Variable compression ratio

The electronic engine controller responds to the pressure on the gas pedal, in real-time, altering the compression ratio seamlessly.

Due to the comparative simplicity of cylinder head design (lacking intake valves) it is somewhat easier to implement in two-stroke engines.

As of late (in the 2000s) this technology has seen some renewed interest, due it being able to burn a wide range of fuels (e.g. including alcohols) such as the Lotus Omnivore.

This engine had a one-piece cylinder head and sleeve, whose distance from the crankshaft was adjusted by a jackscrew operated by cables from a twist grip on the handlebar.

This acts through a rod-crank system with a gear wheel, whose movement adjusts the effective con-rod length and thus the compression ratio in the left cylinder.

[6] SAAB Automobile rekindled interest in variable compression when they introduced their SVC engine to the world at the Geneva motor show in 2000.

SAAB had been involved in working with the 'Office of Advanced Automotive Technologies', to produce a modern petrol VCR engine that showed an efficiency comparable with that of a Diesel.

The SAAB SVC was an advanced and workable addition to the world of VCR engines, but it never reached production due to the company's bankruptcy in 2016.

The design, an implementation of the Larsen VCR engine,[7] consisted of a monobloc head, which contained all of the valve gear, and the crankshaft/crankcase assembly.

The two blocks are hinged together at one side (imagine a book, lying flat on a table, with the front cover held an inch or so above the title page).

By pivoting the upper block around the hinge point, the Vc (imagine the air between the front cover of the book and the title page) can be modified.