Hyway MS460 big bore on a 044 opinions please

[MustangMike]

Definitely not in my opinion!


I see it slightly differently. Basically if an engine is not held back it's carburretion or it's ignition, then the only (?) thing holding it back, i.e. preventing it from revving higher, is how effectively it can flow a dense charge into the CC.

For the reasons you pointed out (muffler, transfers, venturi, etc.) the engine will "run out of breath" at a particular ceiling (i.e. 14 or 15k or whatever). However, by increasing the case compression, I believe that we create a supercharging effect, enabling the system to rev somewhat higher than before.

Well that's my take on things

More pressure, but less volume, it is always a balancing act. Perhaps different blow down for different case capacity???

 

[drf256]

Definitely not in my opinion!


I see it slightly differently. Basically if an engine is not held back it's carburretion or it's ignition, then the only (?) thing holding it back, i.e. preventing it from revving higher, is how effectively it can flow a dense charge into the CC.

For the reasons you pointed out (muffler, transfers, venturi, etc.) the engine will "run out of breath" at a particular ceiling (i.e. 14 or 15k or whatever). However, by increasing the case compression, I believe that we create a supercharging effect, enabling the system to rev somewhat higher than before.

Well that's my take on things

How are you "supercharging" it?

Btw, my statements about adding a spacer is WRONG. On cylinder fed transfers, a spacer does nothing for case volume, as the area under the piston stays the same. Not true of case fed transfers, but that's not a Stihl 1128 series.

You can get the same pressure with a larger or smaller case. When you release pressure is what matters.

Tons of variables here. Intake timing, bore and chamber geometry, transfer geometry/size/number/timing all matter.

In this case, we are just dealing with a model we know will rev higher and lose torque with the larger jug on the smaller case.

 

[MattG]

How are you "supercharging" it?

Lol. Please forgive my jargon, there, Al!

When the inlet port closes with the transfers closed, the f/a mixture, is compressed, correct?

Well, when I said supercharged, I just meant that seeing as the higher displaced volume vs case volume, is in a effect here, then, presumably the above behaviour (i.e. the compression) is more pronounced.

 

[MattG]

Btw, my statements about adding a spacer is WRONG. On cylinder fed transfers, a spacer does nothing for case volume, as the area under the piston stays the same. Not true of case fed transfers, but that's not a Stihl 1128 series.

I'll get back to you another time on this one, Al. Thanks, though.