AutoblogGreen

One option would be a single-cylinder four-stroke engines that runs on two-stroke gasoline, so drivers cannot cause damage by using low quality engine oil. This special type of four-stroke engine consumes ~20% less fuel and emits ~80% less HC+NOx than two-stroke engines of similar rated power.

An 80% reduction in emissions not as good as switching to a four-stroke motorcycle engine with three-way catalyst. However, it's a whole lot better than nothing. The objective here is to offer something cheap and reliable with adequate power, otherwise the vast majority of tuk-tuk drivers will not voluntarily invest in a retrofit. Authorities in India are apparently unwilling or unable to force them to do so.

To illustrate the working principle, here's a for-fee technical article describing a 50cc design applied to a handheld chainsaw.

http://www.atzonline.com/index.php?q=chainsaw&x=0&y=0&do=search&lng=en&sid=69f9a02c6894b740498510c75b176710&site=a4e&filter=a4e

The single overhead camshaft is driven by gears rather than a belt or chain. At 52kW/L of displacement, specific power is comparable to two-stroke engines.

A portion of the air-fuel mixture delivered by the carburetor is siphoned off into the crankcase by the partial vacuum produced by the piston as it moves to TDC. The siphon features a one-way valve, so the crankcase is pressurized as the piston returns to BDC. The gas in the crankcase is vented into the cylinder head via another one-way valve. From there, the air-fuel mixture is returned to the intake manifold via a third one-way valve. Since there is no oil carter, the engine will run in any orientation and is not sensitive to oil fouling by spray water entering the air intake.

An alternate solution is to run the tuk-tuks on pressurized air (cp. MDI air car). The retrofit kit would be more expensive and indirect fuel consumption higher. However, the stationary compressor at the filling station could be powered by electricity or else, a properly maintained four-stroke engine with a catalytic converter and an exhaust system with silencers. In rural areas, the fuel for the compressor could be biogas from an adjacent anaerobic digester (limitations regarding feedstock and engine oil type apply).

Reply

Why not do what they already do in many places (I saw it in Thailand), and use natural gas? Taxis and tuk tuks all over the world use natural gas as a fuel, most often as a supplement to a normal petrol combustion engine. I have seen this from Poland to Thailand. This with the single cylinder 4-stroke engine would have a huge impact.

Reply

@ polandjoe -

unfortunately, CNG may be too expensive a solution. The project documentation also highlights the requirements of dead-easy maintenance and reliability during monsoon season. India also has little fossil gas of its own and no significant gas distribution infrastructure.

GDP per capita (2006 est.):
India: $3800
Thailand: $9200

Reply

In answer to everyones frantic way to not only save our fuels, and the expense, lets look at the Tuk Tuk from Tuk Tuk North America.

Reply