Couple questions to discuss about close loop operation
Posted: Fri Feb 09, 2018 4:29 pm
I have been playing for some months with s300 and I have a couple questions that couldn’t address nor figure out and would like some feedback, I apologize if they sound like dumb, I am not an expert on the field, but again the idea is to discuss and see whats the expert experience with this.
1) When you are tuning and you see that you currently have X correction applied due IAT temperature or ECT temperature, lets say I am currently at +2% IAT correction , the overlay lambda datalogged will take that in account or that gets applied AFTER current lambda calculation?
For instance, assuming you are reading 14.7 for 2000rpm/500mbar , which is my desired target, but I see that I have a +2% correction due IAT , is that 14.7 before or after the correction was applied? What will happen then when IAT correction goes to 0%? Reason I ask is that I don’t know if I should adjust the fuel map to take that in account or not.
2) Is there any way to tell if we are running in closed loop or open loop?
When running target lambda there are a lot of parameters that makes the ecu exit close loop operation, i.e. MAP or TPS values, but I have found that it is really hard to know exactly when you are driving if these conditions meet or not, and we don’t have any on/off Boolean display value that tells the current state?
Background: I have tuned my fuel map for several months now and played a lot with it, and archived pretty good results, when turning on close loop I barely have a short trim of -/+ 3% and LTRIM almost always 0, which is fine, but now I would like to tune it for normal highway speed to be more likely towards 15.1 but I have found it’s kind of difficult as well. I use the Target Lambda LOAD values and set 0 to 60kPa to 15.1 and then back to 14.7.
I tries to archive so but the lambda freaks out all the time moving between 14.7 and 15.3 back and forth, of course, it is trying to adjust and making corrections but it is hard to make it a steady 15.1 at constant speed/tps/rpm.
I have also found that changing the “Rate of change” table helps and improves lambda to be steadier without abrupt changes, but from the default values (17 slow 64 fast) I have to set it to 2 slow 3 or 4 fast … which seems like a LOT of modification from their default value.
Having said that, questions are….
3) What is everyone experience with this, is it safe or normal to reduce the rate of change that much?
4) Is there any other approach towards improve mpg when cruising using close loop or I should just run open loop and modify the fuel map desired cel values to run a bit leaner ?
5) Is there any real world difference by running 14.7 or 15.0 in mpg/fuel consumption numbers or it is not even noticeable, does it worth the try?
Sorry for the long post but I hope I could be as descriptive as possible.
1) When you are tuning and you see that you currently have X correction applied due IAT temperature or ECT temperature, lets say I am currently at +2% IAT correction , the overlay lambda datalogged will take that in account or that gets applied AFTER current lambda calculation?
For instance, assuming you are reading 14.7 for 2000rpm/500mbar , which is my desired target, but I see that I have a +2% correction due IAT , is that 14.7 before or after the correction was applied? What will happen then when IAT correction goes to 0%? Reason I ask is that I don’t know if I should adjust the fuel map to take that in account or not.
2) Is there any way to tell if we are running in closed loop or open loop?
When running target lambda there are a lot of parameters that makes the ecu exit close loop operation, i.e. MAP or TPS values, but I have found that it is really hard to know exactly when you are driving if these conditions meet or not, and we don’t have any on/off Boolean display value that tells the current state?
Background: I have tuned my fuel map for several months now and played a lot with it, and archived pretty good results, when turning on close loop I barely have a short trim of -/+ 3% and LTRIM almost always 0, which is fine, but now I would like to tune it for normal highway speed to be more likely towards 15.1 but I have found it’s kind of difficult as well. I use the Target Lambda LOAD values and set 0 to 60kPa to 15.1 and then back to 14.7.
I tries to archive so but the lambda freaks out all the time moving between 14.7 and 15.3 back and forth, of course, it is trying to adjust and making corrections but it is hard to make it a steady 15.1 at constant speed/tps/rpm.
I have also found that changing the “Rate of change” table helps and improves lambda to be steadier without abrupt changes, but from the default values (17 slow 64 fast) I have to set it to 2 slow 3 or 4 fast … which seems like a LOT of modification from their default value.
Having said that, questions are….
3) What is everyone experience with this, is it safe or normal to reduce the rate of change that much?
4) Is there any other approach towards improve mpg when cruising using close loop or I should just run open loop and modify the fuel map desired cel values to run a bit leaner ?
5) Is there any real world difference by running 14.7 or 15.0 in mpg/fuel consumption numbers or it is not even noticeable, does it worth the try?
Sorry for the long post but I hope I could be as descriptive as possible.