The Nogaro project car came equipped with an unusual intake setup, a BMW Bosch MAF housing with the Hitachi Sensor epoxied into place, and a big honkin’ K&N cone filter feeding the MAF.
This Bosch MAF has grills on both ends, which seems to me to be a bit unnecessary.
It is a relatively large housing at 81.5mm in diameter on the inlet side and 83mm on the outlet side. These readings may be slightly off due to being taken with the grills in place.
I was curious how this combination would flow in comparison to a typical S4 Stage 3 setup that I would use, so I pulled the EPL MAF off the shelf along with a stock airbox. The EPL MAF has a 78.5mm inlet and 85.3mm outlet.
I first did a calibration run with a 400 CFM calibration plate on the flowbench.
Since I was interested in seeing how the MAF and also the K&N filter performed, I first tested just the BMW MAF housing.
Then I added the K&N filter to the MAF and tested it again.
Next I swapped over to the EPL MAF housing. The EPL unit is sized to fit into the stock airbox and RS4 accordion.
Since this airbox does not have the benefit of being modified with the “Darintake” mod I chose to leave the intake snorkel off. If it were included I would expect airflow to drop slightly from what was recorded.
Since the Darintake mod greatly helps with airflow through the airbox I did another run with only the air filter in place, simulating the effect of having the bottom of the airbox opened up.
Collecting the flow results and charting them produced the following:
A few observations about this data.
- The addition of the K&N filter to the BMW MAF housing did not alter the airflow reading in any appreciable way. This was a bit of a surprise, indicating that the K&N filter is less of a restriction to airflow than the BMW MAF housing.
- The EPL MAF housing outflowed the BMW unit by a large amount, despite having a slightly smaller inlet. I attribute this significant difference to the grills on the BMW MAF.
- The unmodified stock airbox dropped airflow through the EPL MAF housing by a great deal. This reinforces the utility of performing the Darintake mod. When this mod was simulated through use of the air filter alone the airflow jumped up becoming much closer to the EPL MAF housing alone, though not equaling that airflow.
Upon inspecting the BMW MAF housing closer it appears that the grills can easily be removed. This leads to the opportunity to test the MAF housing with different grill combinations to determine the affect of the different grills on airflow. It will also enable me to determine if the K&N cone filter becomes a restriction, relative to the MAF housing, at higher airflow rates.