Abstract: An engine air intake structure includes a partition plate and a valve. The plate partitions an air intake passage communicating with an intake port into first and second paths. The valve is disposed in the passage and secured to the shaft. A first path opening is changed variable by the valve. The structure also includes an opposing surface, a stepped surface, an extending surface and a measurement groove. The opposing surface is an inner wall surface of the passage and opposes an end away from the shaft when the opening becomes minimal. The stepped surface is located on the intake port side of the end of the valve at the minimal opening and stands erect from the opposing surface. The extending surface extends from the stepped surface toward the intake port. The measurement groove is formed in the extending surface and extends from the stepped surface toward the intake port.

Abstract: An engine air intake structure includes a partition plate and a valve. The plate partitions an air intake passage communicating with an intake port into first and second paths. The valve is disposed in the passage and secured to the shaft. A first path opening is changed variable by the valve. The structure also includes an opposing surface, a stepped surface, an extending surface and a measurement groove. The opposing surface is an inner wall surface of the passage and opposes an end away from the shaft when the opening becomes minimal. The stepped surface is located on the intake port side of the end of the valve at the minimal opening and stands erect from the opposing surface. The extending surface extends from the stepped surface toward the intake port. The measurement groove is formed in the extending surface and extends from the stepped surface toward the intake port.