Clever value timing to give new Civic Type R 203bhp.

Having cruised through its first 100 years with just a few tweaks along the way, the internal combustion engine must now improve radically if it is to survive beyond about 2020. So let’s focus on one of the petrol engine’s potential saviours: improved flexibility through advanced valvetrain systems, in particular Honda’s i-VTEC design being used on new models including the Civic-based Stream seven-seater, Civic Type R and StepWGN minivan.

T he story began more than a decade ago. Concepts for both hydraulic and electromagnetic valve control may have broken out like a rash lately, but Honda’s VTEC (variable valve timing and lift electronic control) made its production debut in 1989 billed as the first system controlling both valve lift and timing.

The reasons for developing something like VTEC have always been compelling. In broad terms, big valves and extreme high-lift camshafts with substantial overlap of inlet and exhaust valves, while essential for top-end power, are not particularly compatible with a dawdle to the supermarket. Multiple valves helped, but what was really needed was an engine that could switch camshafts in mid-stream. Such an engine would deliver the best of both worlds

TEC gave us the next best thing. Normally, each valve is opened by a cam lobe acting on a rocker arm. For each pair of valves, Honda added a third lobe and rocker which, at low to medium revs, have no effect. But when the engine is running at higher revs, the three rockers link together like dancers’ arms. Each pair of valves is opened by the third lobe, which has higher lift and opens the valves for longer.

Valve lift and timing are more fully integrated in i-VTEC design, evolved from the 12-year-old VTEC system.

For around-town driving, the engine is placid and manageable. Hit the open road, increase the revs and things get much livelier.

Several versions have appeared, including a three-stage system for some markets. Recent examples have included the dohc VTEC on the S2000 and sohc VTEC on the new Civic, but a slight limitation has always been that lift and timing happens in two stages rather than on a continuous basis.

The new i-VTEC goes some way to overcoming that. The high-speed cam lobe increases valve lift, but retains the same timing as the low-speed cam. Instead, overlap is adjusted on the inlet cam using a new device called VTC (variable timing control) which, thanks to data from the engine management system, responds to load as well as speed.

The icing on the cake is a variable-length inlet manifold which lengthens at low engine speed to increase gas velocity. A dohc 2.0-litre, 158bhp i-VTEC will first appear in the Stream in June, and the potent Civic Type R version which screams out 203bhp at 7400rpm comes in October.