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Old 02-20-2012, 01:13 AM   #1 (permalink)
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Kill-switch/TPS-based Cruise

I have a couple additions planned for my new car, a 2001 Toyota Corolla.
The first is a kill switch to shut off the fuel injectors, allowing me to coast in neutral, thus eliminating engine drag. I have a few reservations about this process and was hoping that someone could clear things up a bit:
I read that about 0.001% of cars in production have DFCO(deceleration fuel cut off - shuts off fuel injectors while coasting above a set speed). Is this true? Am i extremely lucky to have one that does, or is this statistic/my testing(scanguage reads 9999MPG when pedal is released) faulty?
If i do indeed have DFCO, then it doesnt make much sense to install a cut-off. For the rare instances when i will be coasting(a 3 mile down-hill, about 4 times a week), i can just deal with the extra hassle of using the key.
I would like to install a cruise control/hand throttle device. Basically, i know what the most efficient throttle position is, but i hate the hassle of using my foot to maintain it. I want to install a cruise control device that operates with several buttons, these would include a way to set the throttle position, a momentary push button to increase by 2, and one to increase by 4. In addition, one to decrease by two. For example, i could set it at 17, start going downhill with a fair-grade incline after, increase to 21 temporarily, then reduce to 19 right as i hit the hill. I would speed up to 72-75, then top the hill at 58-60.
Any thoughts on this? I would like to make it automatic, basically, set a permanent set of parameters on how far to deviate from the set speed, a maximum and minimum throttle position, and if possible a way to detect the current incline in degrees, pos./neg. of 90. I have very little programming knowledge - i tried to learn it, but the best i can do is a simple script in C++. Most of the interface needs to be mechanical/electrical, and not digital, or have someone else write the script, and give me a circuit diagram.
Thank you for any input you provide. All comments are welcome.

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Old 02-20-2012, 02:24 AM   #2 (permalink)
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Probably more like 99% of currently produced cars have DFCO. Since it severely shortens coasting distances, I believe most hypermilers rarely use it. Neutral coasting works far better.

See this thread for a good discussion of load-sensitive cruise control, particularly jomelmaldonado's posts, since he made one work for his car.

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Old 02-20-2012, 02:48 PM   #3 (permalink)
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Once I installed my kill switch I used engine off coasting a great deal more. Wen I decelerate my order of preference is engine off coast then DFCO in 5th then down shifting then brakes.

My hand throttle is a bicycle shiftier routed to the peddle. get the power setting dialed in with my foot then set it with the lever mounted to my shifter. very low tech but it works and was simple.


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