speed density vs mass air
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
The main difference is in how the computer determines the amount of air entering the engine. A speed density computer infers the amount of air based on the air temperature, throttle position and manifold vacuum. A mass air computer uses a mass air meter to directly determine the mass of the air entering the engine. The computer uses the barometric air pressure sensor and air temperature to fine tune what the mass air meter senses.
Neither one is more reliable than the other. The most common ones are all EEC-IV, mass air and speed density. The mass air computer is better at adapting to modifications that change the airflow characteristics of the engine. In general, mass air computers also fire the injectors sequentially (truck computers, cars had sequential speed density computers) instead of batch fire, where four injectors are fired simultaneously.
Neither one is more reliable than the other. The most common ones are all EEC-IV, mass air and speed density. The mass air computer is better at adapting to modifications that change the airflow characteristics of the engine. In general, mass air computers also fire the injectors sequentially (truck computers, cars had sequential speed density computers) instead of batch fire, where four injectors are fired simultaneously.
Posting Guru
Joined: Dec 1999
Posts: 1,903
Likes: 2
From: Copley, OH
Unless you go with a radical change to the camshaft or swap for a set of full-race ported heads, it's pretty likely that the S/D system won't care. There is no simple bolt-on mod that will upset S/D. The best of all possible worlds is a 95 truck with MAF and OBD-I
Senior User
Joined: Apr 2003
Posts: 164
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From: Heart of Dixie
