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MAP vs. MAF—What’s the difference?

Anyone who’s been around cars a while will inevitably hear the acronyms “MAP” or “MAF”, which refer to specific types of sensors in the intake. Pretty much every car we buy today has factory computers that take the readings of these sensors in order to calculate the amount of air going into the engine, which is important for proper combustion. But what exactly are these sensors? And what’s the difference between them?

 

Manifold Absolute Pressure (MAP):

A MAP sensor is typically located inside the intake manifold. It sends the ECU (Engine Control Unit) vacuum and positive air pressure readings to indicate how much calibrated fuel is necessary for optimum combustion. Most turbocharged or supercharged vehicles use a MAP sensor, since there is a turbocharger or supercharger pressurizing the intake tract. In the case of a naturally aspirated vehicle, the MAP sensor will read vacuum only.

Mass Air Flow (MAF):

A MAF measures the mass flow rate or volume of air going into the engine. The two most common kinds of MAF sensors used today are the Hot Wire MAF and the Hot Film MAF. The Hot Wire places a thin heated wire in the path of the air stream to directly measure air mass. The Hot Film version uses a metal film grid to read the airflow. Both types serve the same purpose of providing a particular reading to the ECU so it can trigger the right amount of fuel for proper combustion. Most of today’s cars use the Hot Wire MAF.

 

What are some differences between a MAP and MAF sensor?

While a MAF sensor is always located before the throttle body, a MAP sensor can usually be found attached to the intake manifold. Because it is in the intake tract, A MAF sensor will also have its own housing (usually plastic) to hold it in place.

In a MAP sensor-only setup, however, it needs to be located after the throttle body (and usually inside the intake manifold) to be able to measure both vacuum and positive air pressures.

There is the rare occurrence where you can find a MAP sensor in the intake tract, before the throttle body. In cases like this, there is a MAF sensor as well. The computer may be using the MAP sensor to measure only the positive air pressure coming from a turbocharger or supercharger. This combo may also be found in setups where a larger MAF may become too turbulent at low load, and the MAF is used at high load for more accuracy in a naturally aspirated motor. Whatever the case, the car manufacturer is striving for the best of both worlds when using the pair.


CRV Engine Bay

MAF and MAP Sensor Locations on a 2016 Honda CR-V

CRV Engine Bay

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