Mercedes wanted a 320 bhp engine based on the 136 bhp Mercedes M102 2.3 litre 4-cylinder engine . The task was given to Mike Hall , who design the famed DFV and BDA engines . The request was a huge surprise for Cosworth , and the original brief for a 320 bhp engine based on the 136 bhp Mercedes M102 2.3 litre SOHC 4-cylinder engine was passed duly passed to Mike Hall , who â drew the famed DFV and BDA engineâ .