Background:
The GTI is currently equipped with the Shuenk IS48 turbocharger. The turbo is an alternative to the IS38, aiming to enhance reliability by operating at tuned IS38 boost levels at lower rotational speeds than the IS38 turbo does.
One of the selling points for the turbo is that it can operate with off-the-shelf (OTS) IS38 tunes. I have used the Eurodyne software before and decided to try it with the IS48 turbocharger.
Eurodyne offers an OTS IS38 tune with set parameters, along with one that allows the user to make adjustments for different Octane, Boost, and Ethanol content. I chose to try the IS38 Adjustable tune.
Accommodations:
The GTI is not currently set up to operate with an OTS tune due to the presence of an RS3 Low-Pressure Fuel Pump (LPFP) and 5-bar MAP and PUT sensors.
Neither of these will affect how the turbocharger functions with the OTS tune; however, adjustments need to be made to the software to account for the different voltages that these aftermarket products operate with.
I reached out to Mabotech, who offer tuning with the Eurodyne product, to learn if they could make adjustments to the IS38 OTS tune so that I could operate the GTI with it. They were able to make the necessary changes, and I was on my way.
Test Process:
I chose 23 psi as the operating boost pressure for the tune. As shown during the custom tuning with Russell Road & Racing, the IS48 turbocharger is capable of holding greater boost pressure than this. (Image below)
The reason for selecting 23 psi is two-fold: lower power output allows me to log in third gear, which I prefer due to the lower speeds, and the ability to capture multiple consecutive data points. Another reason is that since the IS48 is a larger turbo, if it is going to overboost, perhaps the lower operating pressure will reveal this.
A series of third-gear pulls at full throttle is initiated around 2,000 RPM and concludes around 6,500 RPM. Performance data is recorded during these pulls.
An overview of this data collection is shown in the chart below.
Test Results:
The intake air temperature (IAT) during the testing is unlikely to have an adverse effect on turbocharger performance with respect to boost pressure control; however, I routinely check for abnormalities that could indicate something unexpected is occurring during the testing.
Nothing unusual was noted.
The boost curve shown is very similar to what I logged with the IS38 turbocharger a couple of years prior.
The wastegate duty cycle also exhibits no abnormal behavior.
The following chart combines the boost pressure and wastegate duty cycle data for the eight pulls.
Calculating the estimated WHP for the 23 psi tune, the average peak is around 335 WHP.
Note: This is over 110 WHP less than the high power tune produced.
Conclusions:
The Eurodyne off-the-shelf (OTS) IS38 Adjustable tune was loaded on the GTI to check how the IS48 turbocharger would perform when using an IS38 tune. This tune required two changes to accommodate a higher capacity LPFP and 5-bar pressure sensors that are currently installed on the GTI.
There was no indication of abnormal control of the IS48 turbocharger when using the IS38 OTS ECU tune at 23 psi of boost pressure.