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Message: [QUOTE="murf007, post: 1336431, member: 100344"] The Future Of Two Strokes And Your Dirt Bike This is a unique page on my site. It relates to the future of two strokes in general, but ties in with how this will affect you and your choice of dirt bikes. The information here comes from Tim Hickox who will be putting up regular posts using his many years of experience with engine design. So, if you are interested in what's happening out there in regards to engine design and dirt bikes... read on and be sure to check back as this page is updated! A quick introduction with Tim... "I can't put a lifetime into a bottle, but: I got my first motorcycle when I was 14. After owning a Greeves, CZ, OSSA, Honda, Suzuki, et al., I had a pretty good idea of what worked and what didn't. Engineering was my destiny. I was service manager for a motorcycle importer/manufacturer; I was Technical Editor of a motorcycle magazine and then Technical Analyst for the Motorcycle Industry Council. I worked for Honda on the early development and testing of their trials machines, and so on. I wanted to stay in the motorcycle industry, but it was going in the "wrong" direction for me (pushing everything up-market to maintain dollar-volume as unit-volume fell). So I went into aerospace. I worked on the Space Shuttle and on many earth-observation satellites. I am now writing a book (philosophy) and working on a unique vehicle (with a two-stroke engine!) that can get 300-mpg at 65-mph." Tim Hickox -------------------------------------------------------------------------------- 3rd Nov 2008: I understand the point on dirt-bike specifics, but if we really try to limit it so, there isn't much to talk about! This is the problem! What I really think is needed is to offer an alternative to the misinformation that has confused so many people. There are many ways to build two-stroke engines. People must understand that what has been offered to motorcyclists in the past is not "a two-stroke engine". That is, the future of two-stroke dirt bikes, if there is going to be any future, need not be, in fact cannot be, more of the same. The guys seem to think that what was, is no longer acceptable, therefore we have to chuck the whole idea of "two-stroke engines" and switch to four-stroke engines. You see, what we really want to talk about is... two-stroke engines of the future! But that future is not here, so how can we possibly put limits on what it "is". The 2009 Skidoo 600 E-TEC is the best two-stroke going now that could represent the direction in which some future motorcycle engines may go. But I must make this point: If the two-stroke engine does not return as a viable transportation option for two-wheelers in developing countries, I think it will die. I think this is really what the Japanese companies have been saying. If they can't build and sell two-stroke bikes to the masses, at the low-end of the spectrum, they aren't going to support the type anywhere. So... what may be needed now, to ensure the future of "two-stroke dirt bikes", is a low-tech (i.e. cheap), clean, economical two-stroke motorcycle. The "death" of two-stroke dirt bikes has come after the loss of two-stroke motorcycles in general; and I believe that the future of two-stroke dirt bikes may have to come after a revival of the wider market. What I want to get across to people now, which is about all there is to talk about, is the potential... what two-stroke engines can be - the future of two strokes. Whether one sticks such an engine in a dirt bike, a street bike, a lawnmower, or whatever, is an issue somewhat outside the realm that I will address. Within that realm, I must refer to a lot of things that are even outside the world of motorcycles, like the Skidoo. Because that is what we have or have had. Otherwise, I can only talk of theory, of thermodynamics, which most people won't understand, and which would leave me open to any and all contradicting theories. -------------------------------------------------------------------------------- 17th Nov 2008: Let's get right to the question: What is wrong with the two-stroke engine? Nobody seems to dispute that the two-stroke is smaller, lighter, and cheaper to make than a four-stroke of equal performance. I think it has also been conclusively demonstrated that a high-performance four-stroke engine is more expensive to maintain. This is a very impressive list of advantages. So what's wrong? Somebody is going to say that fuel consumption and exhaust emissions are too high. But wait! Is anybody screaming about the fuel consumption of Formula-One cars? Does anybody care about NOx emissions in NASCAR? Why is the racing two-stroke going away? A lot of people blame the government. But the "EPA ban" on two-strokes is a myth. The EPA has said over and over that their regulations can be met by four-stroke and fuel-injected two-stroke engines. The problem is: there are no fuel-injected two-stroke motorcycle engines in production. (I'm ignoring a few "scooters".) So we have to look first at the fuel-injected two-stroke engines made for other applications, which could be adapted to motorcycles. Let's skip over motocross and other closed-course racing that is run on private property - where (like NASCAR) anything goes. "Enduro" bikes may operate on public land, and the government does regulate what happens there. You should not be surprised to hear that a snowmobile operated on public land gets treated the same as a motorcycle. So, back in year-2000, the SAE (Society of Automotive Engineers) created the "SAE Clean Snowmobile Challenge", a competition to stimulate the development of cleaner snowmobiles. (Too bad they didn't choose motorcycles!) What happened? I am going to tell you why - technologically - the future of the two-stroke engine looks extremely bright! -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- 1st Dec 2008: As expected, the CSC was a four-stroke affair. Nobody thought of building a "clean snowmobile" with a "dirty" two-stroke engine. But then, somebody always has to show off. After winning the CSC in 2002 and 2003 with a BMW, fuel-injected, four-stroke engine, the University of Idaho decided to do the unthinkable. The fact remained, they said, that "...avid snowmobile riders still prefer the lighter and more powerful two-stroke engine." They pointed out that a "simple" four-stroke snowmobile only made a little more than 50-hp. A high-tech, 750-cc with turbocharger and fuel injection made about 85-hp. The lighter Ski Doo, two-stroke, made 120-hp. So the UICSC team switched to a stinker. They won again in 2007. What they did was adapt a direct-fuel-injection system (E-tec) from an Evinrude outboard motor. What you should appreciate is that everyone else in this competition was trying to get the best out of some four-stroke. And all the testing was done by engineers, based on EPA 2012 standards. No hype, no bias. The two-stroke won! To put this into a dirt-bike perspective, a snowmobile is much heavier than a dirt bike - 500+ pounds. And the power transmission (a belt-track) is very inefficient (which is why they need so much power). So the snowmobile engine must work much harder, burn more fuel, and create higher exhaust emissions than a dirt bike, given the same use. If a two-stroke snowmobile is not a problem, a two-stroke dirt bike would be a party. For 2009, there is the Ski Doo 600 E-tec (do a Google, and you will find pics and details). So let's imagine that we wanted to build a killer enduro bike. One half of that Ski Doo motor would give us a 300-cc, single-cylinder motor with 60-hp. It would have lower exhaust emissions and lower fuel consumption than any four-stroke of equal performance. And, of course, it would still be a simple, compact, light, easy-to-maintain two-stroke. All the real engineering has already been done - it works, the parts are in production. If we went to Rotax, in Austria (Evinrude, Ski Doo, and Rotax are owned by Bombardier, in Canada), who builds the Ski Doo engine, and motorcycle engines, we could just tell them to take parts that they are already making and put them together into this killer enduro bike engine/transmission assembly. I'm sure they would be very happy to do this (for a nice chunk of money, of course). The UICSC team estimated that the cost of E-tec, for the twin-cylinder, would be about $300. So what's wrong with the two-stroke? And where is the future of two strokes? Hold on, it gets better! -------------------------------------------------------------------------------- 15th Dec 2008: To reiterate: Clean, efficient two-stroke engines (making 120-hp!) are in production and used in off-road vehicles on public lands subject to EPA regulations. Unfortunately, those "vehicles" are not motorcycles! Let's look now at what Honda was doing just before they announced to the world, "No more two-strokes!" The story really begins a long time ago when people discovered that two-stroke engines would sometimes run without spark-ignition. That is, one could pull off the sparkplug lead, while the engine was running, and it would continue to run as if nothing had changed. People said, "It's dieseling." Actually, what was happening was very different from combustion in a diesel engine. The phenomenon was best explored by Shigeru Onishi in the 1970s. He called it "Active Thermo-Atmosphere Combustion (ATAC)." He said, "With ATAC the fuel consumption and exhaust emissions of two-stroke cycle, spark-ignition engines are remarkably improved, and noise and vibration are reduced." He eventually showed that a carbureted two-stroke engine could be more efficient (lower fuel consumption) than a diesel engine. But only within a narrow range of speed-load conditions. In the 1990s, Honda R&D Chief Engineer, Yoichi Ishibashi, wanted to clean up two-stroke motorcycle engines. He called "ATAC": "Activated Radical (AR) combustion." Onishi`s engines ran generators at nearly a constant speed. Ishibashi needed to greatly extend the range where "AR" combustion was stable. He found that throttling the exhaust was the secret. He developed a 400-cc single-cylinder engine. For real-world testing, several of these "EXP-2" engines were put in endurance-racing chassis. They ran in the Granada-Dakar Rally and the Baja 1000. The results were good enough for Ishibashi to press on and develop the engine further. -------------------------------------------------------------------------------- 29th Dec 2008: Two bikes were entered in the Dakar - both finished. As Ely Kumli reported in 1997: "The race results were very good even though the bike was not designed to win races, but to test new technology. When the dust settled, the EXP-2 had earned 5th overall and first in both the under-500cc and experimental classes..." As it turned out, the second-string riders had been given the better equipment! "Compared to Honda`s NXR780 four-stroke twin rally race bike," said Kumli, "the EXP-2 has very similar performance, with several advantages. While the single-cylinder EXP-2 produces 54hp to the big NXR`s 71hp, they both make 58 lbs-ft of torque, but the EXP-2 is 118 pounds lighter giving it a slightly better power-to-weight ratio. What all this boils down to is that the EXP-2 has about the same real-world performance as the 780, but with substantially better fuel economy and lower emissions." As good as that sounds, Ishibashi was just beginning. The exhaust valve prevented most of the fresh charge (fuel-air mixture) from getting lost out the exhaust port, but he needed to scavenge the cylinder with air only, and admit the fuel late in the cycle. He came up with a "pneumatic injection system" that used a standard four-stroke-type fuel injector. Ishibashi summarized the results: "...PDI-AR Combustion drastically decreases HC emission close to the level of four-stroke, and CO and NOx level is 1/5 and 1/7 of four-stroke level respectively. Furthermore, fuel consumption is improved 15% compared with the four-stroke." His English isn't perfect. I will add: A Honda four-stroke engine giving equal performance had carbon monoxide emissions 500% higher and oxides of nitrogen emissions 700% higher than his two-stroke. Without an oxidizing catalyst, the two-stroke hydrocarbon emissions were slightly more than the four-stroke's, but with a cat, the levels of HC were the same. The CO levels dropped, but the two-strokes avantage over the four-stroke was actually greater. (NOx is unaffected by an oxidizing catalyst). Obviously, Honda had a good engineer doing good work. He had one more song to sing before the bean-counters dropped the axe on him... -------------------------------------------------------------------------------- [/QUOTE]

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