A
crossflow cylinder head is a
cylinder headIn an internal combustion engine, the cylinder head sits above the cylinders and consists of a platform containing part of the combustion chamber and the location of the valves and spark plugs...
that features the intake and exhaust ports on opposite sides. The gases can be thought to flow across the head. This is in contrast to
reverse-flow cylinder headA reverse-flow or non-crossflow cylinder head is one that locates the intake and exhaust ports on the same side of the engine. The gases can be thought to enter the cylinder head and then change direction in order to exit the head...
designs that have the ports on the same side.
A crossflow head gives
better performanceEngine tuning is the adjustment, modification or design of internal combustion engines to yield optimal performance, to increase an engine's power output, economy, or durability. It has a long history, almost as long as the development of the car in general, originating with the development of...
, but the popular explanation put forward for this — that the gases don't have to change direction and hence are moved into and out of the cylinder more efficiently — is a simplification since there is no continuous flow because of
valveA poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
opening and closing.
But since there is overlap between the intake and exhaust profiles there is a point in which both valves are open.
A
crossflow cylinder head is a
cylinder headIn an internal combustion engine, the cylinder head sits above the cylinders and consists of a platform containing part of the combustion chamber and the location of the valves and spark plugs...
that features the intake and exhaust ports on opposite sides. The gases can be thought to flow across the head. This is in contrast to
reverse-flow cylinder headA reverse-flow or non-crossflow cylinder head is one that locates the intake and exhaust ports on the same side of the engine. The gases can be thought to enter the cylinder head and then change direction in order to exit the head...
designs that have the ports on the same side.
A crossflow head gives
better performanceEngine tuning is the adjustment, modification or design of internal combustion engines to yield optimal performance, to increase an engine's power output, economy, or durability. It has a long history, almost as long as the development of the car in general, originating with the development of...
, but the popular explanation put forward for this — that the gases don't have to change direction and hence are moved into and out of the cylinder more efficiently — is a simplification since there is no continuous flow because of
valveA poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
opening and closing.
But since there is overlap between the intake and exhaust profiles there is a point in which both valves are open. At that point the inertia of the exhaust gases leaving the cylinder helps to aspirate the intake gases into the cylinder. The other main reason for a crossflow's performance is that the ports and valves can be larger and its physical separation of the hot exhaust manifold keeps the air in the intake manifold cooler. Most modern engines are of a crossflow design.
"Crossflow" is often used to refer specifically to
Ford Motor CompanyThe Ford Motor Company is an American multinational corporation based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford, Lincoln, and Mercury brands, Ford also owns Volvo Cars of Sweden, and a small stake...
's
Kent Crossflowborder=0 align=right|-|The Ford Kent is an internal combustion engine from Ford of Europe. Originally developed in 1959 for the Ford Anglia, it is an in-line four cylinder overhead valve type engine with a cast iron cylinder head and block....
4-cylinder
OHVAn overhead valve engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block , and uses pushrods or rods to actuate rocker arms above the cylinder...
engine. This unit has been used in cars from the 1960s up to the present day, albeit with the addition of
fuel injectionFuel injection is a system for mixing fuel with air in an internal combustion engine. It has become the primary fuel delivery system used in gasoline automotive engines, having almost completely replaced carburetors in the late 1980s....
and a modern engine management system. The term was also briefly used in the early 1980s in Australia for the revised 4.1 litre inline six-cylinder engine in Ford's Australian large family car, the Falcon. This was in response to the post-1979 fuel crisis where the Falcon was a comparatively fuel-inefficient car compared to its contemporary rivals.
This term is used for engines which have only one intake and one exhaust valve per cylinder; four (or five) valves per cylinder engines get their superior performance from total port size, not the relative location of the ports.