Both vehicles work generally the same using a MAF sensor to measure air mass for fueling calculations. Both ECUs have higher resolution tables for Closed-Loop (CL) fueling targets, then switch to more simple RPM-based fueling tables for Wide Open Throttle (WOT) fueling targets. Calibrating the MAF sensor is the most critical thing to to on both of these vehicles in order to allow for consistent fueling under CL and Open-Loop (OL) conditions.
The Gen2 platforms appear to have very different logic when it comes to fueling during boost spool up. The Gen2 platform demonstrates a very different response when DI Fuel Pressre drops. As DI Fuel Pressure drops below ~1600psi on the Gen2 platform, the ECU will immediately increase fueling by increasing the Injector Pulse Width (IPW)...which puts increased demands on the fueling system further dropping the DI Fuel Pressure. The additional fuel is a good safety measure, but this behavior makes it so Stage1 (S1) calibrations will be calibrated to stay within the capacity of the stock Camshaft Driven Fuel Pump (CDFP) and not calibrated to their full performance potential. Yes, a S1 vehicle with a upgraded CDFP will likely be able to make more power because more boost can be safely generated and higher DI Fuel Pressure can be targeted. This also means that no Stage2 (S2) calibrations will be created using the stock CDFP unless users want to have boost limited to ~14psi.
Due to this new ECU logic...no aggressive AccessPORT OTS calibration can be run without the installation of a quality aftermarket CDFP (Camshaft Driven Fuel Pump). The S1 calibrations will perform better than stock and will likely have less reports of Knock Retard (KR), but to experience the full potential of the S1 hardware, an upgraded CDFP is recommended.
Any vehicle making over ~330 WHP will need to also have the in-tank feeder fuel pump upgraded to keep up with the aftermarket CDFP. Fuel supply is only as much as is greatest restriction point...which is the stock in-tank fuel pump at this time.
Every test vehicle that was running a quality CDFP has not exhibited this over fueling issue. The performance of the vehicle will not be at its full potential if you try to run an OTS calibration that keeps boost low enough to allow the stock CDFP to keep up with fueling demands. As mentioned above, the ECU appears to be calibrated to increase the fuel injector pulse width once it sees DI Fuel pressure drop below ~1600psi. When this occurs, the ECU will run the engine with excessive fuel hindering torque production.
As mentioned, for those that have a stock CDFP, we are going to need to release calibrations that keep the turbo boost within the fueling capacity of the stock CDFP. The car will not be slow, but it will not be accelerating at its full potential unless the engine has the hardware necessary (high quality CDFP) to support a higher performance calibration.
We understand that this may be sad news for some of you. We are not trying to force you to purchase more hardware, but the data is telling us that this is how upgrades need to proceed for the 2010 MS3.