Small Intake Ports

[DarkFalcon]

I really can't answer that question, as i doubt can anyone.  I'm no fluid dynamicist, just a head guy.
What i can tell you is it will flow a touch more peak lift on flowbench.  And on dyno they always show more power.  And on track they go better both from rider feedback, trap speeds and datalogging analysis.
I'm guessing the reason is as you straighten the port you are causing less turbulence at high engine speed, so pumping losses are decreased and fuel won't drop out of suspension without the sudden area change of the bowl.  The old theories on bowls i always read was "it gives a pool of air behind the valve".  Well yes, maybe when its a 1960's design motor revving to 6krpm, but when you are pushing 11-17k on the modern bikes i just don't feel this applies.

The very small venturi throat or nozzle area plus tuning of the port upstream of the venturi provides an exceptionally high flow velocity through the nozzle. The long diffuser downstream of the venturi efficiently converts the high-speed flow into elevated gas pressure. The large lower head volume holds the pressurized intake air for blow down through the intake valve(s) into the working cylinder. The large cross section area of the head also enables an exceptionally high port flow coefficient Cd to be attained. The venturi is located far upstream to provide a large head volume plus port length needed for providing a high efficiency diffuser. Placing the venture far upstream permits the venturi nozzle area to be exceptionally small and in turn the ram velocity exceptionally high. The combination of exceptionally high ram velocity, high efficiency diffusion, large head volume, and high flow coefficient Cd values made possible by the large head cross section area provides an exceptionally high volumetric efficiency and in turn exceptionally high engine torque levels. Torque is significantly improved throughout the engine's full operating speed range in most embodiments of the present invention.

The above was taken from a patent and explains the function of the bowl in the context of contemporary cylinder head design. It was not posted to suggest a design but rather to define the function of the diffuser. If I had to geuss, there is some type of  tradeoff between pressure recovery versus raw velocity.

[gazza414]

DF, in your mind what influence does opening up the throat/valve dia ratio ie edging towards 90% have wrt the above?

[enginetuna]

Torque drops over 90%.

On filling the bowl, i get the same results of the yoshimura graph i posted.  Every single time.  Just more peak power and better spread.  Have another look at that graph if you are not sure what i mean.

Gazza, see the port picture of the gsxr on the speedtalk thread, that also will answer your question on the ssr and bowl shape.  What you see there is what every world and national gsxr superbike head i've seen looks like.  Really, its no secret what they are showing there, its been common practice to do that shape for like 10 years now, maybe more.

Look guys, i've given you plenty of information here and a link that will answer a whole heap of your questions.  I'm not going to sit here and draw diagrams and show photos of my stuff because its cost me a fortune to know what i know and you wouldn't learn if i just gave it all away.  Same goes for WRTH, he's not going to give you all his information either.  Theres more than enough data and ideas here to go away and experiment.  Just looking at those F1 port pictures should answer all questions on bowl areas, they are after peak rpm power and nothing else, so all you bonneville and drag guys have a close look.

[gazza414]

thx ET, the link needs one to register..I'll do that , as it sounds worthwhile.