This is a very bad idea. The electric motor is an integral part of the power plant. When you accelerate to pass other cars or merge onto the freeway, the electric engine provides the initial torque required because the gasoline engine in the Prius is not efficient at providing start up torque. You stated that "mechanial power" is more desireable at freeway speeds than electrical power. Actually, the Prius system uses both the electric motor and the gasoline engine to provide mechanical power to the wheels, so I don't understand your distinction here.
Assuming you could do it, shutting off all electrical regeneration would, in short order, shut down the electric motor by allowing the battery charge to drop below operating levels. The gasoline engine, alone, is not sufficient to provide you with enough power to operate safely on the freeway. There have been accounts of people making it to gas stations on electrical power alone, but this too is a bad idea because the battery needs the regenerative charge from the gasoline engine. They are a pair and you can't split them up.
I don't think you understand the "transmission" in the Prius. There aren't gears in the sense that your old car had, say, five gears. Prius uses a planetary gear system that allows either or both gasoline and electric engines to operate; the computer determines the optimum use of each based on the load being put on the car and the charge in the battery. So, there isn't anything to lock up. When you start up a conventional car, the lower gears and the engine take the stress of moving the two tons of car from a stop to forward motion. This is the hardest strain on the gears and the engine. The Prius uses the electric motor to do that both because the motor is ideal for low rpm/high torque situations and because electric motors are direct drive and don't need gearboxes to translate piston rpms to wheel rpms. The gasoline engine in the Prius is allowed to operate within its optimum rpm range and with a minimum of start and stop stresses imposed on it. That's the inherent beauty of this system: each power plant operates in its optimum efficiency range. Why mess with it?
Toyota got it right and you most likely won't be able to tweak the system for any added hidden efficiencies without voiding your warranty and possibly ruining your car.
Bob
Assuming you could do it, shutting off all electrical regeneration would, in short order, shut down the electric motor by allowing the battery charge to drop below operating levels. The gasoline engine, alone, is not sufficient to provide you with enough power to operate safely on the freeway. There have been accounts of people making it to gas stations on electrical power alone, but this too is a bad idea because the battery needs the regenerative charge from the gasoline engine. They are a pair and you can't split them up.
I don't think you understand the "transmission" in the Prius. There aren't gears in the sense that your old car had, say, five gears. Prius uses a planetary gear system that allows either or both gasoline and electric engines to operate; the computer determines the optimum use of each based on the load being put on the car and the charge in the battery. So, there isn't anything to lock up. When you start up a conventional car, the lower gears and the engine take the stress of moving the two tons of car from a stop to forward motion. This is the hardest strain on the gears and the engine. The Prius uses the electric motor to do that both because the motor is ideal for low rpm/high torque situations and because electric motors are direct drive and don't need gearboxes to translate piston rpms to wheel rpms. The gasoline engine in the Prius is allowed to operate within its optimum rpm range and with a minimum of start and stop stresses imposed on it. That's the inherent beauty of this system: each power plant operates in its optimum efficiency range. Why mess with it?
Toyota got it right and you most likely won't be able to tweak the system for any added hidden efficiencies without voiding your warranty and possibly ruining your car.
Bob