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What is the lead time of the ECU in a Tacoma? Meaning that if something changes (different gas, different plugs, supercharger added, whatever) how long does it take for it to adjust? I often read about people saying/thinking it can take days or even weeks to adjust however this just doesn't make much sense to me. If it has say a 60Hz sampling rate, wouldn't it be adjusted in a matter of seconds or even less? I do understand that *supposedly* modern ECU's can detect driving styles (although the practicality of that feature might be a bit exaggerated) which I could see taking a while to adjust to.

...or maybe it intentionally takes a while to adjust to that it doesn't reset the entire system because of one small anomoly. dunno, any comments?
 

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i think it "adjusts" after a few miles and a re-start or two.
i could be wrong.
 

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KRYPTO(dale) said:
i think it "adjusts" after a few miles and a re-start or two.
i could be wrong.
It adjust's instantly if you reset it by pulling the battery or EFI fuse. And as per the Toyota 1-800 # it takes about 200 miles to adjust if left on its own.

Tim
 

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Discussion Starter #4
I wonder why it takes so long. They must build that in so that it's not constantly trying to adjust for every little thing.
 

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97TacoDude said:
What is the lead time of the ECU in a Tacoma? Meaning that if something changes (different gas, different plugs, supercharger added, whatever) how long does it take for it to adjust? I often read about people saying/thinking it can take days or even weeks to adjust however this just doesn't make much sense to me. If it has say a 60Hz sampling rate, wouldn't it be adjusted in a matter of seconds or even less? I do understand that *supposedly* modern ECU's can detect driving styles (although the practicality of that feature might be a bit exaggerated) which I could see taking a while to adjust to.

...or maybe it intentionally takes a while to adjust to that it doesn't reset the entire system because of one small anomoly. dunno, any comments?
Even though the computer may sample 60 times a second, what it does with the information affects how quickly it adjusts. First think of it as a running average, and for simplicity, say it keeps only the previous 10 samples. If the first nine samples are 5, and the last sample is 10, the running average becomes 5.5. Even though the value jumped to twice the amount, the average didn't change much.
I believe this is how the ECU uses information. It doesn't adjust according to the sample value, but rather the average value. If something changes and remains changed (altitude, octane, etc.) it takes a while for the data to reflect that change.
 

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Discussion Starter #6
wow somehow I am a "Senior Member" already...
 

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97TacoDude said:
I wonder why it takes so long. They must build that in so that it's not constantly trying to adjust for every little thing.
Part of why it takes so long may have to do with OBD-II readiness tests. Those tests (which determine proper function of various emissions systems of a number of miles, usually 150-200, with varied driving conditions) take a while to complete. Therefore, the ECU will not, short of a major change in air/fuel or some other input, make drastic changes. It will essentially listen to all its sensors and inputs and slowly learn in order to minimize tailpipe emissions and return an appropriate amount of fuel/spark and power.

Ed
 

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22RToy said:
Even though the computer may sample 60 times a second, what it does with the information affects how quickly it adjusts. First think of it as a running average, and for simplicity, say it keeps only the previous 10 samples. If the first nine samples are 5, and the last sample is 10, the running average becomes 5.5. Even though the value jumped to twice the amount, the average didn't change much.
I believe this is how the ECU uses information. It doesn't adjust according to the sample value, but rather the average value. If something changes and remains changed (altitude, octane, etc.) it takes a while for the data to reflect that change.
In addition to averaging to reduce noise in the data, it may (probably does) react differently to different data. Protecting the engine from knock would have far higher priority than tweaking out maximum performance, hence it would use less filtering one way than the other.

I also read (no clue if it is true) that the knock sensors are so noisy the ECU largely ignores them below 3000 rpm.
 

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It will vary from condition to condition since the computer is constantly learning and adjusting, but for the most part it is a matter of 200-500 miles. However, it can only adjust those conditions which you introduce after said changes. Like highway driving will not adjust city driving conditions per say no matter how many miles you drive. Here is a good site for those that want to know more:

http://www.4x4wire.com/toyota/4Runner/tech/OBDII_ECU/
 

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Although I'm not an expert, this is what I've learned from my wonderful :mad: experiences with TRD and Toyota service depts. The newer Taco's have what is known as a "learning ECU". This "learning" capability allows the ECU to optimize your "long-term" fuel trim values to things like your driving style and environment, thus making your truck more efficient, which gives you better mpg and minimizes harmful emmisions. As someone mentioned above, you can reset these learned values by removing one of the battery leads (I think someone recommended that I leave it off for more than 30 secs). I have also heard that there's some "best" way of re-teaching your ecu to get more HP sooner, but I don't remember what it was...
 
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