Measuring crank case pressure

[Chris@VargasTurboTech]

I agree with this, mostly. I've even asked someone who measured this with a mechanical gauge and got nothing (at idle). There is also the question, why do people remove their filter or use very large ones, much larger than most of is? Clearly they are seeing benefit to running a massive filter to increase the surface area and reduce restriction. If there is restriction at high boost levels (aka high volume compressor CFM?) then there will be some vacuum generated, although it might be quite small. This supposed vacuum idea has been used as a sales pitch, so I'd like to quantify it in terms the value it brings for that specific marketing point.



No hard feelings, I think I was having a bad day. Facebook life drives you to the brink. Got people demanding me all day to act on their reports immediately, as if I'm their slave. Much easier to kick them out and stop paying the therapist.

Also, I spoke with @MoistNapkin he explained to me what he is doing. With a variable or two, I believe it could work for people who would like to run a single catch can and have what is effectively the same as a two can setup with high and low side.

Personally, I've taken it a step further:
View attachment 36767

This is all you need.

Anyone can understand this system, the only people who won't understand this are people who have been lead to believe it needs to be more complicated. But again, I'm going to take a little bit of data and see if this is sufficient. As you can tell, there isn't much labor or R&D to sell here.

Vaccum in your intake means restriction. Same as boost pressure means restriction. Remember pressure/vacuum and flow are not the same thing. Its why a fuel pump can flow some much more at 0 pressure because you have no restriction which is needed to create pressure. You want 0 vacuum in your intake. This does not mean flow. It means there are no restrictions to flow even when that flow demand increases. If your intake vacuum goes up as flow requirements increase it means your intake is restrictive to the flow needs of the engine. Some OEM's do build a little restriction into the intake to help the PCV system. Many OEM's these days put the PCV inlet as close to the compressor inlet as possible. Its the best way to get a working PCV system without building a little restriction into the system. If you look at the RS3. The PCV connects to the side of the intake pipe, but they actually cast a pathway that goes down to right in front of the wheel. Trying to maximize crankcase venting without adding restriction to the inlet.

 

[Cruizinmax]

Vaccum in your intake means restriction. Same as boost pressure means restriction. Remember pressure/vacuum and flow are not the same thing. Its why a fuel pump can flow some much more at 0 pressure because you have no restriction which is needed to create pressure. You want 0 vacuum in your intake. This does not mean flow. It means there are no restrictions to flow even when that flow demand increases. If your intake vacuum goes up as flow requirements increase it means your intake is restrictive to the flow needs of the engine. Some OEM's do build a little restriction into the intake to help the PCV system. Many OEM's these days put the PCV inlet as close to the compressor inlet as possible. Its the best way to get a working PCV system without building a little restriction into the system. If you look at the RS3. The PCV connects to the side of the intake pipe, but they actually cast a pathway that goes down to right in front of the wheel. Trying to maximize crankcase venting without adding restriction to the inlet.

There are ways to create vacuum in the intake path without restriction. OEM's have been doing it for years. Have you ever noticed many pcv fittings in the intake tube are often cut at a 45* angle?

 

[Chris@VargasTurboTech]

There are ways to create vacuum in the intake path without restriction. OEM's have been doing it for years. Have you ever noticed many pcv fittings in the intake tube are often cut at a 45* angle?

If you want to argue semantics go ahead, we are not going to indulge you. Tyler was talking about putting a port into his intake to measure vacuum. If he sees vacuum in his intake through that port, he is reading restriction. If you want to argue that is not the case, have a ball

 

[doublespaces]

I don't really know what we are talking about, but what I'm trying to do is pretty clear. This test will be depend on the filter you use and also if you use one at all.

Now that we've gotten that out of the way, we can all agree that some form of vacuum is behind the filter for some people, for some there may not. I'd like to measure any that may be there and I'd like to measure pressure in a couple different places.

When that is done I'll present my ventilation setup and likely point people toward it every time they say they don't understand the pcv setup. People complain about it being simple yet use a bunch of different hoses and check valves to accomplish a simple task in a complicated way, then wonder why people don't understand.

For fun, here is a photo that shows a venturi I was going to put into the intake pipe.


Being steel I decided against it considering the unlikely benefit and also my intake pipe is aluminum.

What I couldn't get answered for however, is if the restriction vacuum would compound or override(or be nullified) the Venturi vacuum in this scenario. I don't see a mathematical reason it would compound but never got any confirmation on that. It's a stupid question but this should be an easy one for someone. I'll consider putting the fitting in my downpipe instead. I've not seen any accurate readings down there either.

 

[noorj]

What I couldn't get answered for however, is if the restriction vacuum would compound or override(or be nullified) the Venturi vacuum in this scenario. I don't see a mathematical reason it would compound but never got any confirmation on that. It's a stupid question but this should be an easy one for someone. I'll consider putting the fitting in my downpipe instead. I've not seen any accurate readings down there either.

I would try to find an aluminum venturi or change your intake to a stainless tube to use the one you have. Any vacuum provided to the ventri will be added to the vacuum in the intake (say your compressor inlet pulls 5kPa @ WOT, venturi gives additional 2 kPa, you would then read 7kPa in the hose connecting the venturi to the crankcase.

 

[doublespaces]

I would try to find an aluminum venturi or change your intake to a stainless tube to use the one you have. Any vacuum provided to the ventri will be added to the vacuum in the intake (say your compressor inlet pulls 5kPa @ WOT, venturi gives additional 2 kPa, you would then read 7kPa in the hose connecting the venturi to the crankcase.

Oh really? I ordered this part hoping that might be the case and when it came time to install I had realized the intake was aluminum and began to assume the vacuum forces wouldn't be combined so I left it out.

 

[twinturbos]

This is your current setup?

If so, then in my opinion that is great. If you've got your head ports plugged, the only thing I'd suggest is instead of routing them to the air, route them to your intake pipe(pre turbo, not charge pipe) or run a hose from the cans under your car a bit so it doesn't smell by getting into your cabin filters.

This is essentially what I'm suggesting people should do, except my picture has just a single line. I'm going to test it with up to three ports however(two on back, one on front).

This is what I am currently working on. I have a dual catch can on the way but am still confused on the high/low side part since both come from the top of the valve cover. I was planning to run some hose under the car to avoid the nasty smell. At the same time I'm wondering if I should route this all the way to the back of the car just in case it could catch on fire from the fire coming out of the wastegates ? Is it flammable at all or should I not worry about it ?

 

[doublespaces]

This is what I am currently working on. I have a dual catch can on the way but am still confused on the high/low side part since both come from the top of the valve cover. I was planning to run some hose under the car to avoid the nasty smell. At the same time I'm wondering if I should route this all the way to the back of the car just in case it could catch on fire from the fire coming out of the wastegates ? Is it flammable at all or should I not worry about it ?

If your head ports are plugged and you don't intend to run a low side into the intake manifold/throttle body, then all you have is a pair of vents to think about and it will run fine that way. The crank case fumes have more of an oil build up risk than any thing else, so don't allow it to drip on something hot. Your catch can may not grab it all so there's a chance of oil dripping out of the hose over time. How much is probably dependent on your catch can and health of your engine. What I do know, is that more comes out of those vents than if you have the typical high/low side. All that gunk that normally gets sucked into your engine through the low side will now get pushed out the vent.

If you look at the photo I posted, plugged head ports is the only prerequisite. Then any orifice on your valve cover becomes a normal vent hole, so long as you don't start putting check valves on them and running them into the engine. Just vent them.

 

[noorj]

Oh really? I ordered this part hoping that might be the case and when it came time to install I had realized the intake was aluminum and began to assume the vacuum forces wouldn't be combined so I left it out.

Yeah because the venturi creates a pressure delta, the absolute pressure it's under doesn't really matter, it will still create it's delta pressure thus improving your crankcase scavenging. Another way to think of this would be, does a venturi still work in Colorado at elevation (say 85kPa baro)? Yep, therefore it will definitely work for your case.

Either way interested to see your results!

 

[JimboFresh206]

So you guys are planning on putting a pan evac venturi on the intake?

Its been done, Im not sure of the effectiveness, but interested in the results.

Would be cool if this works, because the speed-tech inlet is perfect for it.