Quote:
Originally Posted by piloto
x2 on this question. If it works just damn fine, why not have it? In fact, it creates more space and allows the S65 to fit in there, whereas a double wishbone or other type of multi-link would use up more space towards the center of the car.
OP, to get into the details of the intake design, you'd have to really get with the engineers that designed it. But to oversimplify it, the enclosed "box" allows matching cylinders to help scavenge air into one another. Each closing set of intake valves under each trumpet essentialy creates a pulse wave (different wave characteristics over the range of engine speed). For each closing set of intake valves, there is a set that is opening. So for a given RPM, or in some cases RPM range, you can match cylinders to help "push" air from the one whose valves are closing to the one whose valves are opening. The plenum design, and where the trumpets are located, the trumpet's diameter, and trumpet's length all factor into this, along with intake and exhaust valve diamater, lift, , exhaust header diameter, header length, etc.
Though not exactly accurate, but it helps visualize it, think of the air inside the intake chamber as large baloon that can change shape, and is under constant pressure. The baloon's shape is such that it follows the contour of the intake manifold, and extends to the bottom of each trumpet. Now, as a set of intake valves close, imagine that they push air up through the trumpet and onto this baloon. The baloon is feeling the pressure but has no where to go, but within a nansecond, another set of intake valves open (or the throttle plate under the trumpet), and suddenly the baloon forces its way down that trumpet, due to the pressure it was feeling through the air pushed up from the closing set of valves.
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Cool thanks a lot!
I am always amazed at how much engineering there really is that goes into a proper intake manifold. A lot of cars have a variable length intake with 2 or 3 paths depending on RPM. I am wondering why the m3 did not go this route with this engine as from what I have heard it gives you the best of both worlds at all rpms values.