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First, saying ,“between a RE engine and ,*other* ,sports bike engines”, implies that RE engines are sport bike engines. They aren’t. Second, the differences are just SO huge, that you could probably write a thesis on it. I’ll try to list some. Number of cylinders: Most sports bikes have a multi cylinder engine. Generally 2 or above. Fuel injection: ALL sports bikes will use FI. RE has only one bike that does. OHC: Over head cam shafts. Usually two of them, hence DOHC. Only two RE(Himalayan & 650 twins) have OHC, and that’s still a single setup i.e. SOHC. Short stroke: Sport bike engines are usually long bore short stroke, hence can reach very high RPMs and generate huge amounts of power there. For reference, a Duke 390 (375cc) will produce 43hp at 9500RPM, whereas the RE 350 produces just about 19bhp at 5000RPM. The RE engine literally cannot rev above 5250RPM. 4 valves per cylinder: Sport bike engines will nearly always have 4 valves per cylinder instead of 2 like the RE. 4 valves = better breathing, better scavenging, better spreading, better performance. Compression ratio: Most sport bikes will use pretty high compression ratios, well above 10:1. RE has a compression ratio of just about 8.5:1. Higher compression ratio = better combustion, better power output, better fuel economy. Liquid cooling: Most sport bikes will have a liquid cooling system, which will allow the engines to generate more heat, which means the engine can be designed to rev higher and produce more power. There’s just so much more, but what you’re essentially doing is comparing a Pixel/iPhone to a landline telephone. (RE fanboys can please bugger off).
DOHC stands for Double Over Head Camshaft OHC or SOHC stands for Single Over Head Camshaft In Double overhead camshaft two different camshafts are used. One is for intake and the another one is for exhaust whereas in Single overhead camshaft only a single camshaft is used. In DOHC generally there are 4 valves, 2 for inlet and 2 for outlet so one camshaft is used for inlet and other is one for exhaust. In SOHC there are only 2 valves, 1 is for inlet and 1 is for outlet. This whole mechanism works by the help of pushrod. As when camshaft moves, it allows pushrod to move up and down to regualte the movememnt of inlet and outlet valves.
In modern cars they are separate entities (not always true historically). The pistons go up and down inside the block, with connecting rods attached to the crank shaft. This is also known as the bottom of the engine. The top of the block is a flat ‘deck’, and the “head’ goes on top of that, separated by a ‘head gasket’ The head contains the valves and the spark plugs. Valves in the head are called “overhead valves’ (OHV). Both coolant and oil are supposed to flow between the block and the head through holes in the gasket. Depending on the engine, the cam shaft(s) are either in the block (pushrod) or close to the heads as “overhead cams” (OHC). With overhead cams, there can be one per head (single overhead cam SOHC) or a separate cam for the intake and exhaust valves (dual overhead cam DOHC). Pushrods are simpler and cheaper, and smaller. Overhead cams are more complicated and expensive, but can perform better, especially at high RPM. Blocks and heads can be an aluminum alloy or iron/steel. It was once common to have iron block and iron heads, but now aluminum is frequently used for both. Mixed iron block and aluminum head was tried, but it was always problematic as the metals expand at different rates as the engine heats and cools, and leaks at the gasket were common problems.
OHV stands for overhead valve. That is the valves are located on top of the combustion chamber. These are normally operated by a cam shaft working off the engine. There are variations. On early engines the inlet could be atmospheric, opening with the vacuum created by the piston movement. Early engines placed valves to the side and under the combustion area and worked directly off the cam which was geared off the crankshaft, as it was the simplest solution. The downside was that it produced a strange combustion chamber shape, making it inefficient. OHV engines were originally operated by a low cam shaft linked to push rods and rockers to transfer the movement to the tip of the valves. OHC are OHV engines where the cam shaft has been transferred to the top of the engine, reducing the number of linkages. SOHC is the above where there is a single cam operating the inlet and exhaust valves and DOHC is where there are two cams, one operating the inlet and the other the exhaust cams. So an OHC engine can be either single or double cammed.
TLDR; SOHC - Single Over Head Cam DOHC - Double Over Head Cam Both are, overhead camshaft, mechanisms which control the opening of the valves of the engine and is situated above the cylinder head. This kind of system is an improvement over the ,overhead valve, mechanism using lifter, pushrod and rockers. Since Quora prefer long answers here we go with a bit of background story. To increase the maximum power from an engine it should breather better (Volumetric efficiency). The more air is filled and left from the cylinder the more power is extracted. Adding more valves was the answer found by most manufacturers. But this came at a cost of more moving parts. More parts means more points of failure. It started out with OHV (Overhead Valve) and now OHC (Overhead Camshaft) is more popular due to its simplicity. A camshaft is 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. OHV GIF 1 OHV configurations use a centrally located cam shaft (central to the engine block), and actuates the valves through the use of lifters, pushrods, and rocker arms. The OHC configuration does away with most of this for the reduction of mass in the valve train. This reduction of mass usually means the engine can run safer and cleaner at higher engine speeds due to less inertial pressures on the valve train. SOHC GIF 2 SOHC uses a single camshaft to open both inlet and outlet valves. Notice in GIF 2 the position of camshaft and the lack of lifters and pushrods. Image 1 - Example of 4 cylinder 12 valves ( 2-Inlet and 1-Outlet per cylinder). But even with this system it still uses rocker arms to space the valves properly inside the engine cylinder. That means it could be still improved by getting rid of the rockers. This is the main reason for the development of DOHC. DOHC GIF 3 DOHC uses one camshaft to actuate inlet and other for outlets. They usually house more valves per cylinder and cam lobes directly actuate the poppet valves. Image 2 - 4 Cylinder 16 Valve (2- Inlet and 2 Outlet per cylinder classic design) Notice the absence of rockers. The actuation is hence more precise and with fewer moving parts gives a predictable performance in the higher rpm. Since there are two separate camshafts, using VVT to alter the timing of the valves became possible and improving the lower and higher rpm operation. Some manufacturers preferred altering the phase (angle or delaying) and some modified the lift. Conclusion DOHC is a better system if performance is concerned, but with its reduced cost and affordable performance SOHC is still used on regular engines. PS : Most of the points in this answer is shamelessly taken from this excellent answer ,what is difference between DOHC and SOHC?
I would say that probably the only advantage to having an OHV (overhead valve) is that the engine can be more compact, especially in height and it is a proven concept as it has been used for so long. Having said that a SOHC (single overhead cam) and a DOHC (double overhead cam) are far superior as they allow for a more direct connection with the cam itself rather than using pushrods meaning greater control. An OHC setup has opened the door to variable valve timing where control is critical and the ability to easily add more valves per cylinder.
SOHC - single over head cam DOHC - double over head cam A precise explanation of the two is given below. SOHC- SOHC refers to Single Overhead Camshaft. In the days before DOHC, it was known as OHC, with no need to differentiate between a single or double camshaft. In SOHC, the camshaft is situated in the cylinder head, above the valves. The valves are opened and closed either directly with a shim between the cam lobe and the valve stem, or via a rocker arm. SOHC engine valve configurations typically have 2 or 3 valves per cylinder. It is also possible to have 4 valves per cylinder using SOHC but this translates into a complicated combination of rocker arms and cam lobe shapes. 2. DOHC- DOHC refers to Double Overhead Camshaft. This arrangement uses two camshafts in each cylinder head. Two cams per cylinder head means that a DOHC V engine has 4 camshafts because it has 2 banks of cylinder heads. This allows the manufacturer to easily implement a 4 valve per cylinder setup. Most of the time it also allows the engine to rev higher. It also allows better placement of the valves in an optimized setup that gives you maximum performance. But the disadvantage of such a setup is more weight, more cost and more complexity. It takes more stuff to drive two camshafts. The main reason to use DOHC is to drive more valves per cylinder. SOHC has better low-end power, DOHC has better high-end power and overall maximum power. [picture courtesy- samarins.com]