LO 9-2 Describe the functions, construction, composition, types, and applications of diesel engine cylinder head assemblies

Reverse Flow Cylinder Heads

A newer engine design for V-type engines is called the reverse flow cylinder head that uses a cross flow valve port design. On a V-block engine using reverse flow heads, the exhaust ports are located inside the engine “Vee” rather than in their traditional location on the outside of the cylinder head. Instead, intake ports—not exhaust ports—are located on the outside surface of the head. This port arrangement shortens the connection distance between the exhaust ports and the turbocharger, or an exhaust aftertreatment system catalyst. The result is a quicker, more powerful turbocharger response. If the exhaust catalyst is closely coupled to the engine and located between the cylinder banks, it will heat up more quickly to enable faster breakdown of noxious emissions. Without outboard exhaust manifolds, engines using reverse flow heads can occupy a smaller footprint beneath the hood of a vehicle where space is limited Figure 10. In fact, when these heads are used in SUVs, pickups, and vans, they take up less under-hood space than the spark ignition engine they replace Figure 11.

FIGURE 09-10: The Ford 6.7 Power Stroke uses reverse flow cylinder heads.

FIGURE 09-11: This Ford 6.7 L Power Stroke uses CGI cylinder heads and a reverse flow cylinder head manifold arrangement.