Why not make a 2 piece head and get all the compression you want. Nice by the way.
no ,it will be the same still ,displacement is bore times stroke ,if you moved the big rod pin outwards and raised the jug ,you could increase it ,or a bigger mm piston will increase it example 50 to a 52 mm either longer crank stroke ,or bigger piston is only way to increase size that i know of .What about lowering the jug and cutting squish band? You add displacement if you don't raise the exhaust to match the distance the jug lowered.
I see where squarefile is going with this. I too have wondered if compression can be high enough for the pressure to slow the piston down right before tdc. But then again it takes several pumps for a comp tester to reach full capacity, so there might not ever be enough pressure on one stroke to cause that.
You would actually be decreasing volume of the cylinder anyway, that's why it increases compressionWhat about lowering the jug and cutting squish band? You add displacement if you don't raise the exhaust to match the distance the jug lowered.
Did I confuse displacement with combustion area?no ,it will be the same still ,displacement is bore times stroke ,if you moved the big rod pin outwards and raised the jug ,you could increase it ,or a bigger mm piston will increase it example 50 to a 52 mm either longer crank stroke ,or bigger piston is only way to increase size that i know of .
I should have described what I meant in a better way. Lowering the jug and raising the roof to match. No tightening the squish, no increase of compression. No raising the exhaust. Simply lengthening the combustion area of the stroke. I thought that little bit extra was an increase in displacement.You would actually be decreasing volume of the cylinder anyway, that's why it increases compression
I think what you are describing is timing ?I should have described what I meant in a better way. Lowering the jug and raising the roof to match. No tightening the squish, no increase of compression. No raising the exhaust. Simply lengthening the combustion area of the stroke. I thought that little bit extra was an increase in displacement.
Agreed, when talking about exhaust height it really depends on what you want to do with the saw, limb or cant race or pull a long bar stumping. Same goes for intake height as well but it's just the opposite with where you gain torque or speedI think a clarification needs to be made here between 'compression ratio' and 'corrected compression ratio'... the first is the ((total cylinder displacement + head volume)/head volume).. though it's widely used, it's not very indicative of anything... the latter is the volume from exhaust port closing, and that's what your compression tester will read.
If you do nothing but lower the exhaust port (somehow), you'll get more compression on your gauge, the saw will be torquier, but you probably won't make any more power. If you raise it you'll lose grunt, but gain top end power (in other words, torque at high RPM)
Now if you leave the ports where they are and decrease the head volume, you get a higher reading on your gauge, but the truth of it is you aren't trapping any more air in the cylinder, or helping it breathe better.. Any gains to be had would be from a better, more compete burn. Decreasing squish (or any other method of reducing the surface area to volume ratio such as well designed chambers) are good for that, but I think the number on a gauge isn't all it's cracked up to be. It's not the be all and end all of making power.
....but I think the number on a gauge isn't all it's cracked up to be. It's not the be all and end all of making power.
There can be no increase in a motors displacement unless the stroke is lengthened or bore diameter increased.I should have described what I meant in a better way. Lowering the jug and raising the roof to match. No tightening the squish, no increase of compression. No raising the exhaust. Simply lengthening the combustion area of the stroke. I thought that little bit extra was an increase in displacement.
I think a clarification needs to be made here between 'compression ratio' and 'corrected compression ratio'... the first is the ((total cylinder displacement + head volume)/head volume).. though it's widely used, it's not very indicative of anything... the latter is the volume from exhaust port closing, and that's what your compression tester will read.
If you do nothing but lower the exhaust port (somehow), you'll get more compression on your gauge, the saw will be torquier, but you probably won't make any more power. If you raise it you'll lose grunt, but gain top end power (in other words, torque at high RPM)
Now if you leave the ports where they are and decrease the head volume, you get a higher reading on your gauge, but the truth of it is you aren't trapping any more air in the cylinder, or helping it breathe better.. Any gains to be had would be from a better, more compete burn. Decreasing squish (or any other method of reducing the surface area to volume ratio such as well designed chambers) are good for that, but I think the number on a gauge isn't all it's cracked up to be. It's not the be all and end all of making power.
Agreed, when talking about exhaust height it really depends on what you want to do with the saw, limb or cant race or pull a long bar stumping. Same goes for intake height as well but it's just the opposite with where you gain torque or speed
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