Air

A compressed air car is an alternative fuel car that uses a motor powered by car. The car can be powered solely by air, or by air combined (as in a hybrid electric vehicle) with gasoline/diesel/ethanol or electric plant and regenration. Instead of mixing fuel with air and burning it to drive pistons with hot expanding gases; compressed air cars use the expansion motors and motor development of compressed air to drive their pistons. Several prototypes are available already and scheduled for worldwide sale by the end of 2008, though this has not happened as of January 2009. Companies releasing this type of car include (MDI).

Gas turbine

In the 1950s there was a brief interest in using gas trubine engines and several makers including Rover and Chyrsler produced prototypes. In spite of the power units being very compact, high fuel consumption, severe delay in throttle response, and lack of engine braking meant no cars reached production.

Rotary (Wankel) engines

Rotary wankel engines were introduced into road cars by NSU with the Ro 80 and later were seen in the Citreon GS Birtor and several Mazda models. In spite of their impressive smoothness, poor reliability and fuel economy led to them largely disappearing. Mazda, beginning with the R100 then RX-2, has continued research on these engines, overcoming most of the earlier problems with theRX-7 and RX-9.

Rocket and jet cars

A rocket car holds the record in drag racing. However, the fastest of those cars are used to set the Land Speed Record, and are propelled by propulsive jets emitted from rocket turbojet, or more recently and most successfully turbofan engines. TheThrustSSc car using two Rolls-Royce Spey turbofans withreheat was able to exceed the speed of sound at ground level in 1997.