I just think its not really worth the effort because the valves still get filthy. So why bother.

 

Lou tuned my car and he is the best in service and knolowledge. Prototype-r.com has a great article on catch cans. And no there not for keeping your valves clean.

 

That's precisely why everyone installs them. To keep the valves and intake runners clean.

 

I know this is an older thread, sorry for reviving it.

With that being said, I have worked in the automotive industry since the 1980s, no one that I know (including myself) uses catch cans to keep their valves / intake clean. Catch cans are meant to keep the blow by gunk from messing with combustion / prevent knock. I can't recall hearing anyone ever say they used a catch can to help reduce the coking / carbon build up in their intake system (that's a new one to me). The build up isn't from the blow-by, if anything the blow-by would help reduce the coking / carbon build up, since moisture tends to clean things a bit. Back in the day we would get the engines nice and hot and spray a fine mist of water/meth over intake, while reving the engine, to bake off the carbon deposits. Problem with doing that, is you can cause all kinds of issues, like clogging catalytic converters, or god forbid a chunk breaks free and damages a cylinder.

What causes the coking / carbon build up on direct port injected engines, is a flaw in the way modern engines are designed. Many engines utilize a form of the atkinson cycle, Otto cycle or something similar such as Late Intake Valve Closing (LIVC). This leaves the intake valves open for a short duration during compression strokes or when expelling exhaust gasses, which was designed to reduce pumping losses and increase thermal efficiency. The downside, direct port injection has no intake cleaning action like port injection does, so you get a huge build up of gunk on the intake and valves.

So all that to say, you can have a catch can that is 100% efficient and that won't stop your intake from getting dirty. You would have to redesign the engine and or eliminate the LIVC system.