I drive frequently on interstate and other limited access highways through modestly rolling terrain (MT, WY, and CO.) Since I generally use the speed control and am also concerned with fuel economy, I have learned to use the up(+) and down(-) on the speed control stalk to adjust my speed according to the terrain. Each approxiamates a change of 1mph.

Caveat:
For my unique driving situation, please keep in mind I am usually alone on the road and don't have much traffic enforcement to deal with. When I am driving in traffic, I don't use speed control.

For example, when travelling downhill or downwind, I gradually bump up my set speed with the stalk, usually about 1mph every few seconds. I watch the instant fuel efficiency gauge to vary the rate of accelleration. I will stop increasing the speed when I reach my maximum or the mpg gauge reads less than 40mpg. Then, on level or uphill, I slowly knock the set speed down with the stalk, until the car registers 40mpg again, or I reach the minimum speed I desire. When I am cruising the open roads with no traffic, I can ease my way uphill and bomb downhill. With this strategy, I have been able to consistantly average 68mph(actual) at 44mpg(calculated) or better on the highway.

I realize that this strategy is mostly playing around with the car's kinetic energy and gravitational potential energy, converting one to the other and then back again over and over.

What I am doing a simple electronic device or software code could do even better and without my constant scanning of the mpg gauge; which, in some driving environments can be distracting.

Question finally:
Does anyone know of a way, either modifying the speed control software or through an external electronic device, of a way to accomplish this automatically? Here is what I imagine would take place.
You set your target speed on the speed control, e.g. 70mph. Previously, you defined an envelope of your maximum and minimum speeds, e.g. +7mph and -10mph. In this example, your actual velocity would range from 77mph to 60mph. Then the computer or device would vary your speed through this envelope, depending on the instant fuel economy. Thus, when able to accelerate using little fuel, such as travelling downhill or with a tailwind, the speed would increase. The opposite when instantaneous fuel economy decreased. The car would gradually slow until your minimum speed was acheived or fuel economy stopped decreasing.


I know speed and fuel efficiency data are output from the diagnostic port and can easily be read and analysed by computers. Is it possible for a computer to send the up(+) and down(-) signals to the speed controler?


I hope I haven't confused anyone and will try to clear up questions posted. Sorry about syntax and grammar, English isn't my native language.

 

From this thread, https://www.greenhybrid.com/discuss/...control-20021/, it seems some of you are also using the speed control as I am. Does anyone know about possibly automating this strategy through electronics?

Thanks

 

Before they invented fancy cruise control electronics, they used to have a thing called a "hand throttle". A hand throttle allowed you to fix the throttle in one position, as if you just held your right foot stationary. It allowed the vehicle to slow down on the up grades, and to speed up on the down grades. And, in the process, a hand throttle avoids using quite a lot of fuel to maintain speed on those up grades.

Modern electronic cruise controls try to maintain constant speed by modulating the throttle position. In the process, they waste rather a lot of fuel.

I think it should be easy for the software developers to program the cruise control to behave more like a hand throttle. They really just need an input to tell the software when the driver desires that behavior. I would nominate the "ECO" button: When the ECO button is not engaged, the CC should behave normally and maintain a constant speed. But, when the ECO button is engaged, the CC should use a running average of speed measurements, and allow a wider range of speed, to generate behavior more like a hand throttle.

 

My Sienna has laser guided cruise control which automatically slows the car when approaching another car. The CC switch arm has a fourth position. From the center/normal position, up will resume or increase the set speed and down will set the target speed or decrease it, just like the three positions of the TCH CC switch arm. Additionally, by pressing the arm forward (towards the dash), you can switch from laser guidance to normal CC behavior. A display area at the bottom of the speedometer dial clearly identifies which mode you are in (and whether a vehicle in front is laser dectected, and other info).

This fourth "forward" momentary switch position would be perfect for switching the CC of the TCH from speed hold mode to max econ mode.

I think I would design the max econ mode to take advantage of low "throttle" acceleration up to 5 MPH over the set speed, and minimize any throttle setting getting less than 40 MPG down to 10 MPH under the set speed, with no throttle setting getting less than 15 MPG. That is, a pretty conservative (i.e., not the very best FE), but otherwise excellent FE with minimal chance of jeopardizing safety anywhere it is safe to use CC to begin with. (All MPH & MPG threshold values subject to more informed/more reasonable values!)

-- Alan

 

This is actually very feasible. The CC needs to able to be programmed to generate a certain amount of torque rather than speed. By holding the available torque to the desired limit, the vehicle would lose some speed on the uphill, but gain it again on the downhill.