RPM Knob install?

Good day all.

Would it be possible to add a RPM knob on the dash?

My thought is that as good as cruise control is, there are times where you just want to set the rpm. As the car has an electronic accelerator pedal, could you just add a potentometer inline so you could just turn up the rpm and have it hold there?

Weird thought I know, but has anyone done that? I have a SR5, no crawl control. But I realize that crawl control changes a lot of other settings as well. I just want the RPM to hold in a spot, no other changes.

Thanks in advance,

Doftya

 

Welcome to the forum!

Under what circumstances would you just want to set the rpm?

The cruise control has safety protocols built in. For example, it will cancel itself when the brake pedal is pressed. Do you have a similar solution for your scheme?

 

It might be simpler to investigate the operation of the factory crawl control and go from there.

 

I’m going to say no one has ever thought about this.

 

My dad told me that I shouldn't play with my knob while I'm driving, I may get into an accident!

 

You don’t want knob fluid going everywhere.

 

My thought would be like cruise control, but more fuel efficient because it won't rev up for hills. I'm aware of the safety stuff, but didn't want to invest too much for a more complex system. I'd just have to ride it as if I was driving without cruise control, but just not using my foot. Could also be used for a slow crawl in 4lo, but again without all of the extra bells and whistles.

It was just a thought, if the safety issues or other integration issues are too big, then I won't pursue it.

 

As far as on-road use is concerned, the idea of having to take a hand off the steering wheel to dial the knob down during a panic stop is a non starter.

If the cruise control didn’t rev up for hills, the car would slow down, possibly impeding traffic.

Off road: crawl control is as dependent on brakes as it is on the accelerator. Just like on the road, you don’t want to have to take your hand off the wheel to throttle down.

Don’t be discouraged from asking questions like these. Pursuits like these are excellent teachers.

 

I, to date, have not seen this ever (On gas passenger vehicle engines), except on diesel idle speed control.

Would like to see this in action on a 4Runner, On a closed course.

 

Stop.

 

Most random idea.

no one optimizes for rpm while using cruise control.

it’s counter to safe driving. Keeping with the flow of traffic matters.

do not want people doing weird stuff like keeping the rpm constant, while the other dimensions such as speed, varies

 

My grandfather was an engineer at General Motors. In the 60s, the first "cruise control" I ever saw was on my grandfather's Pontiac GTO that was his daily driver. In those days he got a LOT of speeding tickets. He learned about something called a "speed control", and he installed one. Back then, his speed control got a signal from the distributor on the engine - and that signal regulated the RPM of the engine by adjusting the throttle on the carburetor. I don't recall if there were any safety systems, such as what happens when the brake pedal is depressed.

Later in 1980 when I had my own car, a 1977 Oldsmobile Cutlass, I installed an aftermarket Cruise Control. It had magnets that were stuck with adhesive and lockwired around the driveshaft that provided a "speed" input to the control module, got a signal from the distributor (don't remember why...), used vacuum from the engine to create a servo that would move the throttle on the carburetor, had a simple electronic module with a control mounted on one of the stalks on the steering column, and a splice for the brake switch on the brake pedal to cancel the cruise control operation if the brake was pressed. It worked pretty well and only cost around a hundred bucks or so.

While your idea of setting the RPM would work, it is not so practical. Most people want to set a speed to be maintained while going down the road.

 

That is fascinating and I know what you’re getting at, but I don’t think it’s something anyone has researched. Rather than RPM, an option to hold throttle input might be more your speed but that’s just my thinking.

Sometimes I miss how cruise worked in my ‘98 Sienna where, unless my memory is horribly flawed, it operates only the throttle to maintain a minimum speed but does not shift to reduce speed.

Anyways, I use classic cruise and toggle it on/off depending on declines.

But as things stand today, this is not feasible.

 

I would be interested in a device that would bring the idol up a bit while in Park.
Like when I'm parked with the A/C on to help reduce the possibility of compressor failure.
The two things that I see to help is drawing in more air through the A/C condenser/radiator coolant.
I think that it only needs to be bumped up to about 1,100 RPM's. It's not much but, it sure makes it more comfy on hot days.
And to lay my foot on the accelerator pedal to get the right RPM's, is not as easy to do given that there is no cable to actuate the throttle blade.

Also it would bring up the oil pressure a bit for my peace of mind.

 

I believe locking the rpm is essentially what a cruise control wants to do by design. For example, if doing 70mph happens at 2000 rpm in 5th gear, it will be the same rpm no matter if going uphill or downhill, as long as it stays in 5th gear. The gearing ratio of a gear will always mean that the relationship between rpm and speed is fixed.

But autos won’t stay in gear when the the engine cant make enough power to keep rpms the same. Their job is to maintain speed, and it will take advantage of the transmission to do that. First the torque converter unlocks to raise rpm slightly, or it will kick down a gear to maintain speed.

If this was a manual transmission car, it would do what you seem to want it to do. On a manual, the throttle is the only thing the cruise can use to maintain speed uphill. It will increase throttle to maintain rpm, until it can’t. At that point rpm/speed will simply start to decay (or the cruise will disengage).

I suppose if you found some way to lock the automatic transmission into one gear it would do what you want. Not sure if there are any products out there that do that, but I would imagine it’s possible if you figured out how to get the ECU to do that.

 

When I had a Defender I installed an accessory hand throttle (the intended purpose of which was to be used with a PTO). It pulled a cable connected to the bell crank at the throttle body. I didn’t have any PTO driven equipment and just wanted to use it as a cruise control. Fortunately I figured out that it was a bad idea before an accident occured.