tiburon423

OK, I know the stock ECU learns and adjusts to the proper air/fuel ratio. So I assume the ECU has some sort of standard settings or range for the air/fuel ratio at different RPMs and throttle inputs.



I also know that bolt on breather mods, such as intake, header, high flow cat, and exhaust create a slightly leaner air/fuel ratio, since more air is moving in and exiting easier. As a result of the slightly leaner air/fuel ratio, you produce a little more power since our cars run pig rich.



If the ECU learns and adjusts the air/fuel ratio, wouldn't it just adjust it back to the stock range by sending in more fuel to compensate for the extra airflow the mods produced? I guess I'm just trying to figure out how our cars run leaner after breather mods. It seems like the ECU would learn and bring the air/fuel back to stock, negating the new airflow (even if you did reset it after install). Can the ECU just not learn enough or what?



Thanks in advance!

turbosocks

not really experienced in ECUs and how they work/learn, but if i had to guess, i would say that doing mods of the sort wouldn't be out of the 'threshhold' for the ECU to adjust it..



say it would adjust it if there was a +- 10% change only. lets say these mods add 8% more airflow, thus the ECU has no need to make an adjustment..



totally a guess by the way.

Stocker

Assume for the moment that fueling returns to the ratio the computer wants to see after it learns to deal with your new mods*. Then you have stock fueling - but on more efficient parts. Could you get still more power with better fuel tuning? Yes, likely; but when you stop throwing power away on restrictive stock parts and put in some stuff that's easier for the engine to breathe through, it doesn't have to work as hard.



This goes for any car, BTW.



*It does. this takes from 1/2 second to 3 drive cycles to happen, until you spend more than the car is worth in performance upgrades. If you leaned out the engine beyond the ECM's ability to compensate, you would get anything from a check engine light to a minor explosion. If you aren't using forced induction or huge reground cams, the computer will probably be able to tune fuel back to stock trims with ANY bolt-ons.

Juanra

We had that problem, especially when tuning a piggy back ECU. So we disconnected the O2 sensors so the OEM ECU don't know whats happening. We wait and give the car a few rides so it goes in limp mode (safe mode however you call it) and then we tune.