Tuesday, October 13, 2009
The V8 with a crossplane crankshaft (see below) is a very common configuration for large automobile engines. V8 engines are rarely less than 3.0 L (183 cu in) in displacement and in automobile use have gone up to and beyond 8.2 L (500 cu in) in production vehicles. Industrial and marine V8 engines can be much larger.
V8s are generally only standard on more powerful muscle cars, pony cars, sports cars, luxury cars, pickup trucks, and SUVs. However they are often optional on vehicles which have a V6 or straight-6 as standard engine. In many cases, V6 engines were derived from V8 designs by removing two cylinders without changing the V-angle so they can be built on the same assembly lines as the V8s and installed in the same engine compartments with few modifications.
The traditional 90° big-bore V8 engine is generally too wide and too long to fit easily in vehicles with a transverse engine front-wheel drive layout, so its application is mostly limited to rear-wheel drive sports cars, muscle cars, pony cars, luxury cars and light trucks. The shorter and occasionally narrower V6 engine is easier to fit in small engine compartments, but a few compact V8 engines have been used in transverse FWD and transverse AWD engine configurations in larger cars, such as Cadillacs and Volvos. These engines often have tighter cylinder bore spacings, narrower cylinder bank angles, and other modifications to reduce their space requirements.
V8s are common in purpose-designed engines for racing cars. They usually have flat-plane crankshafts, since a crossplane crankshaft results in uneven firing into the exhaust manifolds which interferes with engine tuning, and the heavy crankshaft counterweights prevent the engine from accelerating rapidly. They are a common engine configuration in the highest echelons of motorsport, especially in the USA where it is required in IRL, ChampCar and NASCAR. V8 engines are also used in Australian motorsport, most notably in the V8 Supercars . Formula One began the 2006 season using naturally aspirated 2.4 L (~146 cu in) V8 engines, which replaced the 3.0 L (~183 cu in) V10 in a move to reduce costs and power.
Heavy trucks and railroad locomotives tend to use the straight-6 configuration since it is simpler and easier to maintain, and since the straight-6 is an inherently balanced layout which can be scaled up to almost any size necessary. Large V8s are found in the larger truck and industrial equipment lines, however.
Although it was an early choice for airplane engines, the V8 engine is seldom used in modern aircraft engine since the typically heavy crankshaft counterweights are a liability. Modern light planes commonly use the flat-8 configuration instead since it is lighter and easier to air cool, in addition to which it can be manufactured in modular designs sharing components with flat-4 and flat-6 engines.