engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

design, the penta engine (or penta ''head'') is an arrangement of the upper portion of the

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

and valves that is common in engines using four valves per cylinder. Among the advantages is a faster burn time of the air-fuel mix. It is similar in concept to the

hemi engine A hemispherical combustion chamber is a type of combustion chamber in a reciprocating internal combustion engine with a domed cylinder head notionally in the approximate shape of a hemisphere (in reality usually a spheric section thereof). An en ...

, both in design and purpose, but a hemispherical cylinder head is limited to only two valves without the use of a more complex sub-rocker assembly. The four-valve penta engine design was invented by

Peugeot Peugeot (, , ) is a French brand of automobiles owned by Stellantis. The family business that preceded the current Peugeot companies was founded in 1810, with a steel foundry that soon started making hand tools and kitchen equipment, and the ...

of France, to be first used in the 1911 Indianapolis 500 race. The penta engine (also termed pentroof combustion chamber) is the most common design used today by many manufacturers for four-valve-per-cylinder engines producing relatively high horsepower for displacement, for both racing engines and engines for passenger cars.

References

Internal combustion piston engines {{Tech-stub