Using technology and design together to create a hybrid supercar is Velozzi. The company claims the first working model indicates a 0-60 time of 3 seconds and 200 mph top speed. The car achieves anywhere from 100 to 200 mpg in normal driving conditions. The key to this high performance parallel hybrid is the micro-turbine. The super efficient engine is designed to run on any "heavy" fuel - such as diesel, gasoline, biodiesel, or ethanol. The micro-turbine acts as an onboard generator to charge the batteries. Low vehicle mass is achieved by use of space age polymers and composites, along with super-light lithium ion batteries. Velozzi wants people to buy green machines, and figures the best way to do that is give them something fun to drive. He also wants to make the technology non-exclusive and available to whoever wants to license it. Says Velozzi, himself: "We want to change the public perception that environment-friendly cars look like boxes and that they are under performing. It is not so!"
A startup called Rosen Motors was developing a similar concept based on a single-stage microturbine genset and serial hybrid transmission to 4 electric hub motors via a 400VDC grid. Their design used a superflywheel for temporary energy storage because the batteries of the day were crap. However, this raised all kinds of manufacturing/cost, packaging and crash safety issues.
The one bit of the company that was successfully spun off is Capstone Turbine. Their latest models deliver thermodynamic efficiencies of ~22% at full load. Small turbines simply cannot be cooled internally, so the material they're made from sharply limits the peak process temperatures. In part load, basic gas turbines exhibit high SFC.
A parallel hybrid layout is particularly problematic because single-stage turbines are inherently unstable under varying loads, i.e. they either stall or run away. You'd have to use either a separate power turbine or a highly dynamic electric hybrid system that actively stabilized turbine revs. Either measure would increase SFC.
The above claim that the proposed drivetrain layout would achieve 100-200MPG is almost certainly pie-in-the-sky.