speed density of maf
#2
07-14-2006, 09:37 PM
RE: speed density of maf
A CPI motor does not have a MAF sensor. The throttle body has a TPS (throttle position sensor), IAC (idle air control) valve, and just a bit behind the TB is the MAP (manifold absolute pressure) sensor. There is also an air temp sensor in the plastic ducting just before the throttle body.
#4
07-15-2006, 10:40 AM
RE: speed density of maf
yeah, you are correct in that. A speed density system really doesn't actually know how much air is entering the system like a Mass Air Flow system does. Inorder to swap out a cam or really take advantage of any other mod, you would have to have the PCM (powertrain control module) tuned to your specific upgrades. Here's a little peice on the speed density systems (see below). What's interesting is that pretty much all of the aftermarket EFI conversion systems for older vehicles are speed density based, but they come with easy to use ECM (engine control module) editting software for their own custom ECMs.
Speed Density
Speed Density systems accept input from sensors that measure engine speed (in rpm) and load (manifold vacuum in kPa), then the computer calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engine’s volumetric efficiency (VE) under varying conditions of throttle position and engine speed. Engine rpm is provided via a tach signal, while vacuum is transmitted via an intake manifold-mounted Manifold Air Pressure (MAP) sensor. Since air density changes with air temperature, an intake manifold-mounted sensor is also used.
Production-based Speed Density computers also utilize an oxygen (O2) sensor mounted in the exhaust tract. The computer looks at the air/fuel ratio from the O2 sensor and corrects the fuel delivery for any errors. This helps compensate for wear and tear and production variables. Other sensors on a typical Speed Density system usually include an idle-air control motor to help regulate idle speed, a throttle-position sensor that transmits the percentage of throttle opening, a coolant-temperature sensor, and a knock sensor as a final fail-safe that hears detonation so the computer can retard timing as needed.
GM’s Tuned Port Injection (TPI) set-ups used Speed Density metering from ’90-’92, as did ’91-’93 LT1 engines. All ’86-’87 and ’88 non-California Ford 5.0L-HO engines used Speed Density metering. Most Mopar fuel- injection systems have used Speed Density too.
Because a Speed Density system still has no sensors that directly measure engine airflow, all the fuel mapping points must be preprogrammed, so any significant change to the engine that alters its VE requires reprogramming the computer.
Speed Density systems accept input from sensors that measure engine speed (in rpm) and load (manifold vacuum in kPa), then the computer calculates airflow requirements by referring to a much larger (in comparison to an N Alpha system) preprogrammed lookup table, a map of thousands of values that equates to the engine’s volumetric efficiency (VE) under varying conditions of throttle position and engine speed. Engine rpm is provided via a tach signal, while vacuum is transmitted via an intake manifold-mounted Manifold Air Pressure (MAP) sensor. Since air density changes with air temperature, an intake manifold-mounted sensor is also used.
Production-based Speed Density computers also utilize an oxygen (O2) sensor mounted in the exhaust tract. The computer looks at the air/fuel ratio from the O2 sensor and corrects the fuel delivery for any errors. This helps compensate for wear and tear and production variables. Other sensors on a typical Speed Density system usually include an idle-air control motor to help regulate idle speed, a throttle-position sensor that transmits the percentage of throttle opening, a coolant-temperature sensor, and a knock sensor as a final fail-safe that hears detonation so the computer can retard timing as needed.
GM’s Tuned Port Injection (TPI) set-ups used Speed Density metering from ’90-’92, as did ’91-’93 LT1 engines. All ’86-’87 and ’88 non-California Ford 5.0L-HO engines used Speed Density metering. Most Mopar fuel- injection systems have used Speed Density too.
Because a Speed Density system still has no sensors that directly measure engine airflow, all the fuel mapping points must be preprogrammed, so any significant change to the engine that alters its VE requires reprogramming the computer.
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Pipewrench Dale
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