How do vacuum cruise control units work?

[serhan]

I see the installation tips/tricks, tutorials on the forum, and they are all fantastic.

Taking one step back, how does the Audiovox CC100 work? or any Vacuum cruise control unit? What does the vacuum refer to in this context? Does it operate on the engine's vacuum? How does the electrical piece of the unit work and what does it do? Are these systems reliable? How do they react to the decline/incline of the road? Do they effect the fuel consumption?

Can anyone give a high level intro?

Thanks,

Serhan.

 

[Silent]

Vacuum pressure within an engine changes as the RPM's rise and fall. Vacuum cruise reads the vacuum and tries to hold it at the same point, usually resulting in a steady fixed speed.

Clickie

 

[GunMD]

I don't know how or why it works, but my Audiovox CC that I installed with TONS of help from Kaitsdad (thanks Hal) is probably my favorite farkle. I will never have another bike w/out cruise control. I love it.

 

[SLK50]

Well, in simple terms, the AVCC consists of two components. The actuator which is a vacuum diaphragm connected to the throttle via a cable. The diaphragm is moved by engine vacuum. And the controller, which attempts to maintain constant engine RPM under varying loads, using engine vacuum to open or close the throttle hopefully resulting in more or less constant MPH.

 

[chrisflock]

I'll make an attempt.

You've got a hose that runs up to the intake manifold, providing manifold vacuum to the cruise unit. Inside, there is an electronically actuated valve that is basically a bleeder valve. The engine vacuum pulls on a diaphragm inside the unit, which pulls the throttle cable. The computer brain looks at input from whatever system is being used to determine vehicle speed/rpm, and then it opens and closes the bleeder valve to increase or decrease the amount of vacuum acting on the diaphragm. Additionally, any change in engine load will increase or decrease the manifold vacuum, which of course impacts the vacuum in the unit.

The system is somewhat self-regulating because of the vacuum, as an increase in load causes an increase in vacuum which gives the bike more throttle. I think this is how some early cruise systems worked, but the electronics added on make it work a lot better.

I've found it works great on my bike, as good as any automobile cruise I've ever used. It will maintain speed going up a hill well past the point where you should have downshifted. Downhill, it maintains speed until you are going down a steep enough hill that the bike will coast faster than the set speed, just like a car.

 

[ELP_JC]

As a side comment, cruise is good for not getting tickets, but not better for fuel economy than a throttle lock, especially on mountainous areas (they're about equal on straight roads). The reason is throttle is cut on downhills wioth c/c, and opened a lot going uphill to maintain speed. Much better to leave the throttle open the same amount, which would have you speed up a little downhill and slow down some uphill. I said that because I don't know what's your motivation to get cruise control. A throttle lock like the Throttlemeister would have almost the same effect, much cheaper, and it's a snap to install by comparison. I was very used to c/c myself, but am very happy with my TM now (I use c/c or TM very little though). Just a thought. Good day.

JC

 

[wfooshee]

So far most of the responses seem to imply that the system monitors vacuum to regulate speed. One even said that load increases vacuum, which is wrong. Idle or coasting produces the highest manifold vacuum.

The system utilizes vacuum to trigger an actuator. Speed is monitored by an electronic signal from the vehicle speed sensor, a wheel speed sensor, or a tach signal. We use the tach signal with the Audiovox unit on our FJRs.

The unit has a vacuum tank built into it, connected to a vacuum port on the intake manifold, with a check valve in the line. The unit does not use engine vacuum directly, it uses stored vacuum in its own tank. Adding an external vacuum tank of some sort with its own check valve increases the unit's capacity, and most of us use an external tank. If it tried to use engine vacuum directly, it would not be able to accelerate, as acceleration drops engine vacuum, so there'd be nothing to pull the throttle with.

The actuator is a vacuum diaphragm with a sealed chamber on one side, and open to the air on the other. If vacuum is applied to the sealed chamber, the diapragm pulls the throttle cable. If air is vented into the chamber, the diaphragm releases the throttle cable. There are two electric solenoids controlled by the system's control unit. One opens the actuator to the vacuum tank, the other vents the actuator to the air.

The system monitors the vehicle's speed and applies or releases vacuum as needed to increase or decrease throttle as needed.

For safety, the controller monitors the brake light circuit, and disengages the cruise control when it sees the brakes applied. It also disengages if the speed sensor input rises faster than a certain rate, so it cuts off if you grab the clutch.

Summary: Ride bike to desired speed, set the cruise. If the bike slows down below the set speed, vacuum is applied to the actuator to open the throttle slightly. If the vehicle goes above the set speed, vacuum is vented to close the throttle slightly. Apply brakes or grab clutch to disengage the cruise control.

 

[Bugnatr]

Great explanation, are you considering getting some type of cruise control? A throttle lock of any type is ok for short/day rides it will give your wrist a break and is a fairly easy install but will not maintain an even speed for very long as most roads are not that flat. The audiovox is more of true cruise control, it will keep a constant speed. It is a more difficult install but well worth it for long rides or trips and is excellent for avoiding tickets. ( we all know how easy it is to drift well above the limit with your rightr wrist).

No cruise control of any type is for use in hilly, twisty or mountain riding. I just finished a 4K trip where my Audiovox stopped working, I was able to trace it to a faulty power connection and after a quick fix it worked like a champ. The trip would been less enjoyable without it. It's the Bees Knees when it comes to one of the best farkles you can install.

Great explanation, are you considering getting some type of cruise control? A throttle lock of any type is ok for short/day rides it will give your wrist a break and is a fairly easy install but will not maintain an even speed for very long as most roads are not that flat. The audiovox is more of true cruise control, it will keep a constant speed. It is a more difficult install but well worth it for long rides or trips and is excellent for avoiding tickets. ( we all know how easy it is to drift well above the limit with your rightr wrist).

No cruise control of any type is for use in hilly, twisty or mountain riding. I just finished a 4K trip where my Audiovox stopped working, I was able to trace it to a faulty power connection and after a quick fix it worked like a champ. The trip would been less enjoyable without it. It's the Bees Knees when it comes to one of the best farkles you can install.

 

[Bugnatr]

opps I see you are in Kansas. Perhaps the roads are that flat, even more reason for some type of cc to give you wrist a break.

 

[ELP_JC]

I was referring to straight mountainous roads, where you ascend and descend constantly. And as a counterpoint, you shouldn't use c/c on a bike without the hands on the bars, period. With a throttle rocker (my favorite mod), you can relax your hand without removing it from the bars. I only use c/c or TM when I need to use my right hand for something, like scratching my back, pushing helmet, etc. I only used the c/c on my BMW and GL1800 for maybe 5 minutes combined. And that's why it wasn't a big deal to have a TM instead. If people want to use c/c on a bike to remove both hands from the bars, it's a stupid thing to do, but to each his own. But on such extensive use, c/c is definitely better than a throttle lock. Take care. Signing off.

JC

 

[serhan]

Thanks for all the replies. I am thinking about getting a CC, mostly for all reasons discussed above. I like taking long trips, I had a brakeaway on my previous bike, and I loved it. Probably the only thing I miss from my old bike. It didn't fit the FJR so I had to sell it. I see that the brakeaway doesn't work with heated grips on FJR either, so I starting thinking about a proper CC to consider all options, as noted I live in KS and it is terribly flat, so even a throttle lock will be a great improvement.

Thanks again,

Serhan.