4 stroke chainsaw is it in the future?

[drkptt]

Why not?



I have a few opinions on your post:

Don't worry. They'll get lighter.

This is irrelevant. Folks were afraid of fuel injected cars 20yrs ago.

Can't argue this.

In about 10-15yrs someone's going to build a 50-60cc 4 stroke saw that turns 11k rpm reliably.

The 2 stroke is a dying breed. As the years go by, there are fewer and fewer 2 stroke engines available. Look a watercraft, snowmobiles, motorcycles, lawn mowers, weed whackers, leaf blowers. Chainsaws are the last of it and I don't believe they'll hold out forever.

I explained why not in an earlier post. You provide counter arguments to the negatives, but fail to explain why 4-strokes will take over the chainsaw market.

 

[weimedog]

Have read all the pros and cons...but no matter what I read I can't warm up to the 4-stroke idea. More complexity, weight, and expense and 4-stroke's will never beat the simplicity & power to weight advantages inherent to the two stoke design.....Having voiced my frustration based on my Motorcycle life, there is one potential "power" related advantage in chainsaw applications for four stroke's....the chainsaw two strokes are severely limited by space & weight for both cooling and tuned exhaust... so that leaves an opening as the four stroke can do with valves what an expansion chamber does on true performance 2-strokes...and cooling? HP makes heat. Not certain a four stroke has an advantage there other than the efficiency of the four stroke cycle may make up for the thru put of air thru the typical 2 stroke motor.

I lived thru the four stroke mandated world that is now off road motorcycles & off road racing...the 450 four stroke's running with the 250 2 stroke's...the 250 four stroke's running with the 125's etc..the added expense to racing and the weight and all that crap. Don't want to see it repeated here.

Lest you see me as afraid of new stuff...four strokes aren't new. And I totally endorse the electronic control systems that have now become common to racing. The Fuel injection & ignition timing curves that you now can control in the typical motorcycle ( and other performance machines) might really be fun to the typical tech hack here to fine tune a modified saw.

I have to say millions have been spent on the racing four strokes in the motorcycle racing world..and with moto cross weight is a priority. SO All the BS and theory aside..if you want a glimpse of the true difference...take a 125 two stroke and a 250 four stroke put them side by side, and your going to get an idea how the four stroke will relate to a comparable two stroke. Number of moving parts, cost of manufacture, cost of maintenance over a race season....weight...etc. Whats the advantage? Four strokes have a wider and more forgiving power band, granted. Biggest advantage is all the race classes were slanted to favor the four strokes disadvantages. Oh yea..because of the class structure changes a bunch of motorcycles had to be sold to compete in these new class structures...drove the cost of racing up in a big way.

 

[bbb]

How does 9.5 hp at 17k rpms from a single cylinder 50cc 4 stroke sound? Actually, I bet one running would sound sweet. Honda did it 50 years ago with the RC111 GP racing motorcycle. It did have a razor thin power band, so just bump the displacement to say 70cc or so and fatten up the power band for chainsaw use.

Such a motor could be made to weigh very little if advanced materials were used. Spendy would probably be an understatement.

 

[weimedog]

And remember the game Honda played to compete at the same displacement as two strokes...valve cross sectional area and RPM...they had 4 and 6 cylinder four stroke to compete with contemporary two strokes....many just twins. Once the four cylinder OW's (TZ's) came out, even 17,000rpm oval pistoned four strokes just didn't have a prayer...the only thing that put Four Stroke's back in the winning circle was changes to rules and class structures. How many years did "obsolete" TZ-750's smoke all comers at Daytona?

 

[CJH1]

I am absolutely a 2 stroke fan and agree they are lighter and less complicated to maintain. Going with a four stroke vs two, comparing the motorcycles, you need roughly twice the displacement to have comparable power. Just think about being able to say you have a 250cc saw!!!! :msp_smile:

 

[weimedog]

For those who either forgot or are too young to see these...here is the series of road racers that put an end to four strokes until the rule changes..

TZ350 and 250 Website


The Four Strokes last Hurrah's..and a good read to understand the challenge of matching 2 strokes with the same size four strokes.

http://www.motorcyclespecs.co.za/model/Classic Racers/honda_nr_500_gp_racer_1979.htm

 

[CTYank]

There are a couple of things that can keep 2-strokes' emissions under the limit (in no particular order):
1) stratified charge
2) catalytic converter (unless folks insist on ripping them out)
3) electronically controlled direct fuel injection (could make stratified charge redundant)
4) rotary valves (a la Rotax) for intake (and exhaust?) would get you past the unwanted symmetry relative to piston motion, of opening.
5) metered oil injection (as in outboards and Mazda Wankel cyl lube)

Then there were diesel chainsaws, like the norwegian Comet.

 

[drkptt]

There are a couple of things that can keep 2-strokes' emissions under the limit (in no particular order):
1) stratified charge
2) catalytic converter (unless folks insist on ripping them out)
3) electronically controlled direct fuel injection (could make stratified charge redundant)
4) rotary valves (a la Rotax) for intake (and exhaust?) would get you past the unwanted symmetry relative to piston motion, of opening.
5) metered oil injection (as in outboards and Mazda Wankel cyl lube)

Then there were diesel chainsaws, like the norwegian Comet.

Numbers 4 and 5 won't significantly reduce emissions.

 

[David (saltas)]

4 stroke diesel over hydraulic powered chainsaws

The electricity used hydraulic powered hand held saws and pole saws.

The trucks have two hydraulic lines from the pto to the bucket on the bucket trucks.

the saws both hand held and pole saws have two flexible hydraulic lines with quick disconnect snap couplings

The hydraulic couplings are mounted on the outside of the bucket just under the lip.

these are 4 stroke diesel over hydraulic powered chainsaws.

I assumed that these were very unlikely to be stolen but apparently the get stolen all the time, farmers hook them up to their tractors etc.

 

[David (saltas)]

air powered chain saws
Air Chain Saws at CS Unitec / chain saw, chain saws

hydraulic chainsaw and log spliter video

[video=youtube;3DWCFm1MCVo]http://www.youtube.com/watch?v=3DWCFm1MCVo[/video]

another hydraulic chainsaw carving this time

[video=youtube;yugyghEI-ws]http://www.youtube.com/watch?v=yugyghEI-ws&playnext=1&list=PL81F12E819CDF3249[/video]

 

[Knuckles]

Fuel injection is not a valid argument as it was simply a different way to regulate fuel in a 4 stroke engine, the engines for the most part were the same. Adding more moving parts to anything is adding more parts to ware out or fail, plane and simple. More parts = more weight. Working on them takes longer and time = money, not only for the repair shop/manufacture, but also the owner of the product.

You're really looking at this through a straw, there is much more to manufacturing than most know, from R&D to assembly, all of which is more involved aka $$$ with 4 cycle engines, something Stihl and most hand held OPE manufacture are not familiar with. Mercury marine, Honda and others are.

Will two cycle engines be around forever? no, but one could say the same for any internal combustion engine. Fact is OPE two strokes are hear to stay for the foreseeable future, likely until we're all gone.

Damn you've got me beat all the way around. I just like having a good discussion about engines and things like we all do.

I believe the Dolmar 500V turns 12,500. Also if Dolmar released the 500V it would have a price tag in the $1200-$1400 range.

Ouch

I explained why not in an earlier post. You provide counter arguments to the negatives, but fail to explain why 4-strokes will take over the chainsaw market.

Well, I really think that it will be quite a few years away yet (if ever) or the EPA outlaws 2 strokes all together.

Have read all the pros and cons...but no matter what I read I can't warm up to the 4-stroke idea. More complexity, weight, and expense and 4-stroke's will never beat the simplicity & power to weight advantages inherent to the two stoke design.....Having voiced my frustration based on my Motorcycle life, there is one potential "power" related advantage in chainsaw applications for four stroke's....the chainsaw two strokes are severely limited by space & weight for both cooling and tuned exhaust... so that leaves an opening as the four stroke can do with valves what an expansion chamber does on true performance 2-strokes...and cooling? HP makes heat. Not certain a four stroke has an advantage there other than the efficiency of the four stroke cycle may make up for the thru put of air thru the typical 2 stroke motor.

I lived thru the four stroke mandated world that is now off road motorcycles & off road racing...the 450 four stroke's running with the 250 2 stroke's...the 250 four stroke's running with the 125's etc..the added expense to racing and the weight and all that crap. Don't want to see it repeated here.

Lest you see me as afraid of new stuff...four strokes aren't new. And I totally endorse the electronic control systems that have now become common to racing. The Fuel injection & ignition timing curves that you now can control in the typical motorcycle ( and other performance machines) might really be fun to the typical tech hack here to fine tune a modified saw.

I have to say millions have been spent on the racing four strokes in the motorcycle racing world..and with moto cross weight is a priority. SO All the BS and theory aside..if you want a glimpse of the true difference...take a 125 two stroke and a 250 four stroke put them side by side, and your going to get an idea how the four stroke will relate to a comparable two stroke. Number of moving parts, cost of manufacture, cost of maintenance over a race season....weight...etc. Whats the advantage? Four strokes have a wider and more forgiving power band, granted. Biggest advantage is all the race classes were slanted to favor the four strokes disadvantages. Oh yea..because of the class structure changes a bunch of motorcycles had to be sold to compete in these new class structures...drove the cost of racing up in a big way.

Alot of my discussion came from my experience in MX racing. IMO I welcomed 4 strokes. While it did drive the price of racing higher, I think that they are easier to ride fast. The powerband is broader than a comparable 2 stroke. Not as much shifting or fanning the clutch. Need more power? Just turn the throttle and it's there. The new 250f's are making more power than 250 2 strokes did 10yrs ago.

I am absolutely a 2 stroke fan and agree they are lighter and less complicated to maintain. Going with a four stroke vs two, comparing the motorcycles, you need roughly twice the displacement to have comparable power. Just think about being able to say you have a 250cc saw!!!! :msp_smile:

Hell yeah:rockn: