How to do the boosted car crankcase breathing right
03-13-2015, 05:16 PM
#137
Nordschleife Master
Thread Starter
You can quite easily attach a vacuum gauge to the head breather ports or the OFN ports - as to data logging it automatically - you need the same sensor and a PC acquisition method. Do-able.
More interesting still is logging the actual blow-by volume at the same time with some kind of flow meter (Tuomo has one)
The dipstick tube is harder to attach to reliably. The other issue there for normal running is making sure the dipstick (and tube to pan) actually seals well.
More interesting still is logging the actual blow-by volume at the same time with some kind of flow meter (Tuomo has one)
The dipstick tube is harder to attach to reliably. The other issue there for normal running is making sure the dipstick (and tube to pan) actually seals well.
The problem is that the flow out the chimney in the block and the breather ports in the heads is nothing like steady flow. It's huge pulses, not dampened by the oil pan like in many other V8's because our oil pan volume is so small. So you'd really need high-speed pressure transducers, which I also own but it's a 50 hour project to hook that stuff up.
I have a research plan on this with long list of experiments. I thought I'd get something done early this year, but instead I am up to my eyeballs in European export firms financials. Maybe I'll get something done in Q2 on this.
It's interesting that ProVent 200 can't handle the oil coming out of Alan's in-block baffle on a 5.4L motor.
On a 5.0L motor, John Kuhn's in-block separator box (with the scrubber in) gets rid of enough oil such that the ProVent 200 works fine. The problem for this current engine iteration that we're working on now is the anticipated flow volume: I anticipate the the in-block separator box with the scrubber in will not flow enough gas when oily. It remains to be seen whether the baffle box separates well enough without the scrubber for something like ProVent not to get overwhelmed. But the only way to know is to try it.
In designing the in-block baffle or separator box, there are two fundamental design trade offs. First, the separator box opening may be at a location that sees high gas pressure and high amount of oil splash. Or it can be in a location that sees less oil splash, but then it will also see a lower gas pressure. You kind of pick your poison there. Second, the box has volume limited by the block, and will therefore either flow a lot of bag but not separate very efficiently or separate very efficiently but then not flow a lot of gas. Pick your poison there as well. Those are the two trade-offs that I see, and which way one chooses will determine how the rest of the system must be designed.
Last edited by ptuomov; 03-13-2015 at 05:42 PM.
03-13-2015, 07:59 PM
#138
Electron Wrangler
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In designing the in-block baffle or separator box, there are two fundamental design trade offs. First, the separator box opening may be at a location that sees high gas pressure and high amount of oil splash. Or it can be in a location that sees less oil splash, but then it will also see a lower gas pressure. You kind of pick your poison there. Second, the box has volume limited by the block, and will therefore either flow a lot of bag but not separate very efficiently or separate very efficiently but then not flow a lot of gas. Pick your poison there as well. Those are the two trade-offs that I see, and which way one chooses will determine how the rest of the system must be designed.
Here is a basic conceptual diagram. baffles can be more elaborate and still flow OK as there is more room. Top port would actually be to the front but you get the idea. Orienting the baffles front to back allows shorter wider paths - so you could fit more 180's so probably better still...
Alan
03-13-2015, 09:48 PM
#139
Nordschleife Master
Thread Starter
There's more than one way too skin the cat...
Thanks for sharing your design, Alan.
Here are some considerations when evaluating this and other designs:
I can see an "impactor" in the sketched design. The baffle plates in the separator work as impactors only if the mixture (gas and oil) travels fast enough towards the baffle plate. There's a minimum velocity depending on the dimensions above which oil droplets can't turn with the gas and instead hit the baffle (and separate). That minimum velocity is hard to obtain over different operating conditions. That's why new car air-oil separators have nozzles that accelerate the mixture before the mixture flow faces the baffle. Furthermore, all of the new expensive German cars that use an impactor design seem to have variable geometry nozzles. Most are spring loaded in which more of the nozzle opening or more nozzles are exposed to the flow as the crankcase pressure increases, keeping the flow thru the velocity constant. Looking at the Mahle demo pieces or AMG E63 passive separator, the anchorman quote is appropriate: "That escalated quickly..."
Centrifuge was mentioned in an earlier post. Centrifuge is another design similar to the impactor, which also depends on the gas velocity and a similar nozzle system is needed to keep the separator working in different operating conditions.
I can also see a volume separator there in that design sketch. Unlike with the impactor design, volume separators rely on the fact that the mixture usually starts separating at below 1 m/s velocities. This is for separators with a large enough cross-sectional area. For small cross-sectional area passages, such as hoses, the oil can flow up the hose at much lower mixture velocity, because it flows attached to the hose wall. (For the same reason, if you look at blow by flow ejected from the crankcase thru a transparent hose, you can't really visually judge the amount of oil flowing thru the hose because it's mostly attached to the hose walls and it gives the visual illusion that the whole hose is full of oil.)
The 928 oil separator in the valve covers is an example of a volume separator. It works ok as long as the gas velocity doesn't exceed some critical value. That's why there's a restrictor there in the elbow. The restrictor keeps the gas flow in the tube slow enough that air and oil separate. If you drill that elbow open and make no other changes, you'll have a worse, not better, crankcase breather oil problem. If you got oil coming out of the elbow and you want to stop it, in most cases adding a smaller than the 5mm restrictor in the hose should help. It of course doesn't flow as much gas then either.
Then there's the simple shroud in the design. Usually we think of the air/oil mixture as small oil droplets flowing with the gas. Sometimes though the droplets are large and travel at high speed, more like water from a hose. In the case of the 928, there's a spray coming into the block chimney from two rod bearing side gaps and possibly from an additional rod bearing side gap and a main bearing side gap. The opening in the separator needs to be shielded from that kind of direct spray. Understanding the spray direction is necessary if one wants to come up with a good design.
Finally, there's the pressure at the inlet. If the separator inlet faces against the crank rotation, it'll see a higher pressure and flow more gas. If the separator faces away from the crank rotation direction, it'll see a lower pressure and flows less gas. The catch 22 is that the locations that see high gas pressure (good) are usually the locations that have the worst shrouding (bad).
Effective separators usually have very large volume or combine all of the above designs.
Here are some considerations when evaluating this and other designs:
I can see an "impactor" in the sketched design. The baffle plates in the separator work as impactors only if the mixture (gas and oil) travels fast enough towards the baffle plate. There's a minimum velocity depending on the dimensions above which oil droplets can't turn with the gas and instead hit the baffle (and separate). That minimum velocity is hard to obtain over different operating conditions. That's why new car air-oil separators have nozzles that accelerate the mixture before the mixture flow faces the baffle. Furthermore, all of the new expensive German cars that use an impactor design seem to have variable geometry nozzles. Most are spring loaded in which more of the nozzle opening or more nozzles are exposed to the flow as the crankcase pressure increases, keeping the flow thru the velocity constant. Looking at the Mahle demo pieces or AMG E63 passive separator, the anchorman quote is appropriate: "That escalated quickly..."
Centrifuge was mentioned in an earlier post. Centrifuge is another design similar to the impactor, which also depends on the gas velocity and a similar nozzle system is needed to keep the separator working in different operating conditions.
I can also see a volume separator there in that design sketch. Unlike with the impactor design, volume separators rely on the fact that the mixture usually starts separating at below 1 m/s velocities. This is for separators with a large enough cross-sectional area. For small cross-sectional area passages, such as hoses, the oil can flow up the hose at much lower mixture velocity, because it flows attached to the hose wall. (For the same reason, if you look at blow by flow ejected from the crankcase thru a transparent hose, you can't really visually judge the amount of oil flowing thru the hose because it's mostly attached to the hose walls and it gives the visual illusion that the whole hose is full of oil.)
The 928 oil separator in the valve covers is an example of a volume separator. It works ok as long as the gas velocity doesn't exceed some critical value. That's why there's a restrictor there in the elbow. The restrictor keeps the gas flow in the tube slow enough that air and oil separate. If you drill that elbow open and make no other changes, you'll have a worse, not better, crankcase breather oil problem. If you got oil coming out of the elbow and you want to stop it, in most cases adding a smaller than the 5mm restrictor in the hose should help. It of course doesn't flow as much gas then either.
Then there's the simple shroud in the design. Usually we think of the air/oil mixture as small oil droplets flowing with the gas. Sometimes though the droplets are large and travel at high speed, more like water from a hose. In the case of the 928, there's a spray coming into the block chimney from two rod bearing side gaps and possibly from an additional rod bearing side gap and a main bearing side gap. The opening in the separator needs to be shielded from that kind of direct spray. Understanding the spray direction is necessary if one wants to come up with a good design.
Finally, there's the pressure at the inlet. If the separator inlet faces against the crank rotation, it'll see a higher pressure and flow more gas. If the separator faces away from the crank rotation direction, it'll see a lower pressure and flows less gas. The catch 22 is that the locations that see high gas pressure (good) are usually the locations that have the worst shrouding (bad).
Effective separators usually have very large volume or combine all of the above designs.
03-13-2015, 10:14 PM
#140
Electron Wrangler
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I agree there are lots of considerations. However a stack like this simply as a pre-separator (like a Greg Brown crank baffle on steroids) is likely to be more effective than the current version, one can envisage different baffle configurations internally to cover a spread of conditions with some reasonable effectiveness.
For me this would still only be stage 1 of the separation plan. I'd plumb the output to the vacuum pump and follow-it with another more effective separator. I don't imagine it would ever be enough solely on its own.
That's not so different than I do now, and the vacuum pump means there is a certain minimum flow around the recirculation loop all the time.
Alan
For me this would still only be stage 1 of the separation plan. I'd plumb the output to the vacuum pump and follow-it with another more effective separator. I don't imagine it would ever be enough solely on its own.
That's not so different than I do now, and the vacuum pump means there is a certain minimum flow around the recirculation loop all the time.
Alan
03-13-2015, 10:34 PM
#141
Nordschleife Master
Thread Starter
It would be nice to use all four ports in the valve covers to vent out in addition to the chimney in the block, but then there's the problem that parts of the chimney are at a (relative) low pressure area and gas may start flowing in thru the chimney and out the valve covers. That in turn would hurt the oil flow down the drains.
I think that Ake's plan is the best one if you're building an ITB engine from scratch. Add enough breather channels to the inside of the block (and enough pan volume), after which you can breathe the crankcase out whichever way you want and only have normal modern V8 level of oil separation problems. But that plan doesn't help people who aren't building an engine ground up.
03-14-2015, 03:36 AM
#142
Nordschleife Master
The vacuum pump that Alan, and all the cars running my system, are running is a GZ Motorsports pump.
These pumps require a little oil to pass through them to ensure that everything remains lubricated.
For my system, it can be used both with and without the under filler neck separator without any difference.
However my installs are much simpler than what Alan did in his setup.
first of all, all the stock ports at the base of the filler neck (if you have them), are capped.
All valve cover ports but the forward port on the 1/4 head, are capped.
If you have a GTS you can use the stock 5/8" nipple coming out of the filler neck, if using an S4/GT filler neck, you need to drill a hole and set a 5/8" fitting into the filler neck.
Connect a 5/8" hose from the filler neck to the vacuum pump inlet.
The outlet of the vacuum pump is again 5/8" hose, which goes to my custom air oil separator.
The oil return is high on the separator and uses a 1/2" hose. This hose uses a small portion of the factory forward breather port hose and a couple elbows, to return all separated oil, and some air back in to the crankcase.
The return of the oil and air into the crankcase is what limits the available vacuum that can be produced inside the crankcase.
The pressure differential between the atmospheric air, and the reduced pressure inside the crankcase is what returns the oil and air back in to the engine.
The remainder of the crankcase vapours are exited into the factory smog pump filter housing on the factory dual fan shroud. I recommend a small paper towel to collect any mist which may come out. But from there, the fumes are routed forward, and are then returned into the air tubes which feed the engine it's air. So while it is not a 100% closed loop system, it is pretty close to being fully closed loop, as the fumes after being fully separated out, are returned in to the engine.
I have had this on my own car since 2011, I have inspected my bearings, ZERO wear.
I have seen zero downsides.
This system is now also on the following people's cars,
Jake Myers (Ducman),
Joe Milbourne (uranium metalurgist??)
Roger Tyson,
Ken Schims (not on RL),
I have a few more out there, but have not gotten confirmation that they have been installed yet.
Needing to still get one off to Louie Ott, and put one on another boosted car in the area.
Hopefully some of those members will speak up as well.
These pumps require a little oil to pass through them to ensure that everything remains lubricated.
For my system, it can be used both with and without the under filler neck separator without any difference.
However my installs are much simpler than what Alan did in his setup.
first of all, all the stock ports at the base of the filler neck (if you have them), are capped.
All valve cover ports but the forward port on the 1/4 head, are capped.
If you have a GTS you can use the stock 5/8" nipple coming out of the filler neck, if using an S4/GT filler neck, you need to drill a hole and set a 5/8" fitting into the filler neck.
Connect a 5/8" hose from the filler neck to the vacuum pump inlet.
The outlet of the vacuum pump is again 5/8" hose, which goes to my custom air oil separator.
The oil return is high on the separator and uses a 1/2" hose. This hose uses a small portion of the factory forward breather port hose and a couple elbows, to return all separated oil, and some air back in to the crankcase.
The return of the oil and air into the crankcase is what limits the available vacuum that can be produced inside the crankcase.
The pressure differential between the atmospheric air, and the reduced pressure inside the crankcase is what returns the oil and air back in to the engine.
The remainder of the crankcase vapours are exited into the factory smog pump filter housing on the factory dual fan shroud. I recommend a small paper towel to collect any mist which may come out. But from there, the fumes are routed forward, and are then returned into the air tubes which feed the engine it's air. So while it is not a 100% closed loop system, it is pretty close to being fully closed loop, as the fumes after being fully separated out, are returned in to the engine.
I have had this on my own car since 2011, I have inspected my bearings, ZERO wear.
I have seen zero downsides.
This system is now also on the following people's cars,
Jake Myers (Ducman),
Joe Milbourne (uranium metalurgist??)
Roger Tyson,
Ken Schims (not on RL),
I have a few more out there, but have not gotten confirmation that they have been installed yet.
Needing to still get one off to Louie Ott, and put one on another boosted car in the area.
Hopefully some of those members will speak up as well.
03-14-2015, 10:38 AM
#143
Nordschleife Master
Thread Starter
Unfortunately, I don't have room for a vacuum pump or centrifugal separator that is belt driven off the crankshaft pulley. So what are the alternatives? Driving anything off the camshaft is too big of an engineering project (for example, AMG engines have a centrifugal separator that sucks blow by gas thru a hollow camshaft that also powers the separator). This leaves the electricity, oil pressure, or manifold air pressure under boost as the power options for the vacuum pump or centrifugal separator. (Mahle appears to offer electrical separator, some diesel tractors may use oil pressure to drive separators, and Parker uses manifold pressure to drive separators.) The power requirements of a vacuum pump make those less practical so I haven't seen vacuum pumps been driven off the oil pressure or air manifold pressure, but those two are all valid powering options for a centrifugal oil separator. Electric pumps repurposed as crankcase vacuum pumps don't seem to last long.
Here's a question: Why isn't there a centrifugal separator integrated to the vacuum pump?
Here's a question: Why isn't there a centrifugal separator integrated to the vacuum pump?
03-14-2015, 10:56 AM
#144
Instructor
I have had Colin's vacuum pump system on my '93 GTS for quite some time and am fully satisfied with its performance. I had previously suffered from all the woes of the factory setup most notably very high oil consumption. I installed other systems that incorporated the Provent only to discover that it was soon rendered unusable due to oil saturation of the internal demisting fabric. This occurred within a few months of installation.
With the Provent system I still had the nasty blue oil cloud most evident on deceleration and suspecting damaged vale stem seals replaced them all. Even with new valve stem seals the blue cloud and high oil consumption persisted.
I then installed the vacuum system Colin describes and have had no problems with oil consumption or leakage of oil into the combustion chamber. Given the results on my car I surmise that the vacuum system provides a number of benefits including equalization of pressure pulses within the crankcase, elimination/minimization of ring flutter, improved driveability and the big one for me - very low oil consumption.
All the best,
Joe
With the Provent system I still had the nasty blue oil cloud most evident on deceleration and suspecting damaged vale stem seals replaced them all. Even with new valve stem seals the blue cloud and high oil consumption persisted.
I then installed the vacuum system Colin describes and have had no problems with oil consumption or leakage of oil into the combustion chamber. Given the results on my car I surmise that the vacuum system provides a number of benefits including equalization of pressure pulses within the crankcase, elimination/minimization of ring flutter, improved driveability and the big one for me - very low oil consumption.
All the best,
Joe
The vacuum pump that Alan, and all the cars running my system, are running is a GZ Motorsports pump.
These pumps require a little oil to pass through them to ensure that everything remains lubricated.
For my system, it can be used both with and without the under filler neck separator without any difference.
However my installs are much simpler than what Alan did in his setup.
first of all, all the stock ports at the base of the filler neck (if you have them), are capped.
All valve cover ports but the forward port on the 1/4 head, are capped.
If you have a GTS you can use the stock 5/8" nipple coming out of the filler neck, if using an S4/GT filler neck, you need to drill a hole and set a 5/8" fitting into the filler neck.
Connect a 5/8" hose from the filler neck to the vacuum pump inlet.
The outlet of the vacuum pump is again 5/8" hose, which goes to my custom air oil separator.
The oil return is high on the separator and uses a 1/2" hose. This hose uses a small portion of the factory forward breather port hose and a couple elbows, to return all separated oil, and some air back in to the crankcase.
The return of the oil and air into the crankcase is what limits the available vacuum that can be produced inside the crankcase.
The pressure differential between the atmospheric air, and the reduced pressure inside the crankcase is what returns the oil and air back in to the engine.
The remainder of the crankcase vapours are exited into the factory smog pump filter housing on the factory dual fan shroud. I recommend a small paper towel to collect any mist which may come out. But from there, the fumes are routed forward, and are then returned into the air tubes which feed the engine it's air. So while it is not a 100% closed loop system, it is pretty close to being fully closed loop, as the fumes after being fully separated out, are returned in to the engine.
I have had this on my own car since 2011, I have inspected my bearings, ZERO wear.
I have seen zero downsides.
This system is now also on the following people's cars,
Jake Myers (Ducman),
Joe Milbourne (uranium metalurgist??)
Roger Tyson,
Ken Schims (not on RL),
I have a few more out there, but have not gotten confirmation that they have been installed yet.
Needing to still get one off to Louie Ott, and put one on another boosted car in the area.
Hopefully some of those members will speak up as well.
These pumps require a little oil to pass through them to ensure that everything remains lubricated.
For my system, it can be used both with and without the under filler neck separator without any difference.
However my installs are much simpler than what Alan did in his setup.
first of all, all the stock ports at the base of the filler neck (if you have them), are capped.
All valve cover ports but the forward port on the 1/4 head, are capped.
If you have a GTS you can use the stock 5/8" nipple coming out of the filler neck, if using an S4/GT filler neck, you need to drill a hole and set a 5/8" fitting into the filler neck.
Connect a 5/8" hose from the filler neck to the vacuum pump inlet.
The outlet of the vacuum pump is again 5/8" hose, which goes to my custom air oil separator.
The oil return is high on the separator and uses a 1/2" hose. This hose uses a small portion of the factory forward breather port hose and a couple elbows, to return all separated oil, and some air back in to the crankcase.
The return of the oil and air into the crankcase is what limits the available vacuum that can be produced inside the crankcase.
The pressure differential between the atmospheric air, and the reduced pressure inside the crankcase is what returns the oil and air back in to the engine.
The remainder of the crankcase vapours are exited into the factory smog pump filter housing on the factory dual fan shroud. I recommend a small paper towel to collect any mist which may come out. But from there, the fumes are routed forward, and are then returned into the air tubes which feed the engine it's air. So while it is not a 100% closed loop system, it is pretty close to being fully closed loop, as the fumes after being fully separated out, are returned in to the engine.
I have had this on my own car since 2011, I have inspected my bearings, ZERO wear.
I have seen zero downsides.
This system is now also on the following people's cars,
Jake Myers (Ducman),
Joe Milbourne (uranium metalurgist??)
Roger Tyson,
Ken Schims (not on RL),
I have a few more out there, but have not gotten confirmation that they have been installed yet.
Needing to still get one off to Louie Ott, and put one on another boosted car in the area.
Hopefully some of those members will speak up as well.
03-14-2015, 11:02 AM
#145
Electron Wrangler
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The vacuum pump is very small - if you are to use it replace the air pump - it has to be. Lots of users of vacuum pumps (primarily racers) don't specifically have have crank ventilation issues - they are using high levels of crank vacuum (15"Hg - 20"Hg) to achieve higher engine outputs.
Does your turbo plumbing encroach on the air pump area - or do you just need to keep the air pump for emissions test reasons?
Tuomo you have implied several times that you think the heads may be at a higher effective static pressure than the main crank - true? if so why? You also seem to imply that the dynamic pulses may be large in the heads - why? - due to interbay differences equalizing through the oil drains? other?.
Alan
Does your turbo plumbing encroach on the air pump area - or do you just need to keep the air pump for emissions test reasons?
Tuomo you have implied several times that you think the heads may be at a higher effective static pressure than the main crank - true? if so why? You also seem to imply that the dynamic pulses may be large in the heads - why? - due to interbay differences equalizing through the oil drains? other?.
Alan
03-14-2015, 12:14 PM
#146
Nordschleife Master
Thread Starter
Nothing but the compressor inlet pipes fit there. If there were room there, I could do hundred different things, including running an oil scavenge pump with integrated separator.
The vacuum pump is very small - if you are to use it replace the air pump - it has to be. Lots of users of vacuum pumps (primarily racers) don't specifically have have crank ventilation issues - they are using high levels of crank vacuum (15"Hg - 20"Hg) to achieve higher engine outputs.
Does your turbo plumbing encroach on the air pump area - or do you just need to keep the air pump for emissions test reasons?
Alan
Does your turbo plumbing encroach on the air pump area - or do you just need to keep the air pump for emissions test reasons?
Alan
03-14-2015, 01:30 PM
#147
Nordschleife Master
My separator is not driven. It works on airspeed and the heavier weight of the oil.
The vacuum pump is slightly smaller than a factory air pump as well.
I would think it very likely that you could mount the vacuum pump and route the pipes around it, unless you're running a 3" pipe.
The other option is to flip the pump around, make a bracket to hold it, and drive it off the AC belt. You will need to reverse the inlet/outlet ports but that shouldn't be an issue.
The vacuum pump is slightly smaller than a factory air pump as well.
I would think it very likely that you could mount the vacuum pump and route the pipes around it, unless you're running a 3" pipe.
The other option is to flip the pump around, make a bracket to hold it, and drive it off the AC belt. You will need to reverse the inlet/outlet ports but that shouldn't be an issue.
03-14-2015, 01:35 PM
#148
Nordschleife Master
Thread Starter
There is not a square inch of space on that plane of timing belt cover.
My separator is not driven. It works on airspeed and the heavier weight of the oil.
The vacuum pump is slightly smaller than a factory air pump as well.
I would think it very likely that you could mount the vacuum pump and route the pipes around it, unless you're running a 3" pipe.
The other option is to flip the pump around, make a bracket to hold it, and drive it off the AC belt. You will need to reverse the inlet/outlet ports but that shouldn't be an issue.
The vacuum pump is slightly smaller than a factory air pump as well.
I would think it very likely that you could mount the vacuum pump and route the pipes around it, unless you're running a 3" pipe.
The other option is to flip the pump around, make a bracket to hold it, and drive it off the AC belt. You will need to reverse the inlet/outlet ports but that shouldn't be an issue.
03-14-2015, 02:12 PM
#149
Nordschleife Master
Well, how about this then, get a small hydraulic motor, and modify the power steering lines so that the power steering pump drives the vacuum pump?
In hydraulic terms you would set it up as a power beyond port.
Then you can mount the vacuum pump wherever you so choose........
In hydraulic terms you would set it up as a power beyond port.
Then you can mount the vacuum pump wherever you so choose........
03-14-2015, 08:46 PM
#150
Nordschleife Master
Thread Starter
Well, how about this then, get a small hydraulic motor, and modify the power steering lines so that the power steering pump drives the vacuum pump? In hydraulic terms you would set it up as a power beyond port. Then you can mount the vacuum pump wherever you so choose........
For example, I've got small but meaningful vacuum at the compressor inlet. I have significant pressure on the compressor outlet. There has to be a way for me to buy an air-oil separator and to create whatever crankcase vacuum with just that.
This powered separator stuff exists out there. The problem for me is to find a unit that is designed to be retro fitted as an external component to an old turbo-diesel engine, such as a marine engine. I've got leads but haven't decided on anything yet. The time to pull the trigger one way or another is close.