Does the ECM Have Adapted Memory
01-06-2008, 10:13 PM
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Does the ECM Have Adapted Memory
Hello everyone. Sold a 02 Lexus ES300 last week to finally get what we really wanted back in 2004 when I bought the used Lexus. I picked up a gun metal gray 05 TL with 20k miles on it. We've only had it a week and my wife and I love it.
I have a question regarding how the ECM on these vehicles handle spark knock due to low octane fuel. On the newer GM vehicles the ECM comes down to the lower octane fuel tables (basically retards the timing) to prevent the engnine from damaging itself. The problem is even if you begin using premium gas the ECM cannot work itself back up to the higher tables. This can only be done by pulling the ECM fuse for approximately 10 minutes. When the ECM is depowered it defaults to the high octane tables and will stay there as long as you run premium and do not encouter any spark knock conditions. Does the Acura system work the same? Since I don't know if the previous owner used premium, will I be getting the most performance by running premium now or do I have to depower the computer to get back to the premium fuel tables (more advance?)
I have a question regarding how the ECM on these vehicles handle spark knock due to low octane fuel. On the newer GM vehicles the ECM comes down to the lower octane fuel tables (basically retards the timing) to prevent the engnine from damaging itself. The problem is even if you begin using premium gas the ECM cannot work itself back up to the higher tables. This can only be done by pulling the ECM fuse for approximately 10 minutes. When the ECM is depowered it defaults to the high octane tables and will stay there as long as you run premium and do not encouter any spark knock conditions. Does the Acura system work the same? Since I don't know if the previous owner used premium, will I be getting the most performance by running premium now or do I have to depower the computer to get back to the premium fuel tables (more advance?)
01-06-2008, 10:53 PM
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Hopefully others with more experience/knowledge will cime in with additional detail and/or corrections where necessary.
It is my understanding that the TL use a knock sensor to determine if there is a need to retard the timing. If knock is detected, the timing will retard to the point that the knock is eliminated, then add back timing slowly to reach the optimum "no knock timing."
If the previous owner used, say, regular, and now you routinely use premium, there is no "learning curve" for the ECU/ECM. It either knocks and timing retards or it doesn't.
The strong concensus is that the TL/TL-S REQUIRES 91+ Octane. The small cost differential is not enough to compensate for the lost mileage and potential engine damage.
Hope that helps.
It is my understanding that the TL use a knock sensor to determine if there is a need to retard the timing. If knock is detected, the timing will retard to the point that the knock is eliminated, then add back timing slowly to reach the optimum "no knock timing."
If the previous owner used, say, regular, and now you routinely use premium, there is no "learning curve" for the ECU/ECM. It either knocks and timing retards or it doesn't.
The strong concensus is that the TL/TL-S REQUIRES 91+ Octane. The small cost differential is not enough to compensate for the lost mileage and potential engine damage.
Hope that helps.
01-07-2008, 04:04 PM
#3
Senior Moderator
Also the TL learns driving patterns, so if the previous owner was a granny driver, the car won't downshift as much as the driver who redlines his car everyday. The car learns your pattern over a course of maybe 100 miles.
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