Just remember that on the US forums they are moslty talking about K03 turbos and not K04 turbos.
On K04 turbo cars – the Fuel curve is no where near as rich as standard on the K03 cars.
With the K04 turbochargers happy to flow a lot more air than the K03 type, the turbo is most likely being stressed a lot less as so there was no need for the engineers to keep the EGT’s as low. K04 cars definitely do not run as rich as the K03 cars do when stock. I have many logs proving this having owned an A3 2.0 TFSI before the S3
Also remember that these cars (In both K03 and K04 versions) do not run an actual exhaust gas temperature probe (as the 1.8T Audi S3 did) – all EGT measurements are ‘calculated’ by the ECU from data tables within the ECU that were loaded during engine tuning on the dyno during development. I am led to believe that the Front lambda probe heater circuit plays a key role as well for feedback.
These EGT tables can become slightly ‘off’ when the car is remapped, therefore to truely know what your EGTs are you would need to insert an EGT probe into the exhaust.
KRL,
I don't mean to be argumentative and maybe this only applies to our understanding of the ecu but I would like to interject the following:
To maintain MBT, the afr needs to be similar to that of a ko3 calibration. 10.5:1 with no exhaust changes other than the ko4 is going to be a pretty good rule of thumb for keeping egt's happy. However, the fuel is dosed or metered in as egt's reach their threshold and continued to dose until the egt's level off below their safe limit.
If you change the exhaust to a less restrictive one you can run afr around 11.2:1 with no fear of the egt limit as long as you properly meter the dosing of fuel toward high rpm to cool egt's.
However, this applies to 2.0T FSI with ko3's that change to a ko4. I would need to research the egt results of a ED30 or S3 to verify your conclusion that the ED30/S3 type engines run leaner afr's and lower egt's standard. However, the explanation for such is that the OEM mapping uses fuel dosing as egt's rise. The lower compression and other engine differences may result in that dosing and richening of the afr being applied to a lesser degree to control egt's on those engines. Its also possible that you haven't worked the turbo hard enough during those logging sessions for the dosing of fuel to occur.
EGT's are like a switch in the ecu that moves to a different fueling surface that is fatter in afr to lower egt's. Once that switch is turned off, you will be on a different fueling surface that is typically leaner. So you need to know which fueling surface you are logging and which one is active to determine what the afr of the vehicle is and should be in that circumstance.
A tuner may disable the "switch" and dictate the ecu must run their determined afr at all times. APR calibrates both surfaces and appreciates the "switch" because its quite useful and is a very nice feature allowing for max power until egt's rise and then allowing for max power with high egt's while they are cooled back down.
The egt model in the ecu is correct until hardware behind the head is changed or cams or other internals like lower comp. We probe the egt's preturbine in all of our testing for calibrations that apply to these types of hardware changes. If you run the oem exhaust on a 200hp engine with a ko4 upgrade, the model is still pretty damn accurate. If you change the exhaust, the model becomes incorrect but you'd be surprised at how slight.
