Garden power equipment 2-Stroke v.s. 4 Stroke

[Dmace]

Anyone used the new propane powered ones?
I saw one at Home Depot recently.

LEHR - Environmentally Friendly Technology
Yard work cleaned up - Los Angeles Times

Now that I would buy, I like that idea! At about $3 per propane tank and an average of 2 hours of run time on each tank, it will cost as little or less then a gas powered trimmer. Next will be propane powered riding mowers with grill sized tanks. I operated a propane forklift in a Home Depot years ago and it was great, I would love to be able to trim under my large deck without choking on exhaust fumes.

4 stroke is much better for the environment due to not burning oil.

True, but a 4-stroke is not better for the environment when it burns the same oil a 2-stroke does as mentioned above.

 

[jinman]

Thanks you Derek, Turbo36, and RobertN for the 4-cycle explanations. Like many things, it seems there are several ways to "skin the oil-sump cat." I've come very close to buying one of those, but my wife needs a very lightweight trimmer. If I am going to get help from her, it needs to be extremely lightweight. I like help, so I bought her a Weedeater Featherlite trimmer. I have a very old Ryobi brushcutter/string trimmer I use that refuses to die. I think it's probably 12 years old and still going. The 4-cycle machines sure are tempting though.

jinjimbob and dillo99: What is coming next? With propane on the horizon, can LNG be far behind? How about a hybrid? It could be a generator driven by one of those screamin' backpack leaf blower engines and powering an electric string trimmer. Now that would be progress, huh?

 

[jwstewar]

I've got a 4 cycle Ryobi that I bought back in '96. It is the type that runs straight gas and you have to do an oil change to it. I've used the crap out of it at every angle imaginable. It is finally starting to get tired. A little hard to start now (it used to start very easy) and now will smoke a little if running it at full throttle. Not bad, but a little. The one I have could use the different attachments. I've got the string trimmer, brush cutter, hedge trimmer, cultivator, and blower. I finally broke the end of the string trimmer in some heavy weeds. I went to Lowes and bought a 4-cycle TroyBilt because it would use my existing attachments. I trimmed twice with it and then was using the little cultivator. It broke the driveshaft of the trimmer. After hearing of several of these breaking since MTD took over, I just got my money back and went to a dealer and bought a 2-cycle Echo. I like it, but hate mixing the gas & oil. It is also very cold natured compared to the old Ryobi. It has to idle for a minute or so before it is ready to go. It will also take the interchangable attachments, but they are very expensive from Echo.

 

[Highbeam]

I propose that a 4 cycle engine burning an oil/gas mix is far cleaner and less polluting than a 2-stroke engine burning the same oil/gas mix. The real reason that 2-stroke engines are smokey and pollute is that there are no valves in the engine and the engine forces the exhaust out of the exhaust port by pushing in the fuel/air/oil mix though the intake port. There will always be overlap and some of the fuel/air/oil mix will be sent out of the exhaust port as unburnt fuel.

The unburnt fuel spooges out of the exhaust and is visible as smoke.

 

[turbo36]

I propose that a 4 cycle engine burning an oil/gas mix is far cleaner and less polluting than a 2-stroke engine burning the same oil/gas mix. The real reason that 2-stroke engines are smokey and pollute is that there are no valves in the engine and the engine forces the exhaust out of the exhaust port by pushing in the fuel/air/oil mix though the intake port. There will always be overlap and some of the fuel/air/oil mix will be sent out of the exhaust port as unburnt fuel.

The unburnt fuel spooges out of the exhaust and is visible as smoke.

Exactly! The little bit of oil that is burned is combusted during ignition, no more pollutants created then with straight gas.

 

[Dmace]

Exactly! The little bit of oil that is burned is combusted during ignition, no more pollutants created then with straight gas.

Wrong, it still burns oil no matter how you look at it. They even post a graph showing how much it burns (37 g/Kwh). It may not be much but it's still more then straight gas.

 

[Scooby074]

I have and have used several 2 and 4 stroke trimmers.

Currently i have a Honda 23? 4 stroke and a Husky 252R 2 stroke. While the honda is quiet, starts first pull, requires no mixing, in my opinion the powerband doesnt suit the job of being a trimmer. A 2 stroke will rev higher, quicker and thats what you need. I find im running my honda at full throttle constantly to "keep the revs up" so im not waiting for the head ot accelerate.

Compare that to a 2 stroke, where im feathering the throttle and am off the gas a lot more compaired to the honda. The head comes up tp speed so much quicker that i dont have to be constantly on the throttle.

Granted, these 2 machines are at opposite ends of the spectrum, but ive used lots of the smaller 2 stroke trimmers and the result is the same.

Then theres the added weight of the 4.

When (if) the honda dies, it will be my last 4 stroke trimmer. Ill likely replace it with a Husky 2 stroke (325 LX), there just so much better in my opinion. Nothing against the honda, i couldnt ask for a more reliable machine, its just the other things that are annoying.

As far as the smoke issue, mine dont. I mix my oil accurately (50:1), use synthetic oil and run premium gas. They run as clean as a 4 stroke. If i mixed sloppy and used crappy oil, then you get the smoke issues.

 

[studor]

A lot of two strokes put as much as 35% of what you put in them back out as UNBURNT fuel (both gas and oil). It is the unburnt stuff that really pollutes.(Sorry Scooby but a two stroke cannot run as clean as a four stroke - period -- the lack of smoke is not a good indication of not polluting) Two strokes generate up to twice as much power for the weight. Problem is that old guys like me who have lots of two strokes that run well are reluctant to give them up for four strokes that cost a lot to buy. At some point the government will probably force manufacturers to give up two strokes. In the meantime I will continue to use whatever I have as long as it runs or until the alzheimers kicks in and I forget to mix and burn it out .JMHO
regards

 

[Scooby074]

Studor, i have to agree that as a whole 2 strokes pollute more than 4 strokes.

However in this case were talking small engines. IMHO the emissions difference between a average 4 stroke, and a well tuned 2 stroke wont make much difference in the big scheme of things. especially when you consinder that i end up running the 4 stroke full throttle the majority of time im using it. I guess i was exaggerating abit in my above post.

larger 2 stroke engines have been making great progress towards reducing emissions. Look at the Skidoo and evenrude Etec.

Quote :Evinrude E-TEC uses up to 75% less than typical 2-stroke carbureted engines and up to 50% less oil than competitive direct injection engines (when run with Evinrude/Johnson XD 100T oil with optional dealer programming of the Engine Management Module, versus normal TCW3 oil). And you'll use 30% less oil compared to a 4-stroke with a typical maintenance schedule under normal operating conditions. '

With a fully stratified combustion system, Evinrude E-TEC outboards are designed to comply with 2006 EPA (Environmental Protection Agency) as well as tough 2006 EU (European Union) standards well into the future. E-TEC even meets the ultra-low 2008 CARB (California Air Resource Board) 3-Star emissions rating. For you, it simply means a cleaner boating environment: no smoke and dramatically lower carbon monoxide emissions.

With the E-TEC system, fuel is injected twice as fast as traditional direct injection engines and unburned fuel never reaches the exhaust port. This means the fuel charge never escapes the combustion chamber as it is burned and turned into pure power. E-TEC also senses when to change fuel delivery into the chamber, depending on engine needs, resulting in precision fuel flow and extreme fuel efficiency. The sealed fuel system also minimizes evaporative emissions.

So the 2 stroke aint dead yet THANKFULLY.

 

[turbo36]

Wrong, it still burns oil no matter how you look at it. They even post a graph showing how much it burns (37 g/Kwh). It may not be much but it's still more then straight gas.

Yes it burns some oil, but isn't gas just a highly refined oil?

You are arguing the wrong point, what is important is the total emission output not how it is generated. This is a very clean way to get the power benefits of a 4-stroke with the weight benefits of a 2-stroke.