Engines with four valves per cylinder made their debut in motorsport as early as the decade of the last century. Applied to the four-cylinder engine, this technique became popular for series production cars from the 1970s. There’s a reason it took so long.
With four you go further. Ernest Henry already knew this, the manufacturer of the Peugeot L76 with 16V engine from 1912. The Grand Prix racer already won several important races in both Europe and the United States. They are the first demonstrable successes achieved by a car with an engine with four valves per cylinder. Initially, the power of combustion engines was mainly determined by the cylinder capacity, under the motto ‘more is better’. The Frenchman therefore received an engine with an impressive displacement of 7.6 liters, divided over four enormous cylinders. By using a cylinder head with semicircular combustion chambers, two overhead camshafts and four-valve technology, the engine could also handle high revs and react faster to the accelerator pedal. It seems that the power source of the Peugeot L76 delivered a power of 140 hp at 2,200 rpm. In 1912, this technique seemed straight out of the future; In fact, the multi-valve technology was still only found in racing cars six decades later.
The legendary Ford-Cosworth DFV-V8, the most successful Formula 1 engine of all time, had four valves per cylinder. In 1972, sixteen-valve technology made its first appearance in series production with the Jensen-Healey. Why the application took so long can be guessed: technology used in motorsport is usually too complex and expensive for series production. Casting and machining a four-valve cylinder head was even work for alchemists in 1912. Experience must first be gained with higher speeds, highly loaded valves and the materials necessary for the construction of these parts.
The advantages of the multi-valve technology are obvious: because the number of valves is twice as large, in theory the inflow and outflow capacity doubles. More combustion air flows into the engine and the exhaust gas flows out more quickly. The central placement of the spark plugs ensures thorough combustion. This results in a better efficiency, while the harmful combustion residues that remain in the engine are reduced. However, without suction paths and exhaust systems with a good flow, this hardly yields anything. For 20 percent extra power, it’s a lot of hassle. It will come as no surprise that the compact and not too complex four-cylinders lead to the breakthrough of multi-valve technology on a large scale.
This is followed by six-cylinder, V8 engines and even diesel passenger car engines with four valves per cylinder. Technology is becoming synonymous with progress and many car manufacturers proudly display it on the tailgate of their models. There are also disadvantages, because at low speeds, the sixteen-valve four-cylinder is hardly more powerful than the faithful eight-valve engine. This technique also does not provide more torque and to be able to use the extra power, you have to make a lot of speed. The 16V engine only wakes up above 3,000 rpm, while maximum power is often only available above 6,000 rpm. But, high revs and a nice growl from freely breathing exhaust pipes means enjoyment! And 16-valves fit in everything: roadster, sports sedan, coupé and race car.
Sometimes more is less
Engines with five-valve technology were not a success. Five valves per cylinder. Three on the intake side for better filling, two on the exhaust side opposite. What a bustle in the cylinder head! The Bugatti EB 110, produced in very limited numbers, came on the market in 1992 with a sixty-valve V12, followed two years later by the Ferrari F 355 with a forty-valve V8 and the Audi A4 with a new twenty-valve four-cylinder engine.
The technique was introduced in series production by Ferdinand Piëch; normally this was mainly used in motorsport. Instead of more power, the technology in the production models had to deliver more torque. Both with naturally aspirated and turbocharged engines. The 20V four-cylinder from Audi, originally the old Typ 827 from 1972, delivered good performance, without jumping out of the band: a few newton meters more, a somewhat lower consumption. In the end, the complex technique did not yield much. Five-valve engines therefore quickly disappeared from the picture.
This article originally appeared in AutoWeek Classics issue 6 of 2018.
– Thanks for information from Autoweek.nl