Multi-displacement system, displacement-on-demand, cylinder deactivation - call it what you will, they're all based around the same principle: turn off some part of the engine when it's not needed. But an engine designed and patented by Carl Hefley takes an entirely different approach to the idea of variable displacement.

Hefley hopes to sell the technology to a major car manufacturer at auction, though it is also available for sale outside of auction for the flat fee of $500 million. That's an incredibly tall price for an essentially unproven technology, but it speaks volumes about the creator's confidence in the product.

"I would really like to see Chrysler, General Motors, Ford or other United States automotive companies take advantage of this unique and totally green engine," said Hefley. "But I'm concerned because so far foreign countries seem to be a little more anxious in the technology. American companies seem hesitant to improving their technology base unless they develop it. Foreign countries look to be ready for new technology."

Using an offset toroidal crankshaft solution that dynamically adjusts stroke length in response to load, the Hefley engine claims to be configurable from three to nine cylinders and across an output range of 50-1,500hp (37-1,119kW). One model currently in development can even be adjusted to use a range of fuels, and another applies the concept to a rotary engine design.

"The Hefley Engine will save billions in fuel and help put Americans back to work making new Super Green power plants for the automotive and other industries," Hefley said.

From a casual observer's standpoint, however, there seem to be at least a couple issues standing in the way of the engine's widespread success. First of all, the eccentric nature of the toroidal crankshaft will become increasingly imbalanced as displacement increases, limiting functional RPMs. Secondly, it will be hugely expensive to manufacture the load-bearing pieces of the system, especially the rod around which the toroidal element articulates, as it is sure to experience some extreme forces.

Perhaps Hefley's patented system already addresses these issues, but even so, it doesn't seem like either of these problems can be solved cheaply, and with a built-in overhead of $500 million, the purchaser would have to have a foolproof plan to recoup the money before the patent's expiration, which will occur on August 9, 2026 - a relatively short window in the automotive business.

To learn more about the Hefley Engine or see it in action, visit the company's website.