Abstract: A knock control system for an internal combustion engine having a plurality of cylinders. Operation of the engine is switchable between a partial-cylinder operation for operating some of the cylinders and an all-cylinder operation for operating all of the cylinders. A determination threshold for determining knocking is set according to an output signal from the knock sensor. A level of the output signal from the knock sensor is compared with the determination threshold, and occurrence of knocking is determined according to a result of the comparison. The determination threshold used during the partial-cylinder operation is set to a value less than a value of the determination threshold used during the all-cylinder operation.

Abstract: In an intake port structure in an internal combustion engine, an edge portion is formed on a lower surface of an intake port at a location immediately upstream of an intake bore 7. The angle .theta. formed by the center line L of the intake port with respect to a deck surface is set smaller than the angle .theta..sub. formed by an exhaust valve seat provided in a pent roof of a combustion chamber with respect to the deck surface. Further, if the height of an apex of the pent roof of the combustion chamber is represented by H.sub.0, and an intersection between an extension of the center line L of the intake port 5 and a straight vertical line L.sub.0 passing through the apex of the pent roof of the combustion chamber to intersect the deck surface at a right angle is represented by P, the height H of the intersection P is set so that a relation, H.sub.0 >H>2H.sub.0 /3 is satisfied.

Abstract: 1,4-Dihydropyridine compound having the general formula: ##STR1## wherein R and R' are independently a methyl, ethyl, or propyl group. This compound has a remarkable liver protective action and a low toxicity.