Designed by Robert Riley, the XR3 is a DIY Hybrid car engineered to average 125 mpg on biodiesel fuel and 225 mpg in hybrid mode. Maxing out at a top speed of 83 mph and weighing in at a mere 1,480 lbs, the XR3 is an uber fuel efficient speed demon, priced at a surprisingly reasonable $25,000. So what’s the catch? The car doesn’t come fully assembled. Riley’s website insists that people with even the most rudimentary knowledge of construction can build the car with ease, and at first glance, the How-To literature appears to be easier to understand than most TV remote programming guides.
From the XR3’s official website, rqriley.com:
Plug-In Hybrid Architecture
The XR3 is a “plug-in hybrid.” This makes it possible to drive on battery power alone on trips of about 40 miles. And when both the diesel and the battery-electric systems are used together, and the car is driven conservatively, fuel economy increases to over 200-mpg. Fuel economy is about 125-mpg on diesel power alone.
Today’s hybrids are called “mild hybrids” or “charge-maintaining hybrids”. They use the electric system to help with acceleration. You can drive on battery power alone, but only for a short distance – around the block, for example. The battery pack is typically used to provide bursts of power for brief periods of acceleration. The combustion engine then recharges the battery between periods of acceleration. But fuel economy suffers while the battery is being recharged. That’s why today’s hybrids do not provide much advantage in fuel economy over a well-designed conventional car.
In order to get the full benefits of a hybrid power system, you have to switch to the plug-in hybrid architecture. Plug-ins will be the next generation of hybrid vehicles. A plug-in hybrid simply means that part or all of the vehicle’s energy is taken from the grid system where it is cleaner and less costly to produce. Most of the world’s automakers are now working on plug-in hybrids.
Virtually Unlimited Options for the Builder
The plug-in power system architecture also allows much greater flexibility in power system choices. With a mild hybrid, like the Honda Insight and the Toyota Prius (also called “charge-maintaining hybrids”), proper control of the power system depends on the fact that the subsystems – the internal combustion engine (ICE) and electric systems – are selected in advance and controlled by a computer. The computer, however, has to be programmed for the specific output characteristics of the two systems. Any modification in either of the power systems (electric or ICE) can cause a mismatch with the control system. So whenever a change is made, the computer has to be reprogrammed.
With the XR3, the two front wheels are powered by the combustion engine, and the single rear wheel is electric powered. The two power systems are not integrated within the vehicle. The connection between the conventional power system and the electric power system is provided by the ground. Proper phase-in between the two power systems is handled by a simple throttle mechanism and a dash-mounted switch to select between ICE power, electric power, and dual power modes. In the dual power mode, the XR3 will have lots of burst power for quick acceleration. If you were to use this acceleration potential to its fullest, fuel economy would be reduced to something on the order of 150 mpg over a 70 mile trip. Fuel economy will also vary according the particular components chosen for the power system, and how heavy you are on the throttle pedal. Performance figures quoted here are conservatively-driven vehicle having a system configured just like the prototype. Plans provide the information necessary for you to select different components if you want to.