The Hindu Business Line : Swirling and tumbling engine tech

By incorporating two intake ports, the TVS CC-VTi engine provides both swirl and tumble motion ensuring an even richness of air and fuel in all corners of the combustion chamber.

Even before the launch of the Flame, the bike and its technology had already been engulfed in a controversy that threatened to keep the two companies involved — TVS Motor and Bajaj Auto — perennially engaged in a war of words.

The issue being debated was whether Bajaj’s rights to a patent granted for the use of twin spark plugs in small two-wheeler engines was being violated by TVS.

Twin spark plug technology has been in use in a number of automotive engines by a number of two-wheeler and car manufacturers worldwide for improving combustion efficiency. Honda uses it in the City’s i-DSI engine.

Among the two-wheeler manufacturers in India, Bajaj was the first to use it in its 150cc bike — the Pulsar. Later, it made this technology the central platform on which a number of other engines for its other scooters and bikes were developed.

TVS has said that the twin spark plug technology is generic and that as such there is no similarity between the CC-VTi engine in the Flame and the DTS-i engines of Bajaj. The matter is pending before the courts and the two companies are still disputing each other’s claims.

More technology

But, aside of the twin spark plugs, the TVS Flame’s controlled combustion variable timing intelligent (CC-VTi) engine has a lot much more technology crammed into the confines of that one cylinder unit.

For one, the 124.8cc Flame engine is the country’s first multi-valve engine in its segment. The engine was developed by TVS R&D along with AVL of Austria.

Regular two-wheeler engines feature an intake and an exhaust port for inflow of the air-fuel mixture and outflow of burnt exhaust gases.

Variations to the air-fuel mixture were attempted by carburettor adjustments or by changes to the intake port.

While these changes were effective in bringing about some improvement, there were still a lot of inefficiencies that existed due to the lack of finer, performance-based adjustments to the air-fuel mixture. The carburettor could adjust the richness of the air-fuel mixture and changes to the intake port could either improve the swirl or the tumble of the mix in the cylinder.

These engine changes could not combine all these attributes — vary air-fuel mix, get both swirl and tumble, and also ensure complete combustion.

TVS’ CC-VTi engine lays claim to having perfected this process.

By incorporating two intake ports, the mix in the engine gets both swirl and tumble motion ensuring a even richness of air and fuel in all corners of the combustion chamber.

The twin spark plugs then ensure that the flame fronts expand and reach the combustion chamber fully, thereby avoiding fuel wastage and delivering optimum power.

The two ports are operated variably depending on the rider’s performance demand and condition of air-fuel mix in the engine.

Lean air-fuel mix (such as during slow speed travel) needs more swirl motion for improving fuel efficiency and torque availability and during high speed travel or while accelerating, the power port ensures a richer air-fuel mix also gets more tumble motion for optimum performance.

The four-stroke CC-VTi Flame engine delivers a peak power of 10.5 bhp at 8,250rpm and a maximum torque of 10Nm at 6,250rpm.

S. Muralidhar

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