Changing the flow rate of the OE oil separator has a pretty pronounced effect on idle quality. You can try to use an adjustable one to see if you can make it work, but I fear you’ll be restricting total flow capability… The solution I was moving toward was to keep the OE oil separator in place (with the outlet restriction only slightly bored-out). At the elbow that attaches the VC lines to the OE oil separator, split off there and insert a check-valve that’s normally closed when the OE system is under vac, then plumb it to an aftermarket oil separator with oil drain. The suction side will come from the intake elbow post-MAF. This should allow for factory idle, yet give the system the capability to evacuate all of the crankcase air in peak conditions. FWP found a few Subaru applications where they use a dual oil separator to the same effect. (Don’t recall it off the top of my head)
You’re right, the diameter of the piping on the Wagner PCV looks really anemic compared to our system. After speaking with Wagner, they will not release any specific peak volumetric air flow or vacuum numbers. However, they claim their adjustable PCV can flow enough volume for any high displacement v8 street engine and most race engines.
I want to approach this problem with data instead of guesswork so I’m currently trying to locate a blow-by meter. I plan to put this in-line with the PCV system to measure the volumetric airflow.
Koolade, wouldn’t the PCV restrictor and diaphragm be the bottleneck on air flow into the IM? That seems like the most restrictive point in the system. The tubing and PCV have far great volumetric flow up to that point, no? It seems the PCV/Oil separator unit is only as large as it is in order to house the cyclonic oil separator and oil collection/draining components. I haven’t actually opened my PCV up and examined the components, so I may be misinterpreting based on the pictures I’ve seen.
“I want to approach this problem with data instead of guesswork”
Why I love this forum. And this thread.
[quote=“komseh,post:22,topic:8291”]
That’s totally the bottleneck…but when you remove that restriction, your idle goes nuts, you wind up with way more crankcase vac than one would like, and the actual oil separation stops working so you wind up with a very oily intake manifold.
That’s why I’ve shifted to the idea of effectively piggy-backing a second oil separator system, you’re allowing the dynamic loads (where the OE oil separator cannot flow enough) a second path to take. This will also allow the OE unit to operate in it’s optimum efficiency range, which will help keep oil out of the IM. You’re already researching oil separator units, so you’re starting to see the wide range of designs out there. This is about where I stopped looking into it because I got distracted by other projects.
I would like to remove the stock unit altogether. There are several points of failure in the system that are not serviceable: diaphragm, piston, and check valve. It’s no surprise a plastic part is one of the weakest links on the car.
The last couple of times I pulled my IM(when I was dealing with the fluctuating idle) the bank 1 side had a nice layer of oil on it. Carbon seems to build up very quickly on my car as well. This is with a PCV that was replaced less than 10k miles ago.
I’m wondering if the vacuum draw @ idle on the venturi port was modified when I deflapped the IM and plugged the check valve underneath. Any thoughts on whether that might affect how the oil separator works?
I’m gonna pull the PCV this weekend and check out the components in question. Where is the oil drain check valve located?
Koolade and FWP, have either of you tried running the motor with the IM venturi port plugged?
I am considering running the Provent 200 and venting to atmosphere or into an exhaust pipe.
The Provent 200 is on the way. I am pretty confident that it will be able to flow enough gas volume.
The provent has a check valve so you dont get back pull right.
Are you referring to the crankcase breather tube? If so, mine’s been capped for months and the intake elbow has a plug in it.
No I meant where the PCV plugs into the IM.
That is good info though.
Oh, no, haven’t done that yet. Should be fine though if you wanted to try that. The issue with idle and short term fuel trims becomes apparent when too much air is getting through the PCV and into the IM. Right now I’m running a PCV that has its inlet “restrictor” (the part that you can push in with your finger and is spring loaded) drilled out a tiny bit, it’s maybe 2mm larger of an opening than stock. This has resulted in an OK idle and between doing that and having my crankcase breather hose plugged, there is noticeably more vacuum when I open the oil cap, but the idle and fuel trims have been unchanged.
Maybe. There is a pressure regulation valve at the output port that might close if backpressure occurs. This oil separator was designed primarily for diesel engines, which will never have negative crankcase pressure. So that valve might not be designed to account for that condition.
I’ll have it in my hands in a few days so I’ll give it a closer look. If I end up having to plug it into the IM I will just need to make an adapter for that port to have a 1" ID connection. Venting to atmosphere is desirable to me for a few reasons:
Easier
Not a drop of oil vapor from the crank case will be recirculated back into my IM.
I don’t think it would be an issue to cap that IM port. As FWP mentioned, we really only saw a problem when there’s too much air going through the IM. There are several people who say VTA, but I’m not one of them. I’ve seen other cars respond (very favorably) by tying into the intake snorkel vs. venting. Having that slight vac/draw is a good thing. I’d go in between the MAF and the TB. If the provent has a drain fitting, re-purpose the OE drain line since you’re effectively deleting the OE oil separator.
You want some vacuum in the crank case, and if you vent to atmosphere, you’ll actually being created positive pressure which is the exact opposite.
If you’re going to vent to atmosphere and route it through an aftermarket catch can, I’d recommend adding a vacuum pump to the system, GM makes one that is electric and about $75. They are installed in their V8 trucks and vans.
Awesome work guys!!!
I believe in the name of the whole community I can say, thank you! Your research and write ups are worth gold!
Thank you for going the extra mile, doing the research and explaining everything as simple as you do.
I did a carbon clean myself last year and had an idea of how the PCV “should” work when I had everything disassembled and in my hands. Now after reading this thread it’s a whole new perspective mind blown and holy hell did Audi complicate everything.
I remember reading one of koolades post last year where he suspected the PCV as the root cause for drastic carbon build-up in our engines. If you will find a holy grail of improving/removing the PCV I’m in as a guinea pig even if it means shipping parts to Europe.
I have two questions:
1.) Apparently I have a PCV on the way out. After all I read here today, are these symptoms maybe caused by something else (as you actually want more negative pressure from your PCV)?
Symptoms:
- a small cloud of dark smoke when accelerating;
- when idling and I open the oil filler cap the engine bogs down a bit and runs in a VERY rough idle at 500rpm;
- the suction at the filler cap is VERY high;
- I got a low oil warning, opened filler cap, the light disappeared and oil level was normal. Wtf?!
- I checked my fuel trim values and they are all fairly within tolerance below +/-10% (taking old fuel injectors into account); they aren’t as extreme as in the first pictures
2.) A stupid question, but just to make sure: I got an O2 MIL, this is probably completely unrelated to the symptoms above?
[quote]008756 - Oxygen (Lambda) Sensor B2 S1
P2234 - 004 - Signal Shorted to Heater Circuit - MIL ON
[/quote]
Check your oil seperator and full PCV system to see if anything looks like its not working.
There is an update to one of the valve covers but I dont think anyone has been able to find out exactly what the update is in the valve cover.
As for the code thats the front sensor on the driver side. That is a main control 02 so you want to keep an eye on it.