(BackgroundArt] The mixture which is more air than stoichiometry is lean mixture. and the engine which has lean mixture combustion is so called lean burn engine. It is one of the main requirements for lean combustion that rich fuel is stratified around spark plug on ignition time. And fuel stratification is enabled by swirl flow. So the method to generate swirl flow is our main concern. In the beginning of engine start, rich mixture is supplied to an engine in order to prevent misfire by less fuel evaporation with low temperature of engine while lots of unburned HC (Hydrocarbon) is emitted by rich mixture. As low conversion efficiency of catalyst at low temperature most of unburned HC at this stage is emitted without purification process. It is very significant to reduce unburned HC to meet the future vehicle emission regulation. The mechanism of swirl generation is very influential to fuel economy, emission and engine performance. So lots of devices were applied to induce swirl flow. MTV (Manifold Throttle Valve [Figure S] is able to block the air flow to one port and air comes into cylinder the other port and swirl is generated. WT (Variable Valve Train) also can activate one valve and deactivate the other valve and make swirl flow. In case of MTV system, there is flow friction at full load engine operation. And VVT has very complicate structure as the cost is raised.

[Disclosure of Invention) This invention is swirl generation intake system with individual air passage for each port in one cylinder. The core concept of this invention is that surge tank is consisted with two rooms (twin room surge tank). One room is connected to one side of port and the other room is connected to the <BR> <BR> other side of port of cylinders ( [Figure 11). And only one room is connected with idle speed actuator lFigure 2]. A throttle body which is in front of surge tank is able to control air flow rate of each rooms of a twin room surge tank at a same time. As the surge tank is divided with two rooms across the central axis of a throttle body, a half of throttle blade which is on a throttle body axis can cover one room and the other half of blade cover the other room ( [Figure 2], [Figure 3], [Figure 4]). And the throttle<BR> body has R ( [Figure 2]) in the inner part of the throttle body.<BR> <BR> <P>[Brief Description of Drawings] [Figure 1] An Engine Intake System of This Invention.

[Figure 2] The throttle position at start or idle operation [Figure 3] The throttle position at part load.

[Figure 4] The throttle position at full load.

[Figure 5] An intake system with MTV (Manifold Throttle Valve) <BR> <BR> X Designations of [Figure 1]<BR> (1) Throttle Body (2) Central axis-Throttle Body 3) Idle Speed Actuator (D Room 1-Surge Tank (5) Room 2-Surge Tank 6 A partition C) Intake manifold 1-Cyl. #1, Intake manifold 2-Cyl. #1 [Modes for Carrying Out the Invention] In the beginning of engine start, the swirl flow in combustion chamber is generated by the air which is supplied to a cylinder through an idle speed actuator connected with only one room of surge tank ( [Figure 2]). Air flow rate is depended on the gap between throttle body inner wall and a throttle blade. As the throttle axis is rotated, one room of a surge tank is open immediately on the other hand the other room is closed within a certain <BR> angle ( [Figure 3]) by the R ( F igure 2]) which is in throttle body inner part. In full load, throttle blade is fully open as like (lFigure 4]).

[Industrial Applicability] As it is enabled lean operation by strong swirl flow in the beginning of engine start or part load operation, HC reduction and increasement of fuel efficiency is expected. There is no additional flow restriction compare to non swirl engine and no reduction of full load performance. It has simple structure and the operation mechanism is simpler than present system that cost reduction is expected.