Optimizing Combustion Space by Omnipower

[Thighs]

how does bigger bore increase compression? doesnt that make the chamber larger, decreasing compression?

[TheChosenOne]

I think he's assuming that when you bore the cylinder walls, you would also be mating them with oversized pistons. Atleast that is, if you want your motor to run.

Really it's all in the numbers. The piston surface area is increasing, while the actual combustion space is staying the same: that is what I cam up with in my own logic. I could be wrong, so by all means, someone confirm this or throw it out.

[Thighs]

I think he's assuming that when you bore the cylinder walls, you would also be mating them with oversized pistons. Atleast that is, if you want your motor to run.

Really it's all in the numbers. The piston surface area is increasing, while the actual combustion space is staying the same: that is what I cam up with in my own logic. I could be wrong, so by all means, someone confirm this or throw it out.

i see what your saying, but unless you increase the fuel/air intake volume along with your bore, you will be putting the same fuel volume into a larger space, lowering the compression. adding a high-compression piston to a bored cylinder would just bring your displacement back to normal by reducing the already-enlarged chamber. i may be wrong but its making sense in my head.

[TheChosenOne]

i see what your saying, but unless you increase the fuel/air intake volume along with your bore, you will be putting the same fuel volume into a larger space, lowering the compression. adding a high-compression piston to a bored cylinder would just bring your displacement back to normal by reducing the already-enlarged chamber. i may be wrong but its making sense in my head.

I see what your saying, but the stroke isn't being changed, so the space is only bigger when the air and fuel are taken into the cylinder. When it is compressed, I have a feeling the cobustion chamber isn't larger at all. But like I said... this is just my own logical theory.

[all-mota]

I see what your saying, but the stroke isn't being changed, so the space is only bigger when the air and fuel are taken into the cylinder. When it is compressed, I have a feeling the cobustion chamber isn't larger at all. But like I said... this is just my own logical theory.

you are correct the combustion chamber stays the same the whole time only the bore size and stroke changes the compression unless it's opened up on the head to match the bore size.