For most drivers, long discussions arguing the merits of mass airflow sensors (MAF) against those of manifold absolute pressure (MAP) sensors won’t come up. Both sensors deal with monitoring airflow and delivering it to the electronic control unit (ECU), data which helps the computer determine how much fuel to meter out at any given time. And a manufacturer might use a MAP or a MAF or even both together, it just depends on the system’s design. For this reason, the question of MAP versus MAF is a hot topic of debate among tuning enthusiasts who like to design or modify their own systems and accurately measure performance.
So, as mentioned above, both MAP and MAFs measure air going into an engine. But why even bother? It’s actually super important to know precisely how much air an engine is taking in because that determines the air to fuel ratio introduced into the combustion process, and without that ratio pretty much on point, you get no booms and no runsies. And because we are constantly putting different load requirements on our vehicles, this ratio must be expertly maintained. This is where the ECU comes in. It takes a reading of incoming air, and adjusts fuel dispersion accordingly.
The MAP Is Not the Territory
MAP sensors are located at the throttle body. Specifically they, like MAFs, are measuring the vacuum to determine airflow. One of the benefits of a MAP is its location. Because of its proximity to the throttle body and the fact that it usually lives in the intake manifold itself, it has a pretty darn good idea of exactly how much air is entering the intake manifold. It takes into consideration the “absolute pressure” because it accounts for both negative pressure (vacuum) and positive pressure (possible leaks, alternative intakes or an open throttle) and delivers that data.
Good at MAF
MAF sensors are located inline with the intake system, just after the air filter. They are usually designed as a short, wide tube through which all air enters the system, measuring the “flow” as a “mass” of “air.” They can also include a thermosensitive element, which reads air temperature. And this is useful because temperature, as well as altitude, determine air density. So these are also extremely accurate in knowing how much air is entering the system, they just don’t account for positive pressure down the line (as would be present if the engine is equipped with a turbo or supercharger).
To sum up, neither is better than the other exactly and when it comes to MAP versus MAF, they’ve just got different strengths. That’s why some engines use them in tandem to get the most and best information to drive performance as smoothly and efficiently as possible. Whichever your vehicle has, you’ll notice when it goes bad because you’ll start going through fuel faster, the engine will run rough, and your air-fuel ratio will be off. And when that happens, you’ll want to know what you’re dealing with.
Check out all the relays, sensors and switches available on NAPA online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about MAP versus MAF sensors, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photos courtesy of Blair Lampe and Wikimedia Commons.
Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter. In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.