| Author | Message | ||
     Jlnance |
I'm trying to figure out if something is "normal." If I'm riding at a constant speed (70 mph on the highway) it feels like the power delivery from the motor fluctuates. Almost like the bike occasionally misses, except I can tell from the sound of the engine that it isn't missing. If I accelerate the sensation compleatly goes away. The bike is very smooth then. It is not particularly annoying, but I do want to know if it is unusual. My theories are that it is either a suspension setup issue, or I'm just feeling the fuell injection adjust itself. | ||
| Pbransonii |
Sounds like surging. BMWs are famous for this. It is usually caused by the fuel injection unit trying to find the optimum fuel air mixture for a certain speed and load. Might want to have the fuel injection checked out. From what I've heard, the Delphi fuel injection is very good and should not cause surging. Might be a weird oxygen sensor sending bad readings or something like that. Paul | ||
| Guybones |
Mine does that occasionally, only when cold first thing in the morning, goes away within a mile or two @ 45 mph, never to return. I warm the engine up before taking off as well. I'm going in for the 1000mi service this Friday, the dealer says it should go away after that. By the way, the fluctuation is very minor. | ||
| Clayman |
Mine has been doing that for awhile, I havnt had time to get it to the dealer. I find that between 3100 and 3400 rpm if i hold it steady it will feal like its missing, kinda gets a bit jerky, but if i throtle up to over 3500 rpm it goes away and runs real smooth. Doesnt sound like the fuel injection issuue , if that was the case it would do id at all rpms wouldnt it. | ||
| Jlnance |
I find that between 3100 and 3400 rpm if i hold it steady it will feal like its missing Thats exactly the RPM range I'm in when I'm crusing down the highway.  | ||
| Cataract2 |
Have you had the TPS and AFV reset since you bought it? | ||
| Jlnance |
I've had the 1000 mile service done, and I believe they are supposed to reset them as part of that service. I have to take the bike back to the dealer next week because my bags should be in. I'll ask them to do it again. AFV stands for air fuel valve? | ||
| Cataract2 |
Was it running fine before the service? | ||
| Al_lighton |
AFV=Adaptive Fuel Value. The ECM compares the injector duration needed to keep the bike at 14.7:1 during steady state closed loop operation with the value obtained from the fuel map table for the same RPM/throttle position. That ratio is the AFV. The AFV is used to scale the open loop response. The nominal value is 100%, but it ranges from 80%-160%. The Digital Technician can see what it has become, and can reset it to 100. An example: say you drive steady state up a mountain. The air gets thinner, the closed loop system figures this out and cuts the fuel by 5%. The AFV algorithms compute that this difference from the internal maps and set the AFV at 95. When you gas it hard, and move to open loop, the injector duration values calculated from the open loop fuel map table are multiplied by .95 to obtain a good fuel mixture. Al | ||
| Jlnance |
Was it running fine before the service? No, it rode no differently after the service. | ||
| Jlnance |
Thanks Al | ||
| Al_lighton |
Several posts here said stuff that merits some discussion. Buell DDFI is VDO, not Delphi and not Magnetti Marelli like HDs use. During warmup, the bike runs on the open loop maps only, and there are some temperature compensation algorithms being used to modify what the injector durations should be. It is not uncommon for there to be some less than perfect running at this time, and it could be different for someone at one altitude/temperature than another. At the transition from the warmup open loop operation to closed loop operation as the bike reaches temp, it isn't uncommon for there to be a hiccup. When I leave my house for work on my S3, I will get that hiccup right about the same place every day. But it's a transient thing, and the bike runs great once warmed up. DDFI has evolved over the years, I suspect that the warmup transition algorithms are improved on a Uly vs my S3. I haven't noticed that same hiccup on my Uly, but I'd bet that there is still some less than perfect fueling at the transition. Anything happening in steady state operation in the 3000 to 3500 range when fully warmed up is definitely in closed loop operation. The bike is running fully on the O2 sensor at that time. What this means is that the amount of fuel that it injects on the current intake cycle is completely dictated by the sensed A/F ratio from the previous cycles. As you advance the throttle, the system senses that it got more air, and then commands more fuel. This stuff is happening many times per second, and the computer is more than capable of keeping up with your throttle position changes. Closed loop control systems are fundamentally based on the fact that sensors can detect an error in the offset, rate of offset, and/or acceleration of the offset, and apply corrections based on that data, to keep things at the nominal setting. In the case of our FI system, the O2 sensor reading is the feedback to the algorithms that hold the A/F at 14.7:1 in closed loop. If there is surging during closed loop operation, I'd sure be looking for something that is affecting the O2 sensor feedback. The O2 sensor is a 0-1V device, and as such, it is extremely sensitive to even very small changes in contact resistance. I would unplug the O2 sensor, and replug it back in a couple times, to break and oxidation at the contact interface. Since it is a single wire system, the ground interface at the installation in the pipe can affect that reading as well, so I'd check that it is tight. On my Uly, the O2 sensor wire was stretched DRUM tight across the rear rocker box cover, and had I not caught it, it would have eventually rubbed through the insulation and caused an intermittent short that would have totally screwed up close loop operation in an intermittent way, so I'd certainly check that wire run. And always remember Al's two rules of motorcycle mechanics: 1) All problems are a grounding problem until proven otherwise. 2) All problems are related to the last thing that was worked on on the bike, until proven otherwise. | ||
| Josh_ |
Hey Al, I'll buy an American Sport Bike T-Shirt with your rules on it as soon as you print 'em | ||
| Crusty |
Hey Al; while on a ride one day, my front brake started dragging, so I stopped at the side of the road and cracked the bleeder. A few miles later, the rear rocker box started leaking oil. When I got home, I replaced the gaskets. Then when I went to start the bike, the starter button wouldn't work, so I replaced the R/H switch housing. When I started the bike, the tail light bulb was burned out. I still haven't figured out how they were all related.  | ||
| Lowflyer |
Crusty, Rules one and two are mutually exclusive. It sounds like you had a grounding problem.  | ||
| Lowflyer |
Lowflyer's motorcycle mechanic rules: 1. Never overestimate the intellect of the average motorcycle mechanic. 2. Never let a motorcycle mechanic borrow your football. 3. Fix it yourself or suffer the consequences. 4. If you can't fix it yourself, see rules 1 and 2.  | ||
| Lowflyer |
Oh, come on...I was just kidding.  | ||
| Debueller |
Excellent explanation on the ECU/FI operation on the system used on Buells. My Uly has hiccuped/stumbled consistently at about the same time during warm-up many times..... just as you described. Well written. Thanks!! |
