With the advent of new trimmers and lawn products that include 4-stroke engines, we are often asked the question: 2-stroke vs. 4-stroke – which is better?
The question is whether these new 4-stroke OPE tools are better than their 2-stroke counterparts (literally: "Which is better, 2-stroke or 4-stroke?") The answer may be simpler than you think, but first, it is The distinction between the techniques is important. Each has its strengths, but we don't think they're an exact match — at least not when it comes to portable lawn care products. Check out our review of the Makita EM2650LH 4-Stroke Corded Trimmer.
Basic knowledge of 2-stroke vs. 4-stroke engines
A 2-stroke (sometimes called a 2-stroke) engine is generally considered to be one that accepts a premixed air-oil mixture. This mixture, in a ratio ranging from 50:1 to 20:1, depending on the motor, fuels and lubricates the motor during operation.
A 4-stroke (sometimes called a 4-stroke) engine is more similar to what you'd find in a car. Four-stroke engines also have a crankcase and an oil distribution system that separates oil from gases when lubricating engine components. Since the oil is separate, it also needs to be changed periodically – usually every 25 hours of use.
Four-stroke engines use the same gasoline you buy for your vehicle, with up to 10% ethanol (you should not use E85 gasoline because it is the same as the 2-stroke or 4-stroke engines commonly found in small lawn trimmers and lawnmowers incompatible machine).
How two-stroke and four-stroke engines work
There are significant differences between 2-stroke and 4-stroke engine operation. As you might expect, a four-stroke motor works in four phases. There is a power (down) stroke, an exhaust (up) stroke, an intake (down again) stroke, and a compression (up again) stroke. It takes two full revolutions of the crankshaft to complete these four strokes. It is the power stroke that moves the piston through each of the remaining three stages.
A 2-stroke engine actually has only two cycles combining the above duties. The first stroke is a combination of power stroke and exhaust stroke, and the second stroke is a combination of compression stroke and intake stroke. When the piston reaches the top of its stroke, both power and combustion occur. At the bottom, exhaust and intake occur. Just one revolution creates two strokes and pushes the piston through the full cycle.
More parts = more breakage
Four-stroke engines have more moving parts. They have crankshafts, camshafts, connecting rods, valves, tappets and pistons. A two-stroke engine really only has three main moving parts. This includes the crankshaft, connecting rods and pistons. In a small two-stroke engine, there are no cams, tappets or valves. As a general rule, fewer parts means less potential for failure and easier maintenance.
In general, 2-stroke engines are generally smaller in displacement and size compared to 4-stroke engines, and many times the displacement and overall size of a 4-stroke engine is almost doubled to get the same power. The reason for this is because a 2 stroke combines two functions in one revolution, it makes power twice as fast as a 4 stroke.
Advantages and disadvantages of 2-stroke and 4-stroke engines
From what has been described so far, you might think that 2 cycle is totally better than 4 cycle…well, it probably is in small marine applications and home lawn care. However, comparing 2-stroke and 4-stroke engines requires more work. In fact, four-strokes have only a few advantages: greater potential torque, better fuel economy, and better emissions. Having said that, let's look at the list of pros and cons of 2-cycle and 4-cycle, with a case for each:
|2 cycles||4 cycles|
|part||Advantage||More moving parts|
|maintain||Advantage||must change oil|
|storage||Advantage||must be level|
|fuel economy||less efficient||Advantage|
|start||Advantage||harder to start|
|weight||Advantage||More parts = more weight|
Comparing 2 strokes and 4 strokes
As you can see, there are definitely several advantages to having a 4-stroke motor for a trimmer or other lawn care application, but for the most part, 2-stroke motors are king these days for a reason. They are very reliable, less prone to damage, and easier to start and use. For high torque, 4 strokes may indeed be the way to go, but in general we recommend sticking with tried and true 2 stroke models – the pros do it!
The bad news is that environmentalist concerns seem to be driving many municipal decisions right now. In the near future, stricter emissions regulations may eventually phase out 2-stroke engines entirely. When this happens, we hope that manufacturers will improve on 4-cycle technology and offer products that are as convenient and hassle-free as their 2-cycle counterparts.