Catch can for crank case breathers on diesel motors

[Johan Leopard51]

We recently had turbo problems on 3000h Yanmar 8LV that I basically blame on the crank case breather pipe looping its air into one of the turbo air intakes. Both turbos could be overhauled by a specialist but one would not even spin by hand.

Anyway, I want to do what some people recommend and fit a catch can. Need some advice please. From internet it seems like some big diesels are not sealed meaning their crank case breather can go into a catch can that itself ends in a little air filter. The landcruiser people say the Toyota 4.5 V8 (which is essentially the Yanmar 8LV marinised) needs negative pressure (?) so the crank case breather must terminate in the turbo air intake - the catch can essentially just sits inline on the crank case breather, catches the gunk and moisture and returns air back to turbo intake.

Anybody have experience with this please?

[MWGDVC]

Have you considered a Walker Air Sep? I have installed one on my Perkins 4.108 to good results. Seems it would address your situation quite well. It provides "vacuum" to the crankcase, and oil collection and return to crankcase.

[Johan Leopard51]

thanks, but can for Yanmar 8LV only see a Walker air filter for the ring intake at turbo, not a oil catch can.

I mainly wanted to know whether it is essential to continue the now-cleaner air where it always went. Catch cans vary a LOT in design. The one the Australians swear by is fancy and expensive featuring both a vacuum release and pressure release valve but seemingly no oil return, you have to replace a cartridge filter in the can every 20,000 miles or so.

[MWGDVC]

Johan,
The way mine works, there is a tube in the intake airflow cut at a 45 degree angle like an automotive road draft tube used in automobiles of the 1920s through the 1960s. This tube produces a low pressure inside the tube. It is plumbed to the crankcase breather in the top of the valve cover. The higher the engine RPM, the higher the airflow over the tube, the lower the pressure in the tube. At high RPM, the oil vapour will be drawn down the intake, and disposed of through the combustion process. At lower throttle settings, the condensed oil vapour drips into an oil catchment ring in the air filter housing. At the bottom of this ring is a drain hose, the other end is plumbed to the crankcase, allowing gravity, and perhaps a bit of suction from the low pressure in the crankcase, to return the oil to the crankcase. This makes more of a closed loop crankcase ventilation system.
All piston engines, regardless of engine health, produce some blow-by. This produces pressure in the crankcase. This system keeps the crankcase pressure below ambient air pressure most of the time the engine is running, taking the pressure off of oil seals and gaskets, which should reduce or eliminate minor, annoying oil leaks.
In my own use case, The Perkins 4.108 uses seal technology from the dark ages. I found the rear main seal leakage went from saturating a small engine diaper in 20 hours, to replacing it every 100 hrs, or annually as part of regular maintainence.
Sorry for the long winded explanation.
Hope this helps,
Mike


P.S. I have no interest in the company, other than being a satisfied customer.

[flightlead404]

First, I have no experience with turbo diesels. I do however have lots of experience with turbo cars (specifically Porsche air cooled) including extensively modifying them.

Some of your questions are unclear or sound a bit odd to me. First, what do you mean by "catch can"? Are you talking about an air/oil separator? When shopping for a part you may want to use that phrase as you are likely to end up with a better set of options than the generic "catch can". For ex, I have a "catch can" under my oil lubricated turbo charger to "catch" oil remaining as the engine shuts down. I have an air/oil separator on my crank case breather to, well, separate the air and the oil to try and keep the crank case air clean(er) before I dump it out the back.

In the Porsche turbo world many people remove factory air boxes or do other intake modifications that end up with crankcase breathers going other places than the factory put them. Crank case breathers are intended to deal with the changing pressure inside the crank case. What causes that? There's essentially no change in crank case volume, as one piston is moving up, another is moving down. (There may be minor changes in volume for inline engines due to crank movement) However, if the crank case was sealed the pressure would increase due to air expansion from heat and potentially a little bit of blow by. There will be some "in and out" not just "out", hence the term "breathing". Your mods should recognize that.

In the Porsche world, those people that simply pop a filter on the crankcase breather generally end up with a fine mist of engine oil over everything in the engine compartment after a while. Filters aren't really going to help contain that much. You are going to want to vent the crank case somewhere to prevent that. That means back into the intake, or overboard. Overboard is probably not an option in a boat (in a 930 its easy, just out the rear).

Most engine installations I've seen, for both cleanliness and EPA requirements, route the crank case breather back into the main air inlet filter box. That lets the engine oil mist get consumed in the combustion process. Unless your engine is pretty unhealthy, meaning needs a rebuild, this isn't a problem. This gets gets your crankcase pressure low enough for your purposes. Getting "Extra negative" is not a value to you.

I'm not sure what you mean by "turbo inlet" exactly, but if you're talking about right at the compressor inlet there could be considerable suction there, probably not what you want at the crankcase. In the performance gasoline engine world reducing crankcase pressure can provide a little bit more HP, from things like increase ring sealing, but this means getting the crankcase pressure close to ambient, not significantly below ambient. I can see no reason to want crank case pressures significantly below ambient air pressure, particularly in a non-performance, constant rpm diesel engine. Further, dumping your crankcase breather right at the inlet side of the turbo will likely result in increased fouling of the compressor, which may be what you are alluding to.

Can you find someone on the airfilter/airbox to vent the breather?

HTH idk if any of this is useful, or if its totally different in the diesel world. Just some things I learned the hard way

[Johan Leopard51]

Thanks both of you.

I am going this route in the hope of avoiding future problems we developed on Yanmar 8LV370 twin turbo. We could ship our turbos to a workshop and overhaul at a specialist, but one (the one where crankcase breather enters turbo intake), could not spin by finger.

At work I have a very big Scania generator and it is entirely different - crankcase breather exits to atmosphere. Why do they on some motors return air to turbo inlet? Essentially it is environmental reasons - to not have that stuff killing critters : combust it and in some theories improve combustion :/

The Toyota guys with essentially my Yanmar motor tend to put catch cans on the line to avoid gunk buildup in turbo and keep EGR clean. I have seen horrific pix of EGR on V8 Toyota but that could also be marketing by the catch can guys.

I disconnected crank case breather from turbo intake and left it hanging in a jar overnight. None of us would want what dripped out that pipe going through our finely engineered turbos and injectors!

We operate our yacht in shall we say difficult QC maintenance environment and with not always lab quality diesel and oils and oil change procedures. So I’m adding this to keep crap out of turbo air intake, as well as fitting a parallel to normal fuel line diesel polishing system made of a twin Racor and a second pump that takes fuel from both tanks and returns clean fuel, running two hours per day at about 250 liters per hour. It costs a bit but I got the Racors from a bankrupt yacht builder auction for a song. And, compared to what I had a month ago with port motor dead due to jungle juice fuel starvation shutdown ECU and taking a cat with one motor into rocky repair yard dock in wind : bargain. No, they don’t have handy “tug” to help so I added 10y to my grey hairs.

When I get back there and do these, I’ll update. Had hoped somebody here had done similar on Yanmar 8LV

[Johan Leopard51]

No need to watch the whole thing but they give fairly good overview by 8minutes

https://youtu.be/XFDQI-NN2MU

[flightlead404]

Originally Posted by Johan Leopard51

Thanks both of you.

I am going this route in the hope of avoiding future problems we developed on Yanmar 8LV370 twin turbo. We could ship our turbos to a workshop and overhaul at a specialist, but one (the one where crankcase breather enters turbo intake), could not spin by finger.

At work I have a very big Scania generator and it is entirely different - crankcase breather exits to atmosphere. Why do they on some motors return air to turbo inlet? Essentially it is environmental reasons - to not have that stuff killing critters : combust it and in some theories improve combustion :/

The Toyota guys with essentially my Yanmar motor tend to put catch cans on the line to avoid gunk buildup in turbo and keep EGR clean. I have seen horrific pix of EGR on V8 Toyota but that could also be marketing by the catch can guys.

I disconnected crank case breather from turbo intake and left it hanging in a jar overnight. None of us would want what dripped out that pipe going through our finely engineered turbos and injectors!

We operate our yacht in shall we say difficult QC maintenance environment and with not always lab quality diesel and oils and oil change procedures. So I’m adding this to keep crap out of turbo air intake, as well as fitting a parallel to normal fuel line diesel polishing system made of a twin Racor and a second pump that takes fuel from both tanks and returns clean fuel, running two hours per day at about 250 liters per hour. It costs a bit but I got the Racors from a bankrupt yacht builder auction for a song. And, compared to what I had a month ago with port motor dead due to jungle juice fuel starvation shutdown ECU and taking a cat with one motor into rocky repair yard dock in wind : bargain. No, they don’t have handy “tug” to help so I added 10y to my grey hairs.

When I get back there and do these, I’ll update. Had hoped somebody here had done similar on Yanmar 8LV

It doesn't go through the injectors! It is in the intake charge air so not an issue.

[Johan Leopard51]

True!

I was thinking more about the jungle juice part of my projects. In the last shutdown the separator bowl had half a salad going around and around. Trying to decide what micron cartridge to put in the polishing system.

The standard separator cartridge was blocked solid and not sure what micron the actual diesel filter at motor is

[skipperpete]

Originally Posted by Johan Leopard51

Thanks both of you.

I am going this route in the hope of avoiding future problems we developed on Yanmar 8LV370 twin turbo. We could ship our turbos to a workshop and overhaul at a specialist, but one (the one where crankcase breather enters turbo intake), could not spin by finger.

At work I have a very big Scania generator and it is entirely different - crankcase breather exits to atmosphere. Why do they on some motors return air to turbo inlet? Essentially it is environmental reasons - to not have that stuff killing critters : combust it and in some theories improve combustion :/

The Toyota guys with essentially my Yanmar motor tend to put catch cans on the line to avoid gunk buildup in turbo and keep EGR clean. I have seen horrific pix of EGR on V8 Toyota but that could also be marketing by the catch can guys.

I disconnected crank case breather from turbo intake and left it hanging in a jar overnight. None of us would want what dripped out that pipe going through our finely engineered turbos and injectors!

We operate our yacht in shall we say difficult QC maintenance environment and with not always lab quality diesel and oils and oil change procedures. So I’m adding this to keep crap out of turbo air intake, as well as fitting a parallel to normal fuel line diesel polishing system made of a twin Racor and a second pump that takes fuel from both tanks and returns clean fuel, running two hours per day at about 250 liters per hour. It costs a bit but I got the Racors from a bankrupt yacht builder auction for a song. And, compared to what I had a month ago with port motor dead due to jungle juice fuel starvation shutdown ECU and taking a cat with one motor into rocky repair yard dock in wind : bargain. No, they don’t have handy “tug” to help so I added 10y to my grey hairs.

When I get back there and do these, I’ll update. Had hoped somebody here had done similar on Yanmar 8LV

The reason your crankcase breather vents into the turbo is basically to avoid having blow-by fumes inside the boat, not environmental….and the “catch can” is a useful addition. The most impressive addition is your fuel polishing system, common rail injection systems require the highest level of fuel cleanliness achievable and you won’t regret that addition. I was unaware that Yanmar was using the Toyota V8 engine, they have a good reputation for reliability here in Australia…..but a bit thirsty.
My 4wd has EGR, arguably the dumbest most destructive advance in diesel engineering and apparently one of the reasons Cat withdrew from the automotive market, they don’t like EGR.

[Johan Leopard51]

Originally Posted by skipperpete

My 4wd has EGR, arguably the dumbest most destructive advance in diesel engineering ….

A lot of landcruiser guys here blank off the EGR but on the newer Toyota/Yanmar if you do that you get error codes. There is apparently a trick to either disable EGR in the ECU, or another trick is fitting a specific resistor on a sensor wire. I need to research that a lot more before I try.

Btw beside the Yanmar 8LV that is a Toyota V8 like in Landcruiser, the Yanmar 6LP is/was the 4.2 turbo diesel straight six from the Landcruiser 100 series. I wish my builder had stuck to the 6LP, it is a bullet-proof and simpler to work on motor than the 8LV. Yanmar marinizes the Toyota, adds their ECU and the yacht bits and then with benefit of unlimited cooling can run the ECU for 100Hp more than a road vehicle can. One trick is that most Yanmar parts are Toyota parts (but be careful about injectors and piston heads) but the Toyota part is ½ the Yanmar price.

[Lou-In-NJ]

Every large diesel engine, especially those with an EGR system, should have a catch-can. Your crankcase vent vapor is full of atomized oil, and this oil will coat everything in its path on your intake system, and since diesel don't get the benefit of a "gasoline wash-down", like port-injected gasoline engines, this fouling just builds up over the years. Worse yet, on engines with EGR, the particulate-laden exhaust gases, combine with the hot oil vapor from the PCV system, to form a tar that makes mechanisms stick and fail, and builds-up over time to severely restrict air flow.

I built a catch-can out of 1-1/2" galvanized pipe, stuffed with stainless steel scouring pads, that has a drain-cock on the bottom. Why is my design so much heavier than most off-the-self units? First, most of the commercially available catch-cans I've seen, have an extremely fine brass screen as part of their filtering strategy, and I can tell you that there is no way that, that screen, is very effective after a short while; and should that screen get clogged, you will build up tremendous pressure inside the engine, and likely blow-out a crankshaft seal, and you'll have serious oil leak. Also, you need thermal mass, and a large area to dissipate the heat from the hot vapor constantly going through the catch-can, especially in the marine environment where the engine is under constant load. That being the case, do not use PVC caps as I did for your hose connections, they will melt, use metal caps and just have them drilled and tapped for your barbed hose connectors.

[Johan Leopard51]

Thanks Lou for experienced advice.

Several catch cans have no element, only the stainless steel wool, but so far only see them with an air filter to atmosphere, not with return air to turbo inlet. Apparently in my V8, having the return at turbo creates low pressure that end of pipe which helps air flow.

I am leaning to the German Mann Provent catch can, maybe the 400 rather than 200 as it is bigger and rated for 350+ Hp motors. Part of reason for going for them is they have pressure relief system incorporated. After seeing some videos of people with your mentioned pressure risk if blocked, that was a worry.

What I will try and work into standard operating procedures is to open a valve on the bottom of catch can each time check the fuel level. To make it simpler and cleaner I’ll have that go into a clear bottle so that we can track over time how much it catches. In vehicles with my V8 the guys get about 300ml every 5000km so call that 300ml every 100h or so. Replacement elements about every 500h or more.

I am digging and digging to figure whether I can cancel EGR in Yanmar ECU. In tropics I really do not need some warm air recirc helping with cold starts. The trick might lie in a resistor on signal cable to make ECU think the EGR is working, whereas in fact it is not working at all. Clamping the air hose stops EGR but then alarms go off.

[Lou-In-NJ]

Originally Posted by Johan Leopard51

Thanks Lou for experienced advice.
...

You're welcome Johan.
Typically, the EGR valve is only open at idle and low load conditions, to reduce NOx. At high load conditions, the EGR valve is closed since all the oxygen entering the engine is used in combustion, and theoretically, leaves no oxygen for NOx to form.

EGR is not typically used to help with cold starting, it's strictly an emissions control. As long as you "dry" your PCV gases, a functioning EGR system should become almost irrelevant to the reliability of your engine. Should you attempt to fool the ECU by blocking the EGR or placing a "dummy load" on the system in some way, if the ECU is sophisticated, you likely will need a circuit that does more than place a dummy load on the EGR motor/solenoid line. Modern engine ECUs use the MAF sensor to check the change in air flow into the engine to determine whether or not the EGR valve did open as commanded, and can detect proportionality. The circuit to defeat that would be a transistor with resistor circuit that triggers upon the EGR open signal, that proportionally controls the signal that the MAF is sending to the ECU.

It's easier to use a good catch can and "dry" your crankcase gases.

[Johan Leopard51]

Thanks Lou,

It seems the internet has many versions of different realities. Most literature about EGR and PCV deals with cars, which operate quite differently from (1) an industrial diesel such as generator running at 80% load for hours and hours (2) marine diesel that for some users means around ⅓ throttle for extended and for others much higher load.

Our Yanmar average coolant temp sits for example between 74 and 80 Celsius, a car V8 and generator diesel probably around 100. I’ll see if I can track oil temp.

If I can avoid then I’ll stick to EGR as is. My catch can mission is borne from having that turbo where PCV enters intake stuck so solid it could not spin at all by hand. It was able to be fully reconditioned, essentially a very good clean. There was no mechanical fault with the turbo, it was just gunked solid. So my start is on air side I take away PCV and on fuel I am going to polish my fuel in tanks every day a bit. Suck out from bottom, return clean at top, regardless of whether motors are running. Have nice little dual Racor for that job.

On last trip we lost port motor fuel starvation due to an aquarium in the inline diesel separator and gunk in diesel filter despite it being under 35h since liquids service. It was bumpy trip to make weather window, but still. It was a nightmare getting a 51 foot cat with one motor, astern into workshop pier to clean fuel, with wind blowing onto the workshop pier. Had to go astern for them to get their gear into our tanks, but that was after first going bow first, so double my trouble. Added 100 grey hairs doing that stunt