I installed the BSH catch can on my S3 as well. It is not a performance mod and is more of a engine longevity mod as has already be said.
The factory PCV is fairly weak and can be prone to failure even at stock so in this case you would see a performance increase by installing a catch can or another pcv fix. When your pcv fails the cr will not be able to produce boost as it should hence a drop off in performance.
How the PVC system works from Phil@BSH -
The PCV system on the 2.0T is a complex one but nothing that's to difficult to figure out once you cut it apart on the bandsaw
The first thing to do is identify what all of these ports are doing.
PCV Gasses enter the valve cover through the port labeled
Crank Inlet .
Once inside the valve cover there are a series of chambers, baffles, and drains. As gasses move through these ports they will eventually come to the Vacuum Control Diaphragm and Diagnostic Port.
The
vacuum control diaphragm is used while the car is in vacuum. When vacuum is applied to the diaphragm it is sucked down to limit the amount of draw applied to everything behind it. In factory orientation if this diaphragm were to become ripped it would allow so much vacuum to be applied to the pcv system that oil would literally be sucked out of the head and into the motor.
Heading towards the intake manifold there is a
Check Valve This is the valve that is known for failing on these cars. When working properly this valve opens under vacuum and closes under boost.
When in vacuum pcv gasses are pulled through the diagnostic port and into the intake manifold. When in boost the pcv gasses go out the other side of the diagnostic port and into a passage molded into the valve cover then out the
Rear Outlet
You can follow along with the flow of gasses through this image.
As far as what the pcv fix cans do it is probably best explained from the horses mouth -
Phil@BSH
Allow me to help you with this. Crank case pressures and blowby gasses are a natural part of the combustion process. In order to achieve a smooth running, efficient motor these pressures and gasses need to be vented as otherwise the engines rotation would have to work against these pressures. Emissions requirements for all modern vehicles require these gasses to be recirculated and burned off. The process of how this is done on the 2.0T FSI is explained in the first post of this thread.
The problem with the factory design is it gives a clear path for positive pressure (boost) to act on the crank ventilation system. In theory the design should work, however in reality the factory check valves leak even on brand new from the dealer parts. This leads to a poor idle, loss of performance, oil being blown all over the place etc. The stage 1 system we offer maintains the factory routing as if the car was always in boost. It utilizes the twin oil separators (one in the oil cooler housing, one in the valve cover as seen above) these are the factory provisions which are decently affective but not even close to perfect. The gasses that are recirculated go through the intercooler piping instead of the alternative is to expose them directly to the intake manifold and intake valve which have no cleaning agent (fuel) passing through do to the direct injection will lead to build up on the valves which creates a huge list of running and performance issues and is an absolute pain to clean.
This brings us to the catch can systems. The catch can systems take the initial design of the stage 1 kit with its benefits of removing boost from ever acting on the pcv system and the other preventative measures and takes it a step further by providing a baffled container to hold blowby gasses to prevent them making its way back into the motor. Our systems are substantially better than the ebay type parts as not only do they come with necessary vehicle components but also a properly designed baffled catch can. We offer three options, Street, Competition, and Race. Each of these systems have their own sets of charecteristics that allow customers to tailor their part selection to their individual needs.
Both the Street and Competition systems are recirculating systems. Meaning, the pressures are returned to the intake after passing through a can designed to separate oil blowby. The path to the intake also has the benefit of creating a draw to the crank case which pulls pressure out. The caveat is that the recirculated system will still allow a small amount of blowby to pass, clearly nothing close to what would of otherwise ended up in the motor however.
The race system is a Vent to Atmosphere (VTA) and has completely different design which utilizes the pressure differential between the crank case and the atmosphere to vent the pressure. Since vacuum is no longer applied to the system we made the very important design decisions to bring in a second port (one for the block, one for the head) to properly vent all the pressures just using the difference in pressures. Properly designed VTA systems will allow 0 blowby to re-enter the motor and is the best choice in this regard. The trade off for this system is since the gasses are vented to atmosphere there is a scent associated with it and the car will not pass a visual emissions inspection in areas where recirculated crank case gasses are required. This is the system we use on our 500 bhp 2.0t FSI.
As you can see, each of our pcv solutions has their own target market allowing all customers to cater their project needs with our parts. This info should be found helpful for anyone who is in the researching stage.
I spent a lot of time researching this so if you have any other questions then please let me know and I will try to help.
As always with Forge products the solution looks well engineered and very good.
