Where is the single turbo option?

I was wondering why we only get the option for twin turbo and not single aswell as the supercharger option love the game just want to try to build a more realistic set-up.

Single turbos are fairly rare on V engines (with one or two notable exceptions) so we figured it’d be best to start with Twin Turbos. Superchargers are coming eventually, but please don’t forget that many features are still in development.