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Message: <blockquote data-quote="taqu" data-source="post: 323044" data-attributes="member: 7651">There're actually 3 air metering ways :1. AFM - airflow meter2. MAF - mass airflow3. MAP - manifold absolute pressure (or speed/density)I'm no expert so I'll just give some link : http://www.promax.uku.co.uk/map.htmSome copy-paste from http://www.teglerizer.com/fi/bem/Basics%20of%20engine%20management.htm Engine loadEngine load is normally determined by one of the following methodsThrottle Position Sensor (no measuring of airflow at all)The most common engine load sensor especially on after market systems. A TPS is a small potentiometer (or ‘throttle pot’) which is connected directly to the throttle shaft and turns with it. It returns a value to the EMS depending on the throttle position. TPS sensors are normally used on performance engines where airflow sensors might become confused because of pulses in the inlet tract, because they do not measure airflow but simply give a throttle position, airflow is assumed to be constant for any given engine speed and throttle position. If the engine is further modified the airflow characteristics may change and the engine may need re-mapping. EMS systems that use direct airflow measurement can often cope with changes more effectively and can alter the fuelling to suit without a re-mapping session.Air metering flap (AFM)Another way of determining the engine load is to measure the airflow into the engine and this can be done using a flap which is deflected by incoming air, this is commonly known as an airflow meter. These are common on older injection systems, but can be confused by reverse pulses in the inlet tract when more extreme cams are used and can be restrictive to the inlet airflow.Manifold Air Pressure sensor (MAP)These measure the vacuum or air pressure in the inlet manifold that in turn gives an indication of load, more commonly used on turbocharged engines to give an indication of boost level. This is often referred to as a MAP sensor, although not to be confused with a map.Hot wire (MAF)This approach uses a heated platinum wire and measures the current required to keep it at a particular temperature. As air passes over the wire it cools it down, the more air that passes, the greater the cooling effect and therefore the greater the current. The hot wire system can be also be confused by reverse pulses when more extreme cams are used.</blockquote>

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