Thread: Intake Question
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Old 08-15-2021, 01:03 AM
jcp240z jcp240z is offline
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I think it is an error on RealOEM. The 5361 (4.4) intake was never used on the 4.6 motor

Here is an explanation from Bimmerforums
Discussion intakes gets strongly into the subject of fluid Dynamics. The 4.6is has more displacement which pulls more air, it revs to 6500 (higher than the 4.4) and has different camshaft profiles, it's quite different to the 4.4. Incidentally, the 4.6 makes both peak power and torque at higher RPMs than the 4.4...

There are so many intricacies regarding airflow, air intakes and getting air into the cylinder that without scientific testing it's difficult to draw conclusions. Typically, thinner runners increases air velocity which is important at low engine speeds when there isn't much suction from the cylinder tonavcelerate the drawn in air. At higher RPM, velocity of the air isn't (typically) the limiting factor and the actual volume of the air in the intake takes precedence when making power, hence larger diameter runners. You compromise one way or the other.

The DISA valve is a good example of an attempt to overcome limitations of a static intake by changing the length of the intake runners (length isn't the same as diameter of ofcourse, but it demonstrates principle, short runners are good for high rpm and long for slow engine speeds) Ferrari laferrari has an absurdly complex "infinitely variable intake length" system too.

So no single intake design is perfect. One may outperform another on average (total area under the torque curve on a Dyno graph) but there is always a compromise.

That said, the velocity stacks is quite an interesting addition that I'd LOVE to see results of with the M60b40 manifold on the tub44...
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