There is something very interesting in engine design these days...
When we hear the word "swirl" we often just pass it off as fluid dynamics mumbo jumbo.... But it has big implications on the design of the intake runner and the inlet valve.
Remember in the naturally aspirated engines days where you wanted as steep as an angle as you can get for runner to increase flow to maximum? The valves were steeply angled and the runner amgle was so outragous you could almost look down into the cylinder!! This makes sense for high flow.. And provides good mixing if you are using port injection.. If you are using direct injection though you will have a problem!! You see the more vertical the inlet port angle the air flow comes down on both sides of the valve and it makes an evloping shape of two swirls that run down the cylinder walls and curl back and crash into each other. Dieing way too early before the injection point. Mixing is haphazard and low down in the cylinder too. Enter the swirl style intake port.. It is counter intuitive to the high angle port... Ultimate air flow is sacrificed for a proper formed single swirl that occurs on one side of the cylinder wall. The swirl propogates longer because there is no other swirl to crash into. The port is more horizontal and the valve angle is made so that the valve acts as a ramp to trip the air stream into a swirl. The air almost only spills over on one side of the valve head.
So because the air is ostly spilling on one side you have to make the valve bigger to make up for the reduced flow path.
So yeah designing for swirl makes a totally different intake runner shape. A totally different look and almost against everything we have seen from the naturally aspirated days.
It makes me wonder how those NA engines would be with dual injection and optimized swirl design?
Honda of course has this design down pat. Because they use it in their road cars. Toyota utilizes it as well. Actually Toyota is probably the leader in overall combustion design i have heard. But anyway.. Imagine how these swirl patterns affect the TJI? So many little nuances...