However, Liyang company did not abandon WS-13 in this regard, and continued to improve and increase the engine’s thrust. Liyang company believed that JF-17 Block-III fighters would undergo major changes, and will use new equipment such as source phased array radar and integrated electronic warfare systems. And the weight of the aircraft would definitely increase significantly compared to the first and second batches. So the need for a larger thrust engine is an opportunity for WS-13 engine.
Liyang company decided to improve the thrust of the WS-13 engine as a transition for FC-31 fighter. The WS-13IPE thrust- enhanced engine adopts a relatively conservative scheme and retains the original four-stage fan, but the blades are swept forward to delay the airflow separation. This increases the fan speed and allows the engine to take in more air, thereby increasing the engine thrust.
After the improvement, the thrust of WS-13IPE engine could be over 9 tons, which can be used for JF-17 Block-III and can also meet the initial needs of JC-31 stealth fighters, especially if JC-31 is chosen as the carrier-based fighter, which would need engines with a higher thrust to carry its increased weight.
https://www.china-arms.com/2020/01/ws-13ipe-for-fc-31/