V6
V6 is a term for an internal-combustion piston engine with six cylinders in a "V" configuration. A V6 is not a perfectly balanced engine and benefits from some counterbalancing and harmonic damping.The first V6 was introduced by Lancia on the 1924 Lancia Lambda, but it made little impact. The design was reintroduced by the company in 1950 with the Lancia Aurelia; this time, other manufacturers took note and soon other V6 engines were in use.
The optimal angle to minimise vibrations in the V6 is 60°.
90° V6 engines such as the PRV have also been produced. The major advantage of this configuration is that it allows production on the same machinery as a 90° V8.1 Many V6 engines built in the United States are also of this configuration, for the same reason.
A 90° V6 can have shared crankpins between two 'opposite' cylinders, but this results in uneven firing. Using a crankpin that is 'split' and offset by 30° of rotation results in smooth even firing. Such a 'split' crankpin is weaker than a straight one, but modern materials and manufacturing give a crankshaft that is quite strong enough.
Narrow angle V6 engines have also been used; the appeal here is the compactness of such an engine, being shorter than a straight-6 but narrower than a conventional V6. Such a design is not optimal for minimising vibration. Lancia's 1924 Lancia Lambda engine was such a narrow angle design, and Lancia went on to produce similar engines until the 1970s but mostly in V4 configuration.
In recent years Volkswagen have become enamoured of this narrow-angle design, largely for its space-efficiency; their engine is known as the VR6. In Volkswagen's design, both banks share the same cylinder head and are extremely close together.
In competition, until the advent of wing-cars, a wide 120° angle was appealing for racing car designers as it permits a low center of gravity. It was even considered superior to the flat-6 in that it leaves more space under the engine for exhaust pipes; thus the crankshaft can be placed lower in the car. Ferrari used such a configuration on the Dino V6 Formula One 1.5 litre2 engine. Other manufacturers, concerned about vibration issues, chose more classic configurations.
In 1973 Renault introduced the Alpine-Renault A440 prototype powered by a new 2 litre 90° V6 the Renault-Gordini CH1 designed by François Castaing and Jean-Pierre Boudy.
Technical optimization should have led to a 60° or 120° design or a flat-6 for the Renault-Gordini engine. The choice of a 90° angle remains questionable. The choice of a cast iron block was also an originality for a racing engine. It seems that marketing considerations superceeded technical considerations, thus the CH1 was designed with the same angle and the same material that the stock PRV engine.
With such compromises it was difficult to imagine that this engine will later become one of the most influential racing engine ever built.
This engine won the European 2 L prototype championship in 1974 and several European Formula 2 titles.
- The PRV V8 was planned but cancelled after the 1973 energy crisis.
- They were several versions of the 1.5 litre Dino Formula One engine, some with a classic 60° V and some with a 120° V.
