Quote:
Originally Posted by mike@x-ph.com
ECU does not show increased boost level with a piggy. The piggy tricks the ECU into thinking its making stock boost
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This is true, but boost isn't the only way the ECU can detect a piggy.
However there are threads talking about hidden ECU codes referring to boost, fuel, and air fuel ratio plausibility codes. For example, piggy backs always cause the ecu to see underboost conditions so the car will allow for more boost, until the piggy back reaches it's new Target and let's the ECU think it reached the boost it wanted to hit. This works well for tricking boost levels, however you cannot trick the O2 sensors because more boost means more air and thus it'll go lean. As a result more fuel is added. This is where the ECU does a plausibility check where it sees how much fuel is being used for a certain boost level. What the car will see is that it's using an abnormally high amount if fuel for such a low boost level (this will get more apparent if the piggy back targets more boost) and it'll trigger a hidden plausibility code. This will be abundantly apparent of a piggy back being present, and these codes may be fully hidden from any dealership level diagnostics (ISTA) and unckearable. but it'll be fully visible when BMW sends engineering down to examine a car, i.e. engine failures or high $ warranty work.
Whether this system exists remains unknown, but there are rumours of it being present.