# To delete or not delete - PCV is the question..



## Solarblaze_uk (Sep 30, 2018)

Can anyone shed any light on whether this is a good idea? I'm aware of the advantages of not filling the intake manifold with carbon deposits (oil) but are there any draw backs from deleting, negative effects, mpg/performance etc


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## FNChaos (Nov 30, 2016)

PCV delete is a terrible idea. Nothing to be gained performance-wise and lots of downside. You can however replace your stock PCV valve with a catch can if your into wasting money :lol:

Maybe you'd see a 'slight' increase in reliability with a catch can (since there is no diaphragm to tear), but a catch can doesn't really serve it's intended purpose as it will not reduce carbon build-up on a DI motor.


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## QS Luke (Jul 13, 2013)

FNC I thought the sole benefit of PCV Delete was to almost negate the carbon buildup?

That said, £350 to have the injectors serviced and inlet decoked isn't horrific and maybe that's a better option every few years?


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## Solarblaze_uk (Sep 30, 2018)

QS Luke said:


> FNC I thought the sole benefit of PCV Delete was to almost negate the carbon buildup?
> 
> That said, £350 to have the injectors serviced and inlet decoked isn't horrific and maybe that's a better option every few years?


I'd happily pay that!


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## andez1781 (May 27, 2015)

FNChaos said:


> PCV delete is a terrible idea. Nothing to be gained performance-wise and lots of downside. You can however replace your stock PCV valve with a catch can if your into wasting money :lol:
> 
> Maybe you'd see a 'slight' increase in reliability with a catch can (since there is no diaphragm to tear), but a catch can doesn't really serve it's intended purpose as it will not reduce carbon build-up on a DI motor.


 Please tell me how this is a bad idea ??


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## Solarblaze_uk (Sep 30, 2018)

The only immediate difference I noticed was that there was no vacuum (suction) on the oil cap and it didn't try to stall the car when removed - I guess that's because no air is getting to the intake that's unmetered.

What makes me wonder though, is, is it better there is vacuum (suction) in the lower half of the engine. Does it make a difference if that vacuum is removed. For that reason, I removed the pcv delete and went back to stock


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## TT-driver (Sep 14, 2010)

I'd look at it this way:

Your engine management with all its sensors works on the basis that the engine has only one entry point of gases (I.e. the air intake) and one exit point (I.e. the exhaust). If you'd introduce one additional opening in this system, the engine management can't properly manage the engine any more. That's why you can't delete your PCV. Want to try? Remove the oil filler cap or the dipstick while the engine is idling and you'll find it will start running rough.


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## Solarblaze_uk (Sep 30, 2018)

Removing the oil cap or dipstick with the pcv deleted has no effect on the car idling - it has no effect


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## TT-driver (Sep 14, 2010)

Solarblaze_uk said:


> Removing the oil cap or dipstick with the pcv deleted has no effect on the car idling - it has no effect


But it does when the PCV is there, like it should be. With the PCV deleted, you already introduced a leak. An additional leak makes no difference then.



Solarblaze_uk said:


> The only immediate difference I noticed was that there was no vacuum (suction) on the oil cap and it didn't try to stall the car when removed - I guess that's because no air is getting to the intake that's unmetered.
> 
> What makes me wonder though, is, is it better there is vacuum (suction) in the lower half of the engine. Does it make a difference if that vacuum is removed. For that reason, I removed the pcv delete and went back to stock


There shouldn't be a vacuum in the engine. The PCV valve guides blow by gasses (gasses that leak past the cylinders and the pistons). There are 2 routes: straight into the intake manifold during idle and towards the turbo inlet while under boost.

If there's too much suction under the oil filler cap, the membrane in the PCV valve is torn.


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## FNChaos (Nov 30, 2016)

andez1781 said:


> Please tell me how this is a bad idea ??


Read up on what your PCV valve does then explain how deleting it is a good idea.

As stated you can replace your PCV valve with a catch can, but it will set you back $$ for very little benefit on a DI motor. Yes, it seems intuitive that removing oil vapor from being re-introduced into your intake tract would help keep your valves clean, but real world evidence shows that this in not the case.

Oil quality, injector spray pattern and valve timing all have more impact on coke build-up than a little oil vapor. When you consider Audi says its OK to burn 1 quart of oil in < 1k miles, a little oil / water vapor added to your intake charge is literally a drop in the bucket.

Additionally, catch cans have been known to clog-up / occlude when used in cold -weather climates due to condensation freezing in the lines. IMHO, spending good money on a non-fix that has the potential to damage your motor isn't smart.


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## Solarblaze_uk (Sep 30, 2018)

With the valve in place there would be an induced vacuum at the oil cap. Whether that's there when driving, I have no idea, have never taken the oil cap off when driving.

What I wonder is, by deleting, removes the vacuum at the oil cap completely, and whether that has a negative effect on the engine


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## FNChaos (Nov 30, 2016)

Solarblaze_uk said:


> What I wonder is, by deleting, removes the vacuum at the oil cap completely, and whether that has a negative effect on the engine


Yes. Your PCV system is vacuum dependent. Without vacuum, exhaust by-products that build up in your crankcase are not scavenged and removed. Instead they end up back in your motor oil.

This cut from your thread on oil/ water emulsion build-up : https://www.ttforum.co.uk/forum/viewtopic.php?f=19&t=1872933



Solarblaze_uk said:


> I'm curious, have you done a pcv delete? I didn't notice this last year prior to deleting. I'm wondering if deleting is restricting the removal of condensation in the oil


This is exactly why you have more build up. You are not effectively removing water vapor (among other things) from your crankcase


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## Solarblaze_uk (Sep 30, 2018)

This is what my concerns were, as it seemed quite a coincidence with the more than usual condensation after deleting.


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## Delta4 (Jun 19, 2015)

The PCV serves a purpose, if your concerned about oil vapor fit a catch can after the pcv not instead of.


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## Solarblaze_uk (Sep 30, 2018)

There doesn't seem to be any inline catch cans to intake readily available, which seems strange, as this would make complete sense - the gases get by, but oil gets catched so doesn't clog the valves


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## FNChaos (Nov 30, 2016)

Delta4 said:


> The PCV serves a purpose, if your concerned about oil vapor fit a catch can after the pcv not instead of.





Solarblaze_uk said:


> There doesn't seem to be any inline catch cans to intake readily available, which seems strange, as this would make complete sense - the gases get by, but oil gets catched so doesn't clog the valves


You could add a catch can inline after the PVC valve but then you would need to add another one-way valve to prevent pressurizing the can during boost. Of course now we are talking about adding more valves instead of deleting them. :lol:

Or you could really go crazy and install dual cans to handle both vacuum and boost situations, but now the solution costs more than the problem it sets out to solve.

For your reading pleasure, here's a link to check out: http://stratifiedauto.com/blog/understanding-your-pcv-system-upgrades-and-catch-cans/


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## Solarblaze_uk (Sep 30, 2018)

I'm starting to think, I'm overthinking all of it, and it's all just best left as-is with a new valve replaced every few years just in case (they're cheap after all).

The advertising for deleting does come across as 'this is the best thing', but perhaps it's not quite so straight forward and a good run out frequently is more than enough to warrant the deletion.


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## Delta4 (Jun 19, 2015)

FNChaos said:


> Delta4 said:
> 
> 
> > The PCV serves a purpose, if your concerned about oil vapor fit a catch can after the pcv not instead of.
> ...


You could add a catch can inline after the PVC valve but then you would need to add another one-way valve to prevent pressurizing the can during boost. Of course now we are talking about adding more valves instead of deleting them. :lol:

Your wrong mate, you dont need to add anything else and the can will only see the same pressure/vacuum that the pcv see,s
the oil vapors pass through the pcv and into the air intake after the MAF so will never see boost pressure, fitting a CC between the pcv and intake is a easy diy job, kits can be found if you look for them but can be pricey, it easier on the pocket if you put the kit together yourself


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## FNChaos (Nov 30, 2016)

Delta4 said:


> Your wrong mate, you dont need to add anything else and the can will only see the same pressure/vacuum that the pcv see,s


Here is a site that demonstrates a myriad of ways to install catch cans.
https://damondmotorsports.com/blogs/damond-blog/53965956-bye-bye-blow-by

Note the use of an additional check valve in several set-ups to prevent crankcase over pressurization. Also note setups shown without check valves are not recommended.


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## andez1781 (May 27, 2015)

Just to be clear I don't have pcv valve delete ... I know exactly how crankcase ventilation works , and how it works on these engines , I was asking because it seemed like you had a real reason why it's a bad thing to do a pcv valve delete. If anyone is going to do one they would be silly to do it without a catch can , but all this talk about adding proplems is daft. i think you and others are over thinking this . If you are to do a proper delete there will be no chance of the crankcase ever seeing boost , that is one of the main reasons to do the valve delete on these engines . not only the fact that why would you want all the dirty oil/fuel/water drawn back into the intake manifold without the chance of removing as much as possible. These Di engines are more of a reason for it. The reason there is a pcv system is purely environmental . As for the issue with milky oil cap , I think it has been explained before perfectly about the reasons for it, pcv or no pcv you will see it dependant on temps and driving habits.


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## andez1781 (May 27, 2015)

FNChaos said:


> Delta4 said:
> 
> 
> > Your wrong mate, you dont need to add anything else and the can will only see the same pressure/vacuum that the pcv see,s
> ...


I don't think you quite understand this


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## andez1781 (May 27, 2015)

Solarblaze_uk said:


> I'm starting to think, I'm overthinking all of it, and it's all just best left as-is with a new valve replaced every few years just in case (they're cheap after all).
> 
> The advertising for deleting does come across as 'this is the best thing', but perhaps it's not quite so straight forward and a good run out frequently is more than enough to warrant the deletion.


You are , and others are over thinking it. :wink: Just remember the delete plates you get without a can , where you are pushing all that oil,fuel,water mix straight to.. no longer on the intake valves (and I've had mine apart to clean them) but now the back of your turbo .


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## TT-driver (Sep 14, 2010)

andez1781 said:


> Just remember the delete plates you get without a can , where you are pushing all that oil,fuel,water mix straight to.. no longer on the intake valves (and I've had mine apart to clean them) but now the back of your turbo .


English isn't my mother tongue, so I might be missing something here....

That oil, fuel, water and what have you mix goes to the back of your turbo?

To me that can mean 2 things:

1) it basically goes straight into the exhaust where it contaminates the catalytic converter.
or
2) it goes into the turbo, through the intercooler, through the intake manifold where it then passes the intake valves.


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## andez1781 (May 27, 2015)

TT-driver said:


> andez1781 said:
> 
> 
> > Just remember the delete plates you get without a can , where you are pushing all that oil,fuel,water mix straight to.. no longer on the intake valves (and I've had mine apart to clean them) but now the back of your turbo .
> ...


 Yes to number two , let me explain , when your car is running off boost your the pcv valve runs open and all the crud goes straight to the intake manifold and as they are direct injection there is no fresh fuel to clean the back of the valves, it builds up unsightly amounts of carbon ( this is why more modern cars have direct injection and port injection at the same time) not the greatest but the valves can take a fair amount . Now if you're car is on boost you're pcv valve gets forced closed so not to pressurise the crankcase and all the gases and vapour are redirected to back of the intake which inturn goes to the the turbo ( have you ever opened the bottom of the intercooler , you will get a fright with the amount of oil/crud in it ) now having all that build up hitting the delicate turbo fins is definitely not a good thing without having a source of collection (catch can ).so that it why if you are to add a blanking plate to the pcv system to reduce the amount of crud going into the intake you really should use a collection system or it negates the reason for having it , that is unless you have a high boost setup and the reason for removing the pcv valve is to remove/ reduce the risk of it failing and inturn pressurising the crankcase... Done correctly there will be no unmetered air entering the system ..


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## TT-driver (Sep 14, 2010)

I get it.


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## SwissJetPilot (Apr 27, 2014)

The 3.2 VR6 already has a built-in "oil catch can" called the *Cyclone Oil Separator* which is located inside the Cylinder Head Cover, in the "hump" on the right side behind the oil filler cap.

There's also a *Crank Case Vent* diaphragm in there too, and if it ruptures, you'll get a vacuum leak. Unfortunately VAG doesn't offer a replacement part, so you have to replace the engine Cylinder Head Cover at around $450 plus labor which won't be cheap since you have to remove the Intake Manifold to get to it. The other option is to order a $30 replacement diaphragm from RKXTech and DIY. Parts source and DIY instructions are listed below.









3.2 VR-6 (BUB) PCV Diaphragm Replacement


After reading the recent post on replacing the PCV valve, I went looking for it on my V6-3.2ltr engine. Evidently there isn't one mentioned in the parts list (see diagram below). I could only find a PCV heating element (N79) but no PCV as would be found in the 1.8 or 2.0 engines. For an...




www.ttforum.co.uk




RKX VW & Audi 3.6 & 3.2 Engine Valve Cover PCV Valve Diaphragm

And if you don't want to go through the cost and hassle of pulling the valve cover, there's this PCV alternative solution using a Toureg PCV vent tube -








3.2 VR-6 (BUB) PCV Diaphragm Replacement Alternative


Unlike the Audi TT Mk2 1.8, 2.0 or 2.5 liter engines, the 3.2 VR-6 (BUB) Pollution Control Valve (PCV) diaphragm is located inside the Valve Cover "hump" directly behind the oil cap. Inside that hump, you'll find the Cyclone Oil Separator (COS) and inside the COS you'll find the PCV diaphragm...




www.ttforum.co.uk


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## kev1900 (11 mo ago)

If you only have direct injection, then the oily crankcase vapors are drawn across the back of the intake valve. With nothing to clean the deposits off, I have seen substantial buildup after only 10k miles. 
This problem is eliminated with dual port since you are blasting the back of the valve with pressurized fuel.
Routing the vapors to a catch can on single port, pretty much eliminates the buildup.


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## delmar.atlas (Dec 9, 2021)

kev1900 said:


> If you only have direct injection, then the oily crankcase vapors are drawn across the back of the intake valve. With nothing to clean the deposits off, I have seen substantial buildup after only 10k miles.
> This problem is eliminated with dual port since you are blasting the back of the valve with pressurized fuel.
> Routing the vapors to a catch can on single port, pretty much eliminates the buildup.



A catch can will not keep the intake valves clean, it can however keep the gunk from getting onto the turbine wheel and then into the intercooler and intercooler piping.

If you want to have a clean intake manifold and valves then run a WMI system into the IM. A few studies and a seldom few users have provided proof that regulate mist will remove some of the carbon build up.


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