This works well for getting extra fuel (and hence power), but is not so good for economy. A 4-strokes oil which must be changed periodically is for lubrication but not combustion, so the outboard produces less smoke. How could it be that a 2-stroke engine is more fuel efficient at . Not even considering EFI when both are carbs the 4 stroke still out performs the 2 stroke by significant amount. Though these solutions add weight to a 4-stroke, it hasnt seemed to diminish their appeal. A former offshore powerboat racing world champion, Kalibat, for one, agrees, though he says it depends on the particular engine. There is thus always going to be a mix of exhaust and unburned gasses in a two stroke engine. The four-stroke engines feature valves that open and close and which eliminate any air-fuel loss. 2-Stroke Vs. 4-Stroke. Motor Vehicle Maintenance & Repair Stack Exchange is a question and answer site for mechanics and DIY enthusiast owners of cars, trucks, and motorcycles. The 4-stroke cycle is completed when the piston returns to its original position and starts the cycle over again. A Yamaha 125cc 2stroke engine gives around 70mpg, A honda 125cc 4stroke engine gives around 153mpg, The EFI version of the above 125 cc honda engine gives around 166mpg. It generates high torque. I however have to disagree with the article stating that the fuel delivery plays a major role in fuel efficiency of older 2-Stroke engines. Clearly today the 4-stroke is an easier sale. They also note the obvious: Both engine types will burn a lot of fuel at wide open throttle, and that boaters can find a fuel burn sweet spot by backing off a bit and watching fuel consumption. link to The 7 Best Fish Finders For Your Pontoon Boat, link to 10 Ways That Boats Cause Pollution And What We Can Do About It. They also have the advantage of being lighter and more compact than 4-strokes, making them a good choice for smaller boats requiring an outboard of up to 150HP. 3. @Anarach You are spewing fuel twice as often, but not necessarily twice the amount, as I understand it. Four Strokes. As can be seen in the data above, the 2-Stroke Evinrude E-TEC G2 is by far the most fuel-efficient engine at 300 hp when we compare it with the Yamaha 300 in several applications. Two-stroke engines are typically more fuel efficient than four-stroke engines, and they produce less smoke and less noise. If a piston moves 2 times in the cylinder, that means, engine is known as two stroke engine and if it moves 4 times in a four stroke engine. Two-stroke and four-stroke motors are based on the same principles of a combustion engine but are engineered very differently. Mercury, for example, last year introduced its Verado line of supercharged 4-strokes. If the cylinder size and compression ratio are the same, then the fuel/air mixture will be the same, not 2x. It has one revolution of the crankshaft during one power stroke. There is a valve for the intake stroke that opens and closes . Yamahas Grigsby says the companys HPDI lineup is what it is right now 150 hp to 300 hp and the company will be prepared if the 2-stroke market goes away in the next couple years. 4-Stroke. They demand more oil and lack the agility offered by four-stroke engines. As time goes on theyre able to improve 4-strokes to perform more like 2-strokes, Kalibat says. 4-stroke engines are now commonplace and are available in all HP ratings; 4 stroke outboards have a longer life span; The use of 2-stroke oil is not necessary in a 4-stroke engine as it is in a 2-stroke, which leads to cleaner . 4-stroke engines are quieter than 2-stroke engines. Answer (1 of 29): A Four Stroke cycle engine will have a higher Volumetric Efficiency (VE). In my mind, if they can overcome that, theyll have a very serious and viable alternative to 4-strokes, says Marie. I rarely have an issue with my 4 stroke, but with the 2 stroke, it was a lot more common. A proprietary injector that can oscillate a few times or thousands of times per second, much like the speaker in a stereo and its proximity to the spark plug. Reduced complexity helps to increases mechanical efficiency. So these are the quite few difference between the 2-stroke engine and 4-stroke engine, let me know . This resulted in unburned fuel going straight through the engine. In simple words, stroke is the distance of cylinder between piston moves. 4-stroke outboards have more moving parts than a 2-stroke, so more to go wrong, 4-stroke outboards are more complex to maintain than traditional 2-strokes. Weight Comparison: 2-Stroke vs. 4-Stroke. Mielke says Mercury has found that for a given horsepower the new technology. We are constantly striving to make our website as helpful as possible, if you have any suggestions on how we can improve please feel free to get in touch using the contact us section. Thus wasting fuel as it's expelled. I think Anarach's assertion that a two-stroke consumes twice the fuel twice as often is wrong. One of the most significant advantages of choosing a 4 stroke ATV engine is that the engine can generate more power at lower revolutions per minute (RPMs). Four-Stroke Outboard Motors In a four-stroke engine, the five combustion cycle steps occur in four strokes of the piston. Or simply the cylin. In this article, we will explore the differences between 2-stroke and 4-stroke engines, and help you decide which one is the best fit for your needs. That tells you theres not going to be a lot of wear and tear. However, Shields notes that the technology hasnt been around long enough to see if this is the case. The closest rival on the 2-stroke side may be the Evinrude E-TEC 2-stroke outboards from BRP formerly Bombardier Recreational Products which are said to run as quietly as a 4-stroke. The peak 39 HP is lower than the 2 stroke, but that is only relevant if you can ride in the power band on the stroker. 4-stroke engines are now commonplace and are available in all HP ratings, 4 stroke outboards have a longer life span. @IhavenoideawhatI'mdoing: I don't think we have any real data to go on. The 2 stroke engine does have a major advantage over the conventional 4 stroke engine. 2-strokes are more fuel efficient than 4-strokes when run at or just above idle, and again above three-quarter throttle, because the fuel is being monitored so precisely. The cylinders are not scavenged of exhaust gases by the piston forcing them out, they simply escape because the outside air pressure is lower than the cylinder pressure after the spark ignites the fuel. What is the efficiency delta between rotary and modern four-stroke engines. While BoatTEST.com typically tests more than 100 boats a year, with five outboard brands each with 3 to 11 models between 200 and 300-hp, and more than 6,000 different boat models worldwide, finding a perfect match of boat-on-boat comparison is like finding a needle in a haystack. We hope you liked this article and found it helpful. Being more fuel efficient means less fossil fuels are burned, making . Power. Less pollution :- As power is generated once every 4 strokes & also as no oil or lubricant is added to the fuel; 4 stroke engine produces less pollution. Today, Yamaha 2-stroke snowmobiles are used to traverse the icy cold environment of Russia, and our 2-stroke outboard engines are widely used across Africa for fishery. Mercury's 2-stroke direct injection OptiMax 225 weighs 497 pounds, and BRP's V-6 E-TEC 225-hp 2-stroke weighs 516 pounds. Jeff Kalibat, owner of Yamaha dealer K&K Outboard in Island Park, N.Y., says a good rule of thumb is if you spend a lot of time above three-quarter throttle, get a 2-stroke, but if you spend most of your time below that mark, opt for a 4-stroke. Four-stroke engines are heavier; they weigh upwards of 50% more than a comparable 2stroke engine. Also, a certain amount of potential output is consumed operating a 4-strokes valve train. Two stroke engines are less efficient and produce more smoke whereas 4 stroke engines are more efficient and produce . 2-stroke outboards can be adapted or built to run on a wider variety of fuels including gasoline, oil, kerosene, and diesel fuel. I highly doubt it , for example. Take a look at how a 4 stroke engine works. The capital cost of equipment will naturally balance to the running costs. The first stroke is the intake stroke, during which the piston moves down to draw fresh air and fuel into the cylinder. Until now its been a real problem in small dinghies, says JJ. Theres no way around it.. A 2-stroke engine goes through 2 stages, or one complete revolution, to complete one power stroke. 4-stroke engines are typically heavier than 2-stroke engines. What do you call an episode that is not closely related to the main plot? A cylinder head design that is essentially a small combustion chamber unto itself that is all that is needed at low rpm. The 2-stroke aspect comes into play more to provide low- and mid-range torque as well as requiring less maintenance during the life of the engine. The use of 2-stroke oil adds to running costs. Some might require valve adjustments or replacement timing belts. More fuel efficiency :- 4 stroke engines have greater fuel efficiency than 2 stroke ones because fuel is consumed once every 4 strokes. The crankshaft makes two rotations for every one cycle of the piston. A 4-stroke engine is a type of internal combustion engine that completes the process of combustion in four strokes. On the contrary, in 4 strokes engine, charge is fully burn and does not mix with burn charge in ideal condition. That percentage is based on how an average boater would use an outboard, he says. You've only seen one page. The performance of this engine is lower compared to the 4-stroke engine, as it has a lower volumetric efficiency and the exhaust is less efficient. In a 4-stroke engine, we see higher volumetric efficiency because the intake capacity of the engine is more. We have seen no test data from any other 4-stroke engines that contradicts this data. The best answers are voted up and rise to the top, Not the answer you're looking for? Following the explosion of the previous cycle, the piston in a 2-stroke engine is forced downwards on its power stroke. 2. Conversely, a 2-stoke only needs two movements of the piston to complete the same action. As can be seen in the data above, the 2-Stroke Evinrude E-TEC G2 is by far the most fuel-efficient engine at 300 hp when we compare it with the Yamaha 300 in several applications. Hence a potentially large amount of unburnt fuel disappears straight down the exhaust having performed no useful function (beyond maybe cooling the engine a bit). Just so we're on the same page as to how two strokes work, here's a pic. Nonetheless, Yamaha 2-stroke products have a simple, lightweight construction and comparatively easy maintenance, and their high reliability keeps them popular in many regions. Each type has its own unique benefits and drawbacks, which can make it difficult to decide which one is right for you. 4-stroke engines are quieter than 2-stroke engines. A: Oil is added to 2-stroke fuel for applications such as dirt bikes because the fuel doubles as a lubricant for the engine. It has a far broader and smoother power band, which runs through the mid-range, and up to the dizzy heights of 14,000 RPM. David Grigsby, marine group product manager for Yamaha, says the two engine types generally burn fuel at equal rates at idle and again at wide open throttle. Mercury sells 4-strokes from 4 hp to 275 hp (including its Verado line) and OptiMax direct injection 2-strokes from 75 hp to 225 hp. Each has its advantages and disadvantages. A 2 stroke doesn't have a valvetrain; so in addition to producing more HP per pound they are much lighter due to the lack of a camshaft, valves, lifters, etc. 2-strokes were competitive against low-compression, low-speed flathead engines for seasonal use only until metallurgical and manufacturing advances made it possible to build cheap 4-stroke OHV engines with electronic ignition and fuel injection so ignition and fuel tuning became automatic and optimal for the more automotive and seasonal applications like snowmobiles, ATVs, outboard motors, outdoor power equipment like string trimmers and leaf blowers and other consumer products. As fuels get scarcer, price will increase and move the market to more efficient designs which will be 'allowed' to have a higher capital cost. Torque. I would also like an explanation of how the amount of power strokes per revolution is related to fuel efficiency. Honda marketing manager Senger says 4-strokes can run tighter tolerances than 2-strokes, which expose pistons and rings to a lot of wear with so many ports in the cylinders. A 2 stroke outboard motor has a faster pick-up speed than a 4 stroke. A naturally aspirated 4-stroke cannot be tuned to provide the same performance at as broad an rpm band as the 2-stroke. Comparable Mercury and Yamaha 4-strokes weigh 583 pounds, Honda's BF225 4-stroke weighs 599 pounds, and the Mercury Verado 225 weighs in at 649 pounds. He says a 200-hp Yamaha 4-stroke isnt as responsive as a 200-hp high pressure direct injection Yamaha 2-stroke, but the new F150 4-stroke will stay right with a 150-hp HPDI. 2-stroke engines also have fewer parts and are lighter. As the name implies, the two stroke engine only requires two piston movements (one cycle) in order to generate power. In comparison to 4-stroke engines, they are also easier to repair. In four-stroke engines the exhaust ports are generally opened just prior to bottom dead centre piston position, thus giving a maximum expansion ratio. When compared with a 4-stroke, a 2-stroke engine presents more fuel consumption. Electronic ignition system improvements and dedicated, application-specific carburetion and professional grade performance expectations and price points are barely keeping 2-strokes competitive in industrial/commercial machines like portable cutting tools. Joe Frohnhoefer chairman and CEO of Sea Tow Services International, whose fleet is equipped with close to 2,000 engines notes that a 4-stroke powerhead has more working parts than a clean 2-strokes, which increases the chances of encountering problems. A 4-stroke engine can burn that fuel, but it can cause issues. In a 4-stroke outboard, the piston needs four movements (strokes) in order to complete a cycle - intake, compression, combustion and exhaust. Most of the extra work comes from the two strokes being older. Are witnesses allowed to give private testimonies? ArcticCatZR800. (The EPA is in the process of writing possible new rules.). We dont even check the spark plugs until 400 hours, he says. Two Strokes. Heres a quick rundown of the key differences between 2-stroke and 4-stroke outboard engines: So, which type of outboard engine is best for you? Re: yamaha 225 efi 2 stroke vs. 225 4 stroke. Because of this E-TEC outboards might be difficult to sell, he says. Finding matches for both 2-stroke and 4-stroke engines is even harder, and is not helped by the fact that both Yamaha and Mercury have quietly discontinued selling 2-stroke engines in the U.S. Now, Evinrude is the only 2-stroke game in town. Boatbuilders are modifying hulls to accommodate heavier engines, and some companies, such as North Carolina builder Southport Boatworks, are designing models expressly for use with 4-stroke power. Typically, a 2-stroke engine creates more torque at a higher RPM, while a 4-stroke engine creates a higher torque at a lower . Browse other questions tagged, Start here for a quick overview of the site, Detailed answers to any questions you might have, Discuss the workings and policies of this site, Learn more about Stack Overflow the company. A 2-stroke is less complex with fewer moving parts than the 4-stroke. With such a system air can be taken in to the engine with the fuel only injected once the exhaust port is closed. The XCU03PT1 has a brushless motor that delivers up to 70% more run time than previous models, and . It generates less torque. The use of 2-stroke oil is not necessary in a 4-stroke engine as it is in a 2-stroke, which leads to cleaner running and fewer emissions. It only takes a minute to sign up. Whether you have a smaller or larger boat, weight should be a consideration when purchasing an outboard motor. Not even considering EFI when both are carbs the 4 stroke still out performs the 2 stroke by significant amount. An amount of the air-fuel mix on a 2-stroke is lost via the exhaust opening on the upward piston stroke. Without needing to contain valves the combustion chamber can be far more easily shaped to suit the purposes of that particular engine. And keeping oil out of the combustion process results in longer spark plug life in 4-strokes, says Hondas Senger. FREE Boater Bootcamp for newer boat owners gives you the insights on boat ownership basics, navigation and practical rules of the water and how to avoid, be . Shields says over the long run, a 4-stroke requires more service than a 2-stroke. In a 2-stroke the fuel is also the lubricant and coolant and mixing oil with gasoline increases the energy content of the fuel while decreasing the octane so 2-strokes have to run fixed ignition timing and super rich fuel-air mixtures made even richer by the high-energy, low-octane oil mixed in. Affiliate disclosure: As an Amazon Associate, we may earn commissions from qualifying purchases from Amazon.com. 2-stroke engines are noisier than 4-stroke engines. Two-stroke oil is formulated for lubrication and combustion. Two-Stroke Diesel Engine - Do they use forced induction on them? Carburetted 2-stroke outboards have been banned in the US and EU since 2006. The biggest issue is probably that the exhaust port is open while the intake mixture is being taken in. Characteristics of the 2-stroke Otto Cycle. [2] The engine is able do produce power after one cycle because the exhaust and intake of the gas occurs simultaneously, [3] as seen in Figure 1. In a conventional two-stroke engine, the exhaust must open very early in the power stroke to enable the cylinder pressure to fall well below that of the incoming charge, in order to avoid spent gases entering the transfer ports and mixing with the fresh charge. Essentially, the answer to why the Evinrude E-TEC G2 2-stroke is so much better than the old 2-stroke technology can be attributed to four basic things: 1. As for environmental concerns, 4 stroke outboards produce far less harmful emissions, which can be as much as 90% cleaner than those from a similar sized 2-stroke motor. But which engine is right for you? What's the best way to roleplay a Beholder shooting with its many rays at a Major Image illusion? As the downstroke begins the pressure in the cylinder is high allowing the exhaust gases to escape and forcing the intake reed valve closed. This engine produces higher torque at low speed (rpm). No break-in is required [with E-TEC], says Shields, who is a dealer for Yamaha, Honda, Evinrude and Johnson outboards. Brett Shields, owner of Shields Marina in Saint Marks, Fla., says a lot of boaters are under the mistaken impression that they will be outlawed from using 2-strokes in the future, or that 4-strokes are more durable. How clearly dilineated are the four strokes of a four-stroke engine? Hence, it completes the power cycle faster than 4-stroke engines. Is there any alternative way to eliminate CO2 buildup than by breathing or even an alternative to cellular respiration that don't produce CO2? 3. Modern design reduces but cannot entirely remove these efficiencies which appear still to be more taxing than the 4 stroke method of turning the engine twice to get one work stroke. Theoretically for the 2 stroke work output is double that of 4 stroke for a single revolution of the crankshaft and so is the fuel input. Two-Stroke vs Four-Stroke. Theres not that lag time, says Jim Morgenthaler, general manager of Tohatsu America, which builds 2- and 4-stroke outboards. VE is the ratio of mass density of air fuel mix drawn into the cylinder at atmospheric pressure (during intake stroke) to the mass density of the same volume of air in intake manifold. However, repairs are generally needed more frequently, unless you actively maintain the engine. It has two revolutions of the crankshaft during one power stroke. What is happening when a two-stroke engine is said to be "four-stroking"? Shields says he has a customer with 6,000 hours on an old-style 2-stroke, and that advances with metals on the Evinrude E-TEC could equate to much longer engine life. However, once running, both offer speed and power. The lighter engines produce a greater power-to-weight ratio as a result. Yamaha still sells many of its popular, powerful and lightweight carbureted 2-strokes in addition to 4-strokes and HPDI 2-strokes. The main reason being efficiency - Although a 2-stroke engine is technically capable of more power output, a 4-stroke engine uses less fuel to produce the same power output. Further it only works at certain rpm ranges. A 2-stroke engine accelerates better than a 4-stroke because it has a broader power band or range due to its better breathing, or how efficiently it draws air in and pushes it out. The Makita 4 stroke chainsaw is an excellent option for a powerful and fuel-efficient saw. So efficient! 2. Once baselined and up to date we rarely work on our fleet of two strokes. Were going along with a dual strategy because we think theres room for both., 2022 Active Interest Media All Rights Reserved. 4-stroke engines produce less pollution than 2-stroke engines. What is this political cartoon by Bob Moran titled "Amnesty" about? LawnMowerGuru.com, All Rights Reserved. We have lots more on the site to show you. Generally, the expansion ratio is equal to the expansion ratio in piston ported two-stroke engines. This site is all about boating, we love boats, but we also have to be mindful of the environmental impact that boat ownership can cause. Four-strokes have begun to dominate the market below about 40 hp because of the complexity and expense involved in trying to make a light, small engine operate with the electronic controls necessary to run a direct injection system. But what is it that causes two-strokes to be less fuel-efficient? Comparing fuel efficiency is a good starting point. Engine inertia is going to be a negligible factor in motorcycle MPG, so if you really want to measure it you're going to have to run two similar unloaded engines at the same RPM and measure their fuel consumption. Can you say that you reject the null at the 95% level? By comparison, standard 2-strokes blow 1/3 of their oil directly into the air/water. But it's not as simple as that. MPG is not a good measure for this discussion because it brings in factors like gearing which I want to keep out of this discussion. Four-stroke engines are taller than their equivalent two-stroke counterparts. How to Drain Gas from Lawn Mower Without a Siphon. E-TEC engines wont need scheduled maintenance for a warranty period of three years or 300 hours of normal recreational use, according to BRP. 2-stroke engines are less fuel efficient than 4-stroke engines. As the upstroke happens the pressure in the cylinder is now low because the escaping exhaust gases cause a small pressure wave of escaping gas that now opens the reed value and draws in new fuel / air mixture.
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