Audiovox surging at slow speeds

[bigtallguy]

So I finally got around to installing my cruise control (audiovox) and took it for a test ride. It worked ok at 60-70mph, dropping off by about 5mph initially, then back to where I set it and stayed.

Then the slow speed test had a lot of surging, constantly bouncing around the set speed of 35mph by 3-4mph. It settled for a few seconds then started hunting again so I cut it off. The rpms were at about 3-3500 rpm. I'm using one vacuum port and a vac canister from murphskits. The cable is routed as straight as I could get it, going from the right side below the seat, under the tank, then around and through the frame where the throttle cables and other stuff runs.

Any ideas why it's doing that? I did try to search but didn't find any threads with the answer. Thanks!

 

[Shane]

I find that mine is not particularly happy cruising at slow speeds in the "normal" gear for the speed.

One gear higher than normal is smoother. Like running in 4th instead of 3rd at around-town speeds.

I believe the reason is that at slower speeds, the FJR simply responds too aggressively to relatively minor throttle changes in the correct gear. At higher speeds, the effect is less dramatic--eliminating the hunting or surging.

The CCS will never equal the dexterity of the human hand, so this makes perfect sense to me.

I rarely have a reason to run the CCS around town, so this is just observation while testing like you are.

No issue, at least as far as I'm concerned.

Good luck,

Shane

 

[mcatrophy]

I agree with Shane that using a higher gear will help the surging, I use 4th gear for holding 30mph, but even this gets a little unstable when going gently down hill. It sounds as if you're using 2nd gear in your 30-35mph range (from my gearing calculator), I'd say this is bound to cause the CC some problems.

I find it curious that you say yours drops a few mph initially; mine always goes over by a couple of mph then eases back to the set speed, which seems to be the behaviour of most that I've seen posted. I don't know whether this indicates an issue, or if it's just a symptom of using a low gear.

One other point, having installed mine, I sealed the actuator to prevent water ingress (mine's mounted inside the passenger footrest). I found it wouldn't control well until I'd put in an air vent to allow vacuum relief.

It may be worthwhile checking air can enter its body.

(click on image for larger view)

Air relief pipe into cover . . . . . . . . . . Pipe ends under seat

 

[JR'SFJR]

I regularly drive a 35mph rolling road along the intercoastal river for miles. If I run in 5th, both my FJR and LT have trouble holding speed, but shift to 4th, both do well. Don't know about 3rd. FJR has 2 vacuum check valves because it would drop out on long hills, while the BMW has only one.

 

[petey]

So I finally got around to installing my cruise control (audiovox) and took it for a test ride. It worked ok at 60-70mph, dropping off by about 5mph initially, then back to where I set it and stayed.

Then the slow speed test had a lot of surging, constantly bouncing around the set speed of 35mph by 3-4mph. It settled for a few seconds then started hunting again so I cut it off. The rpms were at about 3-3500 rpm. I'm using one vacuum port and a vac canister from murphskits. The cable is routed as straight as I could get it, going from the right side below the seat, under the tank, then around and through the frame where the throttle cables and other stuff runs.

Any ideas why it's doing that? I did try to search but didn't find any threads with the answer. Thanks!

Why in the world would you want to use your CC at that speed?? If it performs normal at higher speeds, you got a winner...

 

[FJRGuy]

I musta got lucky with my install. Running off a single port (#3 iirc) with the actuator under my seat. Holds well at speeds from 30 to... well... let's just say 'higher speeds!'

Not being an expert at all, seems like more of an input (sensor) issue than an output (vacuum) issue. All I can think of for your issue is where/how you connected to the coil signal. I recall tapping the coil wire as close as possible to the ECU based on the collective knowledge around here. Could someone smarter than I comment of if noise or weak signal could be causing that issue? Having listened to the noise induced in audio devices at different speeds/RPMs, I'm postulating that the noise on the signal wire would vary as well.

Just a thought. My AVCC was one of the best farkles I added to my bike bike. I Love it! Good luck tweaking yours!

 

[bigtallguy]

I'm probably not going to use it at those speeds, just part of my test that had me wondering if I screwed something up.

I made a Y connector for the coil connection under the panel on the right instead of tapping into the wire. I soldered it together and used heat shrink tubing on it so it should be a solid connection.

 

[JR'SFJR]

I use mine at 40 mph mainly on miles of lazy rolling river road to keep from getting a ticket. River on one side, expensive homes on the other and it's patrolled.

 

[Fred W]

Mine will also surge at lower speeds when in a normal (meaning lower) gear and the rpms up above around 4k. Probably because the power and responsiveness are too high for the servo feedback loop's electronic damping.

And I have my dip switches set to the least sensitive position (it just gets worse at more sensitive settings).

Best to keep the rpms down (and limit the engine's power that way) by using a higher than "normal" gear if you really want to use the cruise control below ~50 mph.

 

[ionbeam]

+1 to Fred's suggestion. When using the AVCC it is best to keep the engine loaded by using a higher gear and lower rpm, it really smooths things out. Don't lug the engine but do slow the engine response down by keeping it loaded.

My AVCC will cause surging at higher rpms and very low engine load. My FJR also causes surging during those very same driving conditions. In fact my FJR is one of the bikes that has significant surging. It also has abrupt decel cutoff after the throttle is rolled off and when rolled on it will pause to be sure that I really mean it then it will suddenly give me all the accel at once. Thank dog for the Power Commander that smooths it all out.

A really cool thing is the response time of the AVCC and the FI response of my FJR being exactly out of sync. The cruise will see the reduced need for power when going downhill and roll off the throttle causing the FJR's FI to perform a decel fuel cutoff. The cruise sees the sudden loss of power causing it to energetically pull on the throttle. The FJR sees the sudden demand for acceleration causing it to abruptly deliver all the power at once. The cruse will see that acceleration forcing it to reduce the throttle which makes the FI perform an abrupt decel fuel cutoff. At each cycle the AVCC reacts more strongly which makes the FJR react more strongly. In 4-5 cycles it starts to get real interesting, I believe that if I let it go an additional cycle or two automatic wheelies may be possible

 

[SnowAviation]

Mine will also surge at lower speeds when in a normal (meaning lower) gear and the rpms up above around 4k. Probably because the power and responsiveness are too high for the servo feedback loop's electronic damping.

+1

Exactly.