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There is no baffling on the same side parallel to the oem hole, so you would see more oil coming from there into your catch can. Doing this and just putting an air filter on both ports would produce similar results to my first test with VTA and would not maintain vacuum under all conditions = less efficient than sealed setup.
I disagree with you, and take it from someone who actually tried it, there was no more oil in the catch can than when I had it recirculated in the air filter pipe, when I had a catch can, now they are both completely vented, no filters, no catch can.
No, my testing has shown me that it has less than 0 under boost, marginally less, but still less. This test was done 6 years ago.
Of course there are baffles on both sides :
Marios
Last edited by Evo8cy; Aug 15, 2017 at 12:54 PM.
Reason: typo/added pic
Thank you for your response. Having performed this test several years back (~33psi GTX3576r) and posting the results I am familiar with the subject. To summarize my results I saw little to no difference between VTA and a closed catch can and neither produced vacuum on the block. I was venting from both the oil cap breather as well as the stock intake manifold PCV using a press-in -10 fitting as shown below.
I don't doubt your results, but when looking at your setup it would seem your intake filter is sized insufficiently for the flow you require at 40psi. If you look at my setup I have a 12" filter with a 5" opening hooked to a velocity stack and that was barely enough to meet my flow requirements with the recommended pressure drop.
My point is that if you under size the intake filter it will cause a large pressure drop across the filter leading the turbo inlet to create excessive vacuum. If you were to remove the intake filter and repeat the test I suspect you would not see any difference when comparing VTA vs closed catch can. Again, not doubting or criticizing your results, but it might be dependent on other variables as you previously stated.
Thank you for your response. Having performed this test several years back (~33psi GTX3576r) and posting the results I am familiar with the subject. To summarize my results I saw little to no difference between VTA and a closed catch can and neither produced vacuum on the block. I was venting from both the oil cap breather as well as the stock intake manifold PCV using a press-in -10 fitting as shown below.
I don't doubt your results, but when looking at your setup it would seem your intake filter is sized insufficiently for the flow you require at 40psi. If you look at my setup I have a 12" filter with a 5" opening hooked to a velocity stack and that was barely enough to meet my flow requirements with the recommended pressure drop.
My point is that if you under size the intake filter it will cause a large pressure drop across the filter leading the turbo inlet to create excessive vacuum. If you were to remove the intake filter and repeat the test I suspect you would not see any difference when comparing VTA vs closed catch can. Again, not doubting or criticizing your results, but it might be dependent on other variables as you previously stated.
Interesting point regarding the filter.... dont think I am having an issue with the intake creating too much vacuum. I'm running a 3.5" opening on a 8" filter and with as high as 45 psi never experienced anything abnormal.
Interesting point regarding the filter.... dont think I am having an issue with the intake creating too much vacuum. I'm running a 3.5" opening on a 8" filter and with as high as 45 psi never experienced anything abnormal.
I don't want to say its an issue, but a matter of efficiency. When you size a filter the flow (cfm) is based on a standard pressure drop. In the case of K&N they take the flow reading (cfm) when the pressure differential is 1.5" H20 using a SuperFlow flow bench. So it you want to make 700hp you want a filter to flow ~700 x 1.5= 1050cfm at standard pressure drop. Pumps, such as a turbo, are not designed to have restrictions on the inlet side as it affects the efficiency/flow.
Let's say your filter only flows 500cfm at standard pressure drop and you are trying to make 700hp with it. It is not that the filter can't flow 1000cfm, but the pressure drop across the filter will be significantly higher. What this means is the turbo inlet tube is creating additional vacuum pressure because the filter is a restriction. This is really no different than sizing an intercooler, flow vs efficiency vs pressure drop.
If you pulled your filter off and hooked a vacuum gauge to the turbo inlet and compared it to the readings with filter on you will see a substantial difference especially at 40psi.
240z is on the case...
1000CFM through a 3.5" tube would generate about 0.5psi of dynamic pressure...if my numbers are correct (spent about 1 minute on it so I could be off). If you are seeing 1psi or more of vacuum...it's because of inlet restriction.
Venting back into the intake track has pros and cons. No amount of baffling is going to take out all the oil vapor from the air so you will be injecting oil into the intake system. It does have the benefit of reducing moisture build up in the catch can though, which is probably like 3/4 of the fluid volume you will end up with in there.
I go for the vent to atmosphere method simply because I don't want oil contamination in the intake track as it reduces intercooler efficiency and potentially lowers detonation resistance.
Last edited by 03whitegsr; Aug 15, 2017 at 04:41 PM.
I don't want to say its an issue, but a matter of efficiency. When you size a filter the flow (cfm) is based on a standard pressure drop. In the case of K&N they take the flow reading (cfm) when the pressure differential is 1.5" H20 using a SuperFlow flow bench. So it you want to make 700hp you want a filter to flow ~700 x 1.5= 1050cfm at standard pressure drop. Pumps, such as a turbo, are not designed to have restrictions on the inlet side as it affects the efficiency/flow.
Let's say your filter only flows 500cfm at standard pressure drop and you are trying to make 700hp with it. It is not that the filter can't flow 1000cfm, but the pressure drop across the filter will be significantly higher. What this means is the turbo inlet tube is creating additional vacuum pressure because the filter is a restriction. This is really no different than sizing an intercooler, flow vs efficiency vs pressure drop.
If you pulled your filter off and hooked a vacuum gauge to the turbo inlet and compared it to the readings with filter on you will see a substantial difference especially at 40psi.
240z is on the case...
1000CFM through a 3.5" tube would generate about 0.5psi of dynamic pressure...if my numbers are correct (spent about 1 minute on it so I could be off). If you are seeing 1psi or more of vacuum...it's because of inlet restriction.
Venting back into the intake track has pros and cons. No amount of baffling is going to take out all the oil vapor from the air so you will be injecting oil into the intake system. It does have the benefit of reducing moisture build up in the catch can though, which is probably like 3/4 of the fluid volume you will end up with in there.
I go for the vent to atmosphere method simply because I don't want oil contamination in the intake track as it reduces intercooler efficiency and potentially lowers detonation resistance.
^
1.)I make a disclaimer several times that there are different ways to do this and get different results.
2.)this was done for general knowledge of people with similar setups or considering similar setup, not to start a debate. Use the information as you see fit.
3.)in reference to your comment, if you watch the video i clearly point out the second catch can off the PCV which remained unchanged for the test. venting off the block is really not necessary on these cars unless you have excessive blow by. You want to keep the oil in the engine and reduce pressure at the same time. I have proven this system is working efficiently at that without having to vent the block itself. Your Mazda may be different but that's a whole other application.
No matter what you post here, there will always be at least one person that will want to argue it in some way, make you justify your post, and/or go off an a tangent.
No worries, we get what you are saying.
I'm taking mental notes on this thread and bookmarking it for the info above. That's good stuff. I need to make me a notebook or something with all these tidbits of info.
No matter what you post here, there will always be at least one person that will want to argue it in some way, make you justify your post, and/or go off an a tangent.
No worries, we get what you are saying.
I'm taking mental notes on this thread and bookmarking it for the info above. That's good stuff. I need to make me a notebook or something with all these tidbits of info.
There are definitely lots of aspects to consider when choosing between VTA and sealed.
Main considerations I see are:
- Keeping crankcase pressure under control.
- Removing moisture and fuel from crankcase.
- Polluting intake track with oil vapor.
In my mind, the #1 issue is keeping the crankcase free of contamination. If that's not happening, engine life will be significantly reduced, especially on E85. A working sealed system that pulls air through the valve cover is the best for keeping the crankcase clean. However, an improperly designed sealed system that only pulls a vacuum without allowing fresh air to enter the crankcase is a step backwards for removing contamination because it prevents dry air from entering that can better pull out water vapor and fuel. A properly designed sealed system will maintain the two key elements of the factory system - the PCV system that pulls on the crankcase and the breather attached to the intake pipe. As the PCV pulls on the crankcase, the breather draws in fresh air. A check valve that safeguards against a backfire will prevent that needed airflow, so I suggest against using one. If the force of a backfire makes it all the way to the intake pipe with sufficient intensity to pressurize the crankcase, a lot of other worse things will also be occurring.
One other comment is that if you want to maximize crankcase vacuum under boost, redo your connection on the intake pipe to make it a 45 degree merge and then add a little shield inside the intake pipe on the upstream side of where the breather line enters the intake pipe.
Aug 15, 2017, 11:45 AM
