Cosworth Subaru EJ20/EJ25 Timing Belt

Cosworth Cosworth is a high-performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing (motorsport), mainstream automotive and defence industries. Cosworth is based in Northampton, England, with North American facilities in Torrance, Indianapolis and Mooresville.
Cosworth has had a long and distinguished career in Formula One, beginning in 1963. Cosworth's 176 wins make it one of the most successful engine manufacturers to race in F1, second only to Ferrari in victories.[1] Cosworth supplies engines to one team in 2013, the Marussia F1 Team.[1]
Since 2006, Cosworth has diversified to provide engineering consultancy, high performance electronics and component manufacture services outside of its classic motorsport customer base. Current publicised projects range from an 80 cc (4.9 cu in) diesel engine for unmanned aerial vehicles, through to an engineering partnership on one of the world's most powerful normally aspirated road car engines. (Wikipedia)
Kevlar High Performance Timing Belts
Cosworth Cosworth is a high-performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing (motorsport), mainstream automotive and defence industries. Cosworth is based in Northampton, England, with North American facilities in Torrance, Indianapolis and Mooresville.
Cosworth has had a long and distinguished career in Formula One, beginning in 1963. Cosworth's 176 wins make it one of the most successful engine manufacturers to race in F1, second only to Ferrari in victories.[1] Cosworth supplies engines to one team in 2013, the Marussia F1 Team.[1]
Since 2006, Cosworth has diversified to provide engineering consultancy, high performance electronics and component manufacture services outside of its classic motorsport customer base. Current publicised projects range from an 80 cc (4.9 cu in) diesel engine for unmanned aerial vehicles, through to an engineering partnership on one of the world's most powerful normally aspirated road car engines. (Wikipedia)
Kevlar High Performance Timing belts are 300% stronger than original equipment timing belts and are the perfect compliment when installing Cosworth Cosworth is a high-performance engineering company founded in London in 1958, specialising in engines and electronics for automobile racing (motorsport), mainstream automotive and defence industries. Cosworth is based in Northampton, England, with North American facilities in Torrance, Indianapolis and Mooresville.
Cosworth has had a long and distinguished career in Formula One, beginning in 1963. Cosworth's 176 wins make it one of the most successful engine manufacturers to race in F1, second only to Ferrari in victories.[1] Cosworth supplies engines to one team in 2013, the Marussia F1 Team.[1]
Since 2006, Cosworth has diversified to provide engineering consultancy, high performance electronics and component manufacture services outside of its classic motorsport customer base. Current publicised projects range from an 80 cc (4.9 cu in) diesel engine for unmanned aerial vehicles, through to an engineering partnership on one of the world's most powerful normally aspirated road car engines. (Wikipedia)
camshafts  In internal combustion engines with pistons, the camshaft is used to operate poppet valves. It then consists of a cylindrical rod running the length of the cylinder bank with a number of oblong lobes protruding from it, one for each valve. The cam lobes force the valves open by pressing on the valve, or on some intermediate mechanism as they rotate.
Material
Camshafts can be made out of several different types of material. These include:
Chilled iron castings: this is a good choice for high volume production. A chilled iron camshaft has a resistance against wear because the camshaft lobes have been chilled, generally making them harder. When making chilled iron castings, other elements are added to the iron before casting to make the material more suitable for its application.
Billet Steel: When a high quality camshaft is required, engine builders and camshaft manufacturers choose to make the camshaft from steel billet. This method is also used for low volume production. This is a much more time consuming process, and is generally more expensive than other methods. However the finished product is far superior. When making the camshaft, CNC lathes, CNC milling machines and CNC camshaft grinders will be used. Different types of steel bar can be used, one example being EN40b. When manufacturing a camshaft from EN40b, the camshaft will also be heat treated via gas nitriding, which changes the micro-structure of the material. It gives a surface hardness of 55-60 HRC. These types of camshafts can be used in high-performance engines.
Timing
A steel billet racing camshaft with noticeably broad lobes (very long duration)
The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of the air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain. Direct drive using gears is unusual because the frequently reversing torque caused by the slope of the cams tends to quickly wear out gear teeth. Where gears are used, they tend to be made from resilient fibre rather than metal, except in racing engines that have a high maintenance routine. Fibre gears have a short life span and must be replaced regularly, much like a cam belt. In some designs the camshaft also drives the distributor and the oil and fuel pumps. Some vehicles may have the power steering pump driven by the camshaft. With some early fuel injection systems, cams on the camshaft would operate the fuel injectors.
An alternative used in the early days of OHC engines was to drive the camshaft(s) via a vertical shaft with bevel gears at each end. This system was, for example, used on the pre-WW1 Peugeot and Mercedes Grand Prix cars. Another option was to use a triple eccentric with connecting rods; these were used on certain W.O. Bentley-designed engines and also on the Leyland Eight.
In a two-stroke engine that uses a camshaft, each valve is opened once for each rotation of the crankshaft; in these engines, the camshaft rotates at the same speed as the crankshaft. In a four-stroke engine, the valves are opened only half as often; thus, two full rotations of the crankshaft occur for each rotation of the camshaft.
The timing of the camshaft can be advanced to produce better low RPM torque, or retarded for better high RPM power. Either of these moves the overall power produced by the engine down or up the RPM scale respectively. The amount of change is very little (usually < 5 deg), and affects valve to piston clearances.
Duration
Duration is the number of crankshaft degrees of engine rotation during which the valve is off the seat. As a generality, greater duration results in more horsepower. The RPM at which peak horsepower occurs is typically increased as duration increases at the expense of lower rpm efficiency (torque).[citation needed]
Duration can often be confusing because manufacturers may select any lift point to advertise a camshaft's duration and sometimes will manipulate these numbers. The power and idle characteristics of a camshaft rated at .006" will be much different than one rated the same at .002".
Many performance engine builders gauge a race profile's aggressiveness by looking at the duration at .020", .050" and .200". The .020" number determines how responsive the motor will be and how much low end torque the motor will make. The .050" number is used to estimate where peak power will occur, and the .200" number gives an estimate of the power potential.
A secondary effect of increase duration is increasing overlap, which is the number of crankshaft degrees during which both intake and exhaust valves are off their seats. It is overlap which most affects idle quality, inasmuch as the "blow-through" of the intake charge which occurs during overlap reduces engine efficiency, and is greatest during low RPM operation. In reality, increasing a camshaft's duration typically increases the overlap event, unless one spreads lobe centers between intake and exhaust valve lobe profiles.
Lift
The camshaft "lift" is the resultant net rise of the valve from its seat. The further the valve rises from its seat the more airflow can be released, which is generally more beneficial. Greater lift has some limitations. Firstly, the lift is limited by the increased proximity of the valve head to the piston crown and secondly greater effort is required to move the valve's springs to higher state of compression. Increased lift can also be limited by lobe clearance in the cylinder head construction, so higher lobes may not necessarily clear the framework of the cylinder head casing. Higher valve lift can have the same effect as increased duration where valve overlap is less desirable.
Higher lift allows accurate timing of airflow; although even by allowing a larger volume of air to pass in the relatively larger opening, the brevity of the typical duration with a higher lift cam results in less airflow than with a cam with lower lift but more duration, all else being equal. On forced induction motors this higher lift could yield better results than longer duration, particularly on the intake side. Notably though, higher lift has more potential problems than increased duration, in particular as valve train rpm rises which can result in more inefficient running or loss of torque.
Cams that have too high a resultant valve lift, and at high rpm, can result in what is called "valve bounce", where the valve spring tension is insufficient to keep the valve following the cam at its apex. This could also be as a result of a very steep rise of the lobe and short duration, where the valve is effectively shot off the end of the cam rather than have the valve follow the cams’ profile. This is typically what happens on a motor over rev. This is an occasion where the engine rpm exceeds the engine maximum design speed. The valve train is typically the limiting factor in determining the maximum rpm the engine can maintain either for a prolonged period or temporarily. Sometimes an over rev can cause engine failure where the valve stems become bent as a result of colliding with the piston crowns.
Position
Depending on the location of the camshaft, the cams operate the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders. In the past when engines were not as reliable as today this was seen as too much bother, but in modern gasoline engines the overhead cam system, where the camshaft is on top of the cylinder head, is quite common.
Number of camshafts
Main articles: overhead valve and overhead cam
While today some cheaper engines rely on a single camshaft per cylinder bank, which is known as a single overhead camshaft (SOHC), most[quantify] modern engine designs (the overhead-valve or OHV engine being largely obsolete on passenger vehicles), are driven by a two camshafts per cylinder bank arrangement (one camshaft for the intake valves and another for the exhaust valves); such camshaft arrangement is known as a double or dual overhead cam (DOHC), thus, a V engine, which has two separate cylinder banks, may have four camshafts (colloquially known as a quad-cam engine[6]).
More unusual is the modern W engine (also known as a 'VV' engine to distinguish itself from the pre-war W engines) that has four cylinder banks arranged in a "W" pattern with two pairs narrowly arranged with a 15-degree separation. Even when there are four cylinder banks (that would normally require a total of eight individual camshafts), the narrow-angle design allows the use of just four camshafts in total. For the Bugatti Veyron, which has a 16-cylinder W engine configuration, all the four camshafts are driving a total of 64 valves.
The overhead camshaft design adds more valvetrain components that ultimately incur in more complexity and higher manufacturing costs, but this is easily offset by many advantages over the older OHV design: multi-valve design, higher RPM limit and design freedom to better place valves, ignition (Spark-ignition engine) and intake/exhaust ports
(Wikipedia)
or cylinder heads  In an internal combustion engine, the cylinder head (often informally abbreviated to just head) sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket. In most engines, the head also provides space for the passages that feed air and fuel to the cylinder, and that allow the exhaust to escape. The head can also be a place to mount the valves, spark plugs, and fuel injectors.
In a flathead or sidevalve engine, the mechanical parts of the valve train are all contained within the block, and the head is essentially a metal plate bolted to the top of the block; this simplification avoids the use of moving parts in the head and eases manufacture and repair, and accounts for the flathead engine's early success in production automobiles and continued success in small engines, such as lawnmowers. This design, however, requires the incoming air to flow through a convoluted path, which limits the ability of the engine to perform at higher revolutions per minute (rpm), leading to the adoption of the overhead valve (OHV) head design, and the subsequent overhead camshaft (OHC) design.

Detail

Internally, the cylinder head has passages called ports or tracts for the fuel/air mixture to travel to the inlet valves from the intake manifold, and for exhaust gases to travel from the exhaust valves to the exhaust manifold. In a water-cooled engine, the cylinder head also contains integral ducts and passages for the engines' coolant - usually a mixture of water and antifreeze - to facilitate the transfer of excess heat away from the head, and therefore the engine in general.
In the overhead valve (OHV) design, the cylinder head contains the poppet valves and the spark plugs, along with tracts or 'ports' for the inlet and exhaust gases. The operation of the valves is initiated by the engine's camshaft, which is sited within the cylinder block, and its moment of operation is transmitted to the valves pushrods, and then rocker arms mounted on a rocker shaft - the rocker arms and shaft also being located within the cylinder head.
In the OHC design, the cylinder head contains the valves, spark plugs and inlet/exhaust tracts just like the OHV engine, but the camshaft is now also contained within the cylinder head. The camshaft may be seated centrally between each offset row of inlet and exhaust valves, and still also utilizing rocker arms (but without any pushrods), or the camshaft may be seated directly above the valves eliminating the rocker arms and utilizing 'bucket' tapets.

Implementation

The number of cylinder heads in an engine is a function of the engine configuration. Almost all inline (straight) engines today use a single cylinder head that serves all the cylinders. A V (or Vee) engine has two cylinder heads, one for each cylinder bank of the 'V'. For a few compact 'narrow angle' V engines, such as the Volkswagen VR6, the angle between the cylinder banks is so narrow that it uses a single head spanning the two banks. A flat engine (basically a V engine, where the angle between the cylinder banks is now 180°) has two heads. Most radial engines have one head for each cylinder, although this is usually of the monobloc form wherein the head is made as an integral part of the cylinder. This is also common for motorcycles, and such head/cylinder components are referred-to as barrels.
Some engines, particularly medium- and large-capacity diesel engines built for industrial, marine, power generation, and heavy traction purposes (large trucks, locomotives, heavy equipment etc.) have individual cylinder heads for each cylinder. This reduces repair costs as a single failed head on a single cylinder can be changed instead of a larger, much more expensive unit fitting all the cylinders. Such a design also allows engine manufacturers to easily produce a 'family' of engines of different layouts and/or cylinder numbers without requiring new cylinder head designs.
The design of the cylinder head is key to the performance and efficiency of the internal combustion engine, as the shape of the combustion chamber, inlet passages and ports (and to a lesser extent the exhaust) determines a major portion of the volumetric efficiency and compression ratio of the engine.

(Wikipedia)
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Art.Nr.: RSD-CS-20004953

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