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Old 05-28-2009, 07:40 AM   #91 (permalink)
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I'll probably have time to poke under the dash today and get some data.

Step one: to make a signal generator to replace the vss signal.

Step two: link the new vss signal to the throttle position sensor so that when the accellerate button is pushed, the 'fake' vss signal will increase. This should fix the problem of the cruise pushing the throttle to wide open due to a lack of feedback. It also means I don't have to hack into the cruise control itself. Unfortuneately, the TPS signal is variable voltage, not variable pulse like the VSS.

As I write this, putting in a ford MAF sensor and linking to that like another poster did is starting to sound like a simpler solution.

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Old 05-29-2009, 10:24 PM   #92 (permalink)
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This page here (Vehicle Speed Sensor Questions: Questions About a Vehicle Speed Sensor | Suite101.com) suggests the output of the VSS is 0.5 volts AC.

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Old 05-29-2009, 11:52 PM   #93 (permalink)
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Having a steady throttle setpoint may not be so good of an idea.
Removing the feedback loop from an analog circuit often causes undesirable results.
The very little part throttle needed to cruise on level ground can cause the vehicle to slow severely up a hill. While this can be corrected by a bit of right pedal, what happens when the reverse is true?
The vehicle will continue to accelerate downhill, possibly to a dangerous level.
A control circuits logic needs 3 parameters, a setpoint, a reference input and an analog output.
When watched on a graph, they get real funny when the input doesn't respond to the output. The PID gets more aggressive trying to make them match.
Given a reference that "behaves", as with the Ford MAP sensor, they will modulate correctly and "settle in" as tests show.

Readers Digest version: Controllers need real feedback not a faked signal or thay doan work so good.
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Old 05-30-2009, 08:17 PM   #94 (permalink)
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I don't think I'm going too far on a limb here. Many motorcycles have a throttle lock for highway cruising. Obviously, if going up or down a steep hill, adjustments have to be made. I wouldn't do this on my ford taurus because it has a lot of momentum carrying it down a hill. The echo; not so much.

My VSS reads 2.1 V AC and the Hz changes with speed (as I would have hoped) from 0 to 80 HZ
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Old 05-31-2009, 12:01 AM   #95 (permalink)
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I know this is an old thread, but I stumbled on it and it made me think of my grandfather tonight. Years ago he had a device that was sold commercially that hooked up to the throttle and held it at a constant position. A lever set the position to the desired speed and you could move the lever up or down to tweak the speed. There was one safety feature that would disengage the thing if you stepped on the brake. It had a solenoid that released the mechanism. My guess is that something like like this would accomplish what you are talking about. It would drive all the other motorists crazy, but then it's not much different than me staying in leanburn in traffic. My grandfather's device was chrome and kind of ugly and probably only made to work for cars in the 50s and 60s that had big dashboards, etc., but for it's time it was a ecomoder-type device. All I have left of that device today is the solenoid
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Old 07-08-2009, 01:06 AM   #96 (permalink)
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Originally Posted by Zotz View Post
Perhaps a little cross pollenation: jeepers use hand throttles a lot offroad and it's a simple mod, probably adaptable to most cars. Here's an installation.

Many simply get the parts from a bike shop. Goes unsaid that you have to be a bit careful using it.
Thank you for the inspiration. I made one of these for my car in preparation for an out of town highway trip and it worked great! Though it was more to give my right leg some relief than for mpgs. (Here's my build thread)

I did it kind of quick so it would be ready for my trip, and had improvements in mind to add later, but since it looks like I'll be upgrading to a car with cruise control in a month or two I put the improvements on hold, but my vehicle upgrade set me to thinking about stock cruise controls:

It seems to me that if the transmission were prevented from downshifting a cruise control provides a form of P&G. With the cruise set, when a hill is encountered, the speed drops and the throttle is increased to compensate. If the speed doesn't return to the setting the throttle will continue to increase. If at full throttle the ECU over-riches the air/fuel mix, than limiting the throttle travel might also be required.

On the downhill, when the speed returns to the set speed the throttle is released until the point the set speed is maintained. The main downside is that if the hill is steep enough to permit gravity alone to maintain the speed the engine will DFCO instead of neutral coasting, but a modified cruise could suffer from that same problem. (And perhaps a hand throttle or other mod could be used to keep the engine out of DFCO.)

I may be way off base, and haven't had a chance to compare techniques with any sort of documentation; this is just theory, (and perhaps flawed theory at that). Just thought I'd add my 10 cents (inflation is affecting everything ) to the conversation.
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Old 02-14-2010, 04:46 PM   #97 (permalink)
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Originally Posted by Harpo View Post
I add a step or two of ACCEL at the bottom of the hill then remove those as I feel the load. That tends to keep the rapid throttle additions (adjusting to instant decels) down to a minimum. I've been using that in the RAM for years to eliminate that overcompensation.
I do the same thing. Tap down one or two mph when I climb, and add one or two back going back down. If the hill is too steep, I cancel the cruise until I pass the hill because mine will actually downshift the trans when going downhill in order to maintain speed.

Oldertech, my grandpa did the same thing with his 79 diesel Rabbit. He got an aircraft throttle control and connected it to the injector pump throttle lever. This he could lock at a throttle position and would not have to worry about hills.
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Old 02-15-2010, 03:15 AM   #98 (permalink)
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Lightbulb A Better way of calculating going up and down hills

ok so why not use a electronical level to calculate the degree of incline or decline on the hill, by using the speed you could figure out the momentum and be able to program in when to set the gas and how much also depending on the incline or decline, whats your thoughts?
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Old 02-15-2010, 08:35 AM   #99 (permalink)
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The inclinometer has no way of knowing that you are on a short dip in the road, or a long hill.
Maybe the inclinometer output could be logically ANDed with hill data on file and a GPS to tell the controller where you are.?.

A few years ago (1998), I was thinking about some 'Electronic Counter Measures' using GPS w/ a CPU to memorize the RF spectrum vs location, I sent some ideas to the makers of Radar Fuzz-Busters, got no replies.

Now I see that one of the companies might have read their email.
Since they are now selling a Radar Detector with built-in GPS so they
can map out false-alarm areas and areas where known speed traps exist.
It works as an early warning system, (before you enter the trap area).

Uniden | A World Without Wires - GPSRD

A similar program could be used to map out your area for good coasting hills using a learn mode. Otherwise, it would have to use a large pre-made data-base of hill data.

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Last edited by Xringer; 02-15-2010 at 09:00 AM.. Reason: breakfast break
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Old 02-15-2010, 11:02 AM   #100 (permalink)
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good point

gps would be a great way of going but capturing the info would be hard, but really it wouldnt matter, your looking at the deceleration rate compared to the incline so if it reaches a certain bottom end then it gives gas, another way of doing it would be with a timer. (even small hills without the right momentum might need some gas)

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