rh10 head

A 32mm port is 114% more cross sectional area of than of a 30mm port. (32^2/30^2)

In theory, you can use that increased area as it will give identical velocities; only 620 rpm higher and with more air. In laymans terms - this moves the power/torque band up.

Basics, is to move same volume of air though a small or larger tube, the smaller one has to flow faster, which is the mystery part to narrow down w/o restricting total flow volume. On the other hand is the hydrid situation of starting rather big to funnel down trading sluggish air pressure for more kinetic energy speed up, that mixes, stirs and rams mixture in. Jim's finding the special seat contours is about as cutting edge technology as it gets in power making secrets. The best there is on this first does trial error by gosh and by hand on a specific engine head type and valves/ports then measures for CNC data to reproduce tooling to do em all like that. Flow can get so high it gets interference to increase much more d/t sonic shock pressure fronts called the mach number. Ideal is ~.7 Mach, if can even approach that unboosted, if so then it becomes worth while to open up bigger to flow more power in/out, for max top end power at least.

This is cool video on the flow dynamics in heads and bench testers metering.
http://www.youtube.com/watch?v=oUd4WxjoHKY


Here's what our miracle head workers go through for us
http://www.youtube.com/watch?v=ycrm5We06Mg

Valve seat hi tech today
http://www.youtube.com/watch?v=Z3JCioHMcIw

Oh yeah air flow past a curve surface tends to make it adhere and back flow while crossing over a sharp edge lets it separate more to jet on by.

Dances with Shrapnel said:

A 32mm port is 114% more cross sectional area of than of a 30mm port. (32^2/30^2)

In theory, you can use that increased area as it will give identical velocities; only 620 rpm higher and with more air. In laymans terms - this moves the power/torque band up.

Click to expand...

Do you mean 14% more cross sectional area?

Glen

Dances with Shrapnel said:

A 32mm port is 114% more cross sectional area of than of a 30mm port. (32^2/30^2)

In theory, you can use that increased area as it will give identical velocities; only 620 rpm higher and with more air. In laymans terms - this moves the power/torque band up.

Click to expand...

It would if the valve were big enough. With a 1.5 inch valve and a poor bowl to port design then you will never be able to reach good velocity in a 32MM port. Even if you had 1 liter pistons and 10,000 rpm.

If the 32mm port is shaped very good and still using a 1.5 inch valve you can just reach good velocity at the upper reaches of the rpm limit. Jim

Can't wait to fire this badboy up! Thanx again Matt & Jim.

worntorn said:

Dances with Shrapnel said:

A 32mm port is 114% more cross sectional area of than of a 30mm port. (32^2/30^2)

In theory, you can use that increased area as it will give identical velocities; only 620 rpm higher and with more air. In laymans terms - this moves the power/torque band up.

Click to expand...

Do you mean 14% more cross sectional area?

Glen

Click to expand...

Yes, that is what I mean - 14% greater cross sectional area.

As Jim alludes to, (port manifold dia.)/(port throat dia.) ratio is critical and controls the amplitude of the pressure wave in the system. The greater amplitude, the better the opportunity for improved performance.