Forklifts are classified as small-engine vehicles, the same category wherein lawnmowers are classed. Forklift engines all follow the principles of internal combustion. Different forklift models and brand names would have varying engine layout and design. Forklifts are made more toward generating high torque rather than for speed. They generally are geared to low speeds. The engine runs the drive wheels of the forklift. The engine is also required to lower and raise the forks through a series of chain pulleys. Nearly all forklift engines that are modern are fueled by propane because they will be utilized for indoor applications, where diesel and gasoline engines would be inappropriate due to the exhaust they make.
A four-cylinder engine-block is usually found in a lift truck. Much similar to the engine in small automobiles, the engines of the forklift have cylinders containing pistons connecting to a camshaft. Each and every cylinder head consists of an exhaust hatch, a spark plug and an exhaust hatch, each of them spring-loaded and one-way.
Propane passes through the opened throttle-plate in a fine spray, once the operator starts up the forklift engine. This fine spray mixes with air that comes from the mass air intake before moving into the cylinder's head intake hatches. Every one of the four pistons is staggered to rise in a precise sequence, that compresses the air and propane mixture as every piston rises to the top of the head. With timing which is very precise, the battery and alternator of the engine generate an electrical current which passes through the spark plug. The fuel ignites resulting in an explosion that drives the piston back down to the bottom of the cylinder, resulting in a continuous turning of the camshaft. In the cylinder, an air pressure imbalance causes the exhaust to be drawn out through the exhaust hatch when more fuel passes into the cylinder. Propane burns cleaner than gasoline and diesel and the exhaust is not as harmful.