Here we will discuss various aspects of tuning the Veloster N on the SIM2K-250 ECU. These notes are comprehensive, and feature discussion for both consumers and professionals.
The core of our guide delves into the various facets of ECU tuning, including:
We need to start with a baseline on Veloster N performance, so let’s look over some quick data. In a factory data log, we see that boost pressure peaks around 14-15 PSI (this chart shows boost + ambient). The boost pressure tapers toward redline due to the small size of the turbocharger. At this point, the turbo is running a wastegate duty cycle (WGDC%) of about 27%. This means that the wastegate is 27% open, and 73% closed. This duty cycle is fairly high considering the turbo is only making 14-15 PSI. This will come into play as we increase the pressure later.
We can also see that fuel pressure is set around 200 bar, and ignition advance climbs to a final value of 21 degrees at redline. The high pressure fuel pump is a known issue with the 2.0T in the Veloster N, so we will also need to keep an eye on this.
The last item we will look at in our baseline is the AFR demand. Here we can see that the ECU is requesting a fairly rich AFR as time goes on.
When tuning the Veloster N's ECU, I employ a target Airflow/Pressure/Torque (APT) based system to precisely control the boost upstream of the throttle plate. This approach hinges on a critical table referred to as Pressure Up Throttle Setpoint (PUT_SP), which essentially sets the target boost pressure. To achieve higher boost levels, I adjust this setpoint upward, which acts as my guiding parameter for the tuning process.
In my experience, unlike some vehicles where the target boost table serves merely as a ceiling, allowing adjustments primarily through torque request and mass air setpoint tables, the Veloster N requires a more direct approach. I log the pressure during tuning sessions, especially when pushing for increased boost, to ensure the ECU's commands align with the turbocharger's actual output.
A common hurdle involves the Maximum Airflow tables, officially termed "Mass Air Set Point for Torque Intervention." These tables must be calibrated to accommodate higher airflow volumes; otherwise, the desired boost increase may not be realized. If adjustments to the PUT_SP don't yield the expected boost rise, it's usually a sign that these Maximum Airflow tables are the bottleneck.
Interestingly, much like the systems used in some Volkswagen models, the Veloster N doesn't rely on physical turbo speed sensors. Instead, it calculates an estimated turbo speed setpoint based on various engine parameters and operating conditions. Elevating the target boost pressure necessitates increasing the limits within these turbo speed tables to avoid any system errors due to perceived over-speed conditions.