Constant throttle cruise control ?

[illflem]

I am cutting this out of the topic New high idle controller hopeing to get more response to something I feel would be an excellent mod to our trucks,so it may seem a bit out of context.

jponder,I like your idea for the constant throttle cruise. I even have an extra $99 magnetic sensor CC without a home. Was your idea to use the $99 CC's vacuum servo(does the 24v use one of these,I have a 12er) or just tie into the existing factory servo if it's compatible with the $99 CC's electronics?
It seems like a rheostat supplying voltage to the control pin on the servo would also work,but it would take some wiring and a relay to include the brake safety feature. Would also need a diode to isolate the pcm from this voltage. You would then have a dial in steady rpm and a resume button. You could use this for warm up rpm and for driving. Could also use the factory CC if you wanted. Would be safer than a tractor type throttle,especally with a auto where you can't disengage by pushing in the clutch. Seems pretty cool to me.

I have found I get better mileage using my foot rather than the CC. I was driving into a strong,gusty headwind a couple of days ago. With my foot on the throttle pedal and the CC engaged I could feel the throttle moving with the gusts,not good for fuel economy. Started using just the pedal and my speed remained pretty constant without all the varying the CC causes. Even noticed with using my foot that when strong wind gust came that the boost climbed with it.

I think that if we put our heads together we can come up with a very useful add on. My wiring diagrams leave much to be desired in this area,would like to see what the voltages to the servo run.

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95' 25004X4,AT,Driftwood,Banks Stinger,Warn fender flairs and running boards(work truck)
95 3500,5 speed 3:54,BD E-brake,Driftwood,Banks&Psycotty,34,000 GCVW apple and tractor hauler(works harder truck)

 

[adiabatic]

Cruise on a governed diesel does seem like overkill. The governor is trying to keep rpm constant anyway. DC could have done it by using a solenoid to fix the throttle linkage position. The solenoid would be wired to drop out when the brake lights come on.

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1997 4x4 CC 5spd, CPL1553 pump, Horton fan, Sport headlamps, Optima RedTops, 98 shift levers and console, RS5000 shocks, Yaesu VHF radio, and BCT7 scanner in the overhead console... N7DAL.

 

[yogibear]

Sound like something for Cannonball to work on. He's real sharp on elect. gadgets. I see he has come up with an add on to save our grid heaters from cycling on & off after the temps get to 125*, saves on alt. and batt.
How about it Gordon.

 

[jponder]

Originally posted by yogibear:
Sound like something for Cannonball to work on. He's real sharp on elect. gadgets. I see he has come up with an add on to save our grid heaters from cycling on & off after the temps get to 125*, saves on alt. and batt.
How about it Gordon.

I betcha he could draw it all out on paper in less that 30 minutes. Help us Gordon

 

[yogibear]

Hey Bill, after I read that I didn'like the way it sounded. Didn't mean you guys couldn't do it, just thought Gordon might help. Sorry about that. #ad

Larry

 

[illflem]

Larry,no problem. Would appreciate some help,if I go doing on my own there's likely to be a lot of trail and error.

 

[yogibear]

Hell, I do almost everything by trial and error! And its mostly error! BTW, got the Raytec, its pretty neat.
Larry

 

[Jim Guidry]

Does anyone remember the "Poor-man's Cruise Control" that JCWhitney used to sell? I installed one on a friend's Chevy back in the early eighties. It was a cable, (held the throttle in one position) that disconnected when you hit the brakes. I can't remember the name of the darned thing, and Whitney doesn't carry them anymore. I've been searching the 'net, and cannot find anything on them. This would seem to be the perfect solution, for both steady-state cruising, and high idle warm-up. I'll keep looking!

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'96 Regular Cab, 118k, SLT 2WD auto 3. 54, Vista topper, Pillar-mounted Autometer Boost/Pyro, transmission temp and oil pressure guages under dash, starwheel spun, stock plate and housing slid ALL THE WAY!!

 

[jponder]

Jim> That would be awesome do you remember how it disconnected when you hit the brake? I say simpler is better and I would rather something mechanical. I just dont know how a cable could be rigged to disconnect when you hit the brake.

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2001 ETH/DEE ST 4X4 SPACE SHUTTLE

 

[Andy Perreault]

How about one of those hand throttle controls that they had on older big rigs? They had a knob you would turn to dial up the rpm's. In the center of the knob was a release button that you could slap at any time to kill the the thing. For a short time, I drove an older Ford L-9000 that had one. That was quite a while ago, I can't remember if it automatically released when I hit the brakes or not. Seems to me it did. Also, this could be handy for raising the rpm's for warming up the engine.
Andy

 

[jponder]

Andy> Yes I looked at a bunch of those throttle cables and while they are much better than what I have now; I didnt see any that had a disconnect for the brake. They were easy to turn off but some people in a panic situation would just freeze up . I think almost evryone would hit the brake in an emergency sit. The other thing they would not let you do is have a higher governed speed. For that matter I dont know if you can accomplish that with a cruise but it sure would be a neat feature if you could.

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2001 ETH/DEE ST 4X4 SPACE SHUTTLE

 

[illflem]

After pouring over the vehicle speed control system in the service manual,which isn't as descriptive as I'd like,here's what I came up with it's too simple so someone correct me if I'm wrong.

The CC throttle servo is just controlled by a pulse of 12v+ to one of either side of a two way vacuum solenoid valve. A pulse on one side of the valve allows vacuum to enter the diaphragm and increase throttle. Pulse on the other side of the valve releases vacuum and allows the throttle to go down. The length of time that the 12v is applied determines the amount of throttle movement. No voltage to servo and the throttle stays constant. I think in normal CC mode the 12v is cycling back and forth on the valve quite a bit to keep the speed constant.

It seems if you just add a momentary contact push button switch that opens the solenoid to increase throttle,much like the resume button,you will be able to throttle up to any rpm you desire and stay there. A 12v+ pulse from the brake light circuit could be applied to the throttle down side of the solenoid to decrease throttle. I think the servo would return the throttle to idle in less than one second of brake application.

The tests in the manual don't really describe the functions of the four pins on the servo well. What I gather is pin 1 is ground,2 is 12+ whenever the rig isn't moving,but then it says when 12+ is applied to pin 2 of the servo the other 3 pins should read 12v. This is what I don't understand,anyone else feel like taking a stab at the manual and see what they come up with?

If my idea works it will only require a $2 switch and some wire,pretty easy.

 

[Joe G.]

Bill,

Page 8W-33-2 of my '95 manual show pin 1 ground, pin 2 IGN 12V, pin 3 VENT, and pin 4 VACUUM. I suspect the 12V on pin 3 lets some of the vacuum out and pin 4 applied more.

You might try something like this: put single pole double throw switches in the pin 3 and pin 4 circuits so you can isolate them from the other control circuitry. Then put a push button in each line so you can apply 12V. That way one push button would increase throttle (pin 4) and the other would descrease throttle (pin 3). You could selec the stock operation with one position of the switches and fixed throttle control with the other. Might not work, but sure looks like it would.

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Joe George
Eureka, CA

'95 2500 CC auto 4X4,3. 54,Combo EGT/boost guage,custom switch panel,PacBrake,TST #5,BD valve body,Automatic motorhome steps on both sides,Foldacover hard bed cover,Cummins chrome kit,Black steel grill guard,Front hitch receiver

[This message has been edited by Joe G. (edited 02-19-2001). ]

 

[Joe G.]

Oops, forgot. You should put the rear axle on jack stands and let it run on cruise and see what sort of signals you get on pins 3 & 4 before messing around.

 

[jponder]

Iflem> I just had a thought of a possible problem. Will that cruise hold that throttle without any additional inputs. What if on a regular cruise you are always losing vacumn and it is always correcting and giving a little. I mean it would have to be sealed perfectly to hold that vacumn without slowly losing it.

I hope you are right man that sounds real easy to achieve Constant throttle cruise and also high idle.

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2001 ETH/DEE ST 4X4 SPACE SHUTTLE

 

[illflem]

Joe,I looked at 8W-33-2 also and it seems it should work the way you describe. What I still don't get is why it says in the servo check on 8H-9 that when you apply +12 to pin 2 that pins 1,3&4 should read battery voltage. You think this is just the voltage passing though the solenoid coil?Are pins 3&4 ground path or +,why is there a constant +12 and ground to the servo?

I just want this clear in my head before I fry the servo,I will disconnect the servo plug before trying so as not to damage the PCM. Should be able to do all of this with the engine off
(as long as I have some stored vacuum)and a few jumper leads. Biggest problem is I have to remove the battery first and don't want to remove once for just an experiment and another for installation(lazy,what the heck it's a holiday). If it does work my factory CC will be unplugged at the servo permanently. May even use the CC set/resume buttons for throttle up/down.

jponder,I think it should hold vacuum ok,if there isn't leaks, which there shouldn't be. My experience is that it doesn't take much of a vacuum leak to lose it all. If it does creep down it should be slowly,and will only take a tap of the push button to correct. I was more concerned that it may take a computer fast pulse and that a push button switch may be to fast to control well.


[This message has been edited by illflem (edited 02-19-2001). ]

 

[Cooker]

I'm sorry I can't help much on the topic, but it would be great if you all could figure this out. I'd love to have an inexpensive high idle controller. Thanks, Ryan

 

[Joe G.]

Bill (took a break to drive to Sacramento), you might try this to see what's happening. Put straight pins thru the wires to pins 3 & 4. If you have two volt meters you can see what is going on, hook one to each pin and a ground. Run it up to about 50 or so and set the cruise. Since there is no load on it with the axles on stands the cruise should over shoot and hunt. The readings on the meters should be opposite if it works like we think. That is, 12V on one meter when it speeds up and 12V on the other to slow it down.

Maybe the comment about battery voltage refers to a clean voltage with no minor drop because of coil empedance? I dunno, that's just a guess.

[This message has been edited by Joe G. (edited 02-19-2001). ]

 

[David_VT]

Just some ideas...
I had one of those cheapo aftermarket cruise control units in my 76 civic. It had a line that went to the brake circuit. The electronics were sealed, but I suspect any voltage on that brake line would kill the circuit. With Relays you could simply create a latched relay with a momentary 'on' button that would drive this constant throttle circuit. If the power coming into that relay was passing through a set of normally closed contacts in a second relay driven by the brake circuit, the 'latch' would be interrupted once the brakes came on. As a safety, power the constant throttle circuit from the feed to the brake circuit, so it could not work if the brake circuit fuse was blown...
Again, just some untested ideas

 

[Joe G.]

One thing to keep in mind with modern electronic stuff is that it's QUICK! Events are measured in micro-seconds if not nano-seconds. So what seems momentary to us is an age to the circuitry. Bill has a good idea here. I wish I had the time to fool around with it. If the problem can be solved it sure would beat an old fashioned throttle cable.