Here's how a two-stroke engine works: In the first stroke, a mixture of gas, lubricating oil and air in the cylinder is compressed by the upward movement of the piston, which ignites when the spark plug fires. In the second stroke, the ensuing combustion pushes the piston down. Exhaust gases next escape through an open port cleared by the downward moving piston as a result of the combustive pressure. As the piston presses down it turns the crankshaft to power the wheels. The resulting vacuum opens what is known as a reed valve, which lets in the next charge of air, fuel and oil from the carburetor. With the next upward compression stroke, the spark plug fires again, and the cycle repeats anew.
Because two-stroke engines are mechanically simpler, and thus cheaper to operate and repair, they are popular. But they are also dirty: unburned fuel and oil escapes through the exhaust port as soot, whereas the four-stroke engine more thoroughly burns the gas, which is not mixed with oil.
India's industry, for its part, is attempting to diversify the technology available for this transportation alternative. Rickshaw giant Bajaj Auto just announced its first four-wheeled rickshaw-like vehicle. It emits just 60 grams of CO2 per kilometer due to its 400-kilogram weight for low-speed city use, versus 150 grams and 1,300 kilograms for many highway-bound sedans, according to Bajaj. The four-stroke RE60 will also incorporate fuel-injection technology that could deliver 20 percent better fuel efficiency.
"Eliminating two-stroke models will prevent dumping them elsewhere or resale to poorer drivers," Punte says. But simple permit bans for older rickshaws often backfire, as many rickety two-stroke workhorses slip through on a thriving permit black market.
City leadership
To eliminate legacy rickshaws, local leadership is paramount. In 2005 in Ahmedabad officials fretted over India's seventh-largest city's air quality as nearly 300 new vehicles joined its roads daily, including rickshaws. So they mandated CNG rickshaw engine retrofits, installed CNG pumps citywide and facilitated bank loans for prospective rickshaw buyers. Result? In 2009 the city had dropped to the 66th most polluted in the nation, down from fourth in 2005. Today all its 115,000 rickshaws and 1,650 city buses use CNG—and other cities are emulating this CNG example.
And when laws don't work, personal appeals can. Consider the midsize city of San Fernando in the Philippines. In 2001 two-stroke models were 71 percent of 1,600 city-permitted rickshaws—some as much as 30 years old—and each spewing soot emissions on par with 10 jeeps. To encourage a four-stroke shift, Mayor Mary Jane Ortega offered free medical checkups, loans for green upgrades and maintenance seminars, with permit renewals linked to timely repayment. Although efforts were phased, drivers quickly traded up. Today all city rickshaws are four-stroke.
Tackling emissions from rickshaws are also part of global efforts to combat climate change. In February a U.S.-led coalition proposed limiting short-living pollutants like soot and methane because they offer a quick way to restrain global warming. The effort has earmarked funding for simple developing country actions such as adding filters to diesel engines and converting them to run on cleaner CNG fuel. All told, such efforts to restrain methane and soot emissions could help hold back global average temperature increases by more than 0.5 degree Celsius this century and improve public health. In essence, the effort would help other countries catch up to the U.S., where two-stroke engine lawnmowers were banned roughly a decade ago.
Rights & Permissions
See what we're tweeting about
14 Comments
Add CommentWhy don't they make human powered city rickshaws with pedals in the back, too? I know with the driver and both my wife and I pedaling in the back, we could easily keep up with these two cycle menaces.
Reply | Report Abuse | Link to thisCouple a battery/motor assist that's charged by regenerative braking to this planet-saver, and you've got a real solution.
althought the auto-rickshaw is very convenient for urban people,it is a mess for government to deal with the trafic problem.an transport system running under regulations is worth more consideration.
Reply | Report Abuse | Link to thisA- Americans don't want to wait for a tuk-tuk.
Reply | Report Abuse | Link to thisB- Americans are concerned more about peer image then conservation.
C- Americans can't drink and smoke in public transportation vehicles.
D- Carrying groceries farther then the carport of garage to the kitchen door is against the law in some gated communities.
E- Sharing space with stranger is as abhorrent as sharing a bag of french fries for the average American.
F- Everyone in America that owns a SUV will tell you that a tuk-tuk with five people on board is far more polluting then a vehicle getting 18 miles to the gallon empty and heading down wind.
G- Americans would rather pay to park and walk to shop then get dropped off at the front door and risk being seen buy their friends or co-workers.
I could go one to the latter half of the alphabet, but I am sure most people will get the picture by now.
If tuk-tuks were electric powered, offered air conditioning and scantily clad hostesses serving free cocktails and lunch, Americans still wouldn't give up their gas guzzlers.
although the new engines appear "cleaner" . The emissions of nanoparticles have increased. That makes them more genetically / cardiovascular dangerous.
Reply | Report Abuse | Link to thisThere are many alternative engines for that kind of vehicles, and also exhaust emission reducing catalyzers have greatly reduced its cost, but in the general field of this tiny transport means, an issue remains open to me: Am I right in thinking that human traction was long ago considered an unnacceptable way of anything but taking yourself?. Salut +
Reply | Report Abuse | Link to thisTwo-stroke engines are just dirty oddities, good for nothing but industrial archeology museums.
Reply | Report Abuse | Link to this
Reply | Report Abuse | Link to thisI drive a Trike the same size, power, speed except I use EV drive from a golf cart hot rodded with larger tires, higher voltage battery pack.
Such a vehicle would do this service extremely well at 20% to run vs a gas, NG vehicle.
While 4 strokes are better than 2 strokes they still pollute fairly bad in taxi service and still such gas which is $5-10/gal in these countries. Unlikely most are getting over 50 mpg which would cost $.50 in electricity and $.25 in battery. Prices are an average guess but likely close.
So saving $4.50 or more/day quickly pays for the conversion which is rather simple though about $1500 so would be paid for in fuel savings in just a yr.
Fast charging stations can be cheaply set up to charge them to 80% in just 15 minutes for $.50 and can profitably use solar PV now their price has dropped so much and the price doesn't have to ever go up if the taxi owners own the charge station. The above and new light EV's are buy far the most profitable and least poluting they can get.
BTW 2 strokes can be clean but expensive needing direct injection and other goodies. But even if clean they still cost big time at the pump.
Reply | Report Abuse | Link to thisI forgot EV's are far better accelerating with 3x's the torque of an ICE or more. I tow a 13' trailer filled with plywood and 2x4's, 4x4's, etc.
I guess I should mention too mine is made of plywood and epoxy giving a very light and strong chassis that holds the batteries and the suspension bolts to. It's set up as a pickup, 3x4 bed with a trailer hitch for larger loads.
It uses a MC ot moped front end and can go up to 50mph. With a car diff and bigger motor you can get most any speed you want though it better be aero if you want range at speed.
It costs me $2/wk for everything, fuel, battery, tires, tag which is my biggest expense. It gets 33wthrs/mile means a kwhr gets me 30 miles/kwhr and a Kwhr costs me the US average of $.10kwhr. So for $1 of electricity I get 300 miles.
For the price of 1 US gal of gasoline I can go 1200 miles now the price is $4/gal.
Can the 'experts' please elaborate.
Reply | Report Abuse | Link to thisIs the comparison between car and rickshaw done with same fuel.
Cars are having four stroke engines and are (petrol,diesel) based
CNG based auto rickshaws nowadays are having 4-stroke engine. But the old rickshaws were having 2-stroke engines.
Many car owners also fit CNG/LPG kits in the cars.
So is the comparison by 'experts' done only considering Liquid fuel based cars?
What about kite powered rickshaws? Only joking! Has anyone realised that particulates are carbon, that has not been combined with oxygen, to make CO2. So, why not capture the particulates either Dyson style centrifugal action, or by passing the exhaust through water?
Reply | Report Abuse | Link to thispokerplay hits the nail squarely on the head. The root cause of many of the worlds problems is overpopulation, and the worlds population is increasing every day.
Reply | Report Abuse | Link to thissingingflea has got it exactly right. Most Americans don't give a rats backside about the rest of the world, or about environmental pollution, and many of them don't even know where the rest of the world is.
Since the major problem with the Tuk-Tuks is the two stroke engine it would be possible to make a four stroke engine which could be a "drop in" replacement for the four stroke engine.
Reply | Report Abuse | Link to thisAlso since the major problem with the two stroke engine is the "total loss" lubrication system (oil is added to the fuel to lubricate the engine) it is possible to build a two stroke engine using fuel injection and to replace the crankcase compression system of delivering air to the cylinder. This could theoretically be better than a four stroke engine as there would be a power stroke every revolution instead of a power stroke taking two revolutions as in the four stroke engine.
You say "the root cause of many of the world's problems is overpopulation, and the world's population is increasing everyday". As you are free, you can add to the solution of what you think is the cause of exhaust gas emissions from obsolete technologies in developing countries: refrain from reproducing and add to the world no more offspring from you right now. For this you'll need a full sexual abstinence, as there's no 100% efficacious approach to family planning. Salut +
Reply | Report Abuse | Link to thisI also agree that ICEs are not the future, but it may be with us for another 20 to 50 years. We should not forget that electric car is only as clean as the source of electricity. Generating electricity from coal and powering the present time obese and aerodynamically poor vehicles, - makes no sense at all.
Reply | Report Abuse | Link to thisOnce we start to produce electricity from clean and renewable sources, and batteries attain the power/energy density comparable to liquid fuels, obviously the choice will be electric. So far it is a shift from oil and gas... to coal. And that is not clearly explained to consumers... That is too bad.