408 stroker hp vs 6.0 LQ9 hp
03-10-2014, 08:38 PM
#21
Are you familiar with Bernoulli? The size and shape of the port have a major influence on the pressure curve in the cylinder throughout the cycle, both intake and exhaust ports.
03-10-2014, 08:51 PM
#22
That makes sense, but in your example you say tripling the amount you pull on the syringe...which I can see. However here we're not talking about tripling the stroke...we're only talking about just barely increasing the stroke by 10%. In that same example, an extra 10% of pull on the syringe in the same amount of time will not be a large increase in resistance.
It's not just the stroke, this is what I'm getting at. It's the displacement. Let's try some math, using the formula posted earlier:
364ci = 45.5ci/cylinder
408ci = 51ci/cylinder
Let's keep the MCSA constant at 2.55 square inches, which would be typical of a ported head with a 2" valve.
2.55 x 88,200 / 45.5 = Peak Torque @ 4943RPM
2.55 x 88,200 / 51 = Peak Torque @ 4410RPM
So that's a 533RPM drop because we "barely" increased the stroke. Imagine if the bore was larger, like 4.125" or 4.155" and the gain in displacement was larger. Now calculate the difference in power 500RPM can be with the same torque. It's kind of a big deal.
