No problem man...that is exactly what this place is for...asking questions, sharing knowledge, and getting answers...
You are correct...Braden (Turboge) knows his s*** big time, he has successfully tuned Haltech E6X standalone controller...which is a full replacement for the factory ECU...He is now working with a Greddy E-manage piggyback system, that can also control fuel and timing to a point...But it does not replace the factory piece, it more or less intercepts a number of sensor readings, and does some tricks to allow the user to program different aspects of the engine's behaviour...(just a note, and this may be confusing at this point...To my knowledge, Braden ran the Haltech "in parallel" with the facotry ECU...In this case the haltech standalone was completely controlling the fuel math and timing aspects, while allowing the factory ECU to run the other crap, such as the tach, A/C, or whatever else...Generally this setup makes the wiring more simple, and by passes some headaches..However this is a different setup than the E-manage and stock ECU...this thread will probably and hopefully get into that later)
So I will start with what closed loop and open loop is in general...I will try to keep it simple at first, to keep the length down...
Our stock ECU relies on two different "modes" to control the engine...the stock ECU is not tuned for performance, but more for emissions and engine safety...One mode is referred to as closed loop, and one as Open loop...They both pertain to a similar area of the engine controll, but do it in completely different ways...
Closed Loop: Closed loop refers to a negative feedback system that controls the fuel math of the engine...Basically the O2 sensor will "sense" any unburned oxygen in the exhuast gas content, and report back a reading to the ECU...the ECU utilizes this signal to determine the nature of the fuel/air mixture that has already been burned up (this is why it is "negative feedback, a similar way to how a thermostat works...Heat goes up, thermostat recognizes it and shuts off the heat...Heat goes down, thermostat recognizes it, and the heater/furnace kicks back on...)...Through this system the ECU can tell if the mixture is too lean or too rich...and will attempt as much as possible to make it "perfect"...By perfect I mean stoichiometric...This refers to a fuel air mixture of 14.7:1 (14.7 "moles" of O2, to one "mole" of gasonline)...That theoretically is the amount of reactants to make a complete burn...In which there is no CO (carbon monoxide) or unburned hydrocarbon molecules, which is terrible for the environment...the good part is that this is also a good mixture for the engine at certain points...So that is what closed loop tries to do, it takes input from the primary O2 sensor and the ECU uses it to keep the Air/Fuel mixture as close to stoichiometric as possible...When it is stiochiometric, no unburned reactants will be left over in the exhuast...so the O2 sensor notices nothing, and the ECU keeps the same fuel math until the sensor reads problems...and then fuel will be cut to lean it out a little more...
Obviously there is more involved with this...other sensors are used to incorporate more fuel to a less accurate degree (I believe input from the throttle position sensor is used initially...so that more fuel is safely added as the throttle is opened...the O2 sensor aspect runs in the background to keep it more accurate)
Also some things you will notice is what is known as a Wide Band O2 Sensor (or WBO2 sensor, if you saw it and didn't know what it was...)...which cures a fundamental problem with closed loop somewhat...the stock O2 sensor is only designed to notice amounts of exhuast content that are exhuasted from a near stoichiometric mixture...For reasons beyond this initial post, a 14.7:1 A/F ratio is far too lean for an engine once load and revs increase substantially...there is a threshold for the stock O2 sensor, in which once the maximum reading of the O2 sensor is reached...the ECU switches to open loop (as well as with sensors reading amounts of load on the engine...they play a part in the mode switch as well)...the stock O2 sensor only reads a little richer than 14.7:1, so stock closed loop is only used for light load low speed vehicle operation...once load increases, the mixture needs to be richer, and the closed loop system is switched to open loop...which generally no longer uses the O2 sensor...Now a WBO2 sensor has a much more "sensitive" measuring device to notice much more unburned hydrocarbon content...and they are also very expensive...But with a sensor such as this, as well as the proper ECU upgrades to translate the new readings...You can run a mode known as "High Load Closed Loop"...which operates exactly the same way as before, but over a much broader scale...In some cases a user can set target air fuel ratios over the entire rev range and load scale, and use only high load closed loop...That is the easiest way to tune fuel mapping to some, but it is not necessarily the most accurate or "best"...
So that should give you a general idea of how closed loop works...So next comes Open loop...
will help with the understanding of the whole thing...
