This post continues a comparison of results using an open intake versus a closed intake.
The closed intake is from Eventuri and the open intake is the Eventuri, minus the front portion that seals with the GTI grill. The GTI is equipped with an IS38+ turbocharger tuned to produce 28 psi upon boost onset and tapering to approximately 25 psi.
Many open style intakes use a partition to try and keep the engine compartment air from being ingested by the air filter. For this test the setup simulates an open intake that doesn’t have a partition – or one that does a poor job.
This test will consist of a single third gear full throttle pull to above 6,000 RPM. The purpose is to find what difference there is in intake air temperatures and work required from the turbocharger.
Data from using the Closed intake are shown in the chart:
Prior to the pull the air temperature going into the turbocharger (TIP) is approximately 10-12 degF above the outside air temperature (OAT). The IAT is about 20 degF above the outside air temperature. During the pull both temperatures decrease, with the air temperature into the turbo decreasing to approximately 2 degF above the outside air temperature.
Next the Open intake configuration is setup. The results are shown on the chart:
Prior to the pull the air temperature into the turbocharger is approximately 12 degF above the outside air temperature. The IAT is approximately 18 degF above the outside air temperature. During the pull the temperature into the turbocharger begins to increase while the IAT decreases and then levels off.
The next chart overlays data from each test case. The closed intake is shown with dashed lines and the open intake is shown with solid lines.
Note: Multiple pulls were made for each test setup.
Outside air temperature is the same for both and is the straight line on the chart. The IAT between test cases differs from approximately 2-4 degF. Most interesting is the change in the turbocharger wastegate duty cycle (WGDC), an indicator of how much exhaust gas is being directed through the turbine versus bypassing the turbine.
The WGDC is roughly, on average, about 10 percent higher with the Open intake versus the Closed intake.
Comparison of an Open intake versus Closed intake shows that the turbocharger wastegate duty cycle during a third gear pull is approximately 10% higher for the Open intake when using an IS38+ turbocharger boosting to 25-28 psi.