What PCV system are you running on big single?

[jevansio]

Jay the std system works like this, the plenum side breather, the one with the one way valve in it is the low RPM/load breather, in that it only operates when the car is not on boost, once positive boost is reached it closes, and all breathing is done through the exhaust side breather, which has no one way valve,

Many thanks for confirming mate, I was unsure of there being a 2nd check valve on the other side (hence me blocking it off in my tests )

 

It relies on the intake vacuum from the turbos, so by blanking it off you are not seeing a realistic model of how the breather system works.

Yip, I will redo the vacuum tests with just a breather to atmosphere on the ex side

 

I am with Jamie on this leave as pretty much std, IMO you're going to be relying on either an electric motor for officiant breathing, (another device you will need to monitor to re assure yourself all is working OK) or the exhaust valves which as you say are also prone to problems! (do you need the extra worry)

Totally understand where you're coming from on this & I agree, stock is better, but I am in a different situation, as part of my single package I got polished -10an cam covers breathing to atmosphere. I have no option but to investiagte how the stock system work & reproduce it (but with my -10 covers).

 

I'm defo not using an electric motor, that was just being used for test purposes.

 

With everything I have learned & advice on here I think I'm going to reproduce the stock intake side, & just breathe the exh side to atmos, that should be a pretty simple worry free solution.

 

I have to ask as before is the free BHP maybe 20 if you're very lucky, worth it?

Defo IMHO, if I can get a reliable setup that nets me 20bhp without stressing the engine any more at all then that is the best type of power to get.

 

Also the weeps that you are mentioning should not be occurring with the very minimal positive pressure you're seeing on you're tests, i would be looking at the condition of the seals/gasket's.

I have to disagree with you on this one . I have read numerous articles stating the benefits of PCV systems in preventing minor oil weeps.

 

Not only that I tried it for myself and it stopped my oil weep.

 

I have done everything in my power (numerous fms seal changes & a new modified PHR oil pump) to fix the weep and it still slowly comes out.

 

I may even tend to agree with you on the small pressure not being enough, but how do you explain the residue around the oil filler? There is only one way oil could get there & that is being pushed out, if it can slowly be pushed out there surely it can slowly be pushed out a seal?

 

Anyway I'm convinced of the benefits of the PCV stopping oil weeps and I'm happy to try it to fix mine (beats ripping the engine out )

[jevansio]

I've retried with the ex side breathing to atmos with a -10AN fittnig, the 1/4" manifold fitting that pulled -35kpa before was at 0kpa now. I had to reduce the -10 breather down a bit before it would pull -20kpa.

 

Can anyone confirm the hoses inner diameter for both intake & ex covers?

[Tricky-Ricky]

Sorry Jay, i still don't see why you would want to run the stock intake side, IE check valve and into plenum, and then just leave the exhaust side to atmosphere? as that way you loose all the benefits of the PCV that you get from plumbing it into the turbo intake pipe? or have i miss understood you??

[jevansio]

Sorry Jay, i still don't see why you would want to run the stock intake side, IE check valve and into plenum, and then just leave the exhaust side to atmosphere? as that way you loose all the benefits of the PCV that you get from plumbing it into the turbo intake pipe? or have i miss understood you??

I'm not going to do that now , after testing the vacuum it was zero, the manifold was just sucking through the vent to atmos intake breather

 

So what do you reckon the best solution is, I def don't want to plumb it back into the filter. I'm thinking a check valve on the exhaust side ?

[Tricky-Ricky]

You are obviously worried about introducing oil/vapour back into the turbo inlet, so like i said why not just run both cam cover vents to a decent catch can filled with stainless scourers, and run a single hose back to the turbo intake?

 

That way you will achieve a good vacuum and any oil/vapour will have plenty of time/distance to drop out of suspension, and so won't be a problem, but you will still have a good vacuum applied to the crankcase.

 

Thats how i had my set up with the same turbo as you, and i never had any weepings from any seals etc.

Are you running high boost? the fact that you had some positive pressure on your test makes me wonder if you might have not very effective ring seal,

 

Although i must say that IMO for the FMS to leak/weep to me it would indicate a worn oil pump, or damaged/worn crankshaft oil seal interface, crankcase pressure is the last thing i would look at, unless you're running hight boost, around 2BAR, or had ring seal problems.

[Chris Wilson]

The reason the oil pump seal stops leaking when you add crankcase vacuum is the oil seal lip is being pulled into tighter contact with the crank seal surface. The crank is probably worn, fitting a tighter garter spring to the seal will probably fix it, or maybe investigate a repair sleeve for the crank and an O/S seal?

[jevansio]

You are obviously worried about introducing oil/vapour back into the turbo inlet, so like i said why not just run both cam cover vents to a decent catch can filled with stainless scourers, and run a single hose back to the turbo intake?

 

That way you will achieve a good vacuum and any oil/vapour will have plenty of time/distance to drop out of suspension, and so won't be a problem, but you will still have a good vacuum applied to the crankcase.

 

Thats how i had my set up with the same turbo as you, and i never had any weepings from any seals etc.

Are you running high boost? the fact that you had some positive pressure on your test makes me wonder if you might have not very effective ring seal,

 

Although i must say that IMO for the FMS to leak/weep to me it would indicate a worn oil pump, or damaged/worn crankshaft oil seal interface, crankcase pressure is the last thing i would look at, unless you're running hight boost, around 2BAR, or had ring seal problems.

Yes, oil vapour back into the intake is a concern for me. I suppose that is an option, do you know how much vacuum you generated on idle with that setup?

 

I run 1.5 BAR.

 

Oil pump is brand new PHR modified. I understand what you're saying, but I'm not prepared to pull the engine to fix what is effectivly a couple of drops of oil overnight.

[jevansio]

Intake side mine is stock, exhaust side i have a -12 to a catch can, mine has been like this for many miles and i see no reason to change it.

 

Same as mine

Guys when you say you run to a catch can, is that then plumbed back into the intake?

[Tricky-Ricky]

Yes, oil vapour back into the intake is a concern for me. I suppose that is an option, do you know how much vacuum you generated on idle with that setup?

 

I run 1.5 BAR.

 

Oil pump is brand new PHR modified. I understand what you're saying, but I'm not prepared to pull the engine to fix what is effectivly a couple of drops of oil overnight.

 

Sorry but as i never had any problems once i went single turbo, and also due to my testing before going single, i didn't have any reason to test further.

But on idle i wouldn't expect there to be any real vacuum generated, only once the RPMs are up a bit will there be any, and then once the turbo is spooling up considerably more, this effect is enhanced by having a sealed catch can, as its supposed to help to increase the vacuum effect.

Guys when you say you run to a catch can, is that then plumbed back into the intake?

 

I guess that depends on what you class as the intake,? the plenum or the turbo intake? most people run it from the catch can to the turbo intake pipe.

[JamieP]

Guys when you say you run to a catch can, is that then plumbed back into the intake?

 

My intake side is as stock, exhaust side is a catch can vented to atmo, but as i like the clean uncluttered look im changing that soon to just a pipe venting under the car.

 

Just turn the boost up if you want free bhp, that turbo will run 2bar+ on pump fuel.

Edited August 19, 2010 by JamieP (see edit history)

[jevansio]

Sorry but as i never had any problems once i went single turbo, and also due to my testing before going single, i didn't have any reason to test further.

But on idle i wouldn't expect there to be any real vacuum generated, only once the RPMs are up a bit will there be any, and then once the turbo is spooling up considerably more, this effect is enhanced by having a sealed catch can, as its supposed to help to increase the vacuum effect.

 

 

I guess that depends on what you class as the intake,? the plenum or the turbo intake? most people run it from the catch can to the turbo intake pipe.

So maybe you think the best solution, is to keep the manifold generated vacuum on idle, and use a catch tank for the other side routed back into airfilter? Basically stock system + catch tank?

 

By intake I mean pipe between air filter & compressor

[jevansio]

Mine is a catch can vented to atmo, but as i like the clean uncluttered look im changing that soon to just a pipe venting under the car.

 

Just turn the boost up if you want free bhp, that turbo will run 2bar+ on pump fuel.

, I still want this bloody oil leak stopped though

 

But hasn't that rendered your PCV system useless, you may aswell ditch the manifold line in favour of venting that to atmos too?

Edited August 19, 2010 by jevansio (see edit history)

[TLicense]

on idle i wouldn't expect there to be any real vacuum generated, only once the RPMs are up a bit will there be any, and then once the turbo is spooling up considerably more, this effect is enhanced by having a sealed catch can, as its supposed to help to increase the vacuum effect.

 

According to the workshop manual, the GTE should pull 17.7 in.Hg "or more" at idle.

[Tricky-Ricky]

Hopefully you can see how mine was set up, the two cam cover vents are "T"d together to the catch can and then on to the intake.

 

[jevansio]

According to the workshop manual, the GTE should pull 17.7 in.Hg "or more" at idle.

That is a hell of a lot, I don't think I get 17.7 in.hg in my manifold,

 

EDIT actually I think I do , I keep getting confused with all these different units

 

PS I think Ricky meant that the vacuum generated via his setup (ie no manifold) wouldn't be that great on idle

 

PPS that 17.7 is manifold vacuum, not crankcase vacuum

Edited August 19, 2010 by jevansio (see edit history)

[jevansio]

Hopefully you can see how mine was set up, the two cam cover vents are "T"d together to the catch can and then on to the intake.

 

http://i208.photobucket.com/albums/bb118/Tricky-Ricky13/002-2.jpg

Yip, that's spot on bud

[jevansio]

BTW while we are on the subject of plumbing a catch tank back into the intake, can anyone recommend a "great quality" one. I don't fancy using any old rubbish as whatever manages to come out of it would be going straight through my turbo

[jevansio]

Dan, when you installed the ports into the exhuast did you install them like this?

 

 

By instinct I would have installed it 90 deg to the pipe with the slash pointing away from the flow

[TLicense]

That is a hell of a lot, I don't think I get 17.7 in.hg in my manifold,

 

EDIT actually I think I do , I keep getting confused with all these different units

 

PS I think Ricky meant that the vacuum generated via his setup (ie no manifold) wouldn't be that great on idle

 

PPS that 17.7 is manifold vacuum, not crankcase vacuum

 

The crank case and manifold pressure will be the same thing at idle, and in fact at any point off boost as the two are connected via the inlet manifold pcv. On boost, because the one way check valve on the inlet closes, the crankcase is evacuated by the pcv hose on the exhaust side that is connected pre turbo to the inlet.

[jevansio]

The crank case and manifold pressure will be the same thing at idle, and in fact at any point off boost as the two are connected via the inlet manifold pcv. On boost, because the one way check valve on the inlet closes, the crankcase is evacuated by the pcv hose on the exhaust side that is connected pre turbo to the inlet.

Are you sure? During my tests by linking the plenum to the crankcase with different size hoses the crankcase saw different pressures. Just becuase 2 things are linked doesn't mean they will be the same pressure???? Unless I am mistaken

 

To elaborate, when I connected them with a massive -12 hose they were the same, when I connected them with a small 4mm hose the crankcase pressure dropped (rather raised ) significantly, I bet the plenum stayed at it's normal pressure, and the stock system uses a relativley small hose

Edited August 19, 2010 by jevansio (see edit history)

[TLicense]

Fair point. I guess the PCV check valve probably has quite a small hole, so would be quite a restriction.

I guess all you need to do is generate "an amount" of vacuum in the crankcase. In fact I'm thinking as long as you're directly measuring vacuum in the crankcase then you are evacuating the blow by (otherwise it would start to pressurise).

In my mind the blow by would be highest at high rpm but low load (ie on the over-run), so as long as the crankcase is still in vacuum in that case, then you've got enough vacuum.

The problem is probably as you found, and as I think caused me issues, that you can pull too much and you get to the point where you're pulling denser oil spray through.

If you're saying that after investigation, that 8 in.hg is about right, then I would target that. The trick will be making sure that you're pulling 8 in.hg at idle and still pulling some vacuum in the max blowby condition.

[jevansio]

Fair point. I guess the PCV check valve probably has quite a small hole, so would be quite a restriction.

I guess all you need to do is generate "an amount" of vacuum in the crankcase. In fact I'm thinking as long as you're directly measuring vacuum in the crankcase then you are evacuating the blow by (otherwise it would start to pressurise).

In my mind the blow by would be highest at high rpm but low load (ie on the over-run), so as long as the crankcase is still in vacuum in that case, then you've got enough vacuum.

The problem is probably as you found, and as I think caused me issues, that you can pull too much and you get to the point where you're pulling denser oil spray through.

If you're saying that after investigation, that 8 in.hg is about right, then I would target that. The trick will be making sure that you're pulling 8 in.hg at idle and still pulling some vacuum in the max blowby condition.

Yip pulling too much was defo an issue I found. 8 inhg was a figure I found on a couple of articles, it also ties in with Rickys findings on a stock PCV system. When I was pulling 16 inhg it did pull dense oil vapour through and the engine didn't feel great.

 

To get a decent vacuum all the time I think the best idea is to copy Toyota.

 

I'm defo going with a link to the manifold with a check valve for idle/cruise conditions, it's very simple & tidy regarding plumbing..

 

My only unknown at the mo is do I:

1) vent t'other side to atmos

2) as 1) but with a check valve

3) vent straight back into turbo intake (as stock)

4) as 3) but with catch tank

5) use exhaust

 

All have pro's & cons, and some are better than others, but one thing is for sure they are all prolly better than what I currently run. Take for instance 1), it does semm pointless connecting the plenum to one side and leave the other side open as the best I can possibly achive is 0 pressure in the crank, but that is better than what I currently get which is small +ve on idle.

[jevansio]

Can anyone point me at a link that describes how you would connect a tube to the side of the turbo intake pipe to get the best suction, does it sit flush inside, or is it proud, does it have a 45 deg slash cut, is the pipe angled WRT the intake? Diagrams would be good

[dandan]

Dan, when you installed the ports into the exhuast did you install them like this?

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=115585&stc=1&d=1282244205

 

By instinct I would have installed it 90 deg to the pipe with the slash pointing away from the flow

 

Mine comes in just like that picture with two subtle differences. The angle of mine is slightly less than 45 degrees - that is purely related to the piping under the car though. Secondly, mine poke it a significant way...probably more like 20mm. Again this is due to their location. I have them on the inside of a bend in my midpipe where the exhaust flow is negligible and relatively slow. I wanted to poke them in further to where there was some decent exhaust velocity. If they entered the outside of the bend then I'd be happy with them stuck in by 6mm or so.

 

Can anyone point me at a link that describes how you would connect a tube to the side of the turbo intake pipe to get the best suction, does it sit flush inside, or is it proud, does it have a 45 deg slash cut, is the pipe angled WRT the intake? Diagrams would be good

 

I can't point you to any direct links but I can tell you what I settled on....On the intake side to my turbo my "tube" sticks in about 6mm and it is at 90degrees - if my engine bay installation would allow it I would feed it in at an angle like the exhaust but that's not really practical.

 

To get the best (greatest) suction the open part of the breather tube needs to be at the point of max velocity in the pipe (be that the turbo intake or exhaust). There is obviously a compromise here as you don't want a 13mm diameter steel pipe poking halfway across your turbo intake as the flow disturbance wouldn't do you any favours.

Edited October 2, 2013 by dandan (see edit history)

[jevansio]

That's brill mate