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Evolution III Intake Trumpets
Larger diameter

What the trumpets look like without the Plenum

This is what is inside your big black "M Power" intake plenum, for those that have never had it apart. These are the intake runners, sometimes called trumpets (for obvious reasons). These trumpets smooth the flow of air into the throttle bodies and from there into the intake ports. The length of the trumpets is an important criteria in determining the torque and horsepower characteristics of your engine. The intake system is similar to the exhaust side in that there are pressure waves which travel back and forth along its length. The pressure waves coming out of the intake tract will reverse direction at the trumpet entrance. Thus by altering the length of the trumpets it is possible to change the timing of the returning pressure pulse to the intake valve. The complete scenario is quite complicated but suffice it to say that the geometry of the trumpets will affect how your engine makes power.


A look down the polished intake side

The reason that I purchased the Evo III intake trumpets is that they have a larger diameter than the stock 2.3 liter units. Since I was enlarging my throttle bodies it was only natural to match them to larger trumpets (and larger intake ports as well). This helps preserve the "balance" of the system. The finish of the trumpets from the factory is very rough on the newer production units. They require a lot of patient work with porting tools to get them smooth and to match with the throttle bodies. I purchased the trumpets from Nick Alexander BMW in LA since it was convenient. But they are available from sources other than the dealer. Mitch Herman carries them for example.


Evo III Intake Venturi
p/n 11 61 1 315 264
$314 @ Nick Alexander BMW

A look down the polished outlet side

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