RS4 PCV System

B6/7 S4/RS4
#1

Okay, so it’s time we talk about this…

Most people don’t think twice about this system. Like other bits on the car, if it doesn’t make horsepower or cause problems, it’s an ‘out of sight, out of mind’ kinda thing…

Background for those unfamiliar with how the system works. In our engine, when a single piston moves up and down in the cylinder, it’s moving ~ .525L of air. Pulled in from the intake, pushed out through the exhaust, everyone knows that. But that same piston is also moving .525L of air inside the block as well. Now I’m sure you’re saying ‘but there’s another piston going up at the same time, so it’s a net zero’…true, but not exactly. That .525L of air still has to move from one cylinder to another. That air has mass, that mass causes resistance. That mass is moving around inside the block from cylinder to cylinder at 137 times/second at full song. Additionally, any blow-by past the piston rings will increase the amount of air in the block. The more air, more mass, more pressure, more resistance…

Engine designers take this into account when designing the inside of the block, but there’s only so much that can be done with passage and bridge design.

Race engine builders get this…they run vacuum pumps to evacuate air out of the block, to the tune of 40cm Hg and more. Less air, less mass, less resistance… Another inherent benefit is the vacuum in the block also assists in seating the rings. So now you’re probably thinking, ‘Yup, let’s all just run as much vacuum as possible. Problem solved, right?’ …not exactly. Running that much vac inside the crankcase puts pressure on every gasket and seal between the block and the atmosphere (f/r main seals, vc gaskets, timing case covers, coolant pass-through pipes, dip stick, & oil cap). Any vac leak in the block means you’re potentially pulling debris into the crankcase. Race engines are rebuilt more frequently, thus this isn’t a huge deal. Run that motor for 200k…well you get the idea.

Now what about the inverse situation: Positive crankcase pressure due to a clogged, malfunctioning, or undersized PCV system. Where does that air go? All those seals I mentioned above are still affected. Do you happen to have a leaky front main seal? Leaky valve covers? Leaky dipstick seal? All the above? Well what about one more: intake valve seals (some of you probably know where I’m going with this). The intake ports are under vac, meaning the bottom of the seal is under vac. Combine that with the top of the seal under positive pressure, and guess where your oil is going to go…

Now onto how the PCV system on the RS4 works.

I’ll preface this by saying the RS4 has a system designed to work efficiently on a new motor & to pass emissions.

The components:
-There is a breather from the air intake snorkel to the block. It connects just before the TB on the back side, and the other end feeds to the valley underneath the IM. There’s a check valve (rubber diaphragm) that only allows air to flow from the intake to the block, and not the other way around.

-Both valve covers have ports that join together on drivers side and feed into the oil separator. That oil separator has a piston that will compress depending on air flow, through a series of 3 cyclonic oil separators. The air then flows through a diaphragm & restrictor plate to the IM. The oil drains out the bottom of the separator via hose that runs to the valley directly adjacent to the aforementioned breather hose. If you’ve done a carbon clean before, you’ve seen all of this…hopefully I’m connecting the dots on what it’s all doing…

Onto the PCV itself, here’s an exploded view:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9267_zpsxjhsklnf.jpg

The diaphragm serves two purposes, sealing the cap, and creates an adjustable cavity depending on vac/flow:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9263_zpsl78egzs8.jpg

Now you see two plastic parts, one is a spring seat, the other is a restrictor:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9265_zpsawt61qxc.jpg

In stock form, the crankcase maintains ~4cm Hg of vac (which is almost nothing):

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9262_zps8gkvslio.jpg

While the IM maintains ~46cm Hg of vac:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9260_zpsprenys8i.jpg

When you remove the little restrictor, vac kicks up quite a bit to ~35cm Hg. The problem is the car’s idle control is tuned to take into account the flow from the factory setup, so immediately things get out of whack:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9261_zpslbmgfqe3.jpg

Running without the restrictor also creates a ton of flow that the diaphragm doesn’t like very much:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9264_zpsqlxt1niy.jpg

So we’ve been playing with varying diameters of the restrictor to see if there’s a happy medium with improved flow and stock idle:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9259_zps2vgmghw0.jpg

On my car, I’m running a slightly bored out version with the restrictor removed to see how it acts under full vac:

http://i172.photobucket.com/albums/w2/koolade9/Ibis%20RS4/IMG_9106_zps0rz4ersm.jpg

Part of the issue is that the breather from the snorkel is there to bring fresh air into the crankcase that is then fed through the oil separator to IM and is a factor in how idle air is controlled. Changing the restrictor increases flow and affects idle. Capping the breather increases vac and also affects idle. There’s a happy medium in there somewhere…

Basically, FWP has been doing all the testing on his car while I play devil’s advocate and provide snarky comments via text. There are still plenty of variables to play with. We’re both leaning toward an aftermarket oil separator to handle the flow while using a bleed valve/restrictor to keep flow at the IM to a point where the idle is solid and fuel trims are happy. We’re not there yet, we’ve got more ideas, but I just wanted to share what we’re messing with. You can thank FWP for all the pictures and data. He’s really driving the development of this. When we have something that works, you’ll hear about it.

#2

This is a lot of very good insight, looking forward to results as you generate them. Happy to be a Guinea pig if you need, moving forward.

#3

Great post, looking forward to seeing where this goes.

#4

Thanks for the work you guys are doing on this. I have really quick access to my PCV so I’m willing to guinea pig if you need.

#5

I really appreciate the work you’re doing, but I do have to bring up the 800lb gorilla in the room. Do you think testing on FWPs car is the best idea? This is basically a trial and error process and I personally wouldn’t describe his car as healthy and in perfect working order. His past issues with pinging and his altered, most likely watered down tune could really construe a lot of the results. Just my honest perspective on the matter. I’d also hate to see him have some type of serious issue because we all know what path he will go down…the blame game and try to burn JHM to the ground.

It’s pretty apparent when you visit AZ that the Sharks always begin to circle when guys have JHM tune issues. Bootleq25 or whatever tuned his car at 100k plus, put 20k on the tune and is trying to blame a catastrophic failure on ONLY the tune, that just isn’t logical for those of us who have an understanding of how these cars work. FWP was in that thread mostly backing the OP and referencing his misfires/pinging once again, which most of us…including you can agree has to do with a hardware issue and not the software side of things.

#6

Last I heard FWP wasn’t having any problems after changing his PCV.

It would be more productive to forget about the recent AZ thread. It could have 100% been a troll, as Shitpeg25Q didn’t provide a single shred of evidence. Not even a picture of the damage.

#7

He’s found a couple of vacuum leaks that have been fixed and replaced the HP fuel pumps since all that went down. I haven’t seen any recent logs to say it’s back to 100% or not, but I know his car has been running a lot better lately. He & I do have different opinions on the tune, and we’ve come to a silent agreement to not talk about it. Your point is valid nonetheless. To be honest, I’ve either been out of town or working on other projects and haven’t spent any time on the RS. He’s been having oil burning issues at stop-lights in colder weather and it’s his daily. So for him, this is more of an urgent issue which is what’s carried us this far. Whatever solution we come to will be tested on both our cars for sure.

I will say that with that breather capped and the restrictor slightly modified, his car doesn’t burn oil at stoplights anymore, and his fuel trims are back to 0.0%. There’s still a slightly high idle, but it’s looking very promising so far.

#8

Great stuff man, I always appreciate your attention to detail and honesty. I also really want to see his car run the best it can because I know how annoying and frustrating troubleshooting issues everytime you turn around can be…he is lucky to have a guy with your knowledge and abilities close by.

#9

LOL leave it up to you to somehow link this topic with my JHM tune. Nicely done!

#10

My current setup is this - I have the crankcase breather tube capped off and the TB elbow plugged, and I have the “less” modified restrictor installed in the PCV. I’ve had to do a lot of driving over the past two days, and the car has been running really, really well.

During all of this testing and trying different setups, two things were constant - with a 100% stock system, my car would occasionally belch blue clouds of smoke after sitting at idle for a while once I touched the gas pedal again to get moving (like sitting at a traffic like for a minute or two), and with a modified system (no matter what part of it), there is increased vacuum in the system, and I get no smoke, whatsoever. However, with a ton of vacuum in the system, it starts making a really loud/obnoxious whining noise (somewhere in the driver’s side rear of the engine up top, it’s very high pitched but I’m guessing it’s the PCV valve itself being played like a reed), the idle doesn’t settle down until the car is completely stopped, and the fuel trims are through the roof. I think if we can get the vacuum under 20cm at idle, everything might be ok.

But that also creates a new problem - so much flow going through the PCV that it’s no longer efficient and oil blows right into the intake manifold and a little pool starts to develop inside it. So, we’d need a good aftermarket catch can/oil separator, or figure out a way to drain it out of the IM. I’m totally fine with ditching the PCV completely because I think it does suck, and getting something like this set up. Even if it means we initially have way too much vacuum in the system and the car is crying for mercy (literally), but we come up with an in-line restrictor and keep trying different size restrictors until we find the sweet spot where there’s a lot of flow, but not a ton of vacuum and the car is happy.

We’re definitely on to something, we’re seeing big changes, just needs some more dialing in and trial and error. Blake has been great to bounce ideas off of, he’s a very smart dude!

#11

It’s a pretty damn important observation…if koolade understands my concern, that is all I care about. I’ve said numerous time, I wish you oh and your car the best, but when things become frustrating and don’t go your way…you are the type of person that becomes weak and folds to the outside pressure to blame the tune. The tune can’t fix a bad PCV, or vacuum leaks, or hpfp, or bad O2s…this is simply my point from the beginning of your troubles.

Try to look past the fact you don’t like me and just think logically…

#12

Love this . Thanks for sharing your work.

My car chews a bunch of oil. About a litre every 2000 kms or so. Acceptable to Audi. Unacceptable to most of us.

Koolade what common RS4 problems do you think might be related to PCV problems where people are chasing their tail elsewhere trying to solve it ?

Also FWP before you blame my oil consumption on JHM, just know that I’m stock other than JHM exhaust. :slight_smile:

#13

Koolade6 and FWP good for you guys. nice to see.

I dont know if you care to head what I have to add but maybe it will help. You capped off the elbow of the intake but keep in mind that doing so will have an impack on your rings sealing. The FSI motors are subject to high fuel pressure injection due to how FSI works. The pull on the crank case that comes from the elbow is to help seal the ring gap at low speeds where the rings contract. Your rings expand as the RPM rises and heat expands the rings to seal but that seal is lesser when the RPMs lower. You want that back pull on the under side of the piston to help keep that control ring sealing. If you dont get a good seal at low RPM your going to get fuel blow by into the oil and that can lead to bearing failure. If this was a NON FSI car I would say this isnt even an issue as there isnt as much cylinder fuel pressure. So free air bypass is fine

I think to get the results your looking for your going to have to use a catch can. Your going to have to tap back into the intake track on the low pressure side and it might work best if you use that in conjunction with the current oil seperator.

#14

Logs would have showed something wrong with O2’s, fuel pressure, or that I had a vacuum leak, and all JHM could do was scratch their head because everything looked fine.

I fold to outside pressure? How about my car pinged like a mother fucker for months, possibly causing damage, until JHM eventually sent me a watered down tune? I wasn’t getting any answers from them (literally) so I asked on AZ if anybody had any ideas. What’s so crazy about that? Wouldn’t you have done the same?

#15

I hear you about needing to help seal the rings, but that crankcase breather works opposite of what you’re saying. It has a check valve in it that only allows metered air in, but does not allow positive pressure out. (you can blow air into it but you can’t suck air out) With it in stock form, it basically controls pressure so that there is only so much vacuum in the crank case. Capping it increases that vacuum slightly, forcing the PCV valve to draw in blow by gasses only instead of bringing in fresh air via the breather.

I would definitely like to get a catch can installed and ditch the PCV valve all together, but it’s going to come down to controlling how much vacuum is in the system so the computer doesn’t freak out.

#16

FWP & Euro, can we agree to play nice in this thread? No jabs, no digs, let’s keep it positive.

I’ve never really had oil consumption issues, per say, but I’ve had plenty of leaks. When I pulled the engine last year, I had oil leaking from the dipstick tube seal, the front main seal, valve covers (even with the new version on the driver’s side), and I was pushing oil past the seals on the coolant pass-through pipes (in the timing case) into the cooling system. I’ve said it before, but I’ll make the claim that positive crankcase pressure is the #1 cause of carbon buildup. If you think about what’s happening when there is positive pressure, that air is moving passed the intake & exhaust valve seals and pushing oil with it. I can’t really make a direct connection to a performance hinderance unless there’s an actual vacuum leak in the system. As Justin mentioned, there is an impact to sealing the rings. That can definitely cause problems…catastrophic problems. This currently has my focus.

[quote=“justincredible,post:13,topic:8291”]
I think you nailed it. This is exactly where I’m going with it.

#17

In euros defence and defense for the others. AZ has lost most of the very technical and knowledgable guys. Now there are way less kooland like guys over there. Most of them are over here. When people like you need real help you get help from guys who are not even close to honest and some have huge agenda. Some of the guys in the past who had issues went out of the way to show what the issues were. like ben or as some call him ben stlie. Ben had issues showed it was carbon but when he wanted to start selling parts and nobody wanted his parts because they were all getting JHM parts ben started changing stories to try and change peoples mind about his parts. You have guys on AZ that are paid to push parts. guys that got disscounts for blowers or other parts in return for glowing reviews and a constant streem of attacks.

I created a RS4 investigation thread here for guys like you. The facts are RS4s are prone to ping stock. When you add the JHM tune your motor rpm goes by faster so you will hear more of the ping as there are more accounts per second. Flashing to stock wont get rid of the ping it will just make it sound less freaquent as the motor rpm is slower. The RS4 invistagation thread and forum investigation shows there are several hundred JHM tuned RS4s but less than >1% have this issue and since this issue is on stock cars as well we have been working to find the issues.

Some guys have found carbon made this happen. Others have found injectors failing caused this issue. People have logged the pinging issue and showed that there is no change in knock so there isnt anything the ecu can see to fix. JHM worked to make a tune to go beyond what the OEM tune did and this is what helps until people find out what the issue is. The thing you obviously see is you have the support of a company that will make a tune to help a mystery hardware issue that can plauge a few guys.

#18

FWP/Koolade, any progress?

I talked to a few guys in the domestic performance world that specialize in aftermarket oil separators and they all agreed that our PCV/oil separator is an overly complicated design.

To simplify the system and reduce maintenance costs, I think replacing the OE PCV with an adjustable and serviceable PCV valve and a separate catch can might be the ticket.

Something like http://mewagner.com/?page_id=444 might work. There’s an in-line adapter for that as well.

I’ve been looking into high quality catch cans as well. There aren’t very many that have overflow valves built in, but I think that would be a good thing to have if we were to replace the stock PCV with it. That would result in a maintenance-free system since it would drain into the crank case. Or we could just plug the PCV drain port and empty the catch can as part of maintenance.

As you guys have discovered, I think the most challenging part will be tuning the air flow into the IM venturi port so the engine idles properly. That and adapting a connector to the venturi port. Edit: adjustable PCV should allow us to meet the target air flow

These are some of the high quality catch can options that may be adaptable to our setup:
https://www.cantonracingproducts.com/product/23-050/23-050----AIROIL-SEPARATOR-TANK--12AN-INLET--OUTLET--14-NPT-DRAIN/#

http://www.mishimoto.com/mishimoto-baffled-oil-catch-can.html

http://www.conceptualpolymer.com/new_page_1.htm

http://www.uprproducts.com/make-your-own-billet-catch-can.html

http://shop.bobsautosports.com/Bare-Bones-Oil-Separator-Bare-Bones-Oil-Separator.htm

http://jlttruecoldair.com/ZenCart/index.php?main_page=index&cPath=378

Once I verify that the Wagner adjustable PCV can achieve the necessary flow rates, which I think it can, I will proceed with purchasing one for testing.

I’d appreciate any feedback.

#19

So Mann+Hummel makes a series of oil separators that look to be better engineered than anything the tuner market produces. They all have easily replaceable filters and integrated oil return valves with an optional check valve. I think the ProVent 400 is a really good option to explore for our vehicles as a replacement oil separator. https://www.mann-hummel.com/fileadmin/user_upload/service/catalogues/pdf/ProVent_en_2013.pdf

I went ahead and ordered the Wagner adjustable PCV and I will perform initial testing with a cheapo catch can so I’m not out several hundred $ if it doesn’t work.

Edit: Maybe the ProVent 400 is overkill for the PCV flow rate of our motor. Any idea what that number might be? The ProVent 200 might be sufficient.

#20

that was a very interesting find. Im going to try and look over that more later