22MPG (high speed)/18MPG (comprehensive)
Note: MPG is the abbreviation of Miles Per Gallon, which means the mileage per gallon of fuel, the larger the value, the better.
Comparison of US EPA fuel consumption of several medium and large SUVs
Model engine City fuel consumption High speed fuel consumption Comprehensive fuel consumption
2016 US version of Mazda CX-9 2.5L
In-line four-cylinder turbocharged engine
21MPG (11.2L/km) 27MPG (8.7L/km) 23MPG (10.2L/km)
2016 US version of Nissan Pathfinder 3.5L
V6 naturally aspirated engine
19MPG (12.4L/km) 26MPG (9L/km) 22MPG (10.7L/km)
2016 US version of Ford Explorer 3.5L
V6 twin turbo engine
16MPG (14.7L/km) 23MPG (10.2L/km) 19MPG (12.4L/km)
2016 US version of Kia Sorento 3.3L
V6 naturally aspirated engine
18MPG (13.1L/km) 26MPG (9L/km) 21MPG (11.2L/km)
Note: MPG is the abbreviation of Miles Per Gallon, which means the mileage per gallon of fuel, the larger the value, the better. All models in the table are all four-wheel drive models.

Because the combustion pressure of the turbocharged engine mixture is higher and the heat generated is greater, the temperature in the cylinder is higher than that of the naturally aspirated engine. Therefore, the absolute value of the compression ratio is smaller to ensure the stable operation of the engine.

Although the Mazda Chuangchi Blue Sky 2.5T engine has the same overall structure as the Chuangchi Blue Sky 2.5L engine, in order to cooperate with the dynamic pressure turbine, the cylinder head has adopted the mainstream integrated exhaust manifold design. The integrated exhaust manifold can promote heat exchange between high-temperature exhaust gas and engine coolant, improve engine warm-up performance and reduce the exhaust temperature when the engine is under high load. At the same time, the shorter exhaust manifold also reduces the pumping energy loss of the engine to a certain extent.

When the engine speed is lower than 1620rpm, the butterfly valve will close the thicker pipeline, and the exhaust gas can only reach the turbine through the thinner pipeline, thus speeding up the exhaust gas flow rate, enhancing the intensity of the exhaust gas pulse that drives the turbine to rotate, and making the turbine speed up even more. Fast, enhance the engine's low-rotation torque output performance.

Chuangchi Blue Sky 2.5T Engine Cylinder Working Sequence
Crankshaft rotation angle (°) 1 cylinder 2 cylinder 3 cylinder 4 cylinder
0-180 Work exhaust compression Intake
180-360 exhaust Intake Work compression
360-540 Intake compression exhaust Work
540-720 compression Work Intake exhaust

The working sequence of each cylinder of the Blue Sky 2.5T engine is 1-3-4-2, as shown in the above table. In order to analyze the process of dynamic pressure turbine to promote scavenging, let us take an example: cylinder 1 is in the early stage of the exhaust process, and cylinder 2 is in the scavenging phase of the intake stroke (the intake and exhaust valves are opened at the same time), so that the exhaust air flow of cylinder 1 will be The scavenging airflow of the 2 cylinder is “sucked out” from the central exhaust port, which promotes the scavenging effect of the 2 cylinder. With the boost of the boosted intake airflow, the ratio of residual exhaust gas is effectively reduced and the cylinder temperature is reduced. The exhaust of each cylinder can promote the scavenging of the other cylinder, making a turbocharged engine with a high compression ratio of 10.5:1 a reality.

Compression ratio parameters of Mazda 2.5T and other mainstream turbocharged engines with smaller displacement
engine Compression ratio
Mazda 2.5T engine 10.5:1
Toyota 2.0T engine 10:1
Volkswagen 2.0T engine (third generation EA888) 9.6:1
Peugeot Citroen 1.6T engine 9.5:1
Ford 1.5T engine 10:1
Volkswagen 1.4T engine (EA211) 10.5:1
Ford 1.0T engine 10:1

Full text summary:

Mazda Chuangchi Blue Sky 2.5T engine is another piece of work that does not take the usual path in technology. The dynamic pressure turbine used by the engine is its biggest highlight, and it is also an original technology to increase the compression ratio. With more than 30 years of experience in engine research and development, Mr. Renjian Mitsuo has once again impressed the world for Mazda's research and development capabilities. With the mainstream power output and excellent fuel economy, the engine can not ignore its existence in competitors at the same level. It also solves the problem of insufficient power system products of Mazda in the medium and large car/medium and large SUV market. It is reported that the new Mazda CX-9 equipped with this engine may be introduced to the country within this year, and the overall performance of the vehicle's power system is worth looking forward to. (Photo/Chang Qinglin, Auto Home)