The BEST Tuning FAQ Answers ever for EFI
#1
12-05-2007, 07:31 PM
The BEST Tuning FAQ Answers ever for EFI
I found this forum by accident when searching for info on a part number. The following excerpis quite simply the best, most straight-forward explanation of open loop and closed loop EFI systems, tuners, etc, that I have ever seen.
Although it is written by an experienced HD technician/engineer, I find it to be completely unbiased. Hope you all get as much of an education out of reading it as I did! This is great stuff:
How does the EFI system work in simple terms?
The EFI system used on most 06 and earlier models is an open loop system. This system is essentially “dumb” in the sense that it supplies fuel based only on the programmed (calibration) values in the tables that control the injectors. These calibration values are programmed by H-D to match the amount of/how an average stock motor, and its associated components, processes air at any given rpm, load and throttle opening. Environment changes (temperature, altitude, etc) are handled by offset tables which collect information from sensors (IAT, ET, MAP, etc) to modify the main tables. There are “Tuning Constants” that define the overall operational parameters such as motor size, injector size and rev limit. Another offset is the AFR table which uses a mathmatical formula to change the known tailpipe AFR base tuned value (when motors are stock using the original mapping) to the "desired AFR" for best fuel milage and low emmissions. The calibration values are fixed in the open loop system (until physically changed via remapping) and the ECM is incapable of identifying changes in air flow caused by component changes and corresponding needs to make fuel or other calibration changes to synchronize air/fuel or correct constants.
06 Dyna’s and all 07L models (except 07 V-rod) added O2 sensors in the exhaust systems to provide a “closed loop” capability. Production variables of the components used in and affecting the EFI system cause corresponding fuel and air flow differences from bike to bike as manufactured. The fixed, “open loop”, system does not compensate for these differences (just as it cannot compensate for component changes). The Closed Loop O2 sensing system provides feedback, within a limited AFR and specified operating range, to compensate for these production variables, reducing overall emissions. This added feature can compensate for mild component changes but does not memorize those changes (there is an "Addaptive Fuel Value" offset based on the avereage O2 required corrections which moves the entire VE tables rich /lean by +- 10%, remembered and constantly adjusting). This means that each time the ignition key is cycled, the O2 correction (O2 integrator) is at zero and must resample to establish the required correction. The bike may exhibit erratic running, until this is accomplished, each time it is restarted if the required correction values are large.
When do I need to recalibrate my ECM?
Whenever the amount of, or how the motor processes air is changed! Period!!! The major components influencing air flow are the exhaust system, air cleaner, motor size, heads and cams. If any of these are changed, the fuel (via the VE and AFR tables) and, typically, the tuning constants table in the ECM must change to match (synchronize) both the increases and decreases in air flow and physical characteristics of the motor caused by those component changes.
On “closed loop” models, the above is true when the changes exceed the O2’s capability to compensate, to reduce the amount of correction required of the O2's or to change tuning constants (motor size, injector size, etc).
In addition, there are certain “behind the scenes” tables that have strategies to add fuel for extended high rpm runn
Although it is written by an experienced HD technician/engineer, I find it to be completely unbiased. Hope you all get as much of an education out of reading it as I did! This is great stuff:
How does the EFI system work in simple terms?
The EFI system used on most 06 and earlier models is an open loop system. This system is essentially “dumb” in the sense that it supplies fuel based only on the programmed (calibration) values in the tables that control the injectors. These calibration values are programmed by H-D to match the amount of/how an average stock motor, and its associated components, processes air at any given rpm, load and throttle opening. Environment changes (temperature, altitude, etc) are handled by offset tables which collect information from sensors (IAT, ET, MAP, etc) to modify the main tables. There are “Tuning Constants” that define the overall operational parameters such as motor size, injector size and rev limit. Another offset is the AFR table which uses a mathmatical formula to change the known tailpipe AFR base tuned value (when motors are stock using the original mapping) to the "desired AFR" for best fuel milage and low emmissions. The calibration values are fixed in the open loop system (until physically changed via remapping) and the ECM is incapable of identifying changes in air flow caused by component changes and corresponding needs to make fuel or other calibration changes to synchronize air/fuel or correct constants.
06 Dyna’s and all 07L models (except 07 V-rod) added O2 sensors in the exhaust systems to provide a “closed loop” capability. Production variables of the components used in and affecting the EFI system cause corresponding fuel and air flow differences from bike to bike as manufactured. The fixed, “open loop”, system does not compensate for these differences (just as it cannot compensate for component changes). The Closed Loop O2 sensing system provides feedback, within a limited AFR and specified operating range, to compensate for these production variables, reducing overall emissions. This added feature can compensate for mild component changes but does not memorize those changes (there is an "Addaptive Fuel Value" offset based on the avereage O2 required corrections which moves the entire VE tables rich /lean by +- 10%, remembered and constantly adjusting). This means that each time the ignition key is cycled, the O2 correction (O2 integrator) is at zero and must resample to establish the required correction. The bike may exhibit erratic running, until this is accomplished, each time it is restarted if the required correction values are large.
When do I need to recalibrate my ECM?
Whenever the amount of, or how the motor processes air is changed! Period!!! The major components influencing air flow are the exhaust system, air cleaner, motor size, heads and cams. If any of these are changed, the fuel (via the VE and AFR tables) and, typically, the tuning constants table in the ECM must change to match (synchronize) both the increases and decreases in air flow and physical characteristics of the motor caused by those component changes.
On “closed loop” models, the above is true when the changes exceed the O2’s capability to compensate, to reduce the amount of correction required of the O2's or to change tuning constants (motor size, injector size, etc).
In addition, there are certain “behind the scenes” tables that have strategies to add fuel for extended high rpm runn
#3
12-05-2007, 07:49 PM
#4
12-05-2007, 07:52 PM
RE: The BEST Tuning FAQ Answers ever for EFI
Maybe not the best ever, but pretty good explanation of the capabilities of the tuners listed. SERT does have lots of possibilities, but there is a learning curve, and computer proficiency is needed, along with a dyno unless you have a base flash that is really close and you can then tweak it from there.
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