Picture 22 of 29 from Album DIY; MPG Sensitive Cruise Control
Here is a block diagram I created for the MPG Sensitive Cruise Control. The IC 7805 is a 5 VDC Fixed Voltage Regulator that provides power to the Ford's MAP Sensor, this sensor generates a pulsating signal that varies with the existing manifold vacuum. That signal is fed to the Audiovox CCS-100 Servo Assembly through the Speed input wire.
With this modification, when you press the set button, what you are actually doing is locking the MPG that it was giving at that moment. This way you can drive with load to maintain a constant fuel consumption, provided that the car doesn't encounters grades to steep or any other resistance, in this case the MPH will drop to much and you would prefer to accelerate manually.
Picture Added 10-30-2008 01:50 PM Added by jomelmaldonado