.
WHAT IS IT?
Positive Crankcase Ventilation (PCV) is a system developed to remove potentially harmful vapours from the engine and to prevent those vapours from being expelled into the atmosphere. The PCV system does this by using manifold vacuum to draw vapours from the crankcase into the intake manifold. Vapour is then carried with the fuel/air mixture into the combustion chambers where it is burned. The flow or circulation within the system is controlled by the PCV Valve. The PCV Valve is effective as both a crankcase ventilation system and as a pollution control device.
WHY HAVE ONE?Excess crankcase pressure is vented from the crankcase through the PCV system, where it is drawn into the intake manifold and returned by the engine. This recirculated air contains aerated oil from the crankcase which is burned by the engine. Some (not all, I'm told) turbocharged engines, especially when performance modified, can draw significant amounts of oil into the engine through VAG's oem PCV system. An aftermarket oil catch tank system removes and collects the aerated oil so that it can be drained and externally recycled. The resulting sludge looks like a rich banana-coffee milkshake but it sure as hell doesn't smell like one!
Here is a well debated discussion in this linked thread about why you should have one or not:
http://www.mk5golfgti.co.uk/forum/index.php/topic,7040.0.htmlJohn (john_o) says: "The key thing to remember is that the TFSI engine doesn't have a catch can (but everything else is relevant), and oil fumes / water vapour and related gumph are ported back into the engine to try and achieve good emissions. On most cars this is not a problem as fuel washes constantly keeping everything clean. The bad news is that TFSI is direct fuel injection (injectors spray directly into the combustion chamber), so the only thing passing the intake valves is air (and the oil and water vapour gunk), this is really bad news."
THE OEM PCV:
The 2.0T FSI engine comes with a closed PCV valve which obviously functions but as with most oem factory components it is designed and manufactured to restrictive rules and criteria and which can be improved by replacing with aftermarket components. PCV replacement - practiced by most performance engine tuners - is whereby the stock PCV system is substituted with an oil catch can and sometimes a breather filter venting crankcase gases to atmosphere instead of recirculating via the intake. The open types which ventilate to atmosphere almost certainly will not pass a MOT. It seems that VW have been obliged to sacrifice a degree of long term engine maintenance (intake valves) for the sake of more stringent emission controls.
^ Intake valve from stripped 2.0T FSI engine with oem PCV after xx,000 miles.
THE FORGE CATCH TANK SYSTEM:
Forge Motorsport, in my experience, is a typical small British company which strives for high quality in all its products. It's ethos is to design and manufacture the best without compromising quality. Okay, it's not aircraft industry standard but cars don't usually need to fly, and aircraft industry quality would be phenominally expensive. You can judge Forge's quality for yourself, even from the photographs. Additionally, simply supplying the more durable stainless steel jubilee clips instead of cheaper metal ones is a good example of Forge's way of thinking.
Designed as a closed PCV system Forge's offering of course includes the same functional components as most other manufacturers' kits. However, Forge's kit importantly uses hoses which are fluoro lined for chemical resistance and also features an invaluable sight-glass window to visually check when the tank needs emptying. The first kits used an externally mounted clear plastic tube for checking tank levels and this method is used by most other catch tank manufacturers, but Forge thought this through a bit further and decided that using glass would be much more resistant to any possibly abrasive cleaning agents, including petrol, used to clean out the tank between fillings.
^ Fluoro lined hose connections.
^ A replacement screenwash filler assembly (with stainless jubilee clips) is included in the kit.
ALTERNATIVES:There are quite a few out there but mostly universal rather than specifically for the 2.0T FSI engine, and mostly from either America or the Far East. Some of them are works of art in anodised technicolour and I have even seen one system which has a hand-grenade shaped tank! There are also the inevitable universal systems which are cheap but not confidence inspiring.
SOURCE:Direct from Forge Motorsport or their approved stockists. RRP £331.29 incl 17.5% vat for this latest version and JKM offer a 10% discount on all Forge Motorsport products for forum members.
Visit their website or contact JKM for an up-to-date price : -
http://www.jkm.org.uk/performance/tfsimisc.htmINSTALLATION:Straightforward and with instructions online from Forge with a downloadable pdf. I would point out that the current instructions are only for the American market without a charcoal cannister and so include no reference whatsoever to the screenwash assembly. The professional experienced mechanic who installed my Forge kit was not impressed by this and neither was I, but Forge are addressing my criticism across their products as appropriate.
I recommend fitting Forge's screenwash filler
before the catch tank on the shared bolt. This will facilitate the tank's removal later for emptying and cleaning.
CHARCOAL CANNISTER - Fitting Tips:
On the Mk5 GTI the two hose connections on the top of the oem charcoal cannister interfere with the Forge Catch Tank. This can be resolved by undoing the oem spring clip on the rubber hose and twisting the hose out of the way. A special tool is needed for the VAG oem spring clips. While doing so it's also sensible to make sure it routes as low as possible so that the Forge pair of hoses can be positioned over the top - This will ensure much easier access when emptying the Forge tank later. However, as I have an Evoms engine cover, routing the Forge hoses below the charcoal cannister hose makes sure they don't risk getting cut by the metal edge of the Evoms cover. It's easy to access and loosen Forge's stainless jubilee clips anyway.
The second charcoal cannister hose is rigid plastic with a heat welded connection but the round cap can be carefully removed and repositioned at an angle so the rigid pipe avoids physical contact with the Forge catch tank.
MAINTENANCE:Simple and easy to periodically check the catch tank's contents level and helped by the MAX line on the window frame. Emptying and cleaning the tank is straight forward and if you have followed my installation tips by fitting the Forge fluoro lines
above the charcoal cannister hoses, there's enough flexibility to clear the engine bay. And you can easily loosen the jubilee clips as well if you want to completely remove the tank. Best to wash out with petrol.
For further cleaning the sight window can be opened with a small allen key and the 3mm thick polished edge glass taken out for wiping - This shows a lot of consideration.
PLUS POINTS:- Very high standard of design and engineering, giving great confidence.
- Durable sight-glass built into the tank.
- High capacity tank which results in less frequent maintenance.
- Complete replacement screenwash filler assembly included in the kit. High quality and eye-candy.
MINUS POINTS:- Relatively expensive. A Forge Twintake, high-flow tubular air intake, costs only about £50 more.
- No Allen key supplied to open and close the tank.
- UK version (charcoal cannister) installation instructions not available yet, but are expected.
SUMMARY:A catch tank system which collects an oily and smelly sludge which needs disposing of on a regular basis is hardly something to get excited about and especially when it costs over £300. But I have to say that both the high standard of design and engineering and the confidence the Forge system gives, made me feel surprisingly elated. This was simply not the case with the BSH system which my Forge replaced. The BSH was only about half the price and functioned quite well, but is not in the same league. The Forge catch tank system is actually not very expensive when compared with the prices of some of the other American systems but I think the UK market is generally less inclined to spend much money on such modifications.
In the practical real-world of needing to regularly empty a catch tank, having a durable sight-glass is an invaluable feature. Some people may think that the Forge system is over-engineered but I'd far rather that than being under-engineered.
The replacement screenwash filler assembly is a very welcome bonus. Buy an anodised black aluminium coolant bottle cap from Jcaps and the oem bright blue plastic eyesores are all gone and the result is bay-candy.
ADDENDA:In colder climates there have been reports of freezing catch tanks but I know of none which are Forge. Certainly my BSH tank collected a lot of water and that has the potential to freeze. So far, my Forge's residues are far more oily: sludge-and-oil as opposed to sludge-and-water. Regularly emptying the tank in very cold weather will obviously help and this is another example of the advantage of a sight-glass. We'll see how the Forge performs next winter.
I originally wrote this in Summer 2010. The Winter of 2011 was a particularly cold and harsh one and there were no problems with mine.
