| Author | Message | ||
     Jaimec |
Question for the engineering types who hang out here (including Anonymous): When motorcycles switched from carbs to FI, they all lost the "Reserve" valve. I remember reading that running out of fuel can damage the FI system which is why all bikes with FI have a "warning" light instead of a physical "Reserve" switch. What I don't know is what kind of damage can occur if you allow an FI engine to run out of fuel. There are people on a Ducati discussion board (reportedly) saying there IS no danger, and it is purely a cost saving measure to do away with the reserve valve, but I don't buy it. So what's the deal? I'm assuming that OCCASIONALLY running the tank dry isn't that bad, but repeatedly running it dry can and will cause some kind of failure, but what? Thanks in advance. | ||
| Spiderman |
Fuell cools the electric motor. No fuel, No "coolant", Damaged motor | ||
| Hughlysses |
Well, one thing I know that's bad (this applies to cars too, even if you just repeatedly run them low) is that the fuel serves as a lubricant for the fuel pump bearings. Dry tank = dry pump = no lubrication. The pump's not going to instantly seize, but it's a good idea to avoid the condition whenever possible. Repeatedly running out of fuel will definitely shorten the pump life. I don't think anything else in the FI system can be physically damaged from a lack of fuel, but at least in the case of our Buells the ECM has to "relearn" the fuel curve if you run it out of fuel. No biggie, it just takes you running at a constant ~3500 RPM for a mile or two to straighten it out. | ||
| Slaughter |
As I understand the closed-loop system in most FI bikes... (and I'm kinda ignorant of the finer points) What happens is the ECU "sees" a super lean condition if you are trying to run the bike as it's hitting air in the fuel line and it'll shortly try to richen the mixture to compensate. If the engine quits running after it has "learned" to shoot a super rich mixture to the engine and you re-fill the tank, it might not run properly because it "thinks" it needs HUGE fuel gulps. That being said, I've run both my S3 and XB dry - BUT I was CAREFULLY watching for the FIRST hiccup and the INSTANT it coughed, I was ready, pulled in the clutch and hit the kill switch and coasted to a stop. Zero problems. The problem occurs if you try to keep it running to get the last quarter mile out of her after the first air bubble. I'm sure I've missed some finer points but that's kinda my picture. | ||
| Howieshotrods |
I agree about the no fuel, no lubrication being the biggest problem. I thought the reason they took the reserve valve off was due to the fuel pump. Unlike a carb bike that would spit and sputter when it runs out of fuel, hit reserve and gravity feeds fuel and will get the bike going again no problem; if you did the with a high pressure fuel pump you would have priming issues, and if you did that a lot you would also wear the pump out more quickly. That may not be exactly the reason, or said very well, but I am pretty sure it has to do with something along those lines. | ||
| Natexlh1000 |
Slaughter is correct. I've run my bike out of fuel three times. The first time, I was in the mojave desert and was motivated to continue to ride as long as possible. When I finally did get gas into it, it ran terribly. I was afraid that I would foul a plug so I stayed on the throttle. At that time, I didn't know about the closed loop learning thing so I was running it beyond the RPM range where it would learn. The other two times, I was quick on the kill switch and when I got fuel to it, it started right up and ran fine. |
