Baffled about baffles - oil filler baffle
05-06-2015, 10:58 AM
#1
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Baffled about baffles - oil filler baffle
So I'm working on my 85 and not sure what to do about my oil filler baffle. Being an 85 my car has the metal filler neck with the separate louvered baffle. I see a number of aftermarket options are available and after a lot of reading have seen positive and negative comments about nearly all of them. Here are the options as I see them:
1) Keep the stock one and RTV it in place
2) 928 Motorsports version. Unless I'm missing something this doesn't seem much different than the stock one.
3) GB version
4) Kuhn version (which integrates a scrubber)
I'm in the middle of an intake refresh and there seemed to me to be quite a bit of oil in my intake (this car is SC'd) so I'm feeling I should do something more than the stock baffle. What say you?
1) Keep the stock one and RTV it in place
2) 928 Motorsports version. Unless I'm missing something this doesn't seem much different than the stock one.
3) GB version
4) Kuhn version (which integrates a scrubber)
I'm in the middle of an intake refresh and there seemed to me to be quite a bit of oil in my intake (this car is SC'd) so I'm feeling I should do something more than the stock baffle. What say you?
05-06-2015, 11:00 AM
#2
I've not heard, or have, a single complaint with Greg Browns baffle. Used them many times. What I do suggest is using the 78-79 paper gasket and Victor Reinz to seal it up.
05-06-2015, 11:13 AM
#3
Rennlist Member
I have used the GB version - and the only complaint/suggestion I heard was the design be curved slightly to allow the baffle to be installed without having to remove/loosen the water bridge.
05-06-2015, 11:19 AM
#4
Administrator - "Tyson"
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GB version going in my cars.
05-06-2015, 11:54 AM
#5
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Thanks guys... I was hoping not to mess with the water bridge but I guess that wouldn't be a big deal. Do you know if the Kuhn version would require the removal of the water bridge?
05-06-2015, 11:58 AM
#6
Nordschleife Master
In my opinion, it matters to the baffle design and selection whether your priority is to flow a lot of gas out of the oil filler neck and don't care so much about the air-oil separation or whether your priority is to separate air and oil efficiently and don't care so much about flowing the maximum amount of gas out of the oil filler neck.
05-06-2015, 01:19 PM
#7
Former Sponsor
My design incorporates the stock baffle, for optimum results.
I'm not sure I could get enough depth, volume, and internal baffling to build a version which could be installed without removing the water cross-over.
There's a bunch going on with internal velocities that helps separate the oil from the "mist".
Since almost every water cross-over needs a new large O-ring where it seals into the block, this wasn't one of my design considerations.
All my pieces come with a money back guarantee....they flat out work! I'm not building stuff that "might work" or looks like it "should work". My stuff is designed, throughly tested, and proven, long before anyone gets an opportunity to buy it!
I'm not sure I could get enough depth, volume, and internal baffling to build a version which could be installed without removing the water cross-over.
There's a bunch going on with internal velocities that helps separate the oil from the "mist".
Since almost every water cross-over needs a new large O-ring where it seals into the block, this wasn't one of my design considerations.
All my pieces come with a money back guarantee....they flat out work! I'm not building stuff that "might work" or looks like it "should work". My stuff is designed, throughly tested, and proven, long before anyone gets an opportunity to buy it!
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05-06-2015, 03:13 PM
#8
Former Sponsor
In my opinion, it matters to the baffle design and selection whether your priority is to flow a lot of gas out of the oil filler neck and don't care so much about the air-oil separation or whether your priority is to separate air and oil efficiently and don't care so much about flowing the maximum amount of gas out of the oil filler neck.
I've found no way to contain (or separate) the shear volume of oil that gets "stuffed" into that "funnel" area of the block at higher rpms....there's oil being slung off of the crankshaft and also oil being "whipped" up by the crankshaft out of the oil sump.
In every one of my "oil control systems", I vent the crankcase breather exclusively back to the valve cover....and do not allow the crankcase breather to vent directly to the intake system, as originally designed (on all of the 32 valve models.)
In testing, I found that a "scrubber" in the crankcase breather area restricts the air/oil flow (at higher rpms) to the point where the crankcase pressure builds {enough to try to push out (or actually accomplish pushing out) every scrubber we tried.}
Every one of my products helps some.....lowering the oil pan as much as practical (with one of my oil pan spacers) moves the oil level farther away from the crankshaft. (All of my oil pan spacer kits comes with a oil pick-up lowering kit, too.)
A simple windage tray system which allows oil from the crankshaft to pass through the windage trays and then blocks the from oil bouncing back helps. (I make these, of course.) One needs to be careful, with this....too complex of a windage tray can actually "block" the oil that is trying to return to the pan and may cause more problems than it cures.
In short, the problem is not a simple one with a "single point of attack" solution.....but certainly one of my oil filler neck baffles, incorporated with the stock baffle, is the first step.
05-06-2015, 04:55 PM
#9
Nordschleife Master
Point that I was trying to make is that each piece should be consistent with the overall solution approach that the person is taking.
I believe that the pan spacer works. It works for two reasons. First, as you said, it keeps the oil level further away from the crankshaft. Second, it provides a larger cross-sectional area for the piston pumping pulses to communicate between bays in the pan, which in turn means that the piston pumping pulses don't have to communicate thru the valve covers while disturbing the oil drain.
The windage trays can help or hurt. They can help if they prevent the oil rebounding from the pan into to the crank or sloshing into the crank from the car g-forces. They can hurt if they slow down oil drain (a less likely problem in my opinion) or if they direct the piston pumping pulses in a counterproductive way (a more likely problem in my opinion).
In my opinion, for a large displacement V8, it's not worth it to try to get the windage tray or the scraper very close to the crankshaft -- the costs will likely exceed the potential benefits.
John Kuhn makes a baffle with and without the "scrubber." Without a question, the scrubber reduces gas flow compared to the baffle without a scrubber. However, one should keep in mind that there are many different kinds of scrubbers and one generally trades off gas flow vs. oil separation.
Out of curiosity, have you measured the (net) gas flow direction in the hose that connects the oil filler neck and the cam cove in your system? It's going to pulse without a question and flow in both directions, but what's the net flow direction?
I believe that the pan spacer works. It works for two reasons. First, as you said, it keeps the oil level further away from the crankshaft. Second, it provides a larger cross-sectional area for the piston pumping pulses to communicate between bays in the pan, which in turn means that the piston pumping pulses don't have to communicate thru the valve covers while disturbing the oil drain.
The windage trays can help or hurt. They can help if they prevent the oil rebounding from the pan into to the crank or sloshing into the crank from the car g-forces. They can hurt if they slow down oil drain (a less likely problem in my opinion) or if they direct the piston pumping pulses in a counterproductive way (a more likely problem in my opinion).
In my opinion, for a large displacement V8, it's not worth it to try to get the windage tray or the scraper very close to the crankshaft -- the costs will likely exceed the potential benefits.
John Kuhn makes a baffle with and without the "scrubber." Without a question, the scrubber reduces gas flow compared to the baffle without a scrubber. However, one should keep in mind that there are many different kinds of scrubbers and one generally trades off gas flow vs. oil separation.
Out of curiosity, have you measured the (net) gas flow direction in the hose that connects the oil filler neck and the cam cove in your system? It's going to pulse without a question and flow in both directions, but what's the net flow direction?
There's actually no single piece that one can insert under the filler neck to cure all the "evils of design".....everything is a compromise, of sorts.
I've found no way to contain (or separate) the shear volume of oil that gets "stuffed" into that "funnel" area of the block at higher rpms....there's oil being slung off of the crankshaft and also oil being "whipped" up by the crankshaft out of the oil sump.
In every one of my "oil control systems", I vent the crankcase breather exclusively back to the valve cover....and do not allow the crankcase breather to vent directly to the intake system, as originally designed (on all of the 32 valve models.)
In testing, I found that a "scrubber" in the crankcase breather area restricts the air/oil flow (at higher rpms) to the point where the crankcase pressure builds {enough to try to push out (or actually accomplish pushing out) every scrubber we tried.}
Every one of my products helps some.....lowering the oil pan as much as practical (with one of my oil pan spacers) moves the oil level farther away from the crankshaft. (All of my oil pan spacer kits comes with a oil pick-up lowering kit, too.)
A simple windage tray system which allows oil from the crankshaft to pass through the windage trays and then blocks the from oil bouncing back helps. (I make these, of course.) One needs to be careful, with this....too complex of a windage tray can actually "block" the oil that is trying to return to the pan and may cause more problems than it cures.
In short, the problem is not a simple one with a "single point of attack" solution.....but certainly one of my oil filler neck baffles, incorporated with the stock baffle, is the first step.
I've found no way to contain (or separate) the shear volume of oil that gets "stuffed" into that "funnel" area of the block at higher rpms....there's oil being slung off of the crankshaft and also oil being "whipped" up by the crankshaft out of the oil sump.
In every one of my "oil control systems", I vent the crankcase breather exclusively back to the valve cover....and do not allow the crankcase breather to vent directly to the intake system, as originally designed (on all of the 32 valve models.)
In testing, I found that a "scrubber" in the crankcase breather area restricts the air/oil flow (at higher rpms) to the point where the crankcase pressure builds {enough to try to push out (or actually accomplish pushing out) every scrubber we tried.}
Every one of my products helps some.....lowering the oil pan as much as practical (with one of my oil pan spacers) moves the oil level farther away from the crankshaft. (All of my oil pan spacer kits comes with a oil pick-up lowering kit, too.)
A simple windage tray system which allows oil from the crankshaft to pass through the windage trays and then blocks the from oil bouncing back helps. (I make these, of course.) One needs to be careful, with this....too complex of a windage tray can actually "block" the oil that is trying to return to the pan and may cause more problems than it cures.
In short, the problem is not a simple one with a "single point of attack" solution.....but certainly one of my oil filler neck baffles, incorporated with the stock baffle, is the first step.
05-06-2015, 05:43 PM
#10
Archive Gatekeeper
Rennlist Member
Rennlist Member
have you measured the (net) gas flow direction in the hose that connects the oil filler neck and the cam cove in your system?
Apologies, answering questions with questions is never satisying. Especially good questions.
05-06-2015, 06:01 PM
#11
Nordschleife Master
When you say 'measure' the implication is that you want quantitative data. What sort of instrumentation would be capable of measuring such flows? do you stick a tiny anemometer in there and measure the wind speed? Or the bulk flow of entrained liquid in the flow? Or ??? And what sampling rate would one have to have to be able to 'see' shifts in flow in a hose that could be correlated with rpm/throttle position/injector duty cycle/whatever? Would just knowing the direction of gas or liquid flow be enough in conjunction with other engine data? Apologies, answering questions with questions is never satisying. Especially good questions.
Specifically, here's how I am planning to measure it. Run a hose from the valve cover to an empty canister. Run another hose from the oil filler neck to another canister. Connect the two canisters with a hose with a blowby meter. Run the car at max load and rpm on a dyno, and measure the flow in each direction. Two runs needed since the blowby meter that i have measures only the flow in one direction at the time. The role of the canisters is to dampen the pulses a little bit and to get more consistent measurements.
This should work, right?
05-06-2015, 08:20 PM
#12
Former Sponsor
Point that I was trying to make is that each piece should be consistent with the overall solution approach that the person is taking.
I believe that the pan spacer works. It works for two reasons. First, as you said, it keeps the oil level further away from the crankshaft. Second, it provides a larger cross-sectional area for the piston pumping pulses to communicate between bays in the pan, which in turn means that the piston pumping pulses don't have to communicate thru the valve covers while disturbing the oil drain.
The windage trays can help or hurt. They can help if they prevent the oil rebounding from the pan into to the crank or sloshing into the crank from the car g-forces. They can hurt if they slow down oil drain (a less likely problem in my opinion) or if they direct the piston pumping pulses in a counterproductive way (a more likely problem in my opinion).
In my opinion, for a large displacement V8, it's not worth it to try to get the windage tray or the scraper very close to the crankshaft -- the costs will likely exceed the potential benefits.
John Kuhn makes a baffle with and without the "scrubber." Without a question, the scrubber reduces gas flow compared to the baffle without a scrubber. However, one should keep in mind that there are many different kinds of scrubbers and one generally trades off gas flow vs. oil separation.
Out of curiosity, have you measured the (net) gas flow direction in the hose that connects the oil filler neck and the cam cove in your system? It's going to pulse without a question and flow in both directions, but what's the net flow direction?
I believe that the pan spacer works. It works for two reasons. First, as you said, it keeps the oil level further away from the crankshaft. Second, it provides a larger cross-sectional area for the piston pumping pulses to communicate between bays in the pan, which in turn means that the piston pumping pulses don't have to communicate thru the valve covers while disturbing the oil drain.
The windage trays can help or hurt. They can help if they prevent the oil rebounding from the pan into to the crank or sloshing into the crank from the car g-forces. They can hurt if they slow down oil drain (a less likely problem in my opinion) or if they direct the piston pumping pulses in a counterproductive way (a more likely problem in my opinion).
In my opinion, for a large displacement V8, it's not worth it to try to get the windage tray or the scraper very close to the crankshaft -- the costs will likely exceed the potential benefits.
John Kuhn makes a baffle with and without the "scrubber." Without a question, the scrubber reduces gas flow compared to the baffle without a scrubber. However, one should keep in mind that there are many different kinds of scrubbers and one generally trades off gas flow vs. oil separation.
Out of curiosity, have you measured the (net) gas flow direction in the hose that connects the oil filler neck and the cam cove in your system? It's going to pulse without a question and flow in both directions, but what's the net flow direction?
That was pretty much the end of my "scrubber" experiment.....and when I really became aware of the volume of oil (and the pressure) that gets packed into the "built in funnel" under the filler neck.
Up to this point in time, I had been running the baffle that 928 International was having built. I immediately started a design and development project to better separate the oil from the air.
The result of that development is my current baffle. I've sold almost 100 of those baffles and have had only one returned....and that one was returned because the customer used an entire tube of Drei Bond to glue it in with....and after a couple of days, decided to remove it, to be more conservative with the sealant. He "attacked" that baffle with a screwdriver, from one end (in order to pry it out.) Needless to say, this bent the crap out of this poor piece of aluminum. He was unhappy that we had not built the baffle out of a stronger material, which would not have allowed the baffle to be bent. I replaced the baffle for him, suggesting that a tiny bead of Drei Bond would be more appropriate...and if he wanted to remove it, in the future, running a razor blade between the block and the baffle might be helpful.
Last edited by GregBBRD; 05-06-2015 at 08:40 PM.
05-06-2015, 09:17 PM
#13
Nordschleife Master
There's scrubber and then there's scrubber. Coarse and strong material does not behave the way you describe. Hell, I can have one made from open cell aluminum foam that is used in certain rocket fuel cells. However, the scrubber does reduce gas outflow if it removes oil and if it doesn't reduce gas outflow then it doesn't remove oil.
(Car factories mostly use the labyrinth design, impactors, cyclones, and usually not scrubbers. Although the Mahle design in my AMG E63S Wagon has a scrubber type fiber at the end of the impactor. The difference there is that all the blowby gas doesn't have to flow thru the "scrubber".)
Someone smart here once said that there's no substitute to volume in passive (not powered centrifugal) air-oil separator designs. I'd augment that to say that there's also no substitute for horizontal cross-sectional area. The 928 block chimney has a certain area, which from memory is about 115mm x 50mm at it's widest point -- don't quote that number it's a vague recollection! Let's be conservative and say it's 0.004 m^2 of area after baffling and whatnot. Oil separates from air if you flow the mixture up at a rate less than 1 m/s. This gives a physical limitation to the chimney as a volume separator, it'll only handle 8.5 CFM of blowby flow while still separating oil and air even int he best case scenario. This assumes that we've shielded the chimney from direct oil spray, that is, with a baffle in there. Once the blowby flow from the chimney goes over 8.5 CFM, it should by my math start puking oil even if the direct spray is blocked by a baffle. Similar math gives about 4 CFM limit to the shroud tubes inside the valve covers. Once the blowby rate goes above 4 CFM, oil is ejected from the valve cover ports that have the stock separator shroud.
Given these physical limitations, I would want to limit the gas flow out of the oil filler neck to less than that 8.5 CFM and to less than 4 CFM from each of the cam cover ports. The factory tried to accomplish this by metering orifice/orifices in the valve cover port elbows. Many of us simply drill those elbows to maximum size (me including), but that creates the risk of flowing too much gas out of there at which point the shroud tube no longer separates. I've come to the conclusion that if one vents out of the valve covers using the stock shroud tubes and doesn't have a separate external separator, then one should calibrate a restrictor pill to the hose out of each elbow such that the combination of the restrictor orifice cross-sectional area and the pressure inside the cam covers results in a flow rate that is below 4 CFM.
What's my point here? I think that the crankcase breather system needs to be designed as a system with a coherent strategy of where and how gas flows at what rates and where the separation of air and oil is supposed to happen and by what mechanism. Picking and choosing pieces a la carte may lead to disappointing results even if each individual piece is high quality.
(Car factories mostly use the labyrinth design, impactors, cyclones, and usually not scrubbers. Although the Mahle design in my AMG E63S Wagon has a scrubber type fiber at the end of the impactor. The difference there is that all the blowby gas doesn't have to flow thru the "scrubber".)
Someone smart here once said that there's no substitute to volume in passive (not powered centrifugal) air-oil separator designs. I'd augment that to say that there's also no substitute for horizontal cross-sectional area. The 928 block chimney has a certain area, which from memory is about 115mm x 50mm at it's widest point -- don't quote that number it's a vague recollection! Let's be conservative and say it's 0.004 m^2 of area after baffling and whatnot. Oil separates from air if you flow the mixture up at a rate less than 1 m/s. This gives a physical limitation to the chimney as a volume separator, it'll only handle 8.5 CFM of blowby flow while still separating oil and air even int he best case scenario. This assumes that we've shielded the chimney from direct oil spray, that is, with a baffle in there. Once the blowby flow from the chimney goes over 8.5 CFM, it should by my math start puking oil even if the direct spray is blocked by a baffle. Similar math gives about 4 CFM limit to the shroud tubes inside the valve covers. Once the blowby rate goes above 4 CFM, oil is ejected from the valve cover ports that have the stock separator shroud.
Given these physical limitations, I would want to limit the gas flow out of the oil filler neck to less than that 8.5 CFM and to less than 4 CFM from each of the cam cover ports. The factory tried to accomplish this by metering orifice/orifices in the valve cover port elbows. Many of us simply drill those elbows to maximum size (me including), but that creates the risk of flowing too much gas out of there at which point the shroud tube no longer separates. I've come to the conclusion that if one vents out of the valve covers using the stock shroud tubes and doesn't have a separate external separator, then one should calibrate a restrictor pill to the hose out of each elbow such that the combination of the restrictor orifice cross-sectional area and the pressure inside the cam covers results in a flow rate that is below 4 CFM.
What's my point here? I think that the crankcase breather system needs to be designed as a system with a coherent strategy of where and how gas flows at what rates and where the separation of air and oil is supposed to happen and by what mechanism. Picking and choosing pieces a la carte may lead to disappointing results even if each individual piece is high quality.
On the engine that we tested the "scrubber" on, there was little need to try and measure the direction. I was not venting the filler neck area to the valve cover on this particular test, but was running a -12 hose wide open to atmosphere, so I could get a visual idea of the amount of air and oil that was coming out of this area. After about 30 seconds at 6,000 rpms, chunks of the scrubber started flying out the end of the hose that was attached to the filler neck. Eventually, the entire scrubber came out the end of the -12 hose....along with a fountain of oil.
That was pretty much the end of my "scrubber" experiment.....and when I really became aware of the volume of oil that gets packed into the "built in funnel" under the filler neck.
Up to this point in time, I had been running the baffle that 928 International was having built. I immediately started a design and development project to better separate the oil from the air.
The result of that development is my current baffle. I've sold almost 100 of those baffles and have had only one returned....and that one was returned because the customer used an entire tube of Drei Bond to glue it in with....and after a couple of days, decided to remove it, to be more conservative with the sealant. He "attacked" that baffle with a screwdriver, from one end (in order to pry it out.) Needless to say, this bent the crap out of this poor piece of aluminum. He was unhappy that we had not built the baffle out of a stronger material, which would not have allowed the baffle to be bent. I replaced the baffle for him, suggesting that a tiny bead of Drei Bond would be more appropriate...and if he wanted to remove it, in the future, running a razor blade between the block and the baffle might be helpful.
That was pretty much the end of my "scrubber" experiment.....and when I really became aware of the volume of oil that gets packed into the "built in funnel" under the filler neck.
Up to this point in time, I had been running the baffle that 928 International was having built. I immediately started a design and development project to better separate the oil from the air.
The result of that development is my current baffle. I've sold almost 100 of those baffles and have had only one returned....and that one was returned because the customer used an entire tube of Drei Bond to glue it in with....and after a couple of days, decided to remove it, to be more conservative with the sealant. He "attacked" that baffle with a screwdriver, from one end (in order to pry it out.) Needless to say, this bent the crap out of this poor piece of aluminum. He was unhappy that we had not built the baffle out of a stronger material, which would not have allowed the baffle to be bent. I replaced the baffle for him, suggesting that a tiny bead of Drei Bond would be more appropriate...and if he wanted to remove it, in the future, running a razor blade between the block and the baffle might be helpful.
05-07-2015, 02:48 AM
#14
Former Sponsor
There's scrubber and then there's scrubber. Coarse and strong material does not behave the way you describe. Hell, I can have one made from open cell aluminum foam that is used in certain rocket fuel cells. However, the scrubber does reduce gas outflow if it removes oil and if it doesn't reduce gas outflow then it doesn't remove oil.
(Car factories mostly use the labyrinth design, impactors, cyclones, and usually not scrubbers. Although the Mahle design in my AMG E63S Wagon has a scrubber type fiber at the end of the impactor. The difference there is that all the blowby gas doesn't have to flow thru the "scrubber".)
Someone smart here once said that there's no substitute to volume in passive (not powered centrifugal) air-oil separator designs. I'd augment that to say that there's also no substitute for horizontal cross-sectional area. The 928 block chimney has a certain area, which from memory is about 115mm x 50mm at it's widest point -- don't quote that number it's a vague recollection! Let's be conservative and say it's 0.004 m^2 of area after baffling and whatnot. Oil separates from air if you flow the mixture up at a rate less than 1 m/s. This gives a physical limitation to the chimney as a volume separator, it'll only handle 8.5 CFM of blowby flow while still separating oil and air even int he best case scenario. This assumes that we've shielded the chimney from direct oil spray, that is, with a baffle in there. Once the blowby flow from the chimney goes over 8.5 CFM, it should by my math start puking oil even if the direct spray is blocked by a baffle. Similar math gives about 4 CFM limit to the shroud tubes inside the valve covers. Once the blowby rate goes above 4 CFM, oil is ejected from the valve cover ports that have the stock separator shroud.
Given these physical limitations, I would want to limit the gas flow out of the oil filler neck to less than that 8.5 CFM and to less than 4 CFM from each of the cam cover ports. The factory tried to accomplish this by metering orifice/orifices in the valve cover port elbows. Many of us simply drill those elbows to maximum size (me including), but that creates the risk of flowing too much gas out of there at which point the shroud tube no longer separates. I've come to the conclusion that if one vents out of the valve covers using the stock shroud tubes and doesn't have a separate external separator, then one should calibrate a restrictor pill to the hose out of each elbow such that the combination of the restrictor orifice cross-sectional area and the pressure inside the cam covers results in a flow rate that is below 4 CFM.
What's my point here? I think that the crankcase breather system needs to be designed as a system with a coherent strategy of where and how gas flows at what rates and where the separation of air and oil is supposed to happen and by what mechanism. Picking and choosing pieces a la carte may lead to disappointing results even if each individual piece is high quality.
(Car factories mostly use the labyrinth design, impactors, cyclones, and usually not scrubbers. Although the Mahle design in my AMG E63S Wagon has a scrubber type fiber at the end of the impactor. The difference there is that all the blowby gas doesn't have to flow thru the "scrubber".)
Someone smart here once said that there's no substitute to volume in passive (not powered centrifugal) air-oil separator designs. I'd augment that to say that there's also no substitute for horizontal cross-sectional area. The 928 block chimney has a certain area, which from memory is about 115mm x 50mm at it's widest point -- don't quote that number it's a vague recollection! Let's be conservative and say it's 0.004 m^2 of area after baffling and whatnot. Oil separates from air if you flow the mixture up at a rate less than 1 m/s. This gives a physical limitation to the chimney as a volume separator, it'll only handle 8.5 CFM of blowby flow while still separating oil and air even int he best case scenario. This assumes that we've shielded the chimney from direct oil spray, that is, with a baffle in there. Once the blowby flow from the chimney goes over 8.5 CFM, it should by my math start puking oil even if the direct spray is blocked by a baffle. Similar math gives about 4 CFM limit to the shroud tubes inside the valve covers. Once the blowby rate goes above 4 CFM, oil is ejected from the valve cover ports that have the stock separator shroud.
Given these physical limitations, I would want to limit the gas flow out of the oil filler neck to less than that 8.5 CFM and to less than 4 CFM from each of the cam cover ports. The factory tried to accomplish this by metering orifice/orifices in the valve cover port elbows. Many of us simply drill those elbows to maximum size (me including), but that creates the risk of flowing too much gas out of there at which point the shroud tube no longer separates. I've come to the conclusion that if one vents out of the valve covers using the stock shroud tubes and doesn't have a separate external separator, then one should calibrate a restrictor pill to the hose out of each elbow such that the combination of the restrictor orifice cross-sectional area and the pressure inside the cam covers results in a flow rate that is below 4 CFM.
What's my point here? I think that the crankcase breather system needs to be designed as a system with a coherent strategy of where and how gas flows at what rates and where the separation of air and oil is supposed to happen and by what mechanism. Picking and choosing pieces a la carte may lead to disappointing results even if each individual piece is high quality.
Good luck with all that internet gathered theory....I'm more of a "develop until it works in the real world" kind of guy.
05-07-2015, 06:18 AM
#15
Nordschleife Master
I'm having fun reading books and learning about these things.
Good luck to you, too.
Good luck to you, too.