Weight and complexity. Depends on the car of course. For an NSX 2.0 I'd have tried to make a lightweight beast, more akin to a mid engine MX-5 with a roof, than to the bloated grass muncher Honda is trying to sell. For a lightweight car, you'd need to shave off rather minuscule amounts of mass from each individual components, with the hope that the cumulative weight saving from thousands of parts end up being substantial.Andres125sx wrote: I´d say... why would you NOT use as many gears as you can if you have a twin clutch?
In such circumstances, shoving in 9 gears into the transmission results in an unacceptable jump in weight, not just because of the 2-3 extra gears, but also because of the other parts required to make such a gearbox work. Can you imagine how depressing it would be, if you were trying to analyse each fastener to see if you could shave off weight, when the management suddenly decides it wants NINE SPEEDS for marketing purposes? If you make such compromises in every big sub system on the car, the total weight can become quite excessive.