Oil catch can, Help needed.

[my98GST]

Alright, I've got this Greddy catch can. I also have a FP 4" intake without the nipples on the intake pipe. My question is. Do I take the valve cover line into one port, then do I install a barb valve cover and then block it off, and then take another line from the other nipple on the catch can, install the PCV valve in to the line and plug it back in to the intake manifold?

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How would I do this for the JMF SMIM?

 

[Calan]

Yeah I see that after I thought about it a bit. You need some type of arrangement that selects post GM MAF for vaccum, and pre-turbo or atmosphere when under boost. (see edit above)

 

[oldman]

I thought about this before I respond and the only solutions are.

1. Run your GM pre-turbo as draw through in which case a 2G mas would be a much better option due to accuracy.

2. Deal with the unmetered air, it's not like the GM setup is known to be the most accurate metering device anyway.

Good thinking though Calan, didn't think I can find someone more anal about this than I. If there is a choice to be made, relieving crankcase pressure and ventilating blowby under WOT is way more important than slight changes in AFR which can be compensated via tuning, another price to pay for venting your BOV.

We were just discussing this in another thread recently. Of course a catch can on both lines would be ideal. But if having to choose one then it would probably be wiser to run the catch can between the VC and intake pipe. The rationale being that oily buldup in the intercooler will probably affect performance more than buildup in the IM.

Agreed.

 

[bmxrider154]

Yeah, you guys are right, the air entering under vaccuum will still be un-metered with the blow through setup but will be filtered. I mainly set mine up the way it is yesterday for these reasons:

1. I had the vent venting to the atmosphere underneath the car, making a mess of oil.

2. While VTO, I was pulling un-filtered air through under vaccuum.

3. Assists in pulling some blow-by from crankcase under boost.

My setup may not do a whole lot but it's setup right.

 

[snox135]

If you have the GM set up (in uicp) and the VC port hooked up pre turbo, won't that air have been metered twice? Any air from from the crankcase is considered metered right? Atleast that's what I've always been told.

I do agree with your second option oldman. If you have the GM MAF just tune out any issues.

 

[bmxrider154]

When we're talking about unmetered air, we're talking the air that is sucked in under vaccuum. Therefore, no, there is no way that air could be metered if the GM MAF is in the uicp and have the vent ran to the intake pipe, pre turbo. The effects of the unmetered air is very small.

 

[snox135]

But the port on the intake pipe is sucking air from the crankcase under boost.

 

[Calan]

The effects of the unmetered air is very small.

I don't think this is an accurate statement for all cases bmxrider. Depending on your particular setup, that unmetered air could make a pretty big difference I would think. It would depend on if you had other boost leaks, VE of your engine, where your tune was, etc.

If you had no boost leaks anywhere else, then this is 100% of your leak, however much that is. If you're leaking like a sieve from shaft seals, couplers, etc... then it probably doesn't matter at all.

Based on how hard it was to get my car's idle AFR set and the other various issues I was seeing, I'm thinking it was playing a moderate role in things. I could be wrong, but I have a hunch

Here is a semi-working theory on how it could affect performance below boost (the part throttle knock problem ... based on a GM MAF in blow-through with MAF-T):

Assuming you have the MAF-T, AFPR, and other things tuned fairly well... in closed-loop, the ECU is basically going to respond to what it sees happening at the o2 sensor, along with TPS, air flow, etc. Now say you are tooling around at -10 -15hg, and give some throttle up to but not quite boost... you are going to switch maps in the MAF-T (into the "mid" setting) and probably in the ECU... during which time that unmetered air is still being sucked in causing a lean condition. By the time the ECU responds to this via the o2 feedback, the MAF-T, and everything else that goes on...you've already run a few cycles lean, depending on RPM and how fast the ECU refreshes, which could cause a cascading effect on the knock count. This is just a guestimate based on a computer/electronics background ... we need an ECU guru (Steve) to jump in here with ECU sample timing and so forth .

Granted you can tune it out if you go far enough, but in my experience with the MAF-T, it can be hard enough getting things just right even without that unknown amount of unmetered air.

It's interesting any way you look at it

 

[bmxrider154]

But the port on the intake pipe is sucking air from the crankcase under boost.

Yes, that is true. The amount of air entering isn't going to be enough to make a difference in the tune. And if it does, i'll just burn another chip compensating for it or make the small adjustments with my translator.

 

[Calan]

But the port on the intake pipe is sucking air from the crankcase under boost.

I may be missing something (again ), but I believe the only "sucking" that is going on is through the PCV when the IM is at vaccum. When you are at boost, you are basically just venting any excess crankcase pressure through the VC vent. I would guess that having this vent hooked to the intake pre-turbo isn't causing any "sucking" per se... merely to ensure a lower pressure on that side so that the CC will always vent.

Again...Just my guess

 

[Calan]

The amount of air entering isn't going to be enough to make a difference in the tune.

Maybe...maybe not. But with plenty of other crap to worry about on these wonderful infernal cars, I like to eliminate every variable I can

 

[Spoolin4Ever]

OK Oldman and others that are confident in this area; What harm would it do to put a check valve in between the valve cover and the intake, and pointing it so it allows air to suck out? I am thinking about that Krank Vents product, they sell it in 2's, one in-between each.

I know doing this does not allow fresh air into the crank case...but it does assure a good amount of vacume all the time if you did.

WOuld it really be bad or harmful? Like I said, I noticed that's the way Krank Vents instructions says to use it..

I don't know if there would be any benefit in this or not. SOme say it could be bad, even increase oil consumtion, because it's sucking oil out of the crankcase..?

Hmm..and some say the opposite..

While were at it: (In addition to the check valve between the PVC and IM) What if we put a check valve in between the airbox/breather, and the valve cover, only allowing are INTO the VC? Could there be any benefit there? I would think that will make sure it operates the way it is supposed to as well? Any potential harm there?

 

[oldman]

OK Oldman and others that are confident in this area; What harm would it do to put a check valve in between the valve cover and the intake, and pointing it so it allows air to suck out? I am thinking about that Krank Vents product, they sell it in 2's, one in-between each.

I know doing this does not allow fresh air into the crank case...but it does assure a good amount of vacume all the time if you did.

WOuld it really be bad or harmful? Like I said, I noticed that's the way Krank Vents instructions says to use it..

I don't know if there would be any benefit in this or not. SOme say it could be bad, even increase oil consumtion, because it's sucking oil out of the crankcase..?

Hmm..and some say the opposite..

Instead of asking if it would be harmful, what would be the benefit? Building vacuum in the crankcase will definitely increase oil consumption and decrease ventilation as well as possibly induce gasket/seal failures depending on the amount of vacuum built. With that said, it's also known that vacuum in the crankcase will produce some power gains by decreasing windage and promote better ring seals but that will only work with an external vacuum pump (a whole other discussion) in WOT as the stock PCV system will only build vacuum in the crankcase when the system is in idle or part throttle.

 

[Calan]

That's pretty much what I was getting at with regards to the blow-through setup. To keep the desired functionality of the PCV system, you would need a Y arrangement at the VC breather side... one side going through a check valve to the TB after the GM MAS that lets metered air into the VC and through the PCV at vaccum, and the other side of the Y going through a check valve that allows CC boost pressure to vent to atmosphere or turbo inlet, but not be pulled in at vaccum.

I think... but I'm drinking beer and my head hurts from all this thinking at the moment...

 

[kenamond]

While were at it: (In addition to the check valve between the PVC and IM) What if we put a check valve in between the airbox/breather, and the valve cover, only allowing are INTO the VC? Could there be any benefit there? I would think that will make sure it operates the way it is supposed to as well? Any potential harm there?

The only way out of the crankcase under boost is out the VC breather. The only way into the crankcase under vaccuum is the VC breather. It needs to go both ways. If you don't let air out of the crankcase (under boost), you pressurize it and pop a dipstick or something. If you don't let air into the crankcase (under vaccuum), you don't ventilate the crankcase with fresh air, so fuel and exhaust that's blown by the rings can settle in the oil.

 

[romeen]

But the port on the intake pipe is sucking air from the crankcase under boost.

I think the reason that this unmetered "air" may not play a significant role in the A/F ratios is that it really doesn't contain much oxygen at all. And of course it's really the oxygen in the air and how much there is relative to fuel that creates lean or rich conditions. It would probably be more accurate to refer to the crap being sucked out of the crankcase via the VC breather as unmetered blow-by vapors with minimal oxygen content. Unfortunately these vapors contaminate the air/fuel charge leading to less efficient combustion which is one reason that racers run vacuum pumps pumps like Bruce mentioned. I'm pretty sure these systems do not route the blow by vapors back into the intake for the reasons I mentioned.

I may be missing something (again ), but I believe the only "sucking" that is going on is through the PCV when the IM is at vaccum. When you are at boost, you are basically just venting any excess crankcase pressure through the VC vent. I would guess that having this vent hooked to the intake pre-turbo isn't causing any "sucking" per se... merely to ensure a lower pressure on that side so that the CC will always vent.

Again...Just my guess

The spinning compressor actually does create a fair amount of vacuum behind it. When we hear our turbos spooling what we are mainly hearing is air being sucked in to the intake. I think if you were to hold a piece of paper next to the air filter while under boost it would get pulled tight against it.


BTW Bruce, referring to post #53 don't think I didn't catch that "oldermeen" reference. But why do you have to rub it in? ......

 

[oldman]

That's pretty much what I was getting at with regards to the blow-through setup. To keep the desired functionality of the PCV system, you would need a Y arrangement at the VC breather side... one side going through a check valve to the TB after the GM MAS that lets metered air into the VC and through the PCV at vaccum, and the other side of the Y going through a check valve that allows CC boost pressure to vent to atmosphere or turbo inlet, but not be pulled in at vaccum.

I think... but I'm drinking beer and my head hurts from all this thinking at the moment...

That is ASSuming,

1. There will be enough vacuum in the crankcase to activate the check valve on the TB side which I doubt.

2. There will be enough vacuum in the intake pipe to activate the check vavle on the intake pipe side which I also question, now we're talking about sping ratings in the check valve.

The easiest solution for a blow through setup, like I already mentioned, is to tune it out or go back to a 2G mas setup, GM blow through is over rated anyway, I suspect your AFR issue probably has more to due with improper calibration of the GM maf, a known issue on the Link forum.

 

[oldman]

BTW Bruce, referring to post #53 don't think I didn't catch that "oldermeen" reference. But why do you have to rub it in? ......

Didn't think anyone caught that.

 

[Calan]

That is ASSuming,

1. There will be enough vacuum in the crankcase to activate the check valve on the TB side which I doubt.

2. There will be enough vacuum in the intake pipe to activate the check vavle on the intake pipe side which I also question, now we're talking about sping ratings in the check valve.

The easiest solution for a blow through setup, like I already mentioned, is to tune it out or go back to a 2G mas setup, GM blow through is over rated anyway, I suspect your AFR issue probably has more to due with improper calibration of the GM maf, a known issue on the Link forum.

Damn it Bruce... don't go ruining my beer-induced-mega-cool-overly-complicated miracle fix for us guys with the super cool whoosh sounding setup with your logic.

.oO Now where did I put that beer?

 

[Calan]

I think the reason that this unmetered "air" may not play a significant role in the A/F ratios is that it really doesn't contain much oxygen at all.

Ok... I see your point. But it still seems that for a given amount of "air"/fuel mix, there would be a fixed percentage of that mixture allocated to fuel. But again, I'm drinking... see previous post

The spinning compressor actually does create a fair amount of vacuum behind it. When we hear our turbos spooling what we are mainly hearing is air being sucked in to the intake. I think if you were to hold a piece of paper next to the air filter while under boost it would get pulled tight against it.

Ok.. I'll give you that one too I guess.

DAMN IT... I thought I was having some intelligent insight for a while there

 

[romeen]

Ok... I see your point. But it still seems that for a given amount of "air"/fuel mix, there would be a fixed percentage of that mixture allocated to fuel.

Actually you do have a point. I hope I didn't make it sound like I knew that to be true. I was considering other possibilities and hoping for feedback from you guys to see whether it was reasonable or not.

 

[Calan]

Romeen.... My points are usually a mixed bag of guesses, experience, theory, and good beer... take them for what they are worth

I guess Bruce is trailing in the dementia department.. (I hope he saw the other thread and understands that reference

 

[oldman]

I guess Bruce is trailing in the dementia department.. (I hope he saw the other thread and understands that reference

To quote towelly from South Park, "I have no idea what's going on?"

 

[MrBoxx]

Beer is going on, Bruce. You know all about that, right?

I'm still in the camp of an inline filter/catch can, like a Fram G2-style fuel filter, on the valve cover breather to catch oil gunk while allowing ventilation of the valve cover, and keeping the PCV valve in more or less stock form. I suppse I don't understand why some people have the attitude against the PCV valve like it ran over their dog.

 

[Calan]

I suppse I don't understand why some people have the attitude against the PCV valve like it ran over their dog.

 

[romeen]

R.I.P. Fido