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my vehicle for instance didn't have a mass air flow meter. it only has a intake air temperature sensor. is this how the density of air is measured ? because the ecu can work out the difference of the density of the air due to temperature thats being read ?
Exactly what engine management and version are you using? Some systems (eg. Bosche Motronic 2.5 and 2.8) use a hot wire method of measuring the airflow - this uses a property of conductors where their resistance increases with temperature. In practice, a wire in the intake is heated using a fixed voltage across it and is cooled by air passing over it, by measuring the resistance/current of the wire the ECU can calculate the amount of air entering the engine. I believe they also incorporate an air temperature sensor, but not too sure about that.
Dangit, should have gone to Wiki first, much better explanation - https://en.wikipedia.org/wiki/Mass_flow_sensor
It sounds like you're dealing with an ECU that uses the speed density principle. In this case rather than directly measuring mass airflow it's calculated using a MAP sensor, IAT sensor and the ideal gas law. This is the predominant way that aftermarket ECUs function but it's still used by a number of OE manufacturers too.
