Crossflow cylinder head
Encyclopedia
A crossflow cylinder head is a cylinder head
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 head
designs that have the ports on the same side.
A crossflow head gives better performance
, 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 valve
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. The engineering terminology for these benefits is greater volumetric efficiency
.
"Crossflow" is often used to refer specifically to Ford Motor Company
's Kent Crossflow
4-cylinder OHV
engine. This unit has been used in cars from the 1960s up to the present day, albeit with the addition of fuel injection
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 result in engines having superior performance sourced from total port size, rather than the relative location of the ports.
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...
that features the intake and exhaust
Exhaust manifold
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple inputs and outputs.In contrast, an inlet manifold is the part of an engine...
ports on opposite sides. The gases can be thought to flow across the head. This is in contrast to reverse-flow cylinder head
Reverse-flow cylinder head
A 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 performance
Engine tuning
Engine 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....
, 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 valve
Poppet valve
A 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. The engineering terminology for these benefits is greater volumetric efficiency
Volumetric efficiency
Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More specifically, volumetric efficiency is a ratio of what quantity of fuel and air actually enters the cylinder during induction to the...
.
"Crossflow" is often used to refer specifically to Ford Motor Company
Ford Motor Company
Ford Motor Company is an American multinational automaker 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 and Lincoln brands, Ford also owns a small stake in Mazda in Japan and Aston Martin in the UK...
's Kent Crossflow
Ford Kent engine
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 engine with a cast-iron cylinder head and block.-Pre-Crossflow:...
4-cylinder OHV
Overhead valve
An 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 injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol 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
Ford Falcon (Australia)
The Ford Falcon is a full-size car which has been manufactured by Ford Australia since 1960. Each model from the XA series of 1972 onward has been designed, developed and built in Australia and/or New Zealand, following the phasing out of the American Falcon of 1960–71 which had been re-engineered...
. 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 result in engines having superior performance sourced from total port size, rather than the relative location of the ports.