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Fast facts: the combustion engine ain’t dead yet!

12 September 2019



Five technologies keeping fossil-fuel power plants alive

1. Five-Stroke

We’ll kick things off with something you will probably see in production in the very near future. It’s a take on the conventional four-valve engine, except that it allows an additional combustion cycle. So, instead of the spent exhaust gases exiting post-combustion, they are sent into another combustion chamber and compressed for a second time before being exhausted. This second combustion chamber is twice the bore of the first and is common between two fired high-compression cylinders. This effectively increases the expansion ratio of the engine without the side effects that you’d get with an impossibly long stroke.

2. Duke Axial Engine

Developed right here in New Zealand, the Duke axial engine looks like something that belongs in the front of a World War II fighter. Ditching the traditional crankshaft, the cylinders are parallel to the main shaft, with the combustion forces acting on a reciprocator that oscillates around the main shaft in a wave-like motion. Similar to the rotary design, the cylinders slide past both an intake and an exhaust port. A spark plug deletes the need for a valvetrain. Each cylinder completes three power strokes per revolution! All this adds up to one very lightweight, compact, and powerful engine.

3. VC turbo

Just released by Infinity, ‘VC’ stands for ‘variable compression’ ratio — yes, you read that right. Essentially, the stroke of the piston is adjusted to affect compression from 8.5:1, when you’re hard up it, to 14.1:1 during idle and high cruising. How? Instead of the rod connecting directly to the crank, it connects via a bell crank, which centres on the crank. The other end is connected to another cam-like shaft, which is elliptical and controlled by an actuator. The engine also uses a mix of both conventional and direct injection.

4. Gasoline compression engine

Getting diesel-like mileage from a petrol engine is the dream of many manufacturers, but who knew achieving it would be so damn simple? Using compression ignition like a diesel, this 2.7-litre three-cylinder engine uses opposing pistons in each cylinder to compress the air–fuel mix until it ignites, driving two crankshafts joined by one larger gear drive. The first production version is set to hit the market in the US, powering the F-series Ford trucks and offering 201kW and 650Nm.

5. Liquid piston engine

Here’s one for the rotor-heads out there. It takes the traditional Wankel rotary engine to the next level. An eccentric shaft is driven by an oval-shaped rotor that spins inside a housing. The rotor actually carries the air–fuel mix through the combustion cycle, allowing the engine to have a constant volume — unlike a conventional engine, which has constant pressure. Maintaining constant volume in the combustion allows for a higher compression temperature and better atomization of the mix. In short, it’s a far more efficient combustion.