The world’s first production variable compression ratio engine comes from Infiniti (also, check out how it works here), and now it appears Toyota has also been working on a similar idea, according to a US Patent & Trademark Office filing dated February this year.

Toyota’s method for variable compression ratios works in a fundamentally different way from Infiniti’s. While the latter’s VC-T technology helps raise and lower the height of its pistons’ reach by means of an electrically operated actuator arm, the Toyota concept takes conventional connecting rods and mounts a pair of hydraulic pistons atop each one.

A switching pin and check valve determines which of the two hydraulic pistons compresses and therefore which of the two compression ratios it operates with, effectively giving the connecting rod two operable lengths for a high compression ratio and a low compression ratio.

As mentioned, this setup is hydraulically operated, and specifically it is the switching pin which conveys the settings via oil pressure. When it receives a set level of oil pressure, the connecting rod would go to its longer length for a higher compression ratio, and when pressure drops below the predetermined threshold, it will become shorter for a lower compression ratio.

The general idea is to have the best of both worlds in terms of efficiency and outright output, where a lower compression ratio aids fuel economy while a higher compression ratio boosts power. Toyota’s patent for a variable-length connecting rod lowers manufacturing costs and improves reliability for the variable-length items, the manufacturer claims.

Alongside its strong push in developing alternative-fuel powertrains, Toyota appears to still see potential in the slightly more conventional internal combustion engine, albeit with added innovation. It hasn’t made claims for its own technology just yet, though compatriot Infiniti says its own development will have the power of a high-performance 2.0 litre turbo petrol, with the torque and efficiency of an advanced diesel.

Toyota’s patent only refers to the connecting rod innovation, and has no mention of whether the engine is of natural aspiration or forced induction. For the former, Toyota has its upcoming Dynamic Force range of engines which will focus on areas including friction reduction, exhaust flow, cooling and intake improvements. A 2.5 litre version of that range has attained a thermal efficiency of 40%.

It remains to be seen which models Toyota will install this technology into. Infiniti’s version is tipped to debut in the next-gen QX50 SUV.