Quote:
Originally Posted by TomsSVX
Load is determined using the mass airflow rather than manifold absolute pressure sensors like newer ssubies do
Tom
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I've got a MY11 Forester S which runs the same engine / turbo as the MY11 Impreza... running MAF still. The only MAP based Subaru's I know of from factory are some of the MY02 Outbacks (H4 and H6).
MAP sensor is only used for boost cut and barametric compensations. However sometimes you can flash the rom to a Group N version which runs on MAP -
romraider for more.
Quote:
Originally Posted by b3lha
The ECU needs to know the quantity of air it is getting, so it can work out the quantity of fuel to mix with it.
A MAF sensor measures it directly.
With a MAP based system you need to measure pressure and temperature and then calculate the quantity based on those readings. When you step on the gas, Mass Airflow changes almost instantly but Manifold Pressure lags behind. So you have to do TPS delta compensations to guess how the airflow is changing while you wait for the pressure to catch up.
MAF systems are faster to respond and more accurate. So they run smoother, especially at low rpm where precision is important. They suffer from less hesitation and provide better drivability. That's why most modern ECUs use MAF.
MAP tuning becomes a lot more useful when you increase the horsepower beyond what the manufacturer designed for. When your airflow exceeds what the MAF can measure, you either have to fit a bigger MAF (with reduced precision), or go to a MAP based system.
Some aftermarket systems like EcuTek RaceROM and Cobb Accessport can use MAF at low rpm and switch to MAP when the MAF gets maxed out. But obviously neither of those is available for the SVX.
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Well said.