Clown

I don't use an oil catch can is this needed with a PCV setup?

Also does the Supra TT PCV valve work as a dual purpose elliminating the need for the one way check valve or will that also be needed in addition?

I think a kit is in order. Seems like there are many people who may have the same problem out there. Hopefully Ill know if Im one of them soon.

fast951

I use a PCV vlave, it regulates the flow. The Supra TT PCV valve works as a one way valve (double check as as of late some did not), however I recommend adding a second inline 1 way valve. A inexpensive insurance.

I have a kit I was about to release, however considering that just about everything gets copied, it's best (for me) to leave it as a DIY.. I'm sure someone will take the information provided here and will offer a kit!

Clown

Is there any danger in adding a PCV valve system to our cars? Can we create too much vacuum? You speak of insurance what can happen if there is no check valve?

fast951

Adding a PCV is not a problem, but flow must be regulated. You have to look at it as part of a system!
If there is no check valve and you get free flow toward the crankcase, when on boost you will pressurize the crankcase, which causes all sort of problems..

Black51

Sounds like this problem might have just happened to Zermatt...

Clown

Yes I was thinking the same thing. That is why I was getting some more info. I hope his engine is ok. He was a guinea pig for all of us considering this route. I feel bad.

zerMATT951

I don't think I put boost into the crankcase using the blue/black check valve. If anything, I think what happened was too much vacuum from the MAF pipe under full throttle may have starved the turbo of oil (if that's even possible), OR I had a bad rebuild...

fast951

The oil is entering the turbo at 60-70psi. Pulling vacuum on the crankcase is not going to starve the turbo.. Besides, there isn't that much vacuum in front of the turbo. The air will enter through the Air Filter a lot easier than you can vacuum it through the hose...

nick_968

Interesting thread. I never had any smoke at idle previously but I did just put my intake system back together and the car is leaking oil out at the top of the turbo mount at idle. Last time it did this I had the aos line connected to the pre throttle body connection rather than the turbo air in connection. When I switched it back last time it was fine and it is connected right this time. I did fix a couple of vacuum leaks and the line from the aos to the turbo was loose, maybe now its tight I have knocked the balance of the vacuum out? Could I have made an error somewhere else in the vacuum system that is causing this?

carbongecko

wow all this info has been so helpful i have just begun to have the issues mentioned in this thread and seeing how it is fixed i am glad i havent taken apart my turbo on a hunch.

Thom

Hi Nick,

Funny you mention you once had the line to the AOS plugged ahead of the throttle body, as I was wondering if it would provide more or less vacuum to the AOS. On your set up it shows it didn't provide enough and that you get more vacuum from the turbo inlet.

Now that oil is making its way out of the top of the turbo, perhaps it's time to do the plastic bag test and/or let the engine idle for several minutes watching closely for smoke coming out of the exhaust?

mikjel

I did some testing again this weekend. My idle is changing very little with/without the PCV-system, less than what I wrote earlier. When I squeeze the PCV-hose (letting no vacuum through), the rpm is changing less than 100rpm for a few seconds, then it stabilizes at the same rpm as with the hose open. So the PCV-system really does not change my idle rpm. It does not change the vacuum I see on my analog boost gauge either.
Again: In my case I needed only a very little vacuum to stop the smoke at idle. But I think my problem/smoke might be less than some of yours. When I tested and installed the PCV-system, I made more and more restrictions on the hose going to the intake to make the air flow less and less.
This because we clearly want as much of the air entering the intake going through the MAF and turbo, not from the cranckase.
AND: I just have valves (two in series - for safety) on the hose going to the intake, I do not have a PCV-valve on the hose going to the front of the turbo as Matt has in his drawings. Of course I see the benefit of this valve, but I think all PCV/one way valves needs some pressure to open (at least the valves that I have). I think the crankcase to turbo connection should be as free as possible for any pressure in cranckase to escape as easy as possible.
BUT: I opened up the hole on the top of the AOS and made a similar restriction in the hose between the turbo and the T going to my intake. This way I have the same restriction from the cranckase to turbo as stock, but less restriction from the intake to cranckase than intake to turbo. Get it?
I was not sure if this would work, we do not want any/much of the air entering the intake this short cut. In my case it seems to work perfectly (but I think I might need less vacuum than some of you).

Thom, do you know if the 968 has the extra "one way valve" on the hose from AOS to inlet pipe?

Crankcase pressure testing:
I made a hole in my oil filler cap, and installed a "valve" where I connected my digital boost gauge. Pressure checked with cranckase to turbo connection open and oil cap on, like normal running conditions:

Atmosphere pressure before starting the engine: minus 0,05 bar
Pressure at idle with the PCV-system: minus 0,06 bar
Pressure at idle without the PCV-system: minus 0,05 bar.
Pressure when driving with/without the PCV-system: minus 0,06/0,05 bar to minus 0,08 bar.

As you see, on my car there are suprisingly little changes in cranckase pressure with/without the PCV-system and overall. At idle I did not have a measurable change from atmosophere pressure without the PCV-system connected. I did the plastic bag test again too (taking off the oil filler cap), the plastic was not sucked down (I do not think it was pushed up either - rather pulse fast up and down). With the PCV-system connected, vacuum icreased 0,01 bar (from minus 0,05 to minus 0,06), plastic bag was clearly sucked down. When driving with vacuum in my intake (no boost pressure), the difference / readings was the same as at idle. When getting boost pressure, having PCV-system on/off did not make any difference (as it should, because of the one way valves closing). It was interesting to see that the vacuum in my crankcase increased (from minus 0,05 bar to minus 0.08 bar) the more rpm/boost pressure I had. Most vacuum at high rpm (5,5 k+) at WOT (13 psi boost pressure). This because of the vacuum being created in front of the turbo. I was suprised to see that this vacuum was more than any leakdown I may have (which can not be much??). I would have thought leakdown at WOT would be greater than the vacuum pulled from the turbo (through hoses and AOS). It was not.

Thom

Mikjel, thanks much for your feedback.

I must admit I am not sure I understand the need to add restrictions in the PCV line.
If there is no vent to atmosphere in the AOS to turbo line, to which the PCV line is connected, then surely the fueling can be compensated for the amount of additional unmetered air that goes from the crankcase to the intake? Well, at least when using a MAP-based ECU, not a MAF...

mikjel

When you use MAP I unerstand what you mean. But I think we want all (most) of the air entering the intake going through the turbo (spinning it - good for draining - less smoke..). I tried to put gentle pressure to my cranckase with compressed air, and the system is not leak free (some leak in the dip-stick hole, ++). I think it is best to have most of the air going to the intake being fresh air comming from the air filter. The less air going through the PCV-system, the better in my opinion (but I am no expert). At least, there is no point doing the oposite.

Thom

Yes, fair enough.