Shindaiwa C4 Technology next for chainsaws??

[Dennis]

Here is an exerpt from a Shindaiwa brochure...

" By combing the high power to wieght ratio and simplified compactness of a 2 cycle engine with precise metering typical of a 4-cycle, we developed an engine that delivers best of both worlds."

"The C4 Technology engine features overhead intake and exhaust valves, and it cycles in four strokes.

The T2500 is fueled by a conventional 50:1 gasoline/oil mix-just like a 2-cycle to provide continuous flowing lubrication throughout operation in any orientation, including upside down! There is no seperate oil sump; no dipstick to check."

Here is a link for more info.... http://www.shindaiwa.com/c4tech/index.html

 

[eyolf]

Here's a couple of links to "power equipment trade" magazine articles that may be of interest, as well:

<a href= "http://www.poweret.com/vserver/hb/display.cfm?MagazineKey=1&IssueKey=168&SectionKey=21&ArticleKey=1955"> 4 cycle shinny trimmer </a>

<a href= "http://www.poweret.com/vserver/hb/display.cfm?MagazineKey=1&IssueKey=168&SectionKey=21&ArticleKey=2408"> Stihl's 4 strokerz </a>

I remember reading something about Husqvarna and Yamaha working on larger versions of this idea...I think Husky has an injected 2/4 stroke under development for use in personal watercraft that really performs...

When I was younger, my friends and I pretended we could modify 2-stroke snomobile engines for more performance, but usually grenaded them. I moved onto 4 strokers in motorcycles eventually, eventually figuring out how to make Hondas sing a pretty song. I'm thinking the exhaust note of a 150cc 4 stroke saw bellering out of a megaphone at 12,000 rpm might be just what the doc ordered!

 

[seesaw]

Honda has the M4 technology consisting of 22, 25, ans 31cc 4-strokes that is out of this world. They are, however, high torque, low rpm engines not conducive to a chainsaw appl. Honda does have one 50cc 4-stroke that turns 8500rpm already! I'm sure a 10-13k rpm model is not far behind. If you can make enough r's with a 4-stroke, why in the world would you want a bastard hybrid that still spews that exhaust?

 

[eyolf]

If the hype is to be believed, the oil (2% of fuel) has no effect on NOx or CO emmisions, and the particulates are still well below what is allowed for on-road, let alone off-road, diesels.

I'm intrigued by the idea, but not so enthused about some of the design details...a single cam running both intake and exhaust valves means that playing with timing will be tough. Nylon parts bug me, too.

A handy guy with a small CNC mill can remedy most of that, though...

 

[bwalker]

If you can make enough r's with a 4-stroke, why in the world would you want a bastard hybrid that still spews that exhaust?

The hybrids have nothing to do with rpms as fourstrokes are very capable of high rpm(formula 1 streetbikes,etc. The advantage of a hybrid is the motors ability to pressurize the intake cycle with the downward motion of the piston. I dont know how much over atmospheric it boosts intake pressure, but any amount would help with the fourstrokes inherent power disadvantage. The Shindaiwa animation shows this pretty clearly.

 

[bwalker]

If you can make enough r's with a 4-stroke, why in the world would you want a bastard hybrid that still spews that exhaust?

The hybrids have nothing to do with rpms as fourstrokes are very capable of high rpm(formula 1 streetbikes,etc. The advantage of a hybrid is the motors ability to pressurize the intake cycle with the downward motion of the piston. I dont know how much over atmospheric it boosts intake pressure, but any amount would help with the fourstrokes inherent power disadvantage. The Shindaiwa animation shows this pretty clearly.

 

[seesaw]

Yes....4-strokes are obviously capable of high r's. But, are small (30-50cc) 4-strokes capable of obtaining the r's needed in a chainsaw application?

 

[WRW]

I think the main advantage of the "2/4" stroke is that it can be used in any orientation, as opposed to four strokes that burp when turned upside down.

 

[bwalker]

es....4-strokes are obviously capable of high r's. But, are small (30-50cc) 4-strokes capable of obtaining the r's needed in a chainsaw application?

Its easier to make a smaller motor rev higher than a big one. Therefore I say yes it is possible to get high rpm out of a fourstroke. The question is why? With highertorque why not use a small gearcase setup to get high tool speeds. this would be sim ple in a trimmer as they already have a gear assembly.

I think the main advantage of the "2/4" stroke is that it can be used in any orientation, as opposed to four strokes that burp when turned upside down.

I think Honda already solved that problem. A dry sump setup would solvce this problem also, although i imagine it would add weight.

 

[eyolf]

I'm sorry the articles I linked take so long to load, but if Shindiawa'a figures are to be believed, their 25.4 cc 4 stroke trimmer makes 1.1 hp at 8000 rpm. This compares relataively well with the Husky 325 trimmer at 24.5 cc and advertized 1.2 hp.

I'm excited about what this may mean for the future, but then I'm kind of a techno-nut.

 

[tundraotto]

problem is that trimmers are direct drive and 8k rpm doesnt cut it for pro use

 

[bwalker]

problem is that trimmers are direct drive and 8k rpm doesnt cut it for pro use

That could be changed very easily. I have a stihl fs-85. It has a small gear case at the bottom of the shaft. It would not add much weight to add a gear set in the same location.

 

[tundraotto]

then you add weight and more parts....adding to the price....making it not worthwhile

 

[bwalker]

Your right otto, but with the epa twisting the mfg's arm there is not really any choice. I personaly hope they find a way to make cleaner two strokes.

 

[WRW]

Honda does list a gear ratio on their 4-stroke trimmers. Doesn't say what gears, but I'd guess...
It does have a hefty price and is on the weighty side.

 

[bwalker]

Fcae it guys from a power to weight standpoint two stroke are king. This emmisions compliance BS does nothing but hurt the consumer.

 

[eyolf]

From a certain standpoint you are absolutely correct, bwalker. The amount of pollution our chainsaws, string trimmers, and the odd mantis-style trimmer or ice auger add to the atmosphere can't be nearly as great as, for example, all of general motors compact cars when totaled up year by year.

Yet, does anyone really think we could get by any longer by just ignoring one class of products? We just plain will not be allowed to do so. So what's the next best thing?

2 strokes make more power than 4 strokes do, because they have a power impulse every revolution. The actual power DERIVED per impulse is usually a little less for various reasons. The sorts of engines we are discussing are further hampered by being forced to use diaghragm carbs, which are a notorious compromise, metering wise.

The day will never come when the best 4 stroke trimmer performs as well as the best 2 stroke did, and do it as cheaply. But the day isn't far off when they do a completely adequate job. 4 stroke chainsaws will not be far behind.

I grew up in Central Mn, within a 5 minute drive of the Cuyuna range iron mines. Most of them were abandoned by the time I was a teenager, and the spoil dumps were an extremely popular place to play with dirt bikes...we're talking hills as steep as dirt will stand, 100-950 feet high, to try to climb. One particular hill, made entirely of sticky tailings was at a measured 94% grade, 820 feet tall. The first known motorcycle to climb it was not a big Yamaha YZ or any other 2 stroke. It was a 1975 Honda 350, bored 5.5 mm, stroked 6 mm, JP piston at 12.5 :1, megacycle flattracker cam, 40mm Mikuni and 37" megaphone.

4 strokes can get up and talk too.

 

[seesaw]

Originally posted by eyolf


The day will never come when the best 4 stroke trimmer performs as well as the best 2 stroke did, and do it as cheaply.

In my opinion, the day has come. I have my choice of three quality trimmers every time I go to the truck and I always choose the Honda 4-stroke. You may be right on the cost issue although, as seen in almost all "new" technology, the price comes down over time.

 

[bwalker]

Yet, does anyone really think we could get by any longer by just ignoring one class of products? We just plain will not be allowed to do so. So what's the next best thing?

We can and do. The diesel industry is just starting to come under emmisions scrutiny. Large off road diesels such as those found in ships and gensets have no emmisions regs and many of them are two stroke diesels. This crap about going after two cycle power equipment, atvs and sleds is a joke. I suppose these industries are just the easiest to pick on. BTW climing that same hill with a cr 500 would be more fun,eh. Long live the two stroke.

 

[Oregon_Rob]

My Plan

The day is coming, but, there will be a long learning curve. One thing I have learned is that I don’t want to be the first guy to get the new technology. New things, with new technology always have bugs, the manufactures do a lot of product testing on the consumer and I don’t like being the Ginny pig. They even get big firms to come up with really catchy adds to make us really want the new stuff. Eventually, the EPA will mandate our great running saws… out of existence. My plan is to buy new just before the cut off and in 10 years, after the bugs have been worked out and the clear leaders have risen to the top, maybe I will buy again.