Under the Hood: DodgeSRT-4
OK, engine management geeks, that's a 32-tooth crank trigger wheel (34-2). The engine management is model based, which means it constantly calculates the appropriate fuel and timing outputs instead of just looking them up on a table. The throttle position is interpreted by the ECU as a demand for a certain amount of torque, and the ECU does whatever it can to deliver. If it's hot out, or you're at high altitude, the ECU will try to satisfy your demand by increasing the boost to match the power output under normal conditions (presumably a dreary day in Detroit). Helping with the math are a few unusual sensors feeding the ECU valuable information about underhood conditions. The Air Charge Temperature (ACT) sensor measures the temperature of the air exiting the intercooler, and the Throttle Inlet Pressure (TIP) sensor measures pressure before the throttle body. These are used to predict the turbo speed, so the ECU can avoid overspeeding the turbo. The expected Throttle Position (TPS) Sensor and Manifold Air Pressure (MAP) sensor are also there, but there's no Mass Air Flow (MAF) sensor. Mass flow is calculated from the other values. The TIP sensor occasionally pokes its head out and measures ambient air pressure, too. Trick daddy. Both the MAP and TIP sensors have a 2.25-bar range, meaning they'll read from absolute vacuum to just more than 18 psi. Sensors with larger ranges will be included in Mopar's staged upgrades.
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