High-efficiency hydraulic hybrid car could get 170 mpg

INGOCAR is a developmental concept for a 5 passenger car with a hydraulic drive system in place of a conventional power-train. With the weight reduction this offers and other efficiencies in the systems, the designers say their vehicle could get 170 mpg.

The INGOCAR is a hydraulic hybrid vehicle. Like some electric hybrids such as the Chevy Volt, it uses the motor indirectly instead of using the mechanical motion of the motor to move the car. But rather than using a motor as a generator to produce electricity, the INGOCAR has a highly-efficient 2-stroke diesel engine which is used to pressurize a hydraulic tank called the accumulator. Pressure from this tank is then used to turn individual wheelmotors in each wheel.

Hydraulic power makes the regenerative braking of the INGOCAR much more efficient than that in electric motor vehicles, as well. Regenerative braking with hydraulics is able to recover 75 to 85% of the energy which is used to repressurize the system. The wheelmotors that serve as both propulsion and braking for the vehicle are smaller than the disc brakes they replace.

The INGOCAR's efficiencies work to benefit it in several ways. For instance, eliminating the conventional power-train provides a 30% weight reduction for the car. Also, the engine only needs to run for a short period of time to recharge the pressure tank. It can also be smaller since it is only being used to develop pressure, rather than needing to be strong enough to run the car directly.

The vehicle is able to be significantly lighter than an electric hybrid because the motors are much lighter. "A comparable electric power-train, able to recapture the entire braking energy, is significantly heavier. The weight of the currently best electric motors is 20 times higher than that of the new hydraulic motor. The weights of the energy storage devices (battery, accumulator) are about the same. As result, the weight of the car would increase by about 50% - from 2200 lb to 3300 lb - consequently increasing the fuel consumption."

The 5 passenger INGOCAR would weigh 2200 lbs (998 kg). The Chevy Volt's curb weight is expected to be around 3500 lbs, and the current Toyota Prius curb weight is also around 3000 lbs.