4 strokes on trimmers, saw?

[Tony Snyder]

Putting 4 strokes on trimmers or saws can only result in greater cost and greater weight.

The Stihl ad that make it look like a great breakthrough reminds me of the TV stokbrokers ad where the boss says, "O.K.,Lets put some lipstick on this pig".

Then they ad insult to injury by trying to stick it to us by selling us premix fuel.

 

[tony marks]

i gotta agree. the only one ive seen was the ryobi trimmer,which i definitly didnt like.

 

[slowtorque1]

Just my opinion

but there is no telling where this EPA mandating will end. Yes, we have come a long way in the past thirty or so years, but it seems to me what lies ahead is a bloated organization eagerly chasing increasingly more innocuous sources of pollution toward the primary end of justifying their own existence, if not expansion. It will end when the people have had more than enough of this folishness, but this unfortunately depends on an educated poplace. These are generally not the same folks who read Al Gore's book and watch the nightly news or CNN. I wish someone could tell me I am wrong about this.

 

[NevadaWalrus]

I don't believe Stihl has any current plans with this technology being used in saws but somewhere down the road its sure to get there. As for the trimmer, yeah I think it will cost a few bucks more but weight wise its the same as the equal power 2 cycle.

Its oiling system uses 2 cycle mix so the weight of a 4 cycle reservoir crankcase is not added as in other 4 cycles. Also they have a fuel tank about half the size so gassed and ready to go the saved fuel weight off-sets the additional cylinder head and valve weight. The engine runs on about half the fuel use as a 2 cycle so run time remains the same.

So they weigh the same and long term fuel savings will off-set the slightly higher purchase price. With full line extension they both rev the same and the 4 has better torque which makes it better in heavy trimming. The engine is also about the smoothest running you'll find.

For someone using this power output range trimmer its really a win win situation.

 

[bwalker]

Walrus the fact remains that the four stroke hybrid is more complex/expensive and with the pre mix sytem will not last any longer than a two stroke. More parts equal more things to fail. Add to that the fact that if stihl put a equal amount of engineering resources into a simular two stroke it would blow the four banger away in power, weight, and cost.

 

[Newfie]

I wish someone could tell me I am wrong about this.

Probably. With Bushes recent moves on the clean air act and cuts in federal raises, I think you will see the EPA budget slashed and a lot of this BS will go on hold until we have another government controlled by tax spending liberals.

 

[JimL]

Originally posted by bwalker
Walrus the fact remains that the four stroke hybrid is more complex/expensive and with the pre mix sytem will not last any longer than a two stroke. More parts equal more things to fail. Add to that the fact that if stihl put a equal amount of engineering resources into a simular two stroke it would blow the four banger away in power, weight, and cost.

Weight? The new stihl 4 stroke weighs like 4oz more than a FS85.
3 times the fuel economy, less vibration, quieter, and less fumes.
Not sure on cost.

Power I have used the new stihl 4 stroke. Used my FS85 too.
Wheres the powerband on a 2stroke? Wide open for the most part. Where do the landscapers like to run their trimmers? Half throttle. Where is the powerband on the 4stroke? Pretty much from idle too full bore......

Sounds better to me.
The parts to fail might be more. But theres alot of 4cycle engines out there

 

[stihltech]

4 stroke

I saw them run at the factory and talked to the test guys. They are finding no problems with wear and breakage, they even said that the valve train will need minimal maintenance. It is a very simple design, with a minimum of moving parts.
I think what is here will stay, but what is there that we can't live with so far? Not any tougher to work on or use. Way better than those early 70's motors with 3 miles of vacuum hose.
I still believe the shops that progress with the technology will make it. I like old stuff too, but I will never revert back to a carburetor after having fuel injection.

 

[eyolf]

The fears of those who do not want to see a 4-stroke trimmer, or, (gasp!) chain saw, are duly noted. Yes, there are problems to be overcome, but one of the biggest ones is overcome by using the fuel mix to lube the bottom end.

Race-engine nutz will admit that a certain amount of power is lost in any engine turning more than idle speed in dragging the oil around with the rotating assy. Dig into a racing engine to look at things like deep sump pans, windage trays, crank wipers, or on some highly developed engines, dry-sumping, for a clue on power loss not experienced with these new little 4-cycles.

I believe that further technological advances will allow us to eventually have our 4-stroke trimmers and chain saws, and we will have enough power, as well. Personally, I'd like to see a 4-stroke saw at about 120cc, weight around 23#, engine details:
4-valve head, 9:1 comp ratio; dual 10mm spark plugs; If Echo and the RC folks can have electronic advance ignitions, so can we. This engine, stock, would produce close to 85 bhp/liter if well engineered, and be competitive with Stihl 090 (not that out of date!)

Now, for giggles, let's increase valve lift 10%, duration to around 290 deg w/ generous overlap, and increase compression to 10:1. Now we're around 100 hp/liter. Or say 13.5:1, 312 degrees, even more overlap, and burn methanol for 130 bhp liter. We don't have the overall peak HP of a full-house KD 084 or 3120, but it doesn't "fall off the pipe" at 8500, either.

And the sound...Ya gotta love the bark of a full-house four-stroke!

 

[NevadaWalrus]

Eyolf, if for no other reason, your last line hits it for me. There's something about the whinny noise of a 2 cycle that is just plain annoying.

 

[Crofter]

It is nice to have the power to weight ratio that two cycles have but the fuel efficiency sure sucks. Just hard to keep that fuel from rushing out with the exhaust if we want decent performance. The nature of the beast I guess.

Frank

 

[bwalker]

Jiml, Notice I made my comment on the condition that the twos troke recieve equal engineering dollars. Also keep in mind that a four stroke designed to rev like a twp stroke will also have quit a narrow power curve.

There's something about the whinny noise of a 2 cycle that is just plain annoying

Thats music to my ears.

BTW Tech exists to clean small two strokes up. Piagio in italy has a 50cc scooter motor that meets and exceeds all current and future euro standards. It also delivers higher performance, better fuel mileage, less noise, is cheaper, and is lighter than a comparable four stroke model.

 

[NevadaWalrus]

I was pretty sure someone would dis-agree with my noise comment. Gotta remember, I grew up in a time when NASCAR and street rods were running big blocks and anything that doesn't have that low rumble bugs me.

Apparently 2 cycles can be cleaned up. Stihl's decision to go with 2cycle lubrication in their 4 cycle engine was because its not the oil mix that polutes like I and many others used to think. The polution comes from the waste of fuel crossing through and out the exhuast, which as you explained is why you don't concern yourself with improving crankcase flow as there is enough already.

The question is can clean up of emissions be done without in itself increasing the bulk or weight of the engine. This Italion engine, do they have externanal devices bulking it up to make those gains? A scooter application wouldn't be bothered as much in added bulk as would be a hand held piece of power equipment.

As for reving up a 4 cycle to 2 cycle standards, it doesn't need to be done. The inherent torque advantage of a 4 cycle means it can be geared up to gain chain speed to match a 15,000 rpm 2 cycle and still run with its wider power band at the 7500-8000 maximum rpm range that seems to be the point where 4's give up their wide band. F-1 engines rev to 16,000 plus but they can't get out of their own way at 8000. But a 8000 max 4 would still have good low torque, the drive sprocket could be upped to a 10 tooth to match chain speed of a 2 and just might work out OK.

None of the wasted blow through fuel of a 2 plus the far better fuel consumption of a 4, yeah, it may be possible to clean up a 2 but I think under equal dollars spent in R&D that more can be done with a 4.

 

[Tony Snyder]

Again, doeas anyone know if EPA had engine size breaks for chainsaws? And, at what sizes?

 

[seesaw]

4-stroke Honda

I've only had experience w/the Honda. I'ts a true 4 (no hybrid). At this time, it comes in the 25cc and 31cc varieties. Their new 25cc trimmer is 1.5lbs. lighter than their previous 22cc making weight a non-issue. The Honda M4 engine is much more fuel efficient, super quiet, no smoke, plenty of torque same weight and runs on straight gas. I was sold the first time I ran one. The Honda man claims the trimmer will pay for itself in just one season (savings on fuel and 2-cycle oil). So even if the initial investment is a bit more, you will not only make up for that difference but, pay for itself in fuel savings! Uses only 3oz. of engine oil for lube. Honda is putting this engine on everything it can think of. Trimmers, tillers, water pumps, concrete screeds... Honda already has a 50cc 4stroke that pushes 7,000rpm. Seems to be the wave of the future.
Seems to me a, 4-stroke should have a greater life expectancy than a 2-cycle too. I'm not sure on this point but, you wrenches would know better.

 

[Crofter]

Ring and piston life will be better because they don't have to hop - skip and jump over the open ports on the journey up and down. Not sure about valve train dependability though.

Frank

 

[NevadaWalrus]

Regarding longevity of the tiny 4's with a 4 cycle crankcase. I doubt they will last as long as a 2 cycle. These engines ike Honda and Ryobi only hold 3 or 4 ounces and based on the generally very poor maintenance most people provide their equipment, both consumers and commercial, its going to be tough to see equal or better life out of the little 4's. Stihl's version using 2 cycle for lubing is taking advantage of both worlds.

 

[Dieseldog]

Before you all get excited on this 4-stroke trimmer thing I think you should take a look at the new Shindawa 4-stroke just released recently! I had a demo on it and its pretty cool. It still uses a 2-stroke fuel mix for lube and ease yet meets stricter emissions regulations,is resonably light and powerful and has a quieter exhaust tone.Check it out on their web site. Thanks Dieseldog!

 

[bwalker]

Nevada, The piagio engine I spoke of is the same size as a regular two stroke with the exception of a small injector fitted to the head. As far as your comment about the rpkm of a 4 stroke trimmer. Remeber that these trimmers are direct drive so high rpm is needed. Also keep in mind these 2/4 hybrid are not four strokes. They actually use read vlaves and use the downward motion of the piston to raise the pressure of the intake port above atmospheric.

 

[NevadaWalrus]

Well, not really. The reed valve is more to control flow of fuel mix through the crankcase for oiling, its a very small charge compared to a normal 2 cycle. Most of the charge entering the cylinder does so in a normal 4 cycle manner.

The rpm thing I was talking about was "IF" the 4 should ever be fitted to a chain saw. As is with the trimmer, with line fully extended the 4 revs to the identical rpm as the 2 cycle. And its really not a direct drive, it does have a gear head down by the cutter head which in theory could be re-geared. In fact, Hoffco had one years ago that they geared the cutterhead to run slower. The unit had a 21cc Robin that really screamed but suffered a bit under heavy loads, thus the gear down. Commercial guys loved the thing.