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Discussion Starter · #1 ·
Can someone explain how the Self-Learning works on the standard Evo ECU (E6 for example) so I can fully answer an FAQ question - Do I need to reset my ECU after modifying my car?. I know the general concept behind it but need some confirmation to my thinking, and some answers to stuff I don't know, specifically:
1) On the Evo does the self-learning work on both the air/fuel (oxygen sensor) and the ignition timing (knock sensor)? Like most modern cars I assume it does.
2) Does the self-learning affect the boost levels? e.g. reduces boost if you use low RON fuel. I don't think it does on the Evo but according to Scoobynet it does on the Scoobies.
3) After reseting the ECU you are required to run the engine for 20 minutes on idle (once the engine is warm). I assume this is for the ECU to go into closed loop running to self-learn the air/fuel pre-control levels?
4) What happens about self-learning the pre-control Knock levels? I assume it just stores the pre-control Knock levels as the car is driven?
5) I am right in thinking the Knock pre-control levels will be stored for the same range as the whole ignition map (load/rev) and for EACH cylinder?
6) I understand the pre-control levels can be reduced over time by self-learning, if so roughly how long, say if you went from 95RON to 98RON fuel? Is it a case it will take an infinite number of resamples as quoted on the Scoobynet FAQ's? I suppose another important question would be, are people who run 98RON everyday and then switch to 98RON plus Octane boosters for trackdays actually getting the full benefit without reseting the ECU?

Please no second guessing as I can do that :D

Thanks in advance.

Discussion Starter · #2 ·

This wot I know on the subject,

The learning thing is a process by which ECU constantly checks tolerance and changes in all engine sensors. This data is stored in battery backed up RAM so that it always the latest data used by the ECU 2 control engine running. This also applies 2 fault codes. Resettiing clears the RAM and the ECU uses default settings 2 initially run the engine then as the data from sensors is logged the ECU applies best settings appropriate 2 that data.

The main reason 2 reset is to clear the ignition advance trim if low octane fuel has caused the ECU 2 retard ign timing because of low octane fuel. Ignition advance is the only setting the ECU sets 2 a non-default maximum , so after reset the timing is set 4 best performance, but if det is detected timing is retarded.

All other settings will go default , so idle , 02 etc will need some time 2 optimise.

Discussion Starter · #3 ·
Cheers Evoboy that is pretty much how I understand the system but it does throw up the question about is it worth reseting the ECU or not.

Perhaps it's better to explain how I think it works (according to how I read it in the Bosche Automotive Handbook):
On an intitial run of the engine the ECU starts to work out the knock points for each cylinder and for each load/rev point. The ignition is retarded when knock is detected until it can no longer be heard and this setting is stored in the RAM, this becomes the Pre-Control level. Subsequently when you run the engine the ECU knows the Pre-control level for a particular load/rev and will not advance the ignition past that point resulting in no knock heard at all. This is so that the when the engine is operated with rapid load and speed changes the engine will work at optimum efficiency without audible combustion knock.
If knock is later detected for whatever reason (say due to bad batch of fuel) then the ignition is retarded over and above the Pre-control level until knock cannot be heard. Once knock cannot be heard it then gradually advances the ignition back to the Pre-Control level. If it continues to detect knock over and above the Pre-Control then I suspect it may update the Pre-Control level to cope although I am not sure on this point but it makes sense.
The catch 22 question is what if the initial Pre-Control levels are set when using say a low Octane fuel? When you switch to a higher Octane fuel you will not get any benefit unless a) somehow the Pre-Control level is gradually altered in someway or b) you reset the ECU.
Scoobynet says that the level is resampled but and I quote it would take an infinite number of re-sampling cycles for the effect on the average to be overcome. basically they are saying it takes ages for the Pre-Control level to improve and would never reach the optimum level without an ECU reset.
I know some people have said in the past that they use normal 97/8RON everyday and then for trackdays they add Octane Booster. If the above is correct then I can't see that you would get any improvement or only very little?

Again if the above is correct then it seems it would pay to reset the ECU periodically (e.g. during winter) and after some performance upgrades that will reduce detonation levels (e.g. larger intercooler, water injection, higher RON fuels etc.).

I am right? (be gentle :))

Discussion Starter · #4 ·
Basically thats it , altho Mits ECU's will have different strategys 2 Bosch , 2 Marelli , 2 Bendix etc etc.

There's no problem with resetting 2 optimise ignition except that the ECU will take a few days 2 optimise other stuff like O2 , idle speed , throttle position sensor etc.
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