ECU memory retention question
Oct 26, 2007, 01:06 PM
#1
ECU memory retention question
After a lot of searching, I still can't find this answer...
I've observed that CEL lights seem to stay on for a certain number of key-offs until, I assume, the ECU recognizes that the issue is no longer present.
In normal operation, if there is a count of 6+ knock, the EVO's ECU will divert to the low octane fuel map as a safety net and, I think, divert to less aggressive timing.
How long does the memory in the ECU retain an internal change due to knock? For a measured amount of time? Till next key-off? Till the next full up with higher octane fuel? Until you get a better tune?
Thanks...
I've observed that CEL lights seem to stay on for a certain number of key-offs until, I assume, the ECU recognizes that the issue is no longer present.
In normal operation, if there is a count of 6+ knock, the EVO's ECU will divert to the low octane fuel map as a safety net and, I think, divert to less aggressive timing.
How long does the memory in the ECU retain an internal change due to knock? For a measured amount of time? Till next key-off? Till the next full up with higher octane fuel? Until you get a better tune?
Thanks...
Oct 27, 2007, 09:31 PM
#2
Wow, 20 members have read this question and no one has attempted an answer! Is my question too easy or too hard?
In any case, I am genuinely and trying to find an answer...
When I datalog, and there is some knock and timing is clearly being pulled, and then I immediately do another datalog, it appears the timing is still pulled and there is consequently no knock in the 2nd data log. Apparently the ECU remembers knock for longer than simply the instantaneous response.
So, how long does the memory in the ECU retain an internal change due to knock? For a measured amount of time? Till next key-off?
In any case, I am genuinely and trying to find an answer...
When I datalog, and there is some knock and timing is clearly being pulled, and then I immediately do another datalog, it appears the timing is still pulled and there is consequently no knock in the 2nd data log. Apparently the ECU remembers knock for longer than simply the instantaneous response.
So, how long does the memory in the ECU retain an internal change due to knock? For a measured amount of time? Till next key-off?
Oct 29, 2007, 12:29 AM
#5
there is a value called octane number.. if you get enough knock to shift the number, it will interpolate between the high-octane and low octane maps.
generally if you get serious knock, the value will shift from 255 to 0.. normally it shifts a few points then returns over a period of time.
the answer to your question is not black or white. It will return to normal over a short period of time if the knock goes away. However there is also short-term protection (knock sum) that will pull timing every time there is knock.
the reason you got very few answers to your question was its posted in the wrong forum, and the question was a bit hard to follow.
generally if you get serious knock, the value will shift from 255 to 0.. normally it shifts a few points then returns over a period of time.
the answer to your question is not black or white. It will return to normal over a short period of time if the knock goes away. However there is also short-term protection (knock sum) that will pull timing every time there is knock.
the reason you got very few answers to your question was its posted in the wrong forum, and the question was a bit hard to follow.
Oct 29, 2007, 07:02 AM
#7
your observation that the ecu pulls and holds timing is not the usual pattern.
normally a knock event will pull timing for the duration of the event. are you sure your ecu has stepped down the timing? perhaps it just isn't knocking in the same place as before. I've had 13 count knock events come out of nowhere and disappear without any reason. not to be repeated in a days worth of lapping, iow driving the same course the same way.
short answer, have not witnessed the prolonged lower map usage.
from what I have read in the ecuflash forum,
repeated knock events will lower the octane map and should place a higher importance to the other timing maps.
as MJ pointed out log your octane to see if you drop into lower octane maps
normally a knock event will pull timing for the duration of the event. are you sure your ecu has stepped down the timing? perhaps it just isn't knocking in the same place as before. I've had 13 count knock events come out of nowhere and disappear without any reason. not to be repeated in a days worth of lapping, iow driving the same course the same way.
short answer, have not witnessed the prolonged lower map usage.
from what I have read in the ecuflash forum,
repeated knock events will lower the octane map and should place a higher importance to the other timing maps.
as MJ pointed out log your octane to see if you drop into lower octane maps
Last edited by nothere; Oct 29, 2007 at 07:05 AM.
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