Audiovox Cruise-Not enough vacuum???

[Bigjoebob1]

Need help, I am from the FZ1 forum but as a read and seach threads the audiovox cruise control is very popular among FJR owners. Cruise installed and works fine but will not cruise about 76 mph gps. I have taken vacuum from all 4 intake boots and spliced into Audiovox vacuum canister. Bike will resume and accelerate very quickly up to 75ish but will not hold speed any higher. It will set and slowly drag down. Does my engine really not produce enough vacuum at 76 mph (5.5k rpm) to hold any faster???

 

[UselessPickles]

Do you have a check valve for each of your 4 vacuum sources? They allow air to go only one direction so that vacuum can be built up and stored. More vacuum is available at idle than while cruising, and your bike probably doesn't create enough vacuum while cruising above 75 to activate the servo enough to maintain the throttle position required to maintain speeds above 75.

Here's my setup. The white cylinders are the check valves. I used these 3/16" mini check valves.

 

[Bigjoebob1]

My audiovox canister has a check valve in it. Do I still need them in every hose from the intake boots? Do I need a bigger canister? How fast will your bike cruise at?

 

[wfooshee]

If it sets and holds at a lower speed but not above that speed, then you need to reduce your pulses per mile setting. It's getting too many ignition pulses and thinks it's going too fast. I don't know the specific setting choices offhand, but it's switches 1 and 2. That may affect the minimum speed you'll be able to set it, though, but probably that's still gonna be lower than you'd need.

As for the vacuum, if you're pulling from all four cylinders then make sure you have a check valve on each one.

Keep in mind it doesn't use vacuum to hold speed, just to accelerate. The vacuum system is completely binary: it has a solenoid to allow vacuum to the diaphram which pulls the throttle cable, and another to bleed air into the vacuum chamber to release the throttle. While holding throttle both solenoids are closed, no engine vacuum is pulled.

 

[UselessPickles]

My audiovox canister has a check valve in it. Do I still need them in every hose from the intake boots? Do I need a bigger canister? How fast will your bike cruise at?

My guess is that your system is like this (note that the exact details of how the 4 vacuum lines are combined into one is not important):

(vac source 1)-----\
                    |
(vac source 2)------|
                    |------(cannister with check valve)------(servo)
(vac source 3)------|
                    |
(vac source 4)-----/

If that is correct, then some of the vacuum from each cylinder is sucking air in from the other cylinders (because only one cylinder is actually producing a vacuum at a time) instead of building up vacuum in your cannister and servo. You need a check valve on each of the 4 lines before they come together in any way to isolate the 4 vacuum sources from each other so that they all work together instead of fighting against each other. Here's the two basic layouts that will work:

(vac source 1)--(check valve)--\
                                |
(vac source 2)--(check valve)---|
                                |------(cannister)------(servo)
(vac source 3)--(check valve)---|
                                |
(vac source 4)--(check valve)--/

(vac source 1)--(check valve)--\
                                |
(vac source 2)--(check valve)---|
                                |------------(servo)
(vac source 3)--(check valve)---|      |
                                |      |
(vac source 4)--(check valve)--/       |
                                   (cannister)

I've set cruise at 80 before with no problems. That's about the fastest I ever cruise for any period of time wothy of setting the cruise control, so I've never tried higher.

 

[Inlaw1]

Might be you have too much slack in the chain connecting to the throttle linkage and it won't pull it far enough. (?)

 

[Bigjoebob1]

I have got it set at the 4000 ppm setting and low sensitivity. Will a lower ppm make higher speeds more manageable. It will set at 80 plus but then it slows back down at holds at 75 which makes me think it is a vacuum issue or check valve issue.

 

[wfooshee]

Slowing down and holding a lower speed is not a vacuum issue in and of itself, unless you just don't have enough vacuum getting into the canister in the first place. You MUST have check valves on all taps. The taps have to be seprated from each other, not seeing each other's vacuum, or they just bleed over to each other. Once that's done, if it won't set a higher speed, then add a canister of some kind as a reservoir. Finally, try setting the pulses per mile down, but you probably won't need to. Again, it does not use vacuum to maintain speed, just to accelerate. However, accelerating reduces your vacuum source, so if the internal canister is already low on vacuum, there's nothing it can use to pull the throttle. Add another reservoir, like an automotive fuel filter.

 

[Bigjoebob1]

So does the lower (2000) pulses per mile setting allow greater cruising speeds but it will not set at very low speeds?

 

[isuace]

I like to keep things simple. I have one vaccuum line, one check valve, and one small automotive fuel filter inline as a reservoir. With this setup, I was able to maintain 85mph on Highway 17 through the mountains south of Flagstaff.

 

[Bigjoebob1]

The ppm setting is only for VSS users only correct. My tach signal has nothing to do with ppm. Correct me and educate me if I am wrong. So my problem has to be with check valves then. I assume that with no check valves, my canister cannot even fill up because the vacuum lines are bleeding over into each other.

 

[xharleyrider]

I like to keep things simple. I have one vaccuum line, one check valve, and one small automotive fuel filter inline as a reservoir. With this setup, I was able to maintain 85mph on Highway 17 through the mountains south of Flagstaff.

+++1 I just finished my install this past Friday with the simple vacuum going to # 4 and one check valve to the PVC reservoir. I did over 100 miles yesterday and it worked perfect! I was not sure if I was suppose to turn tab #7 off or leave it on. I left it on since I had no problems like some of the others I have read here that have the Gen II's..

So if anyone wants help with their Audiovox that lives in the Dallas area, let me know!

 

[UselessPickles]

I was not sure if I was suppose to turn tab #7 off or leave it on. I left it on since I had no problems like some of the others I have read here that have the Gen II's..

#7 should be off.

The problems other people had were intermittent, so you're not out of the woods yet.

 

[wfooshee]

I believe PPM is used with the tach signal as well, especially if the tach is the only speed signal. The lower PPM setting should move the acceptable speed range up, i.e. sets at faster speeds, may not set at a low speed you're used to using.

The more I read the questions, though, the more I'm convinced he's got vacuum crosstalk between cylinders.

In an automotive application you would find a common plenum in the intake manifold, behind the throttle plate and ahead of the intake valves. The plenum will be a good vacuum source for whatever you want to put on the car.

No such space exists on the bike, though. You have four completely independant intake systems, each pulling vacuum on the intake stroke, but ONLY the intake stroke. The vacuum is not constant at that port, which is why manometers need a restrictor in the vacuum tube: without the restrictor to reduce flow, you just get a vibrating column of fluid. If you tap all four vacuum ports without restricting the vacuum direction, you basically have just connected all the vacuuum ports to each other, and they pull from each other rather than the device you're trying to apply vacuum to. You've made the intake system non-independant, and they bleed vacuum to each other.

Get the check valves, see how it goes. Resistance is futile.

And as pointed out, it's usually good enough to tap one port only and use a reservoir, with a check valve between the reservoir and the vacuum source.

 

[UselessPickles]

I believe PPM is used with the tach signal as well, especially if the tach is the only speed signal.

From the installation guide that comes with the Audiovox:

If the vehicle is a manual transmission and does not have a VSS wire, the cruise can operate from the tach signal only. Program dip switch #1 and #2 for 4000 PPM and move dip switch #3 to the OFF position.

 

[wfooshee]

Well, if you're gonna go and pull the manual out. . . . Geez!

 

[Bigjoebob1]

So the manual confirms that 4000ppm is the only and suggested setting for a tach only signal, like I have? Hopefully check valves that I am waiting on will keep the vacuum hoses from bleeding into each other and let the canister fill up. So if I understand how this works, the system uses vacuum to initial lock the speed (i.e. it needs quite a bit of vacuum to pull the throttle to at 85mph setting). Then is does not use vacuum to hold the speed but just to accelerate. Am I right? If I hit the resume key at 50 it gets to 75 very quickly like it is not starving for vacuum.

 

[Roy Epperson]

So if I understand how this works, the system uses vacuum to initial lock the speed (i.e. it needs quite a bit of vacuum to pull the throttle to at 85mph setting). Then is does not use vacuum to hold the speed but just to accelerate. Am I right? If I hit the resume key at 50 it gets to 75 very quickly like it is not starving for vacuum.

Click for more "The guts"

This is a photo from Ionbean that shows the internals of servo

When the servo wants to advance the throttle, it "adds" vacuum which pulls the cable until it reaches the desired RPM and then holds that vacuum. When it wants to decrease the RPM, it "bleeds" some of the vacuum which relaxes the cable. The initial vacuum demand is when the speed is "set" or reset. Then the vacuum is added or released to hold the RPM. The servo's internal chamber is always holding some amount of vacuum when the servo is pulling or holding the throttle open.

 

[Bigjoebob1]

Well, I went for a test cruise and figured something out I guess. I am still pulling vacuums off of all 4 intake boots with no check valves just splicing together. I was playing with the PPM switches. 2000 setting will not even set cruise at all, 4000 will set and operate normally but cannot set above 76 gps, 5000 operates flawlessly. It will set at 40 and hold smooth, accelerate very well, set and hold at 90 (didnt try much higher), resumes and accelerates very quickly back up to 90. Basically operates perfectly. Take that installation manual! Check valves still probably a good idea.