The difference between Volkswagen's high and low power versions of the EA888 engine

The difference between the high-power EA888 Gen3 and the low-power EA888 Gen3B (three and a half generations) engines is actually very large. Due to the use of completely different combustion systems and performance targets, there are many differences in hardware.

 

The difference between the high-power EA888 Gen3 and the low-power EA888 Gen3B (three and a half generations) engine is actually very large. Due to the use of completely different combustion systems and performance targets, there are many differences in hardware, mainly the following differences:

1. Different combustion systems:

The high-power EA888 Gen3 adopts the traditional Otto cycle, while the low-power EA888 Gen3B uses the Miller cycle to reduce fuel consumption, so the pistons, cylinder head combustion chambers, cylinder head air ports, injectors, compression ratios, etc. of the two are different.

What is the Miller cycle?

The low-power EA888 Gen3B uses early closing of the intake valve to achieve combustion with an expansion ratio greater than the compression ratio, thereby improving thermal efficiency. Generally speaking, the Miller cycle will bring about a very large performance loss. The intake side of the EA888 Gen3B engine is designed with an AVS variable valve lift mechanism, which uses variable valve lift technology to balance part of the performance loss caused by the Miller cycle. Therefore, Volkswagen's goal in developing the low-power EA888 Gen3B is to achieve a fuel consumption level of 1.4T and a performance level of 1.8T.

Principle of Miller cycle

By closing the valve early, the expansion ratio can be greater than the compression ratio, and the pumping loss can be reduced.

 

Piston EA888 1.8T

 

Differences between GEN3 Otto cycle and GEN3B Miller cycle

(1) Differences in valve and piston design: GEN3B's intake valve diameter is smaller and the piston top is higher, which can achieve a compression ratio of 11.7 (GEN

3's compression ratio is 9.8).

(2) Differences in air port and cam profile design: GEN3B is designed with a larger tumble intake port and a low-lift cam profile to achieve the Miller cycle.

2. Differences in variable valve lift AVS design

The variable valve lift system AVS of the high-power EA888 Gen3 is on the exhaust side. This is the traditional AVS layout of the EA888, which has been the case since the second generation. Its main purpose is to improve low-speed torque and supercharger dynamic response and reduce turbo lag.

The variable valve lift system AVS of the low-power EA888 Gen3B is on the intake side, mainly to make up for part of the power loss caused by the Miller cycle (but it still cannot reach the performance level of high power).

3. Differences in oil-gas separator design

The oil-gas separator of the high-power version of EA888 Gen3 is directly connected from the crude oil separator cavity of the cylinder block to the fine oil-gas separator on the cylinder head.

In order to achieve better oil-gas separation and further reduce oil consumption, the low-power version of EA888 Gen3b uses the cavity of the intake-side balance shaft on the cylinder block as the primary oil-gas separator, and achieves primary separation through the high-speed rotation of the balance shaft (the speed is twice that of the crankshaft), and then goes to the fine oil-gas separator on the cylinder head. This design will have lower oil consumption.

4. Difference in crankshaft diameter

The low-power GEN3B engine chooses a smaller crankshaft main shaft diameter to reduce friction and reduce fuel consumption.

5. Difference in fuel consumption

It can be seen that the low-power version of GEN3B is specially designed to achieve low fuel consumption and high efficiency. Therefore, the efficiency of the low-power version of GEN3B can be improved by about 8% compared with the high-power version of GEN3.

The fuel consumption of the engine in all operating conditions has been significantly reduced:

The fuel consumption of GEN3B is also much lower than that of GEN3:

Summarize

There is a big difference between the high and low power of the third-generation EA888 engine. The high power is biased towards performance, while the low power is specially designed for low fuel consumption.