Product Spotlight: M20/M42 Intake Adapter July 06 2016, 0 Comments

For the M20 and M42 engines, BMW uses a Bosch air flow meter (AFM) with a square shaped inlet. This makes it difficult to connect custom or aftermarket intake plumbing, because they almost all have round cross sections.

There are intake adapters on the market that simply weld a round tube onto a flange with a square hole on it.

While this is a cheaper solution, the harsh transition is detrimental to flow, which is detrimental to power.

Unsatisfied with the offerings on the market for our M42 engine, we took it upon ourselves to create a properly engineered AFM adapter. Our AFM adapter provides a smooth transition that helps the flow to transition from a round to a square cross section smoothly. 

In the engineering world, we talk about loss coefficients. These numbers describe how much pressure is lost for a particular type of plumbing feature, such as elbows, tees, inlets and nozzles. The more pressure loss, the less the flow. Here are some textbook figures on inlets. 

Without getting too nerdy, the numbers predict the amount of pressure loss due to inlet transitions. While these numbers are meaningless in themselves without knowing other parameters and doing some math, they give a good comparison between different types of inlets. We know that the cheap intake adapters we commonly see have an inlet designed like the middle figure, which introduces a significant amount of pressure drop. There is definitely improvement that can be made.

Our intake adapter doesn't act like an inlet, but instead almost like a straight section of pipe. We are proud to bring properly engineered and properly fabricated parts to the BMW community. 

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M20/M42 Intake Manifold Adapters