Just Cars Club

The V8 with a crossplane crankshaft (see below) is a very common configuration for large automobile engines. V8 engines are rarely less than 3 L in displacement and in automobile use have gone up to and beyond 8.2 L in production vehicles. Industrial and marine V8 engines can be much larger.

V8s are generally only standard on more powerful rear-wheel drive 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 90° V8 engine is generally too wide and somewhat too long to fit in vehicles with the modern transverse engine front-wheel drive layout, so with a few exceptions its application is limited to front-engine, rear-wheel drive sports/luxury cars and light trucks. A few 60° V8 engines, however, have been used in the transverse engine configuration.

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 V8 engines, which replaced the 3.0 L V10 in a move to reduce 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 with flat-4 and flat-6 engines.

The straight-4 engine is much smoother than one, two, and three cylinder engines, and this has resulted in it becoming the engine of choice for most economy cars, although it can be found in some sports cars as well. However, the straight-4 is not a fully balanced configuration. While it is in primary balance because one pair of pistons is always moving up at the same time as the other pair is moving down, piston speed - as with all internal combustion engines - is higher through the top 180 degrees of the crankshaft rotation than the bottom 180 degrees. Since two pistons are always moving faster in one direction while two others are moving more slowly in the other, this leads to a secondary dynamic imbalance - an up-and-down vibration at twice crankshaft speed. This imbalance is tolerable in a small, low-displacement, low-power configuration, but the vibrations get worse with increasing size and power.

Most straight-4 engines below 2.0 L in displacement rely on the damping effect of their engine mounts to reduce the vibrations to acceptable levels. Above 2.0 L, most modern straight-4 engines now use balance shafts to eliminate the second-order harmonic vibrations. In a system invented by Dr. Frederick W. Lanchester in 1911 and popularized by Mitsubishi Motors in the 1970s, a straight-4 engine uses two balance shafts, rotating in opposite directions at twice crankshaft speed, to offset the differences in piston speed. However, in the past there were numerous examples of larger straight-4s without balance shafts, such as the Citroën DS 23 2347 cc engine that was a derivative of the Traction Avant engine, the 1948 Austin 2660 cc engine used in the Austin-Healey 100 and Austin Atlantic, the 3.3 L flathead engine used in the Ford Model A (1927), and the 2.5 L GM Iron Duke engine used in a number of American cars and trucks. Soviet/Russian GAZ Volga cars used aluminium big-bore straight-4 (2.5 L) with no balance shafts in 1950s-1990s. These engines were generally the result of a long incremental evolution process and their power was kept relatively low compared to their capacity. However, the forces increase with the square of the engine speed – that is, doubling the speed makes the vibration four times worse - so modern high-speed straight-4s have more need to use balance shafts to offset the vibrations.

Four cylinder engines have another problem in that the power strokes of the pistons do not overlap. With four cylinders and four cycles to complete, each piston must complete its power stroke and come to a complete stop before the next piston can start a new power stroke, resulting in a pause between each power stroke and a pulsating delivery of power. In engines with more cylinders, the power strokes overlap, which gives them a smoother delivery of power and less vibration than a four can achieve. As a result, six and eight cylinder engines are generally used in more luxurious and expensive cars. There are four cylinder engines which are “odd fired”, meaning no two pistons are ever at the top of their stroke at any one time.

A V6 engine is a V engine with six cylinders mounted on the crankcase in two banks of three cylinders, usually set at either a right angle or an acute angle to each other, with all six pistons driving a common crankshaft. It is the second most common engine configuration in modern cars after the inline four.
The V6 is one of the most compact engine configurations, shorter than the straight 4 and in many designs narrower than the V8 engine, and is well suited to the popular front-wheel drive layout. It is becoming more common as the space allowed for engines in modern cars is reduced at the same time as power requirements increase, and has largely replaced the inline-6, which is too long to fit in many modern engine compartments. Although it is more complicated and not as smooth as the inline 6, the V6 is more compact, more rigid, and less prone to torsional vibrations in the crankshaft. The V6 engine has become widely adopted for medium-sized cars with engine displacements between 2.4 and 3.2 litres, often as an optional engine where a straight-4 is standard, or as an economy engine where a V8 is a higher-cost option.

The first V6 was introduced by Lancia in 1950 with the Lancia Aurelia. Other manufacturers took note and soon other V6 engines were in use. In 1959, GM introduced a heavy duty 305 cubic inch (5 liter) 60-degree V6 for use in their pickup trucks and Suburbans, an engine design that was later enlarged to 478 cubic inches (7.8 liters) for heavy truck and bus use.

The design really took off after the 1962 introduction of the Buick Special, which offered a 90 degree V6 with uneven firing intervals that shared some parts commonality with a small Buick V8 of the period. Though the Buick Special met consumer resistance due to its excessive vibration, it was the first instance of a mass-produced V6 engine designed specifically for passenger automobiles. In 1983 Nissan produced Japan’s first V6 engine with the VG series.

Modern V6 engines commonly range in displacement from 2.5 L to 4.3 L, though larger and smaller examples have been produced.