I have a Cartek StageII head and H cam set up. When running in open loop, the AF rato is ~12.6. In closed loop it is 14.6. When in open loop the idle surges, even at 850rpm. Do i need to adjust he AF ratio? If so, how?

 

Can anyone help?

 

Open loop is cruise so your afr ratio should 14.7, WOT (closed loop) should be lower say 12.5-13. I am having the same problem with my 50 lb injectors. You need to tweak the injector flow rate tables and possibly the injector offset tables for what ever injectors you have stuck in. You will probably have to play with the running airflow tables to tweak those closer to your actual flow and idle speed. If you have not done injectors you need to look at injector duty cyles.

Gary

 

Isn't closed loop when the car is not warmed up? The AFR of 12 is at idle. Once the car warms up and the O2 goes closed loop, it settles in nicely at 14.7.

 

OPEN LOOP is when the car is not warmed up and CLOSED LOOP is when the car is warm.

The difference between open and closed loop is:
In open loop control, the sequence of commands in the program is carried out irrespective of the consequences. For example, the PCM sets a fixed type of work to do (the instructions).

In closed loop control, the PCM would set work to do, then monitor the progress to make sure that it is done. If things stop working or don't work correctly then the PCM will act. The PCM observes, obtains feedback and takes appropriate action if the target is not being met. A closed loop system is one that involves feedback to ensure that set conditions are met. In most applications, closed loop happens at approximately 150-160 degrees F.


I don't think you're A/F is the cause. An erratic idle is a tell-tale sign of too much timing. What is your IAC? Start here.

In a no load situation you want your IAC no lower than 30, and no higher than 50. Now put a load on your car, D if automatic, and put the AC on. The values here should be no higher than 120 or so. added- do this check in a closed loop condition

Now try adjusting the timing. Be carefull of adding to much timing - it can give you a great no load idle, but with any kind of load will become erratic. To adjust the timing at idle the base spark tables are the best place. The tables are scaled vs. rpm and g/cyl of airflow. The rpm part is apparent. To calculate the g/cyl use the following formula g/cyl = 15 * MAF(g/sec) / RPM
This formula takes massflow per unit time and converts it to massflow per cylinder. The 15 is a constant which corresponds to a V8 running a 4 cycle combustion cycle. The easiest thing to do is to load your log file into excel, export to CSV, then create a formula in excel which applies the formula above.
Good luck

 

The PCM does operate in closed loop mode during normal driving at normal temperatures but it is not simply a matter of whether the engine is cold or warm. During WOT, the PCM operates in OPEN LOOP mode. In open loop mode the PCM uses the MAF, MAP, IAT, and CPK (RPM) sensors, but not the oxygen sensors, to calculate fuel flow (injector pulse width). In closed loop mode, the PCM performs the same calculations as in closed loop but also uses the oxygen sensor signals to maintain a 14.7 to 1 Air-Fuel ratio which is optimal for the catalytic converters. The type of oxygen sensor used in our cars has a very limited useful range and cannot be used when a mixture other than 14.7 to 1 is needed. They are intended for emission control only. Consequently, when a richer mixture is needed, as during WOT, the PCM operates in open loop mode. In open loop mode, the Air-Fuel ratio is determined by tables stored in PCM memory.

 

Installed 30@# injectors. Have extensive experience tuning diff ecu systems. Do NOT like the ls1 ecu much at all. Have in car wideband and all i can seem to change in closed loop is fuel trims. If go waaaaayyyy rich/lean I can get a little response out of the a/f, but otherwise the ecu leans/richens me back to 13.8-14.2 with the new headers. Stock manifolds were just fine on a/f with stock inj and tsp228r cam. No problems out of cam whatsoever. Of course no big action out of can either. Now I have playing hell gettng the a/f/idle I was used to on stock manifolds.


Any expertness????

Thanks

 

Todays cars do NOT run in open loop at WOT, there are 5 PCM modes along with a loop state.

Open loop in OBD-II engines also use A.I.R, runs I/M 240 tests and makes some adjustment as to what S2 O2s report, you would not want these functional during what what your calling WOT which would be in the PE mode.
Via your PCM scanner, monitor engine loop and clearly once above 122 degrees the engine stays in closed loop, and switches from one mode to another.
O2s work just fine, they are not used, not because they are not good enough but because EPA states true WOT condition (engine at 100% load) is rarely used and is not bound to EPA smog requirements and being O2 values are only read once 1 second by PCM they are ignored and PE tables are used to assure enough fuel is added so Cats are not fried and fuel flow meets engine load demand.

 

I think that my previous post is essentially correct. I think that some inconsistent use of terminology is causing confusion. In control system terminology, "closed loop" implies a feedback control system in which the difference between the measured output and the desired output is used by the controller to drive the output in the direction that reduces the difference. In the case of A/F ratio, the measured output is provided by the O2 sensor. When the controller is using the oxygen sensor signal as described above, the PCM is controlling the A/F in closed loop mode. When the PCM is ignoring the O2 sensor, A/F is under open loop control. I believe that A/F is under open loop control during Power Enrichment (WOT) and if the PCM reports otherwise, perhaps it shouldn't.

-Gary