USP Motorsports sells a boost tap for the EA888 engine that allows for the connection of a boost gauge air line to the intake manifold.
To use the boost tap the MAP sensor is removed from the intake manifold and the boost tap is installed in the opening, and then the MAP sensor is reinstalled on top of the boost tap.
While simple to install the boost tap created a problem on my GTI, it led to erroneous intake air temperature readings.
While testing the Unitronic stock location intercooler I observed that the intake air temperatures were less affected by changes in vehicle speed than I had observed with other stock location intercoolers. See the dark blue IAT line in the chart above.
Because I had purchased the GTI used I was unaware that the boost gauge had been setup to use the USP boost tap. After a bit of research I discovered that the boost tap has the potential to affect intake air temperatures. I removed the boost tap and drove the same route recording the data shown by the orange line.
It is clear that removing the boost tap stopped the dampening of the intake air temperature reading changes. From a performance standpoint this is important due to the fact that the IAT sensor will read well above the intercooler outlet temperature except under periods of high airflow. When airflow is increased the IAT sensor reading approaches the true IC outlet temperature.
As shown in the chart above at times 900 and 1200, with the boost tap installed the IAT sensor reading lags under similar conditions to those without the boost tap.
Under boost this will result in the engine computer receiving false information about intake air temperatures being higher than they actually are. This could lead to reduced performance versus what could be achieved had a true air temperature reading been reported to the ECU.
The intake air temperature sensor is co-located on the MAP sensor and the presence of the boost tap is affecting the IAT sensor readings.
Use of the USP boost tap has the potential to unfavorably affect intake air temperature readings in the Mk7 GTI.