Quote:
Originally Posted by mjspiess
VSS = Vehicle Speed Sensor
MAP = Ford MAP sensor with vacuum line hooked to intake manifold
Both VSS & signal wire from MAP are connected to SPDT switch & VSS wire for cruise is installed on the common feed for the switch, so the cruise servo is getting feedback from either the VSS (speed) or MAP (load/MPG).
I haven't programmed anything. I basically did exactly what Jomel Maldonado did initially clear back on page 3. He went a step further by buiding an ardiuno with code to tell the cruise to automatically switch back and forth from VSS or MAP based on upper & lower set speed limits. His setup is "smarter" than mine in that it does this automatically. My setup is all manual. All I have is a Ford MAP sensor, 5 volt regulator, SPDT switch & MPGuino to see live MPG.
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Ok, Mj, let me think of it all:
On any cruise control we have three main elements:
1) A reference or monitor variable, we want to keep constant. We get the value from the engine with a sensor.
2) A control variable, which is the fuel injected per time unit.
3) An effector to execute the control, based on our logic. The solenoid of the cruise control over the throttle on old cars, or using a electronic mechanism in newer cars.
In a standard cruise control system (speed logic), our order is “keep speed constant”, so the monitor variable we use is the speed signal of the car (VSS).
The control variable is the amount of fuel supplied to the engine.
The effector is the solenoid that actuates on the throttle, or an electronic mechanism.
On a mpg logic, our order would be: "keep mpg constant" (or within some narrow range). Let us examine the three elements in this case:
The reference or monitor variable would be different, mpg, value we can get from our onboard computer, MPGuino or such.
The control variable is exactly the same, amount of fuel supplied per unit of time. This is important as allows us to use the same Cruise control system we have, the same hardware.
Yes, because the effector device would be the same, we don´t need to change it.
In yr MAP sensitive logic, the MAP signal is used, hoping this will produce a good mpg result. Your order is: “keep MAP constant”, and the system would supply less or more fuel as to keep it constant.
It makes sense to me.
I drive a diesel car, which hasn´t MAP but has a MAF sensor and signal, which may play the same role as MAP as to be the control signal. My computer gives me mpg in real time, so I can see how good is that MAF signal (or other I may choose) to keep mpg constant at certain level.
See sensors sense here:
Mass Airflow MAF Sensors
Do you think MAF would work on a diesel engine?
OldBeaver