The ECU

The ECU, short for Engine Computing Unit, is the computer brain of just about every car nowadays.  With the invention of Fuel Injection, there was a need for a computer.  The very act of fuel injection requires many calculations solely because fuel is injected as a rate determined by many sensors and desired outputs.  The ECU is responsible for calculating fuel and timing as well as temperature control and even boost control. 

Here is a list of sensors which are monitored by the ECU

1. Pressure Sensor (How dense is the air going into the engine) - Needed for fuel calculations

2. Throttle Sensor (How open the throttle is to allow more/less air in)

3. Water Temperature (What temperature is the engine operating at) - Colder engine equals colder intake air in turn more fuel is needed

4. Intake Air Sensor (How cold is the air going into the engine) - Needed for fuel calculations

5. Fuel Temperature Sensor ( Measures the temp of the fuel) - safety feature

6. Oxygen Sensor (Measures the amount of air left in the exhaust gas) - Needed for fuel adjustments

Switches monitored by ECU

1. Starter Switch

2. Air Conditioning Switch

3. Power Steering Switch

4. Neutral Switch

5. Clutch Switch

6. Stop Switch

7. Catalyzer Thermo Sensor

8. Electrical Load

9. Exhaust Temp Warning

10. Fuel Pump Operation

11. Fuel Pump Control

12. Air Pump Relay

13. Port Air Control

14. Charge Air Control

15. Turbo Control

16. Pressure Regulator Control

In computer terms the stock ECU operated at 8 bit.  Roughly translated that means 8 ones and zeros traveling at the same time.  Imagine a highway with 8 lanes of traffic and each car being a piece of data.  To put that in perspective, that is the equivalent of sending one alphabetic letter all at once.  A modern PC operates at 32 bit allowing for exponentially more information sent at one time.

Aftermarket ECUs like the PowerFC operate at 16 bit allowing for more calculation at any given moment.  Faster response time and overall better system control are some of the benefits to newer ECUs.

For more information on what an ECU does go to the PowerFC page

Larger Pictures (Click to enlarge)

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This site is meant to give information related to the 1993 (o)Mazda RX-7 Twin Turbo.  Anything from rotary engines to wiring diagrams and turbo upgrades to tuning info, this site has it all! efini 93 rx7 13b anfini Turbo RX-7 Turbo RX7 turbo rx7 rx7tt rx-7tt  As well as the Rotary Engine Pickup Truck aka REPU repu