| Author | Message | ||
     Mmcn49 |
Last week I rerouted the crankcase breather lines to outside the air-box on my 07 Lightning, and made the following ECM changes: • Front and rear cylinder Square Idle enrichment. • Advanced the front and rear cylinder idle timing. • Changed the idle circuit from closed to Open Loop. The change is phenomenal. The bike runs great, no more stumbling or rough running. Reading through ECM spy, it appears that the stock fuel map programming and O2 sensor try to keep the air fuel ratio at 14.7 to 1. With the factory fuel map settings my AFV was 100 and the mileage was about 51 MPG. After making these changes the mileage fell to 46 and the AFV is now 105. Based on this information does anyone have a formula for calculating the new air fuel ratio? With a simple proportion I’ve calculated a 13.2 to 1 ratio. Based on AFV percentage I’ve calculated 14.0 to 1. I don’t know if either figure is accurate but tend to believe that 14 to 1 is closer to actual. With the new fuel maps, will the ECM and 02 sensor try to maintain the new ratio, or will it try to revert back to 14.7 to 1? | ||
| Xl_cheese |
My current understanding is that in closed loop the ecm will hover at 14.7. There is nothing you can do about that. You can alter the front cylinder since there's no feedback from it. I wouldn't worry about your afv being at 105. That just means that 105% is being applied to your fuel map to bring it to 14.7 in closed loop. In open loop it will blindly apply 105% to the map disregarding the ratio. As I'm reasearching this stuff I've come to realize there is a misconception about needing the race ecm when you do mods. I've read that mods lean things up so you need the race ecm to make things richer. I belive that is false. The ecm will keep the mix right. | ||
| Xl_cheese |
What could be happening it this: Your idle is lean so during closed loop idle your ecm is correcting it by adding more fuel. As soon as you take off your still adding more fuel and thus running rich and reducing mpg. ...wait... You're saying you turned off closed loop Idle? then disregard what I said. | ||
| Hermit |
I have been running with the closed loop idle off while doing some tuning. One issue I have seen is if you get the engine really hot then stop for a while the engine heats up intake air temperature sensor (IAT). When restarted I got a very lean idle around a 17 AFR until the incoming air cools the sensor down. Would not start without a little throttle. I have not experimented enough yet with open/close loop idle to know for sure what all the effects are. |
