Just out of curiosity, what is the difference between a map and a maf sensor or is there any difference?
General MAF/MAP Sensors
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General MAF/MAP Sensors
they arent even similar.
a MAF sensor is a "hot wire" sensor. a constant voltage is applied to the wire (often called the film). the wire is positioned in the air flow (usually a sampling channel or chamber in the inlet pipe). the current passing through the wire heats it up. as air flows across it, it cools down. the wire is basically just a positive temperature coefficient resistor. its resistance drops when its temperature drops. the drop in resistance allows more current to flow through it (this maintains the temperature of the wire). the current change affects the voltage signal returning to the ecu. this voltage is interpreted as air flow by the ecu. air temperature and humidity are taken into consideration since they also affect the temperature of the wire. this sensor will be affected by air temperature and density so i personally think its the better method to measure mass air flow.
a MAP sensor is completely different. it simply compares the pressure difference between 2 chambers. one chamber is sealed and used as the reference pressure (usually a vacuum) and the other chamber is connected to the intake manifold (usually by a vacuum hose). when the pressure in the intake manifold changes, this will change the voltage signal going back to the ecu from the MAP. a pressure drop will cause a voltage drop. this voltage is only interpreted as manifold pressure. the ecu will also need to use the signals from the rpm sensor and air temp sensor to calculate air mass, pressure alone is not enough. plus any vacuum leaks on the hose, or indeed any other vacuum leaks on the manifold, will affect this sensor's signal, for that reason i think its not a good way to calculate mass air flow.
a MAF sensor is a "hot wire" sensor. a constant voltage is applied to the wire (often called the film). the wire is positioned in the air flow (usually a sampling channel or chamber in the inlet pipe). the current passing through the wire heats it up. as air flows across it, it cools down. the wire is basically just a positive temperature coefficient resistor. its resistance drops when its temperature drops. the drop in resistance allows more current to flow through it (this maintains the temperature of the wire). the current change affects the voltage signal returning to the ecu. this voltage is interpreted as air flow by the ecu. air temperature and humidity are taken into consideration since they also affect the temperature of the wire. this sensor will be affected by air temperature and density so i personally think its the better method to measure mass air flow.
a MAP sensor is completely different. it simply compares the pressure difference between 2 chambers. one chamber is sealed and used as the reference pressure (usually a vacuum) and the other chamber is connected to the intake manifold (usually by a vacuum hose). when the pressure in the intake manifold changes, this will change the voltage signal going back to the ecu from the MAP. a pressure drop will cause a voltage drop. this voltage is only interpreted as manifold pressure. the ecu will also need to use the signals from the rpm sensor and air temp sensor to calculate air mass, pressure alone is not enough. plus any vacuum leaks on the hose, or indeed any other vacuum leaks on the manifold, will affect this sensor's signal, for that reason i think its not a good way to calculate mass air flow.
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OP
OP
Thanks jug, but now would a bravo have both a map and a maf sensor or would one be for the petrol engine and the other for a diesel?
there are no hard and fast rules, it depends on what the manufacturer decided was the best solution at the time, but generally:
-on an N/A engine you would expect one or the other to be fitted, but not both.
-on a turbo you would expect a MAP to be fitted, but you could also have a MAF if the MAP is only used for barometric pressure (rather than both barometric pressure and absolute pressure). in those cases you would usually have the MAP (called a BAP in this case) built into the ecu. so you would have a MAP or a MAF & BAP.
but there are plenty of cars that dont follow either rule.
every car will have a single method of calculating mass air flow, there are actually several more methods than the 2 described here.
-on an N/A engine you would expect one or the other to be fitted, but not both.
-on a turbo you would expect a MAP to be fitted, but you could also have a MAF if the MAP is only used for barometric pressure (rather than both barometric pressure and absolute pressure). in those cases you would usually have the MAP (called a BAP in this case) built into the ecu. so you would have a MAP or a MAF & BAP.
but there are plenty of cars that dont follow either rule.
every car will have a single method of calculating mass air flow, there are actually several more methods than the 2 described here.
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OP
OP
Cool thanks for that my curiosity has now been satisfied 
Yup is a confusing subject acronyms as people often use the wrong ones.
