MASS AIRFLOW -VS- SPEED DENSITY
12-13-2006, 02:10 AM
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MASS AIRFLOW -VS- SPEED DENSITY
I was doing some research and ran across this information. I thought it might be useful to others:
MASS AIRFLOW -VS- SPEED DENSITY
Speed density (SD) and mass airflow (MAF) fuel management systems are alternate methods of gathering information about the quantity of air inducted into an engine equipped with electronic fuel injection. This airflow information is a vital ingredient in computations made by the onboard computer that manage the engine's fuel delivery and ignition spark timing functions to suit operating conditions.
The big difference between SD and MAF is that SD calculates airflow data while MAF measures it. The SD calculation process compares real-time data gathered by an array of sensors against preprogrammed reference maps stored in the vehicle computer. The result is a series of if / then calculations that prompt appropriate fuel injector pulse width and ignition timing events.
In contrast, MAF informs fuel delivery and ignition events by physically measuring the quantity of air moving through the intake tract. It's done with an airflow meter containing a heated wire. Increased airflow cools the wire so more voltage is needed to maintain the specified temperature level. By measuring the voltage increase, MAF is able to calculate airflow.
The primary drawback to the MAF strategy is that the airflow meter containing the heated wire must be positioned directly in the path of the intake tract. Depending on the design, this can restrict airflow and reduce engine efficiency. The primary drawback to the SD system is its dependence on preprogrammed reference maps. When aftermarket parts that increase airflow capacity are installed (cam, intake, heads, etc.), many times the computer's data tables lack sufficient range to compensate and poor performance results. In cases where the computer is user programmable, the operating parameters can be changed with a laptop computer, but its time consuming and risky. On the contrary, MAF, with its feedback system can respond to increased intake air flow and "learn" to adapt by tweaking the fuel and ignition spark delivery to optimize output, with no programming needed. You simply install the system and go!
QR weighed the options and wisely decided that MAF was the way to go with its MASS-Flo system. And by utilizing the modified GM MAF unit, the flowpath restriction argument is nullified.
Source
Quality Roadsters, West Brookfield, MA; 508/867-6733; www.qualityroadsters.com
Speed density (SD) and mass airflow (MAF) fuel management systems are alternate methods of gathering information about the quantity of air inducted into an engine equipped with electronic fuel injection. This airflow information is a vital ingredient in computations made by the onboard computer that manage the engine's fuel delivery and ignition spark timing functions to suit operating conditions.
The big difference between SD and MAF is that SD calculates airflow data while MAF measures it. The SD calculation process compares real-time data gathered by an array of sensors against preprogrammed reference maps stored in the vehicle computer. The result is a series of if / then calculations that prompt appropriate fuel injector pulse width and ignition timing events.
In contrast, MAF informs fuel delivery and ignition events by physically measuring the quantity of air moving through the intake tract. It's done with an airflow meter containing a heated wire. Increased airflow cools the wire so more voltage is needed to maintain the specified temperature level. By measuring the voltage increase, MAF is able to calculate airflow.
The primary drawback to the MAF strategy is that the airflow meter containing the heated wire must be positioned directly in the path of the intake tract. Depending on the design, this can restrict airflow and reduce engine efficiency. The primary drawback to the SD system is its dependence on preprogrammed reference maps. When aftermarket parts that increase airflow capacity are installed (cam, intake, heads, etc.), many times the computer's data tables lack sufficient range to compensate and poor performance results. In cases where the computer is user programmable, the operating parameters can be changed with a laptop computer, but its time consuming and risky. On the contrary, MAF, with its feedback system can respond to increased intake air flow and "learn" to adapt by tweaking the fuel and ignition spark delivery to optimize output, with no programming needed. You simply install the system and go!
QR weighed the options and wisely decided that MAF was the way to go with its MASS-Flo system. And by utilizing the modified GM MAF unit, the flowpath restriction argument is nullified.
Source
Quality Roadsters, West Brookfield, MA; 508/867-6733; www.qualityroadsters.com
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