| Author | Message | ||
     Alessio66xb12r |
hi all please : are there somebody who explain me the differences between "open loop" and "closed loop" and what them means. thank you all. Alessio | ||
| Jlnance |
Alessio - The terms come from control theory. Systems are often controled using something called a feedback control system, where the output is measured, inverted, and fed back into the input. Think of the cruise control in a car. If you're going too fast the system reduces the gas. If you're going too slow the system gives the engine more gas. If you draw a diagram of how information flows in this system, it will form a loop, because the output (speed) is attached back to the input (accelerator). This is where the term "closed loop" comes from. A cruise control is a closed loop system. An open loop system does not use feedback. If you wanted to make an open loop cruise control, it would simply give the engine the amount of gas it though was required for the desired speed. There would be no feedback between the amount of gas and the actual speed of the car. Each system has it's advantages. Open loop systems respond faster than closed loop systems. Closed loop systems can correct for variances in the system (hills in the cruse cont example.) The FI system on the bike uses both, depending on how you are operating. I belive that if you're cruising at a constant speed, you're running closed loop. If you're accelerating hard you're in open loop. I'm not positave about that though. | ||
| Alessio66xb12r |
THANK YOU Jinance i think i got what you explained , but ....transleate this to the buell xb : from which sensors the ecu get informations from in one or in the other case . thank you again Alessio | ||
| Jlnance |
I'm not an expert in FI systems, so keep that in mind. On the bike, your throttle controls the amount of air entering the engine. The FI system controls the amount of fuell added to this air so as to maintain a good fuell/air ratio. When your bike is running in closed loop mode, the ECM gets data from the oxygen (o2) sensor in the exhaust. If there is not enough oxygen in the exhaust it means the mixture is too rich and the ECM reduces the amount of fuell it is feeding the system. If there is too much oxygen, it means the mixture is too lean and the ECM increases the amount of fuell. There are probably other sensors at work as well, but I don't know enough to say. When you're running in open loop mode, I don't think the O2 sensor data is used. I know there is an air temp sensor, and the ECM also knows the RPM and throttle position (TPS.) From this it can calculate how much fuell it should be feeding the bike. I believe this calculation is interpolated from "maps," which are tables of values. This is what people are modifing when they talk about "flashing a new map." | ||
| Court |
I have a better definition of a "Closed Loop Feedback System" but it requires me to cite an example that features my Italian wife. If I told you . . . . well, I'd get my throttle closed. Get it now?  | ||
| Blake |
Not quite, so would you please explain in detail? |
