All it is is crossover percentages. One map is warmup and the other is full temp operation as far as I know. You can set it low like Lucas does and idle in open loop, or if you dont need additional fuel control that low, highway cruising (55-60% or above), around town (30%+), or higher if you want it to stay in closed loop longer.

 

That's kind of what I suspected. I'm guessing that the #1 table is the warmup table and the #2 full temp since the values are somewhat higher in the #2 table for 1000-4000 RPM.

 

30-31mpg on our last road trip, totally stock. Mostly flat, some hills. 65mph or less the whole way even in the 70 zones. You just have to grandma it...

 

John, I thought about doing it that way, but it was just easier right before I left on my trip to drop 104 into the coolant temp box. Yeah, there's a CEL but I have a C reader and check the codes weekly. Nothing but the usual codes expected for such a change. I might convert over to the load attenuation, we'll see but in my case I want to idle rich...cammed car that idles rock solid like stock is fun for me as well.

 

I have a quick question that's somewhat related. By making the ecu go into open-loop in low load and leaning it out in those areas, would it be possible to make a SES for rear o2 stop showing? I would make a mechanical fix, but I'm not sure if my dremel would cut it.

 

I apologize for dragging a thread back up from the dead, but I found it to be really interesting and I have a question. How can you tell when you're in open loop? Is there something you can log that will tell you whether you're in open or closed loop at any particular point?

 

It is loggable, but I don't know if the variable (or request if there is one) has been published yet.

Maybe one of the dissassemblers can help you out.


Eric

 

In Mitsulogger there is a logged item O2FeedbackTrim, when that goes to 0 then you're in open-loop. I don't know if evoscan logs this. It reads 0 during idle too, but you're not in open-loop there unless you did something to make it idle open-loop.

edit: Sorry I misread. I was reading the trim during decel which is 0. During idle there are numbers in there indicating closed-loop fuel adjustments.

 

Are you sure O2FeedbackTrim always goes to 0 when you're in open loop? I have a log which shows some ~80 mph cruise, with throttle in the 30-35% range, with non-zero values for O2FeedbackTrim. It was my understanding from this thread that at more than ~20% throttle you'll be open loop. Then again, my load at those times is very low... do you only go open loop when both throttle and load are above the thresholds?

 

It's either. In 5th gear 63mph at 40% throttle I got a load close to 70. Did you change your open-loop load or throttle maps?

Anyway in open-loop the ecu stops making fuel adjustments so an indicator is the zeros in the O2feedbacktrim.

 

I haven't touched my open-loop load or throttle maps. According to MalibuJack, we switch to open loop above about 20% throttle, but in my logs I'm cruising at 80 mph at 35% throttle with low load with non-zero values in O2FeedbackTrim. There are three possibilities:

1. I was in closed loop, and MalibuJack was incorrect: we don't switch to open loop until somewhere past 35% throttle
2. I was in closed loop, and we don't switch to open loop unless both throttle and load are above certain thresholds
3. I was in open loop, and O2FeedbackTrim is not always 0 when you're in open loop

 

In open loop the car still makes fuel adjustments but its based on calculated air flow not O2 feedback. I can set my cruise AFR to what I want in the lower load maps and it is very nearly exactly what I put it to. For instance a 15.7 with my mods and injectors will yield a 15.5 AFR in cruise.

 

Tom, as far as I have been able to determine its an Either/Or situation. If the load exceeds the setting then it will go into open loop. If the throttle % is exceeded it will do the same, even if the other variable has not been met. You have to remember its based on RPM as well as load percentage so if you were at 3500 rpm at 80 mph (lets disregard throttle for a moment) your load will easily be in the 70-80 range. Cross reference that on the stock map at that RPM and its 95%, but at 4000 its 78% (for load). You could have been there just based on that or very close.

 

I'm sorry, I'm afraid I still don't feel like I understand. Here's a log excerpt below:

If the stock Open Loop Throttle map forces you into open loop at over 20% throttle, then I should be in open loop. However, my O2Feedback is not zero, so either I'm in closed loop, or a zero for O2Feedback doesn't mean you're in closed loop, or I'm not understanding something.

 

Yeah it makes adjustments by reading off the fuel maps.
The adjustments based on the front O2 sensor are different than what you're talking about John. In closed-loop the ecu reads the AFR from the front O2 sensor and makes adjustments to get the AFR to 14.7 (or whatever the closed-loop fuel map is set to). So the O2FeedbackTrim you're reading is how much the ecu is adding or holding back fuel. When the O2FeedbackTrim starts reading all zeros then the ECU is reading off the high-octane/low-octane maps.

How did you get your car to cruise lean? Did you force open-loop on your car during cruise? I might try this and see what gas mileage I get because I drive like 100 round-trip these days.