A major source of outdoor air pollution is carbureted two-stroke engines, which power 100 million "two-wheelers" (e.g. motorcycles, scooters) and "three-wheelers" (e.g. tricycles, "tuk-tuks") across Southeast Asia. Nathan Lorenz, of Envirofit International, walks us through a Direct In-cylinder (DI) fuel injection retrofit kit for two-stroke engines that is cleaner and more fuel efficient than the replacement four-stroke engines.
Hosted by: Mark David Videography by: Curtis Ellzey Edited by: Curtis Ellzey
Amflyer commented on November 20, 2009
If anyone finds a Fuel injection retofit for a 79 Vespa P200 scooter please let me know at Jansen@sfsu.edu Thanks, Jansen
Amflyer commented on August 05, 2009
No you can't get a retrofit if you're not in the third world. This is not a for-profit corporation, It9;s a not-for-profit charity. They have absolutely no interest in designating any production capacity to anyone that easily has the option to buy a 4-stroke. Moreover, if they did, their goal of reducing air pollution might be compromised if people who would otherwise buy a 4stroke bought instead a 2 stroke and a retrofit kit. It's very likely that the final product is still dirtier than a common 4stroke. So don't even bother asking. They wouldn't even tell you where you could get one if they knew.
Amflyer commented on July 27, 2009
The Two-Stroke Lives (cleanly, too) Evinrude's E-TEC engines have done the seemingly impossible: saving the air-cooled two-stroke from oblivion By Christopher A. Sawyer, Executive Editor About 10 years ago, Chrysler’s Joe Goulart was singing the praises of the two-stroke engine as an automotive powerplant. His dream, however, couldn’t pass muster with the EPA. As a result, the automotive two-stroke engine died. Environmental concerns dogged the recreational two-stroke, as well. After years of doing nothing, the EPA set strict pollution limits for recreational vehicles (personal water craft, snowmobiles, etc.), which called into question the two-stroke’s continued viability. Fortunately, no one told George Broughton, director of Engineering, Boats and Outboard Engines Div. for Bombardier Recreational Products (Sturtevant, WI). He and his team created the Evinrude E-TEC family of two-strokes; engines that are clean and darn-near worry free. Fuel Injection That Sings “The trick was to make an engine that would idle at 500 rpm and make 1 hp, and run 6,000 rpm and make 250 hp while meeting the emission standards,” says Broughton. Part of the solution involved using a Lorentz coil. Better known as the voice coil that drives loudspeakers, a Lorentz coil is made up of a permanent magnet and coil winding, and produces a force proportional to the current applied to the coil. Which makes it perfect for devices requiring high acceleration, high frequency application, and a flat force vs. displacement output. Another big advantage is that it can push or pull, so it can be reset between injection events very quickly. “The strength and duration of the injection pulse determine fuel droplet size,” says Broughton, “which varies to meet the unique needs of an air-cooled two-stroke.” At low engine speeds, small droplets offer the greatest atomization, and the most homogenous mixture. This is sprayed over the spark plug, and ignited as a stratified charge. At high speed, larger droplets are used to cool the top of the piston. (Cooling also is helped by use of a NASA-developed alloy three times stronger than conventional alloys at temperature. Broughton’s team found it while searching the Internet.) A swirl-nozzle fuel injector with 0.046-in. tangential slots is another key to clean combustion. “It’s made through metal injection molding,” says Broughton, “and starts as a piece about three or four times bigger than the final product. Then it’s shrunk to size in an oven like a new pair of blue jeans in the dryer.” The fuel rail is pressurized to 30 psi, and the Lorentz coil amplifies this to 600 psi (1,000 psi is possible, but as yet unnecessary) under wide-open throttle conditions. No Battery, Plenty of Spark The E-TEC’s electrical system is based around a magneto – like a Model T – for a simple reason: recreational vehicles are put into storage at the end of each season, then pulled out when the weather turns favorable. Batteries die in storage, so relying on one to drive the fuel injection system and engine controller only adds to customer frustration. “The magneto produces from 150 to 300 volts,” says Broughton, “but that is reduced to 55 volts to drive the oil and fuel pumps and the fuel injectors. It’s further reduced to 14.7 volts to charge the battery, if the boat has one.” Evinrude promises an E-TEC engine will start within one revolution, something most two-stroke owners will find hard to believe, especially for an engine that’s been in storage. The key is the sealed injection system. Though the fuel in the gas tank may oxidize over time, no air can enter the fuel system itself. The gas stays fresh. As the flywheel starts to turn, the magneto sends current to the engine controller, which determines where the piston is, when to inject the fuel and fire the spark plug – all inside of one revolution. At the end of three year’s use, and except for greasing the lower drive unit because of its constant immersion in water, Broughton insists the only item that may need service is the spark plug. “The E-TEC is designed to go three years without any dealer interaction,” he says. Oil and Catalysts But what if the regulations get tighter, won’t two-strokes be at a disadvantage because of their propensity to burn oil? “Oil isn’t a big player,” says Broughton, “because the amount burned is about 1% of the total intake charge, and it never mixes with the gasoline.” (The average user of a 50-hp E-TEC will go through two quarts of oil per year.) Hydrocarbons are the predominant pollutant, a portion of which are scavenged and burned in the next combustion cycle. When emission standards tighten, Broughton will be ready with a simple reduction catalyst he terms, “1970’s technology.” Right now, the engine is clean enough to pass California’s 2008 standards. Broughton doesn’t claim E-TEC technology might have saved the automotive two-stroke, but he does suggest Detroit’s obsession with preventing the lubricating oil from being burned during combustion sent them down the wrong path. “Their concentration on retaining an oil sump, oil scraper rings, and relying on plain bearings instead of roller bearings,” he theorizes, “increased the amount of oil burned, which harmed emissions performance.” And it may be another reason why automotive two-stroke emission performance degraded over time. “The E-Tec actually gets cleaner as it progresses through the EPA test,” he says. “And we never have to worry about the potential for secondary pollution when changing the oil.” Maybe not, but try selling that to the EPA when discussing emission tradeoffs. Tighter emission standards were supposed to mean the end of two-stroke engines for recreational use. Apparently, Evinrude wasn’t listening. It uses a Lorentz coil to drive the fuel injection system, which allows it to produce a stratified mist at low speeds, and larger droplets to cool the piston at high rpms. A NASA-developed alloy that is three times stronger than current piston alloys at high temperatures eliminates a weak spot found in conventional two-stroke designs. Evinrude claims the new design will start in less than one revolution of the engine, and be across its full engine line by MY 2005.
Amflyer commented on July 27, 2009
There was a company in GB talking of 2-stroke injection systems for racing way back in the 70's. They made hot cams, or something. But it proved too difficult. We now have the very sophisticated electronics and the super-fine engineering capabilities to do it at minimal cost. The oiling systems we've had for years, thanks to the Japs and you lazy Yanks, though, of course, it was a European idea from the beginning, Jawa were the first in modern time to develop a system, but the Russians refused to use it and, as the Reds commandeered 99 percent of the production, Jawa had to drop it. Evinrude are proving injection works and beats the 4-stroke outboards in economy and emissions. Norwegian ingenuity at it's finest! Going 4-stroke finished West Bend and Johnson, and even the company who bought them are in trouble? Not having the money either, Evinrude decided to try another way, and succeeded. I think engineering people are again looking at the 2-stroke for 'small-engine applications9;, but don't expect bolt-on parts, but entire engines designed around injection. Not many, or none of, MX bikes have oil-injection, and it's not possible to retro-fit such things. Fuel-injection, yes, on a Jap road-bike already fitted with positive-oiling, but the market isn't there. I'm grinding my teeth already, at being 30 years too old to race, what will I be like when the new 2-stroke MX injection-engines come out!!!!
Amflyer commented on November 10, 2008
I wish I could get a kit for a two-stroke dirt bike. It would be amazing on a KTM 300XC.
Amflyer commented on August 08, 2008
rodger i have have 80´s 50cc tunturi supersport and i was thinking just the same. if anyone knows how could i get one of these kits please tell
Amflyer commented on July 30, 2008
I have an old 1972 T250 J hustler. It runs on a 2 stroke motor. It has paralell heads. Can I get a kit for my bike? Where can I find one?
Amflyer commented on July 13, 2008
Gentlemen, what a great article,I hope and wish you great success.
Amflyer commented on May 23, 2008
There are millions of two stroke lawnmower engines still in use, and I unsderstand that these are also a major contributor to air pollution. Do you have any plans for retrofits for these?
Amflyer commented on May 13, 2008
There are a lot of old 2 stroke marine outboard engines in the US. Have you thought of doing something for us boaters? I wonder if I can get a retrofit for my 1982 140-HP Johnson outboard ?