Cosworth did the engine work on the 2.3 but I seem to recall that the 2.5 was more an in house development than a job farmed out. AMG introduced a power pack for the 2.5-16 engine in evo 1 and 2 forms. It’s unlikely that both Cosworth & AMG were working on the 2.5. The 2.3’d revved much harder than the later 2.5, the 2.5 was an easier car to drive with more torque.
P.S. I had a 2.5-16, I recall it back then as being quite slow but fun, 195 bhp in a relatively heavy car was fun but it wasn’t much if at all faster than a 16v hot hatch of the era.
Boring 190E cosworth poll
Re: Boring 190E cosworth poll
The 2.5 used an update of 2.3's head but developed and made in-house - but the original 2.3 was Cosworth designed (and cast). So I think the 2.5 deserves the Cosworth name as much as the 2.3.
Which is not at all because it was badged a 190E 2.3-16, not a 190 Cosworth
Which is not at all because it was badged a 190E 2.3-16, not a 190 Cosworth