Mass air/speed density explained
2/12/13, 11:34 AM
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Mass air/speed density explained
WHAT IS
SPEED DENSITY...
Speed density accepts input from sensors that measure engine speed in rpm and load via manifold vacuum. The computer then calculates airflow from a preprogrammed lookup table. Engine rpm is read through a tach signal and vacuum through the M.A.P ( manifold air pressure ) sensor and also uses the o2 sensor. The computer looks at the air/fuel ratio from teh o2s and makes needed corrections.
Speed density has no sensors that measure airflow all the fuel mapping must be preprogrammed. So significant changes to the motor require reprogramming of teh computer.
MASS AIR FLOW...
Mass air flow ( MAF ) use a sensor mounted before the throttle body that measures the amount of air going into the motor. The maf uses a "hot wire" to measure airflow. Air moving across the wire draws away some of teh heat so an increase in current is needed to maintain its fixed temperature. The MAF then converts the current reading into a signal for teh computer which equates voltage value to mass flow. Once the ecm knows the amount of air entering the motor it uses other sensors to figure out the motors current state of operation ( idle, acceleration, engine temp, etc. ) it then refers to an electronic map to find the correct air/fuel ratio and select the fuel injector pulse width to match the input signals.
Mass air flow is much more flexible in compensating for motor changes since it actually measures airflow instead of computing it based on preprogrammed assumptions. MAF is self compensating for most reasonable upgrades .
SPEED DENSITY...
Speed density accepts input from sensors that measure engine speed in rpm and load via manifold vacuum. The computer then calculates airflow from a preprogrammed lookup table. Engine rpm is read through a tach signal and vacuum through the M.A.P ( manifold air pressure ) sensor and also uses the o2 sensor. The computer looks at the air/fuel ratio from teh o2s and makes needed corrections.
Speed density has no sensors that measure airflow all the fuel mapping must be preprogrammed. So significant changes to the motor require reprogramming of teh computer.
MASS AIR FLOW...
Mass air flow ( MAF ) use a sensor mounted before the throttle body that measures the amount of air going into the motor. The maf uses a "hot wire" to measure airflow. Air moving across the wire draws away some of teh heat so an increase in current is needed to maintain its fixed temperature. The MAF then converts the current reading into a signal for teh computer which equates voltage value to mass flow. Once the ecm knows the amount of air entering the motor it uses other sensors to figure out the motors current state of operation ( idle, acceleration, engine temp, etc. ) it then refers to an electronic map to find the correct air/fuel ratio and select the fuel injector pulse width to match the input signals.
Mass air flow is much more flexible in compensating for motor changes since it actually measures airflow instead of computing it based on preprogrammed assumptions. MAF is self compensating for most reasonable upgrades .
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