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Does ECU reset really improve MPG?


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4 replies to this topic

#1 friendly_jacek

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Posted 25 May 2004 - 09:18 AM

OK, i understand that ECU reset is a must after major mods.
What about stock car? Any benefits from doing ECU reset to improve MPG?
I have seen recommendations to do so, tried personally, but did not see convincing results.

On the other hand, a common sense dictates that it might work. For example: lets say i worked my subaru a lot over a weekend with hard towing,
near WOT, and thus rich conditions and possible timing retard to prevent knocking. Makes sense that it would be valuable to reset ECU to prevent this learned setting to apply to light driving for city commuting during weekdays.

Anyone with experience with ECU resets?

#2 Legacy777

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Posted 25 May 2004 - 11:32 AM

damn....I had a response all typed up and it crapped out during the post.

Short answer to recap.....if it's only one weekend, and not too many miles....you probably won't see any difference if you reset the ECU. If you took a long trip, 3000 miles....then it might be worth it.

#3 Setright

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Posted 26 May 2004 - 01:19 AM

As ever, I am sceptical. The ECU "reset" only clears the fault memory. The fuel and ignition settings are revised hundreds of times per second.
I don't know what frequency we're up to yet, but Bosch was quoting 300Hz in the late eighties.

Clearing the fault memory after replacing a knock sensor is a good idea, because the presence of the fault makes the ECU retard the timing. So the manouvre isn't pointless in all cases, but if no faults are registered, then it won't help.

#4 teppichkopf

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Posted 26 May 2004 - 06:41 AM

What's the actual procedure for "resetting" the ECU? On a EJ22 for instance. Just disconnecting the battery for a few minutes?

#5 Legacy777

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Posted 26 May 2004 - 08:03 AM

As ever, I am sceptical. The ECU "reset" only clears the fault memory.


This isn't neccessarily true. A "reset" as I call it is removing all power from the ECU. It will clear fault codes as well as clear the a/f learning control and the all the maps return to their stock setup.

A memory clear, i.e. through the diagnostic connectors only clears memory faults, and does not reset the maps.


What's the actual procedure for "resetting" the ECU? On a EJ22 for instance. Just disconnecting the battery for a few minutes?


For "resetting" You can pull the battery connection off for 30 minutes, or you can pull fuse 14 which is labeled EGI/TCU for the same amount of time.

To clear the memory, you can do the same or use the diagnostic connectors and the instructions on my site.




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