2-stroke engines are better or worse?
January 26, 2011 2:07 PM Subscribe
2-stroke or 4-stroke brushcutter (or similar)? What are the differences?
Leaving aside the physical activity of the 2-stroke and 4-stroke engine, which I understand well enough for my purposes, what are the fundamental performance or ownership differences between a 2-stroke and 4-stroke brushcutter (or any other small engine)?
It seems to me that if my new brushcutter was 2-stroke it would be:
+ significantly cheaper
+ a bit more powerful
+ lighter?
- much noisier
- much more polluting
- a little bit less fuel efficient
Would it be more or less reliable (ignoring brand, use, etc)? Any other pertinent differences?
If anyone has reliable insights into why 2-strokes are cheaper that would be interesting.
Leaving aside the physical activity of the 2-stroke and 4-stroke engine, which I understand well enough for my purposes, what are the fundamental performance or ownership differences between a 2-stroke and 4-stroke brushcutter (or any other small engine)?
It seems to me that if my new brushcutter was 2-stroke it would be:
+ significantly cheaper
+ a bit more powerful
+ lighter?
- much noisier
- much more polluting
- a little bit less fuel efficient
Would it be more or less reliable (ignoring brand, use, etc)? Any other pertinent differences?
If anyone has reliable insights into why 2-strokes are cheaper that would be interesting.
(Heh. heh. "shear annoyance." heh. I'll pretend that was intentional...)
posted by disillusioned at 2:18 PM on January 26, 2011
posted by disillusioned at 2:18 PM on January 26, 2011
Two stroke engines are much, much lighter than comparable four stroke engines. They are simpler and have fewer moving parts.
posted by fixedgear at 2:21 PM on January 26, 2011
posted by fixedgear at 2:21 PM on January 26, 2011
There are several reasons 2 stokes are cheaper. No crankcase for oil, can be used in any position and you don't have to change the oil. No carburetor, they use a reed fuel delivery. I have a Stihl trimmer and was told by the dealer to not run it out of fuel after the season like I normally do with 4 stoke motors. He stated it keeps the reed lubricated. I usually run 4 stokes out of fuel to the carb so the carb doesn't gum up. I have not used my lawn mower or trimmer in several months and I'm confident they'll start up immediately should I go out now to start them. Just use a stabilizer in the gas.
As far as noiser, a friend has a 4 stroke trimmer and I don't hear any difference and he paid considerably more for his than I did mine.
posted by JohnE at 2:25 PM on January 26, 2011
As far as noiser, a friend has a 4 stroke trimmer and I don't hear any difference and he paid considerably more for his than I did mine.
posted by JohnE at 2:25 PM on January 26, 2011
If you only have one or two pieces of equipment with small engines, get a 4 stroke. That'll save you the minor annoyances of mixing oil and gas (having two separate gas cans, having oil on hand, getting the mix right, etc.).
The only reason I'd get a 2 stroke in that case is if it's a tool I'll be using all day long and the weight is going to be an issue; which, admittedly, for a brushcutter is not a minor concern.
posted by Nahum Tate at 2:27 PM on January 26, 2011
The only reason I'd get a 2 stroke in that case is if it's a tool I'll be using all day long and the weight is going to be an issue; which, admittedly, for a brushcutter is not a minor concern.
posted by Nahum Tate at 2:27 PM on January 26, 2011
Another notable difference between two and four strokes is the power band; four stroke engines tend to run efficiently at low and high speeds, whereas two stroke engines often have a much more narrow range. It's far less important for small engines, of course, than for two-stroke dirtbikes and scooters.
posted by Fiasco da Gama at 2:34 PM on January 26, 2011
posted by Fiasco da Gama at 2:34 PM on January 26, 2011
It is worth noting that the commonly cited disadvantages of two stroke engines are not inherent - they don't have to be more polluting, noisier, and die sooner, they are just almost always designed that way because cost and simplicity are valued first. There are very efficient very huge two stroke engines that work great, they just don't end up in weed-wackers. That said, between a two stroke and a four stroke brushcutter the four stroke is going to last longer, run better and do less harm to the environment. You'll pay more up front but less over time.
posted by ChrisHartley at 2:41 PM on January 26, 2011
posted by ChrisHartley at 2:41 PM on January 26, 2011
Response by poster: just a few more facts, the brushcutter I was looking at was $170 for a 59 cc, 3.5hp machine (a bit of a monster, but I've got a lot of work to do), versus $260 for a 30 cc, 1.8 hp 4 stroke.
It's quite a price and performance difference versus the noxiousness of the 2-stroke.
Noise, vibration and air pollution are really only going to bother the user (i.e. me), I'm in the country.
posted by wilful at 2:49 PM on January 26, 2011
It's quite a price and performance difference versus the noxiousness of the 2-stroke.
Noise, vibration and air pollution are really only going to bother the user (i.e. me), I'm in the country.
posted by wilful at 2:49 PM on January 26, 2011
Best answer: As for longevity, I find the biggest factor isn't really the engine, but the rest of the weed whacker. The cheap ones just fall apart. Expensive ones are generally better, regardless of engine type. As for emissions, 4 stroke small engines fare poorly, too. I think regulations for such small engines are more lax than they are for stuff like automobiles and even motorcycles.
Also, 4 stroke weedwhackers seem to be just as noisy and two stroke. The reason may be the compactness of the mufflers.
More expensive weed whackers seem to have clutches, which means the business end only rotates when the engine is up to speed. For professionals of folks doing big jobs, this seems like a nice convenience.
The weak spots I find with small engines isn't so much the engine wearing out, but other bits and pieces of plastic and rubber, such a fuel lines and priming bulbs, that rot, and need replacing. Line head/feed systems can also be a headache.
posted by 2N2222 at 4:33 PM on January 26, 2011
Also, 4 stroke weedwhackers seem to be just as noisy and two stroke. The reason may be the compactness of the mufflers.
More expensive weed whackers seem to have clutches, which means the business end only rotates when the engine is up to speed. For professionals of folks doing big jobs, this seems like a nice convenience.
The weak spots I find with small engines isn't so much the engine wearing out, but other bits and pieces of plastic and rubber, such a fuel lines and priming bulbs, that rot, and need replacing. Line head/feed systems can also be a headache.
posted by 2N2222 at 4:33 PM on January 26, 2011
Best answer: Quite a bit of misinformation in going on here...
2-strokes are cheaper, have fewer moving parts, better power to weight ratio. Their main downside when used in portable equipment is the stinky exhaust because of the total-loss cylinder lube and the less-efficient combustion.
There is no reason why a 2-stroke should be inherently noisier than a 4-stroke. If it is noisier it's simply a matter of inadequate input and/or exhaust silencing.
2-strokes have carburetors just like 4-strokes.
The thing to look out for is due to the cheapness of the power plant, 2-strokes tend to be on lower-end equipment built to a price, so I'd look hard at the robustness of construction of the two units you're comparing.
posted by HiroProtagonist at 6:01 PM on January 26, 2011
2-strokes are cheaper, have fewer moving parts, better power to weight ratio. Their main downside when used in portable equipment is the stinky exhaust because of the total-loss cylinder lube and the less-efficient combustion.
There is no reason why a 2-stroke should be inherently noisier than a 4-stroke. If it is noisier it's simply a matter of inadequate input and/or exhaust silencing.
2-strokes have carburetors just like 4-strokes.
The thing to look out for is due to the cheapness of the power plant, 2-strokes tend to be on lower-end equipment built to a price, so I'd look hard at the robustness of construction of the two units you're comparing.
posted by HiroProtagonist at 6:01 PM on January 26, 2011
Best answer: This is definitely a right tool for the right job scenario. Go with the two-stroke for sure. It'll power right through stuff whereas the little 30cc 4 stroke will be lagging and taking twice the time to get the job done.
The problem with the little 4 strokes is that they don't have anything like a flywheel to keep momentum between strokes when you really stress the engine. Just like a typical 4 stroke lawn mower when you hit a thick or overgrown spot. Bam. Engine stops. You don't need a flywheel though, with a 2-stroke because every other stroke is a power stroke.
It sucks about the pollution aspect but at least you'll be getting the job done faster and therefore, theoretically, burning less fuel.
posted by snsranch at 6:15 PM on January 26, 2011
The problem with the little 4 strokes is that they don't have anything like a flywheel to keep momentum between strokes when you really stress the engine. Just like a typical 4 stroke lawn mower when you hit a thick or overgrown spot. Bam. Engine stops. You don't need a flywheel though, with a 2-stroke because every other stroke is a power stroke.
It sucks about the pollution aspect but at least you'll be getting the job done faster and therefore, theoretically, burning less fuel.
posted by snsranch at 6:15 PM on January 26, 2011
Response by poster: FYI, I got the large 2-stroke.
Price wins.
posted by wilful at 4:07 PM on January 30, 2011
Price wins.
posted by wilful at 4:07 PM on January 30, 2011
This thread is closed to new comments.
They are also INSANELY noisy. They will annoy your neighbors. They will annoy you. They are painfully noisy. They are also being banned in some places because they're just horrible.
Even electrics can be noisy, but hardly anything beats a 2-stroke for shear annoyance, fumes, and awfulness in general.
A four stroke has a separate chamber for oil, so it doesn't burn it off, and it's a more efficient engine design by far, but it's more complicated, there are more parts, and it's thus more expensive.
If you can afford it, go 4-stroke. If you can find one that is reasonable for your purposes, go electric.
posted by disillusioned at 2:17 PM on January 26, 2011