Optimum open-loop datalogging conditions

s300 and SManager software questions & answers
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TurboLS
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Optimum open-loop datalogging conditions

Post by TurboLS »

It is my understanding that the ECU neglects changes in ECT, IAT, and other sensors as well when in open loop mode. My question is this: What conditions (IAT, ECT, etc.) are the best ones in which to do all the open loop datalogging. I know if I do a run at 50F IAT and 150F ECT and then at 70F and 200 ECT, the A/F values will be different even if no changes have been made to the fuel map. I see in the s300 parameters that 51F IAT and what looks to be 177F and above for ECT. Should I just datalog and then back calculate the fuel maps to these temperatures with the formulas in the help file??
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jdmspecdc5
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Post by jdmspecdc5 »

just be sure to keep ect and iat as constant as possible meaning everytime you datalog those parameters should be the same or close. consitency is what you are looking for.

TurboLS
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Post by TurboLS »

Well, even if I datalog under the same conditions everytime, what is the guarantee that that will be the fuel map will be adjusted correctly for a different set of temperatures? Do you see what I'm getting at?? Basically, I think that unless I record data at 51F IAT and 177F ECT in open loop mode, the fuel map that I use will be adjusted improperly when I convert back to closed loop. For instance, I can have the car tuned perfectly in open loop mode at 70F IAT and 150F ECT and then when I go back to closed loop, the A/F ratio gets messed up because the next day it's a little colder outside. Unless Hondata knows what temperature I datalogged at and adjusts the fuel maps accordingly, I can't see how the A/F ratio values would stay constant between temperatures.
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locash
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Post by locash »

The ECU does NOT ignore IAT and ECT values in open loop, it uses them, so don't worry about it.

TurboLS
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Post by TurboLS »

so then what is the difference betwee open loop and closed loop, just the long term and short term fuel adjustments??
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scottishpol
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Post by scottishpol »

Long and short term adjustments are fuel corrections that the ecu applies to the map in closed loop only, by means of the o2 sensor.
It will always target 14.7:1 in closed loop untill the closed loop threshold is breached (at around 750mbar).

Open loop means that no corrections (short and long term fuel trims) will be applied. The ecu is reading the exact values from the fuel map with no intervention/corrections from the o2 sensor.

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Post by TurboLS »

So in essence, it may be better to run the car in open loop all the time if we are all targeting 13.5:1 at higher throttle and such... thanks for the clarification. I had that hunch, but i needed a second opinion. Now, my next question is how Hondata corrects for rich/lean conditions when shifting between gears. What I have been trying to do is datalog lambda for each gear and look at the differences. That way, I can use the gear offsets and tune the whole map and it will get adjusted for each gear.
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strider
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Post by strider »

No sure about shifting gears.

But you mentioned hitting a target A/F. In the Parameters window, under Closed Loop, you can set your Target Voltage, which is your target A/F. You have to calculate the voltage to match that of your narrow band sensor. You can also select the Maximum MAP value that closed loop will operate till. So if you select 697 mbar for your Maximum MAP in closed loop operation, the car will try and hit your target A/F until it goes past 697 mbar. After that point it will read off the map. Like Scottishpol was saying. So if you tuned your higher loads (past the Maximum MAP value) to 13.5:1, in closed loop you should still get that.

If that is any help...
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TurboLS
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Post by TurboLS »

cool. that clears things up a bit. thanks a lot man.
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strider
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Post by strider »

FYI: One thing I am not sure about is the target voltage defaulting to .51 volts. When looking at the Stock oxygen sensor voltage settings under the Wideband menu, .45 volts = 14.7 A/F. I would think that the default value would be .45 volts to reach a target value of 14.7 A/F for light load and idle conditions, or closed loop. If I calculated it correctly, .51 volts would equal 14.35 A/F. I hope I am not misinterpreting the ?Target Voltage.?

Sorry if I made this confusing.

Hondata, can you clarify?

Thanks
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Hondata
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Post by Hondata »

The target o2 voltage is actually 0.50V (0.01V rounding error). You cannot convert this to a precise AF ratio as there is a lot of hysteresis from the o2 sensor, but when the fuel is controlled to keep the o2 voltage swinging each side of 0.50V, the AF will on average be close to stoichiometric.

Most oxygen sensor graphs are incorrect. The actual graph has two possible voltages for stoichiometric, depending if the mixture is going from rich to lean or lean to rich. Correspondingly, each voltage will have more than one mixture, again depending on the direction the mixture is changing.
Hondata

strider
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Post by strider »

Thanks for the clarification Hondata. :D

Maybe the documentation could be updated to reflect this. There may be a lot of people confused about this.
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TurboLS
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Post by TurboLS »

well, i guess if we're tuning for power going from 14.7 at low load to 13.5 at high load, then we would want the lean to rich voltage. I guess I could hook up signal wire to the auxiliary inputs to monitor the voltage vs. detected A/F ratio in both cases. I dunno, is there an easier way??
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alblude
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Post by alblude »

I see that Maximum MAP for closed loop in the Prelude basemap is 780 mbar. This is for the H22A4 with 310cc injectors. Should this value be the same for the H22A1 with 345cc injectors? Do you guys by any chance have a basemap for the H22A1?

Thanks.

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Post by TurboLS »

Yeah, I noticed with mine that maximum basemap is where the 13.5 target lambda starts. Alright, on to my next set of questions. In a previous post, I was informed that I do not need to stop datalogging between gears. One of my questions is how Hondata can account for the car being out of gear between gears. What are the best shift points for each gear when datalogging? How fast should the throttle be applied in each gear?? Should I take each gear to redline, shift, let the next gear go to as low a MAP pressure as possible and then increase load?? I'm basically trying to do as much as possible off of the dyno. thanks guys.
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