| Engine Configuration |
Article Index for Engine |
Website Links For Engine |
Information AboutEngine Configuration |
| CATEGORIES ABOUT ENGINE CONFIGURATION | |
| engine technology | |
| configuration | |
| engines | |
|
For many Automobile engines, the term block is interchangeable with engine in this context, for example ''V block'' and '' V Engine '' can often be used interchangeably in American English . This is because the most common forms are all based on a combined Engine Block and Crankcase that are Milled from a single piece of Cast metal. The locations of the major components are largely determined by the shape of this one component. The standard names for some configurations are historic, arbitrary, or both, with some overlap. For example, the cylinder banks of a 180° V Engine do not in any way form a V, but it is regarded as a V engine because of its Crankshaft and Big End configuration, which result in performance characteristics similar to a V engine. But it is also considered a Flat Engine because of its shape. On the other hand, some V-twin engines which have none of the typical V engine crankshaft design features and consequent performance characteristics are also regarded as V engines, purely because of their shape. Similarly, the Volkswagen VR6 Engine is a hybrid of the V Engine and the Straight Engine , and can not be definitively labeled as either. The names '' W Engine '' and '' Rotary Engine '' have each been used for several unconnected designs. The '' H-4 '' and '' H-6 '' engines produced by Subaru are not H Engine s at all, but Boxer Engine s. CATEGORISATION BY PISTON MOTION Engine types include:
OTHER CATEGORISATIONS By Valve placement The majority of four stroke engines have Poppet Valve s, although some aircraft engines have Sleeve Valve s. Valves may be located in the cylinder block ( Side Valve s) or in the cylinder head ( Overhead Valve s). Modern engines are invariably of the latter design. There may be two, three, four or five valves per cylinder, with the intake valves outnumbering the exhaust valves in case of an odd number. By Camshaft placement Poppet valves are opened by means of a camshaft which revolves at half the crankshaft speed. This can be either chain, gear or toothed belt driven from the crankshaft and can be located in the crankcase (where it may serve one or more banks of cylinders) or in the cylinder head. If the camshaft is located in the crankcase, a valve train of Pushrods and Rocker Arm s will be required to operate overhead valves. Mechanically simpler are Side Valve s, where the valve stems rested directly on the camshaft. However, this gives poor gas flows within the cylinder head as well as heat problems and fell out of favor for automobile use. ''See Flathead Engine .'' All modern automobile engines place the camshaft in the cylinder head. There may be one or two camshafts in the cylinder head; a single camshaft design is called OHC or SOHC for (Single) OverHead Cam. A design with two camshafts per cylinder head is called DOHC for Double OverHead Cam. Note that the camshafts are counted per cylinder head, so a V engine with one camshaft in each of its two cylinder heads is still a SOHC design. ''See Overhead Camshaft .'' With overhead cams, the valvetrain will be shorter and lighter, as no pushrods are required. Some single camshaft designs still have Rocker Arm s; this facilates adustment of mechanical clearances. If there are two camshafts in the cylinder head, the cams normally bear directly on to the valve stems. This is the usual arrangement for a four-valves-per-cylinder design. This latter arrangement is the most inertia free, allows the most unimpeded gas flows in the engine and is the usual arrengement for high performance automobile engines. It also permits the spark plug to be located in the centre of the cylinder head, which promotes better combustion characteristics. Very large engines (eg. marine engines) can have either extra camshafts or extra lobes on the camshaft to enable the engine to run in either direction. A disadvantage of overhead cams is that a much longer chain (or belt) is needed to drive the cams than with a camshaft located in the cylinder block, usually a tensioner is also needed. A break in the belt can destroy the engine. |
|
|