boost leak in the breather system discusion

[Pyro]

right ladys and gents was just thinking about a split oil breather system causing boost leaks etc and corect me if im wrong but some of us who have fitted catch tanks vent them to atmosphere do we not, so surely this is the same as a split hoes?
not only that but if vented to atmosphear then theres a big 19mm hole in the system so thats a bigger leak then a split pipe??

corect me if im wrong by all means i just don.t quite get lol

discuss!

 

[Muttley]

Deciphering your spelling, I'm guessing you're talking about crankcase breather systems, which are vented into the inlet system *before* the turbo i.e. the atmospheric pressure side of the inlet.

When you fit a catch can you should plug the hole that the breather leaves in the inlet hose, because it is after the MAF and will cause broken-MAF-symptoms.

 

[Pyro]

In know spelling is an issue but what can I do

I know you need to plug the hole in the tip and the air passing through it is metered air etc etc what I'm saying is that when you get a split breather hose be it from the crankcase or under the inlet manni we say it's a leak yea? So why is plugging the crakcase into a catch can the venting the can to atmosphere not classed as a leak its the same thing!! Or am I missing something

Ps corrected as much spelling as I could and wrote this with my phone. I do try but can't be helped.

 

[sambryant]

Sam. You have it slightly wrong. Crank case pressure (oil breather) is not boost pressure. From the inlet manifold there is a pcv valve with a suction pump the works on vacuum from the manifold , this joins the oil breather system. Now if there is a leak between the manifold and pcv this will result in a boost leak. The pcv (is a one way valve) separates the oil breather system so if there is a leak in the oil breather this in not connected to boost. So venting a catch can to atmosphere is fine, its venting air created by the engine and not boost.
Hope that makes sense

 

[Pyro]

Perfect sence maye as that's what I was getting at so a split oil berather hose will not cause a boost leak so we've all been wrong all this time when saying the that for example the Y pice hose is split so you have a boost leak

It's all lies!!! Lol

 

[sambryant]

Yes thats right m8, how ever it will make the fueling off slightly as the air from the breather system wont be going into the intake. But there is no boost leak.

 

[Muttley]

As sambryant says, the crankcase breather system is not under boost pressure, so leaks in the breather pipes will not affect boost. I'm struggling to understand how you could think that the crankcase would ever be under boost pressure - these aren't two-stroke engines, you know

Crankcase pressure is raised due to blow-by past the piston rings, and needs to be vented or the pistons will lose energy pushing against it.

In the old days there was just a set of holes in the oil filler cap and some metal gauze inside it. Nowadays California's paranoia means manufacturers cannot vent the odd bit of exhaust gas with entrained oil vapour to the atmosphere, and their universal answer is to feed it into the intake system to burn it in the engine.

Not a great idea, as it's the source of all the oil you will find in the boost pipework and intercoolers. Also combines with the exhaust gas from the EGR system (another emissions-reduction idea forced on us by American legislators) to produce crud that slowly strangles the inlet manifold on diesel cars,

 

[Pyro]

i didnt think it was under boost pressure but if you searched through some threads on split beather pieps youll see that its been said sooooo many times that a split Y pice hose will cause boost leak etc and as its been said so much i just didnt argue but after a thought about it the otherday i decided it was wrong and wanted to check i was rite witch i am lol

 

[Nautilus]

1. The failure of the breather system will not cause boost leaks, for the breather system is not under boost, but under suction - the turbo draws crankcase fumes through the black plastic valve in the inlet pipe.

2. The failure of the breather system will sometimes cause an error and a CEL due to difference between metered air, drawn air and unburnt air in the exhaust afterwards.

3. The failure of the breather system is more or less intended by VAG, because the Y-hose (the most exposed to heat of all breather hoses by drawing from the hot cylinder head) is made of just rubber, without the slightest attempt of some mesh reinforcement, and it's the only hose on the car to be made so. Sooner or later, it will split and release oil and fumes in the engine space. And the replacement is in the 30-35 GBP range.

So it has to be replaced by a reinforced silicone hose, from Forge, Awesome GTI or Viper Performance.

~Nautilus

 

[nd-photo.nl]

Or Toyosports/Creations Motorsports as cheaper alternatives Mine was split as well and replaced it with a toyosports if im correct, cheaper and stronger than the original rubber hose.

 

[Nautilus]

There is also the plastic tube which connects an arm of the Y-shaped cam cover hose to a rubber flange on the front side of the block, where the PCV valve sits. It breaks easily. It's a soft rubbery plastic with no mesh reinforcement inside. Mine broke in 2 places just after fitting the Viper silicone hose.

It's also made in silicone (but it's expensive) and it can be replaced this way:

1. Pick a rubber hose with mesh reinforcement and 20mm inner diameter.
2. Pick 2 short copper connectors with 20mm outer diameter, one straight, the other bent to 45 degrees. (From hardware stores, they are used in heating appliances.)
3. Push the straight copper tube in the arm of the Y-shaped hose. Fix with a strong hose clamp.
4. Push the bent copper tube in the rubber flange over the PCV valve. Fix with a strong hose clamp.
5. Slip the 20mm hose over the exposed snouts of the two copper fittings and fix with hose clamps.

The rubber hose does not follow the S-shaped path of the original plastic tube, but it can withstand heat, oily fumes and vibrations much better.

~Nautilus