| Author | Message | ||
     Jraice |
So this weekend I was in the Sierra's. We were staying around 7000' elevation and did an easy morning ride at 4000-7000. In the afternoon I went out for a much more spirited ride, downhill to 1000' elevation then back. It was a long ride. Anyways, about halfway down I started to notice a weird occurance. Power seemed to be noticably down in the lower RPM's, especially at WOT. At first it seemed like it was a time based lag, and would come on after a second or two. On the way back up the mountain I noticed it was more like a certain RPM. Right around 4,000rpm it would go back to normal. I spent plenty of time at lower elevations, I also cruised at 3500rpm to let the ECM relearn the air pressure etc... Nothing helped. It was most noticable in slower corners in 2nd, I would come around them, start to slowly add power and it just wouldnt be as linear or sensitive as normal, it just felt very laggy and right at 4,000rpm it would rip. It was noticable like this (slow application of throttle while leaned over) or just wacking it WOT from 3,000rpm. On the way home I didnt notice it as much (5 hour ride) but its hard to say if its back to normal or not. It feels pretty normal but after the strange occurance I am hyper sensitive to how the power feels and I cant say if it really is down on power under 4,000rpm still, or if my mind is just playing tricks on me. Either way its definetly not as bad as it was before. So any ideas as to what could've caused this? Talked to Al and he said the ECM should've quickly relearned (problem lasted for a long time and seemed to go away after getting back into the higher altitudes) and he said it would've been down on power everywhere, not only under 4,000rpm. Also if it makes a difference, we road through some wet mud like road surface, dont know if dirty water getting somewhere it doesnt belong (air scoop?) could cause something like this. Anyways if anybody has any ideas it would make me feel a lot better. Oh one more thing, when the problem first happened I stopped, gave the throttle a blip, it came down like normal but dipped below 1000rpm a bit, sort of chuffed almost as if it was going to die then regained life and idled normally. Thanks | ||
| Iamarchangel |
I noted a similar thing on a long ride last summer. On the highway, when the bike hit 4100, it seemed like it hit a boost. I posted the question and was answered that 4100 is the designed peak point or something and they will all boost at that point. You'd have to search out the thread, probably last July. I've got to leave the house or I'd look it up for you. | ||
| Jraice |
Yes I have always noticed an increase in the power around there but this was different. I have had the bike for 9,200 miles now. This was a decrease in power below 4000, it was not the normal difference. | ||
| Sloppy |
Correct me if I'm wrong, but there isn't any air pressure sensor. The environment sensors are air temperature and engine temperature, no? The only indication the engine has to your elevation is your exhaust gas oxygen levels and from there it can lean out the fuel based upon the lower oxygen levels at altitude. The "Dynamic" portion of the DDFI would only happen in the closed loop mode... The ECM will go into a "fixed routine" in the open loop mode. | ||
| Greg_e |
Yes that is correct, there is no atmospheric or even manifold pressure sensor (at least not on my 03 9R) | ||
| Jraice |
So any idea as to what could've caused this temporary problem? | ||
| Sloppy |
Sounds like the DDFI had adapted to a specific ride condition (temperature & O2) when the bike was taken to a different ride condition and it didn't have enough data / time to adapt. The reason I say this is because above around 4000 rpm is where the DDFI goes open loop and you report the bike felt good. It goes into a closed loop learn mode under certain circumstances - throttle position, engine rpm and temperature. Once you met the appropriate conditions for a period of time it will "save" these parameters for your engine. By the time you came back to your normal riding area it sounds like it re-learned the appropriate values. But you SHOULD expect a decrease in performance at higher elevations (sorry, but Physics has us on that one). I'm not familier with exact DDFI details, but it is a clever alpha-n fuel injection protocol (alpha-n is used for performance vehicles). The combined closed loop, learning (dynamic) and open loop controls are neat features. They are designed to handle step changes in environments rather than continuous change environments. If you were to STAY in the mountains for a duration rather than going up and down then you likely would not have noticed the difference as much. I've had similar things happen (I rode from Death Valley (- 200') and over Yosemite (+ 10,000') in one day and have had similar reactions - but after a period of time it would go back to normal running. Note - I'm no expert in Buell's specific DDFI code, so I'm sure there are others that could shed better information. If you have engine problems that don't go away after an extended time then it could indicate that your engine sensors may be defective (likely the oxygen sensor), but not so much that it shows an error code. At least that's my theory...  (Message edited by sloppy on October 12, 2009) | ||
| Greg_e |
Riding from a low elevation to a high elevation is exactly the situation that makes some designers put in an atmospheric pressure sensor in the system. That could allow the control unit to adjust the mixture for the different pressure just like it adjusts for the air temperature. If things go as planned I'm going to do this on my bike with a different EFI system called MicroSquirt. It should be able to handle the TPS, air temp, Manifold Absolute Pressure, and a second pressure sensor for atmospheric pressure. You can also use it with a real Mass Air Flow meter, but apparently that gets very complex so the MAP sensor method is advised to start. alternate to having a second pressure sensor for ambient some designs grab the pressure just before cranking and then hold that value for the entire trip. Better than nothing, but not as good as real time adjustment. | ||
| Sloppy |
You can see a write up of an FI conversion with a Megasquirt on an RZ350 at http://www.smcomp.com/~smurph/RZ-EFI/index.html |
