The outer intake ports are indeed canted inwards much like a busa. But thats where the similarities end.
The short turn radius of the intake port is obviously not intended to flow a ton of air. Instead they are shooting the highest velocity center of the column of air at the back of the valve so as to shoot it threw the "window". They did a great job of fixing the chambers from the zx12r chambers. They lowered the eyebrow by widening the chamber instead of laying the eyebrow back like I had to do with the zx12r head and busa head. They increased the volume bigtime and increased the radius of the short turn.
It appears that they are intensionally inducing flow separation from the short turn. Its a sharp edge made to induce this.
I'll bet at low lift the flow reattaches nicely and starts to flow the full 360 of the valve again. Perfect for final stuffing of the cylinder as the valve closes.
It should be very audibly obvious on the flow bench exactly when this separation and reattachment happens. Typically after separation reattachment doesn't happen until the valve is .050" or so more closed then when the separation occurred.
Its really a velocity induced thing and carefully controlling the velocity will controll when the separation and reattachment happens.
I'm not sure but I would think it would be desireable to get the reattachment to happen earlier.
So this would mean that the low lift numbers are VERY important and valve seat timings are critical.
This port could be very difficult.
Do you guys have any thoughts on this?
Jim, I don't think I have examined the port as closely as you have or examined it with eyes of your experience. Anyway, I tend to believe the port has its origins in Ducati and has been designed to produce high levels of "tumble" to generate in-cylinder charge motion to reduce combustion cycle time and promote lean burn. This should reduce pumping losses, improve combustion efficiency and keep the EPA happy. The means of doing this is through directing flow over the top half of the valve so the charge rolls over in the cylinder. As you observe:
The short turn radius of the intake port is obviously not intended to flow a ton of air. Instead they are shooting the highest velocity center of the column of air at the back of the valve so as to shoot it threw the "window". The cost or tradeoff of doing this, though, is reduced flow because of directional bias and not taking advantage of the 360* comprising the valve.
In my mind, it is the axis of flow that drives this port.....not a particular sectional area. From the literature, though, port volume adjacent to the valve stem, the inner radius, the blend from the throat to the seat and the region between the seat insert and the valve are all very important in terms of design.
With very little SSR, I would think the 14 port would tolerate higher average and maximum port speeds than the Busa.....and the higher speeds would contribute to tumble kinetic energy. The velocity field at intake closure is more than likely characterized by many vortices which could make intake valve closing relatively more critical, although these eventually dissipate as the piston approaches TDC. It reminds of the port featured in this patent:
http://www.uspto.gov/web/patents/patog/week09/OG/html/1315-4/US07182057-20070227.htmlIf you would, post a picture or further describe the edge you believe has been placed in the port to induce separation. Separately, if the flow does separate and reattaches at low lift I'm having a little difficulty in distinguishing the benefits from the reattached flow from the typical pressure rise stemming from correct wave timing. In other words, if the pressure spike is present it will get stuffed at IVC no matter what side of the valve the flow may be directed at. Benefits at IVO opening may be a different story.
