4 stroke chainsaw

[scbk]

Seems a funny idea to me 

 

 

 

[Mick Dempsey]

The  4-mix pole pruner and hedge cutter are really good.

I’ve often wondered why they don’t put one of them in a saw. 

Edited January 1, 2023 by Mick Dempsey

[pleasant]

19 minutes ago, Mick Dempsey said:

The  4-mix pole pruner and hedge cutter are really good.

I’ve often wondered why they don’t put one of them in a saw. 

The main reason that there are no 4-MIX engines in a chainsaw is that they do not turn enough RPM's. Most 4-MIX engines run at ~7,000 RPM's while chainsaws run at 11,000+ This is especially important on a small chainsaw when limbing.

[AJStrees]

Interesting concept. Apart from not having to use a 2 stroke mix, I wonder what/if the benefits would be. 👍

[trigger_andy]

15 minutes ago, AJStrees said:

Interesting concept. Apart from not having to use a 2 stroke mix, I wonder what/if the benefits would be. 👍

Torque?

[Mick Dempsey]

27 minutes ago, pleasant said:

The main reason that there are no 4-MIX engines in a chainsaw is that they do not turn enough RPM's. Most 4-MIX engines run at ~7,000 RPM's while chainsaws run at 11,000+ This is especially important on a small chainsaw when limbing.

I’ll take your word for it.

My pôle pruner seems to get through the wood pretty quick mind.

[HillyJohn]

4 stroke could have more torque, but problem in real life is best shown by Makita. Their 42cc 4 stoke motor produces 2hp, and is 5.5KG for bare motor, while an EA4300 chainsaw is also 42cc, 3hp, 4.9kg for whole machine. To their credit, Dolmar/Makita tried hard to get a four stroke chainsaw to work, but never sorted it.

[pleasant]

18 minutes ago, Mick Dempsey said:

I’ll take your word for it.

My pôle pruner seems to get through the wood pretty quick mind.

A short 10 or 12 inch bar with a lightweight chain going through small diameter pruning wood is a totally different performance requirement than say, sticking a 4 mix lump at 7000rpm in an ms261 with an 18" bar felling a reasonable diameter trunk. Wouldn't pull the skin off a rice pudding.

[Dan Maynard]

I think hp per kg is the fundamental. More RPM means more power in general, and in this case the difference is enough to overturn the better efficiency of the 4 mix.

 

You could run a saw at 7000rpm with a bigger sprocket, if you had the hp at that engine speed.

[pleasant]

3 minutes ago, Dan Maynard said:

I think hp per kg is the fundamental. More RPM means more power in general, and in this case the difference is enough to overturn the better efficiency of the 4 mix.

 

You could run a saw at 7000rpm with a bigger sprocket, if you had the hp at that engine speed.

True. My old stihl 090 max rpm is only 7 to 8k. But you have a 137cc lump with a LOT of torque. Won't cut fast, but not designed for that. Make for huge redwoods for example and will slowly chop its way through it with no snagging or bogging.