does the s13 sr20det ecu have any short/long term trim table

[tmh983]

Can anyone tell me if a standard s13 sr20det ecu has any short/long term fuel trim tables?

[Matt]

not that im aware of. I know that O2 feedback info is stored in RAM (temporary memory) which is vehicle battery backed up but not sure on the specifics how that is used

[tmh983]

Looking at the consult stream, I think the sr20 does have a fast and slow learning trim value. The fast trim i'm guessing is part of the main 02 feedback loop, it is constantly changing depending on the 02 sensors's output. If the load is held at one point for a few seconds then the slow table starts to slowly track towards the correct afr. If you move to a different load site then back you will see that the slow trim has remembered the last value it was on. Also if you turn the engine off and back on, the slow trim table remembers the values it last had.

Would it be possible to find where it is storing the slow trim values and present it as a table in nistune somehow? It would be a very useful tool to check if the latency/k values are correct.
For instance if the low load trims were significantly different to the rest of the table it would point to the latency being wrong, or if the whole table was high or low, then the k value would probably be wrong...

[Matt]

its a matter of leaning how it works from undocumented disassembly code (using the AF alpha consult registers as a starting point and trying to map it out). It would have to be one of the lesser known parts of the Nissan ECU but once I did know then could download the RAM map from memory and display it

[nissangts]

Hahaha this sounds like an man who has tuned a few evos

Looking at the consult stream, I think the sr20 does have a fast and slow learning trim value. The fast trim i'm guessing is part of the main 02 feedback loop, it is constantly changing depending on the 02 sensors's output. If the load is held at one point for a few seconds then the slow table starts to slowly track towards the correct afr. If you move to a different load site then back you will see that the slow trim has remembered the last value it was on. Also if you turn the engine off and back on, the slow trim table remembers the values it last had.

Would it be possible to find where it is storing the slow trim values and present it as a table in nistune somehow? It would be a very useful tool to check if the latency/k values are correct.
For instance if the low load trims were significantly different to the rest of the table it would point to the latency being wrong, or if the whole table was high or low, then the k value would probably be wrong...

[tmh983]

i don't get it?

[nissangts]

Normally whenever you u change K value and latency on Evos you log them afterwards to check the long term and short term fuel trims. I figured someone using those jargons would be familiar with evo tuning.

i don't get it?

[tmh983]

fair enough then. I've never even had a ride in an evo, let alone tuned one.