What makes more power

[Dub11]

What would make more power stroking or big boar? This is just a hypothetical question if all conditions were right would going +2mm stroke give more power than +2mm boar?

 

[Red97]

Yes.

 

[Red97]

Bigger bore will allow wider ports (more flow potential)

Longer stroke will likely have more case compression. Narrower ports, but could be taller to get close to the same port area.

Max power output could be the same both ways. No real answer to the question.

I am currently liking small bore long stroke.

 

[Wilhelm]

What do You consider to be "power", kW/HP or Nm , or both?

Not an scientifically reply, but rather a guess!

Bore diameter increase for more power (kW / HP) , longer stroke for more torque (Nm)?!

Granted, a larger bore diameter will also result in torque increase, same as a longer stroke will result in power increase - but i THINK there is an offset balance.

Any saw family featuring the same PH design with different stroke volumes are a good example, never mind if I mention Dolmar and Solo.

Below specs for the Dolmar PS-6400/PS-7300/PS-7900 saw family , same strokes but different bore's.


And then the Dolmar PS-9010 which features the same bore as the PS-7900 but a 5mm longer stroke (wow, never realized it was that much more!).
In Germany the Dolmar PS-9010 is lovingly being nicknamed "Steamhammer" ( Dampfhammer ) for her utter grunt.


Interestingly the Solo 665/675/681 saw family, which is related to the Dolmar PS-6400/PS-7300/PS-7900 saw family, features identical bore diameters but 1mm longer stroke and both power (kW/HP) and torque (Nm) increased similarly/proportionally.



I GUESS increasing both bore and stroke proportionally will make the most power AND torque depending on the PH used - it is a trade off balance act.

Interesting topic, had to look up stuff myself!

DISCLAIMER:
This entire post is just a guestimation with no scientifically proven facts backing it up!

 

[Dub11]

Thanks @Wilhelm great info !!! What Iam more or less trying to find is the most saw friendly power gain for a work saw. So yes a torque increase would be what I'm after.

 

[Red97]

The port timing/ size, shape is different in all on the dolmar jugs. I believe that is the difference in power output.

You could add 2mm bore and stroke to any saw but if the port timing is off it will run worse than the smaller cc stock saw.

 

[Dub11]

The port timing/ size, shape is different in all on the dolmar jugs. I believe that is the difference in power output.

You could add 2mm bore and stroke to any saw but if the port timing is off it will run worse than the smaller cc stock saw.

Well thats what Iam trying to find with the ideal conditions part. Could the longer stroke give a higher compression and maybe move the timing numbers in a more favorable direction?

 

[mdavlee]

Well thats what Iam trying to find with the ideal conditions part. Could the longer stroke give a higher compression and maybe move the timing numbers in a more favorable direction?

Longer stroke raises piston speed at the same rpm. It does change how you can port for power.