A compression release mechanism works to ease the starting of internal combustion engines by allowing them to spin up to starting speed without having to work against the pumping action of the pistons. It does this through a release valve that is incorporated within the cylinder head that vents the cylinder pressure to the outside atmosphere until the engine has sufficient momentum to overcome it. At that point the valve closes and the ignition is engaged.
Early large displacement motorcycles provided riders with a manual control for this when kick starters were used while later models linked them to the kick start lever through a cable for automatic operation. Though it only uses electric start, not kick start, the 2012 Ducati 1199 uses a compression release, which is automatically activated at low engine speed by a centrifugal flyweight on each exhaust cam. This reduces the work of cranking the high 12.5:1 compression ratio engine, allowing a smaller battery and smaller starter motor, for a total weight saving of 3.3 kilograms (7.3 lb). [1]
From the mid-1960s to the late-1970s, engine compression releases were also used to supplement rear wheel braking on many two-stroke engined motorcycles, primarily those used off-road or for various types of dirt-track racing, such as motocross and flat-tracking. Since two-stroke engines normally lack the compression braking effect of four-stroke engines when the throttle is shut off, the addition of a compression release brake on two-strokes essentially mimicked the four-stroke compression braking effect. Using throttle-off engine compression for at least some braking on both two-stroke and four-stroke motorcycles was especially important during that era, since most motorcycles used drum brakes, which fade more quickly than modern disc brakes.
Small diesel engines may be fitted with compression release valves if they are to be started by hand cranking. [2]
US patent US5375570 A of 1994 describes an automated compression release valve actuated by engine oil pressure. [3]
A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.
A starter is a device used to rotate (crank) an internal-combustion engine so as to initiate the engine's operation under its own power. Starters can be electric, pneumatic, or hydraulic. The starter can also be another internal-combustion engine in the case, for instance, of very large engines, or diesel engines in agricultural or excavation applications.
A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:
A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring.
The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. It can also serve as a reversing gear. It is sometimes referred to as the "motion".
In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with variable valve lift systems. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. Increasingly strict emissions regulations are causing many automotive manufacturers to use VVT systems.
A compression release engine brake, compression brake, or decompression brake, frequently called a Jacobs brake or Jake Brake, is an engine braking mechanism installed on some diesel engines. When activated, it opens exhaust valves to the cylinders, right before the compression stroke ends, releasing the compressed gas trapped in the cylinders, and slowing the vehicle.
Engine braking occurs when the retarding forces within an engine are used to slow down a motor vehicle, as opposed to using additional external braking mechanisms such as friction brakes or magnetic brakes.
A rotary valve is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rotary valve. Rotary valves have been applied in numerous applications, including:
A motorcycle engine is an engine that powers a motorcycle. Motorcycle engines are typically two-stroke or four-stroke internal combustion engines, but other engine types, such as Wankels and electric motors, have been used.
The Honda RVF750R RC45 was a fully faired racing motorcycle created for homologation purposes for the Superbike World Championship by Honda Racing Corporation. The RVF750R was the successor to the VFR750R RC30. Like its predecessor, the RVF750R featured a DOHC liquid-cooled V4 4-stroke engine with gear driven cams and a single-sided swingarm, but unlike the RC30 it utilized electronic fuel injection, in a setup very similar to the production 1992 NR750. The US spec engine had a 749.2cc capacity and was rated at 101 horsepower; the European version was rated at 118 horsepower. A simple rewire modification to the PGM-FI box increased power in the US engine up to the 118 hp. It was manufactured from 1994 until 1995 and sold in limited numbers, followed by the VTR1000R SP-1 RC51 in 2000. Unlike the VFR750R RC30 and VFR750F from which the engine was originally derived the gear drive for the cams was moved from the centre of the engine in between the cylinders to the one side allowing a slightly narrower engine.
The Ducati singles were single cylinder motorcycles, made by Ducati from 1950 to 1974. Chief Engineer Fabio Taglioni developed a desmodromic valve system in these years, a system that opens and closes the valves using the camshaft, without the need for valve springs. This valve system has become a trademark feature of Ducati motorcycles.
The L-twin is a naturally aspirated two-cylinder petrol engine by Ducati. It uses a 90-degree layout and 180-degree firing order as is mounted with one cylinder horizontal.
The following outline is provided as an overview of and topical guide to automobiles:
The Yamaha YZ450F is a four-stroke racing motocross bike built by Yamaha Motor Corporation. It was the successor to the previous YZ426F which was discontinued in 2003. It is credited by Cycle World and Dirt Rider magazines as the bike that started the four-stroke dirt bike revolution. The 2006 YZ250F and YZ450F were the first production motorcycles equipped with titanium suspension springs.
The Ducati 848 is a sport bike with a 849 cc (51.8 cu in) 90° V-twin engine made by Ducati. It was announced on November 6, 2007 for the 2008 model year, replacing the 749. The 848 and the 1098 are the same design by Giandrea Fabbro, both use the same frame and bodywork. The first generation 848 makes a claimed 92 kW 10,000 rpm and 90 N⋅m (66 lbf⋅ft) torque at 8,240 rpm. With a manufacturer claimed dry weight of 168 kg (370 lb), the 848 is 5 kg (11 lb) lighter than its larger displacement sibling, the 1198. The first generation 848 covered model years 2008, 2009 and 2010. In July 2009 the 848 Hayden Limited Edition was introduced as a 2010 model as a marketing tie-in with world champion Nicky Hayden racing for Ducati starting from the 2009 Moto GP season.
The Ducati 1199 Panigale was a 1,198 cc (73.1 cu in) Ducati sport bike introduced at the 2011 Milan Motorcycle Show. The motorcycle is named after the small manufacturing town of Borgo Panigale. Ducati had announced a larger displacement 1,285 cc (78.4 cu in) 1299 Panigale for the 2015 model year.
An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to. This replaced the external combustion engine for applications where the weight or size of an engine was more important.
The Ducati Sebring is a 340 cc (21 cu in) single cylinder bevel drive SOHC motorcycle produced by the Italian manufacturer Ducati from 1965 to 1968. At the time of its introduction it was the largest capacity Ducati machine. Production of the original model ended in 1967 when the 'wide case' Mark 3 was introduced, although just over 200 Sebrings were made in 1968 with the 'wide case' engine. Total production was around 3,500 machines.
The Ducati Monza is a 249 cc (15.2 cu in) single cylinder bevel drive SOHC motorcycle produced by the Italian manufacturer Ducati from 1961 to 1968. It was the touring version of Ducati's first 250 cc road bike. Reviews of the Monza praised its speed, road holding, engine smoothness and brakes.