Just been looking at some yank mk3 GTI's and can anybody tell me why they all seem to have the inlet manifold on the other side of the head, instead of both manifolds at the back? Is there a big difference in the yank head? They look a lot easier to work on. Couldn't seem to find any 16v ones, are they all 8v? They all have air-con but the big red GTI badge they carry looks gay.
That looks like a 2.0 8v crossflow head... I think thats why the inlet mani runs accross the top like that. Isn't that the same engine as used in the mk4 2.0's and the beetles??
From wiki 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. The reverse-flow design is accepted to be inferior to a cross-flow design in terms of ultimate engineering potential, however, the reverse-flow design has been shown to be a more practical and economical manufacturing proposition and has similar potential in forced induction applications (where overly-large valves and "through flow" of gasses on cam overlap are not as desirable as under normally-aspirated conditions). The real problem is that of temperature. With the exhaust ports on the same side as the intake ports, the intake air gets some of the heat, which reduces efficiency.
good thing about any cross flow head is that if you run TB's or carbs they can be on the opposite side to the hot exhaust area & have cold air straight into them.
