Tycoon game simulating car industry (you run a car manufacturing company).

Before we start, to avoid confusion let's define two terms COMPONENETS and TECHNOLOGIES. When designing new cars you design COMPONENTS (like engine, chassis) which are later used by the cars you make. There are also TECHNOLOGIES which you invent (like +10% to engine power). So, TECHNOLOGIES affect COMPONENTS.

In this topic I'm not interested in components, it's a separate thing, but in RESEARCH of TECHNOLOGIES (using some sort of research points  or engineers or other mechanic). How to make an interesting RESEARCH TECHNOLOGIES mechanic for a car tycoon game?

Typically it's done like that in car tycoon games: you hire X engineers, then over time new technologies are unlocked and you use -/+ to assign engineers to research those technologies. Once done you have to reassign engineers (which is tedious and I don't like it).

Another approach (more 4X like) is to have a classic tech tree and research points which you spend to unlock techs.