Background:
Questions about the vacuum level inside the PCV port of the Mk7 turbo inlet elbow led to some testing of this property.
Aftermarket elbow:
Here an aftermarket elbow is connected with a CTS Turbo intake and a differential pressure gauge is used to read the vacuum at the PCV port.
![Aftermarket TIP PCV Port Vacuum Check](https://mygolfmk7.com/wp-content/uploads/2024/01/aftermarket-vacuum-check-flow-test-1024x768.jpg)
To gauge the relative amount of vacuum between components the flow bench is operated at a steady 350 CFM and the Vacuum measurement is then recorded.
![Aftermarket PCV Port Vacuum @ 350 CFM](https://mygolfmk7.com/wp-content/uploads/2024/01/aftermarket-vacuum-check-1024x768.jpg)
The vacuum created by the aftermarket elbow is 13″ of H2O at 350 CFM.
Stock elbow:
Next the GTI stock inlet elbow is swapped in for the aftermarket elbow and the procedure is repeated.
![Stock TIP PCV Port Vacuum Check](https://mygolfmk7.com/wp-content/uploads/2024/01/stock-vacuum-check-flow-test-1024x768.jpg)
The stock TIP generates a vacuum of 46″ of H2O at 350 CFM.
![Stock PCV Port Vacuum @ 350 CFM](https://mygolfmk7.com/wp-content/uploads/2024/01/stock-vacuum-check-1024x819.jpg)
Prototype elbow:
Next, a prototype elbow that gradually tapers from a 3″ opening to a 49 mm outlet is tested.
This elbow does not have a PCV port, so the vacuum is measured where the port would be.
The goal of this experiment is to find out if the taper of the pipe is a strong contributor to the vacuum generated near the PCV port location. The taper of the pipe will increase the airflow velocity, which will correspond with a decrease in the static pressure.
![Prototype elbow vacuum check location](https://mygolfmk7.com/wp-content/uploads/2024/01/prototype-vacuum-check-port-768x1024.jpg)
The vacuum created in the prototype elbow is 14″ of H2O at 350 CFM.
![Prototype elbow vacuum check](https://mygolfmk7.com/wp-content/uploads/2024/01/prototype-vacuum-check-port-flow-1024x768.jpg)
This is barely higher than the aftermarket elbow and suggests that the pressure reduction resulting from the velocity increase is small.
![Prototype elbow vacuum measurement](https://mygolfmk7.com/wp-content/uploads/2024/01/prototype-vacuum-check-1024x768.jpg)
Modified aftermarket:
A modification is made to the aftermarket elbow by pressing a small amount of Play-Doh to the side of the pipe just upstream from the PCV port.
![Modified Aftermarket TIP with Play Doh](https://mygolfmk7.com/wp-content/uploads/2024/01/mod-aftermarket-vacuum-1024x768.jpg)
The Play-Doh is covered with a piece of tape to keep it from being pulled down through the inlet by the airflow.
![Modified Aftermarket TIP with Play Doh & Tape](https://mygolfmk7.com/wp-content/uploads/2024/01/mod-aftermarket-vacuum-tape-1024x819.jpg)
The vacuum increases slightly to 21″ of H2O @ 350 CFM with the addition of the bump before the PCV port.
![Modified Aftermarket TIP with Play Doh & Tape Measurement](https://mygolfmk7.com/wp-content/uploads/2024/01/mod-aftermarket-gauge-vacuum-1024x768.jpg)
Thanks for helping with this research!
You’re welcome! I’m glad I was able to help out in a small way.
Excuse my ignorance but what are the benefits/downsides of the different vacuum levels?
As I understand, it plays a part in how efficiently the PCV system functions. Tony who authors Data Driven MQB has been doing research into this and has much better information than what I can provide.