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To improve engine torque and specific fuel consumption in a supermilage vehicle, we experimentally adjusted the valve lift and opening period in rocker arms, testing various follower configurations and adjust screws. Using the follower configuration in a commercially-available rocker arm, we compared 4 different levels of valve lift and opening period in the intake, and 4 different levels in the exhaust, making 16 combinations. Then, utilizing 5 kinds of modified follower configurations of the rocker arms in the intake, and 3 in the exhaust, we also compared 24 combinations (including the commercially-available follower configurations). We tested our experimental supermilage engine under full-load at 2000 to 4500rpm, simulating powering a supermilage vehicle.

Two-stroke engine cylinders have ports to exchange gas. While the engine runs, the piston and its piston rings slide over these ports in the cylinder walls, and the rings may project into the ports. This paper explores this, first, by reporting a simple model of material mechanics that predicts rings might project into ports, and second, our experimental verification. We installed strain gauges on the bottom of the top and second rings, over the intake and exhaust ports, and ran signal wires out of the engine. We then examined the variations of strain while running the engine. Our analysis confirmed how the dimensions and the tension of the rings, and the dimensions of the ports, affect ring projection into ports as static displacements.

To reduce fuel consumption without complicated engine valve systems, we attempted to stop some fuel injectors, while operating both intake and exhaust valves normally, under idling, no-load and lighter load conditions. This study stopped one or two injectors in an in-line four-cylinder gasoline engine, and two or three injectors in an in-line six-cylinder gasoline engine, and then investigated the resulting fuel consumption and variation rates of engine speed. We calculated fuel consumption by measuring fuel injection time and engine speed. Results indicate that, in an in-line four-cylinder gasoline engine, deactivating every other fuel injector, in cylinder firing order, making two deactivated injectors, reduced fuel consumption, compared to the usual condition with all fuel injectors activated, under idling, no-load and lighter load conditions.

In most air-cooled engines, aluminum cylinder blocks are lined with cast iron, which enjoys a higher wear resistance than aluminum. Recently, rather than a turned periphery, an increasing number of cast iron liners have employed as-cast periphery with projections, so the liner better adheres to the aluminum cylinder block, and improves heat transfer. This study attempts to maximize heat transfer while minimizing cylinder weight, by comparing four liners: (1) a cast iron liner with higher projections on its periphery, (2) a cast iron liner with lower projections, (3) a cast iron liner with lower projections, and aluminum-silicon coated on its periphery by thermal spraying, and (4) a high-silicon aluminum alloy liner with aluminum-silicon coated by thermal spraying. These four experimental liners were fitted in a die-cast low-silicon aluminum-alloy cylinder block, to investigate their joint and cooling characteristics.

We aim to maximize the performance of air-cooled engines (such as motorbike engines and small stationary engines) by increasing cylinder cooling and by maintaining uniform temperature around the cylinder circumference. In typical engine designs, air cools the front of the cylinder better than the rear. In an effort to increase cooling at the rear, this research experiments with tapered fins that contract air flow to the cylinder axis between the fins, and with baffle plates mounted between fins symmetrically with respect to a plane through the axis of the cylinder. In a wind tunnel at air velocities between 20 and 60 km/h, we compared cylinders with conventional fins, cylinders with tapered fins, cylinders with baffle plates between conventional fins, and cylinders with baffle plates between tapered fins.

In air-cooled motorbike and stationary engines, waste heat dissipates from the cylinder through the cooling fins to the cooling air. In these engines, the cooling air flow follows the cylinder surface at the front of the cylinder, but separates at the rear, reducing cooling. To increase the distance over which the air flow follows the cylinder surface before it separates from the cylinder, and so to increase cooling at the rear, we experimented with cylinders utilizing contracted flow between fins. These cylinders have fins with different thickness at the front and the rear, so as to contract the air flow around the cylinder. We produced and tested three experimental cylinders with various lengths of contracted fins (tapered fins), in a wind tunnel at air velocities between 20 and 60km/h. We measured the temperature inside the cylinder over time to determine the heat release from the cylinder.

In an air-cooled engine, the cooling air follows the cylinder surface at the front in an air stream. However, it separates from the cylinder at the rear reducing the cooling effect of the air stream on the rear of the cylinder. In order to improve the flow of air to the rear of the cylinder, baffle plates were mounted on the outside of the cylinder or between the fins symmetrically with respect to a plane through the axis of the cylinder. Experimental cylinders with baffle plates at various positions were investigated over a range of air velocities between 20 and 60 km/h in a wind tunnel. The temperature on the fin surfaces was measured to determine the temperature distribution provided to the circumference of the cylinder and the average fin surface heat transfer coefficient. To understand the effects of baffle plates on cylinder cooling, the air flow between the fins was observed with a high-speed video camera by the smoke wire method.

It is important for an air-cooled engine to utilize fins with effective engine cooling and uniform temperature in the cylinder circumference. In order to permit the development of design data, an experimental cylinder was developed having variable fin pitch and number of fin capability. This experimental cylinder was tested in a wind tunnel. Experimental cylinders with five different fin pitches and twelve different numbers of fins were investigated over a range of air velocity between 0 and 60 km/h. The temperature inside the cylinder and on the fin surface was measured to determine the heat release from the cylinder and the fin surface heat transfer coefficient respectively. To understand the operation of cooling fins for each fin pitch, number of fins, and air speed, the temperature in the space between the fins was measured and the air flow between them was observed with a high-speed video camera using the smoke wire method.

During the scavenging of a two-stroke engine, it can be assumed that a very small quantity of fresh mixture flows from the scavenging ports and also from the crankcase through the gap between the cylinder and the piston to the exhaust port, in order to assess the effects of these leakages on fuel economy and hydrocarbon emissions, the authors calculated the quantity of mixture lost using the time-areas of the flow paths and the pressure-time history in the crankcase, and found that this quantity was in the order of 1-3% of the inducted fresh mixture.

The scavenging picture means here the velocity distribution of the scavenging flow in the cylinder measured by a pitot tube. The picture is often used to investigate the suitability of the design of the scavenging system in a two-stroke cycle engine. In measurements by pitot tube only the upward component of the velocity has been measured until now. By this improvement, however, it is well possible to measure the velocity in three dimensions. In other words, it is now possible to measure also the scavenging flow toward the exhaust port after the flow turns downward at the cylinder head.