Turbo sounds stopped working

I was testing out making a small (1L), high boost, high power engine using my 'unbelievably ugly but lots of cooling' car. I was experimenting with changing the pistons to see if I could get away with something other than lightweight forged. I tried each one starting from the bottom of the list but when I got to either the hypereutectic cast, or the forged pistons (I forget which) the turbo noises just stopped being played in either test, even after switching back to the original pistons.
I did try and search to see if this was a known bug, but it doesn't help that 'turbo' and 'sounds' have been put in the list of too common words for searching.
I've attached the engine for you:
And the unbelievably ugly but well ventilated car:
I did try and search to see if this was a known bug, but it doesn't help that 'turbo' and 'sounds' have been put in the list of too common words for searching.
I've attached the engine for you:
And the unbelievably ugly but well ventilated car: