4 stroke chainsaw

[HillyJohn]

Maximum power rpm is only part of this tale, the two Makita engines have identical bore and stroke, 2 stroke makes maximum power at 9,500rpm, 4 stroke 7,500. The 4 stroke power output is only 50hp per 1000cc, pretty pedestrian for a petrol engine. I think limitation might be having the valves running in the same line as the cylinder, so restricting gas flow. This is a consequence of having the cylinder head and bore in one casting, which avoids the weight and sealing problems of a head gasket, but forces a bathtub shaped combustion chamber.

[spudulike]

The biggest drawback is that the Four-Stroke sounded like a super wet fart and not like an 80s Pro Am bike race.

[devon TWiG]

2 stroke engines are much more powerful  for the same cc as 4 stroke , they fire every 2 strokes ,have less moving parts , they are often considered higher revving as you hear more combustion strokes , many modern 4 stroke motorcycle engines rev higher .  15-16000 is not uncommon  , there are now very few 2 stroke engines due to emissions .... 

[gobbypunk]

At the Est I look after we have a Honda 4stroke strimmer and its over 20yrs old and we only kinda look after it and that revs real well hardly uses any oil and is totally the best strimmer I have ever used for sure ,so I spose they could use a similar set up in a saw I wonder why Honda didnt but hey if it aint broke why try and fix it

[pleasant]

Like I stated earlier, the honda lump has a low rpm compared to an equivalent 2 stroke. So no good in a chainsaw enviromnent. The gearing in the brush cutter head allows for an increased rpm of the nylon line head to cut efficiently...if it were direct drive it simply wouldn't. In a chainsaw application. It would be a direct drive and therefore too slow to cut efficiently. The orientation of the honda and stihl 4 mix engines lend themselves to be used in an application that requires a different clutch layout than a chainsaw, so to develop a design for chainsaw application that would still have too low rpms, would be a waste of resources and money.

[Fatboy2017]

If you google Senix 4 stroke chainsaw forums, you find a lot of interesting info 

[Macpherson]

RCV engines, and apologies for the derail

 

I'll put this up again because it's interesting, these engines originally for model aircraft can burn any fuel and so efficiently that they more than pass all emissions tests without needing any jiggery pokery.

 

I've been following, or trying to follow any progress in this for a number of years and at one point they were looking for a business partner to build garden machinery including chainsaws of which they already had working prototypes with a very high power to weight ratio, but it would seem unfortunately, as I'd come to believe and my latest search today confirms, they have mainly been side tracked by the military and power the latest drones.

 

Technology like this and other very similar designs goes back a very long way to the inception of IC engines but back in the day there simply wasn't the materials science or precision engineering to allow reliability and low emissions, so the poppet valve prevailed...

 

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[lurch_917]

to me it doesn't give you enough torque and you need reves in a saw . what i like is the way he says that its a bit slow then says maybe it would be better with a shorter bar and bigger teeth . 

[doobin]

18 minutes ago, lurch_917 said:

to me it doesn't give you enough torque and you need reves in a saw . what i like is the way he says that its a bit slow then says maybe it would be better with a shorter bar and bigger teeth . 

What use are bigger cutters? That’s making extra work for the sake of it. 

[lurch_917]

29 minutes ago, doobin said:

What use are bigger cutters? That’s making extra work for the sake of it. 

i know just watch the clip he even says he dosn't like the rewind starter thing other than all of this its a good review at the end ... i meen the end is the best part of it .