“Reports of my death are greatly exaggerated,” said Mark Twain after an erroneously posted obituary. It’s pretty much what every internal combustion engine would say, too, if they could speak. While hysteria over the car’s contribution to emissions reaches epic proportions, engineers everywhere are working hard to improve internal combustion engines (ICEs) to drive toxic and CO2 emissions down.
The Hyundai Motor Group’s new CVVD (continuously variable valve duration) technology is the latest ICE development to break cover. It’s another example of how new engineering techniques are enabling engineers to revisit the engine fundamentals to leap technical barriers that were once insurmountable. CVVD on the new Smartstream G1.6 T-GDi engine, to be fitted to both Hyundai and Kia cars, improves performance by 4%, fuel efficiency by 5% and emissions by 12%.
Inlet and exhaust valves in the cylinder head of an engine let fuel and air in and exhaust out. When they open and close and by how much depends on what an engine is designed to do. Valves are opened by cams, offset lobes positioned along a camshaft, one for each valve. So a four-cylinder four-valves-per-cylinder twin-cam engine would have an exhaust cam and an inlet cam, each with eight cam lobes, one for each valve.
The shape of the cams is designed to control the lift and the duration (length of time they stay open). How progressively they open and close and at what speed is down to the shape of the cam. In engine tuning, there are lots of different camshafts to choose from to give the characteristics the engine builder wants. The design for a normal, tractable family car engine at one end of the scale will be totally different from the ‘hot cam’ of a race engine at the other.
Clever tech such as BMW’s Vanos varies the valve timing (when the valves begin to open and in relation to the position of the piston and moment of combustion). A second system, Valvetronic, can alter valve lift. Used together, both timing and lift are variable. The ingenious Multiair system, developed by Fiat Powertrain Technologies with the Schaeffler Group, can vary both timing and lift with some cunning electro-hydraulics. Jaguar Land Rover also uses a version of the Schaeffler tech on its Ingenium petrol engine.