Analysis of Volkswagen 1.4T engine cylinder deactivation technology vibration is a problem

Volkswagen unveiled a more economical and energy-saving model at the Geneva Motor Show - POLO BlueGT, and its biggest highlight is that it is equipped with a 1.4T engine with cylinder deactivation technology.

The car uses a newly developed 1.4T turbocharged engine code-named EA211 based on Volkswagen's transverse modular MQB platform. Unlike the 1.4T engine code-named EA111 currently used by Volkswagen, it uses an all-aluminum cylinder block, so the weight of the whole machine will be smaller. Most importantly, technicians have added an ACT active cylinder management system on this basis, which can shut down two cylinders under certain conditions and only the other two cylinders will run.

● Rely on Audi's AVS system to achieve cylinder deactivation

Cylinder deactivation technology is actually not a very new thing. Audi, Chrysler and Honda models all have this technology, but it is currently mainly used in V6 and V8 engines with a larger number of cylinders. This is the first time it has been applied to a small-displacement 4-cylinder engine.

Volkswagen's 1.4T engine with cylinder deactivation technology is a good reference to Audi's AVS variable valve lift technology. Simply put, this AVS system changes the valve lift and timing under different working conditions by switching two cams with different angles. The cylinder deactivation system only needs to replace the high-angle cam in the AVS system with a cam without lift, and this cylinder deactivation technology has been applied to the Audi V8 4.0TFSI.

● Dual cylinder operation will cause vibration and uneven temperature distribution.

But when this technology is implanted in a four-cylinder engine, a very thorny problem arises - vibration. At low and medium loads, the system automatically closes the intake and exhaust valves of cylinders 2 and 3, and only cylinders 1 and 4 are driving the crankshaft to rotate. According to the 1-3-4-2 working sequence of the four-cylinder engine, when only two cylinders are working, the engine's working interval angle reaches 360 degrees. In addition, cylinders 1 and 4 work at the same time, which will inevitably cause the engine to vibrate to a large extent, thus affecting comfort.

The 2nd and 3rd cylinders in the middle stop working and will no longer generate heat. At this time, only the 1st and 4th cylinders at both ends of the engine body continue to work, which leads to uneven temperature distribution of the cylinder body. How to deal with a series of problems such as cylinder deformation caused by this problem is also a difficult problem facing technicians.

This 1.4T engine has a maximum power of 140 horsepower and is equipped with stop-start and energy recovery technology. The acceleration time of 0-100 kilometers on the POLO BlueGT is less than 8 seconds. Volkswagen has determined the optimal time to shut down the cylinders based on its survey of road driving conditions in many countries, that is, to start this cylinder shut-down system under the conditions of engine 1250-4000rpm and torque between 25-100N·m. When the driver steps on the accelerator pedal, the two shut-down cylinders will quickly resume work within 13-36 milliseconds. The system can intelligently detect the traffic environment and congestion of the vehicle and intelligently disable the cylinder shut-down function. The driver can know whether the car is currently running with two cylinders or four cylinders from the multi-function display on the dashboard.

● Fuel consumption will not be reduced by half

After shutting down cylinders 2 and 3, the POLO BlueGT's comprehensive fuel consumption per 100 kilometers can be reduced by about 0.4L. When driving at a constant speed of 50km/h in the third or fourth gear, the fuel saving per 100 kilometers can reach 1L. When driving at a speed of 70km/h in the fifth gear, the system can also reduce the fuel consumption by 0.7L per 100 kilometers. It can be seen that although half of the cylinders are shut down, the fuel consumption will not be reduced by half. This is because the 2nd and 3rd cylinders that are not doing work still have to continue to reciprocate with the crankshaft, consuming some energy. At the same time, the relatively complex vehicle environment also makes it impossible for the engine to often work in the most economical range.

Summarize:

Volkswagen is the first to apply cylinder deactivation technology to a 4-cylinder engine. Few other manufacturers have been involved in this before. If a series of problems such as vibration can be well solved, this technology still has a very broad application prospect. Today, when hybrid power systems are still difficult to popularize on a large scale, the successful application of this technology also shows that people have taken another step forward in tapping the energy-saving potential of traditional internal combustion engines.