Cranckcase breather question regarding V diesel engine

[Nidza]

I will have to split into a few questions, since I have obvious technical question, but also some additional, let's say ecological question:

1. Is it sufficient to have crankcase breather on one side of the engine, if it is a V engine? It seems logical to me, but maybe I am missing something? It is old Cummins V-504 engine in question. Originally, it came without the breather. So I want to help it a bit to prvent potentiall issues on the long run.

After reading a bunch of staff about crankcase ventilation, it seems that for diesel it is sufficient to have an "open crankcase ventilation", which basically means to have an opening of the engine's crankcase compartment (e.g. on valve cover, e.g. instead of oil cap or having modified oil cap or impactor or spomething similar), to add oil vapor filter (e.g. metal wire mesh) and air filter and to put the output in the engine compartment into some "catch-can" just in case.

According to what I have researched, if it would be "closed CV", it would mean connecting output to the engine air inlet instead to a "catch-can". If I would go that route, then I have read that there is a potential issue of "provided dirt" to the input and potentially clogging that part of the system on the long run (reducing maintenance interval). Additional issue I thought of is that I do not know how much of the air should be pulled (is allowed to be pulled) to not generate some new problems and to make it work correct. So I would avoid this route for those two reasons.

I know that there are available many solutions to buy (impactors, etc.) which are easy to install, but I am not interested in that, just in the concept, if it is OK. I can manage with the rest.

2. And an additional question would be a little bit "green-ish", which seems to be popular/hot today. How much I would sacrifice health of the persons on board for the sake of engine? My assumption is that this crankcase gasses would be anyway sucked by the engine since the output is in engine compartment, even though not directly connected to air inlet of the engine. I have read that these gasses are very pollutant and bad for our health. On the other hand, I am questioning if that small amount is really going to be dominant compared to huge amount of exhaust gases from the 8.2 liter engine, which are unavoidable anyway.

3. In that sense (helath/polution), is it better to provide the outlet of the breather and catch-can to the engine compartment or outside the hull? What is the compromise between these two options?

I would appreciate your inputs on this. Thanks in advance!

 

[kapnD]

This may help:
https://www.sbmar.com/articles/crankcase-ventilation
/[URL="https://www.sbmar.com/articles/envirovent-crankcase-ventilation-ccv-for-cummins-marine-diesels/"]EnviroVent Crankcase Ventilation (CCV) for Cummins Marine Diesels https://www.sbmar.com/articles/envirovent-crankcase-ventilation-ccv-for-cummins-marine-diesels/[/URL]

 

[Nidza]

Hi kapnD,

Thanks for the link. I do not understand one thing, circled red on the attached photo below. Maybe it is my English or a bit of explanation info is missing. Is that connection providing filtered or non-filtered connection for the hose towards the bottle and engine air inlet filter? I guess if it would be filtered, the paper element would be easily pluged, especially if engine "pukes" something beside gases. If not filtered, what is the purpose of that initial air filter towards the engine compartment prior to the hose connection? Is it assumed that most of "normal" blow by gasses will be eaten by engine through the hose and in case of excessive blow by, only then it will be pushed out through that "small" air filter in addition? This is not completely clear to me. Or it is simply a way to make a ratio of gasses going to engine compartment room compared to gasses going towards the engine air inlet (combination of this and hose diameter and air inlet vaccum through that hose)? Thanks in advance for answer.

 

[kapnD]

The little filter is to mix cool air into the crankcase gasses, causing them to condense inside the pipe, then drain a significant portion into the bottle at the low point.
There is an adjustable shutter to control the amount of outside air taken in.
What I do know is that this system works very well, and is super simple compared to the Walker Airsep.
An important step towards controlling blowby in any engine is filling the crancase with the correct amount of oil, which may NOT be anywhere near the full mark on the dipstick.

 

[Barry]

An important step towards controlling blowby in any engine is filling the crancase with the correct amount of oil, which may NOT be anywhere near the full mark on the dipstick.

If you need to know what is the correct amount of oil, which may not be near the full mark on the dipstick, how do you determine this amount?

 

[Nidza]

The little filter is to mix cool air into the crankcase gasses, causing them to condense inside the pipe, then drain a significant portion into the bottle at the low point.
There is an adjustable shutter to control the amount of outside air taken in.
What I do know is that this system works very well, and is super simple compared to the Walker Airsep.
An important step towards controlling blowby in any engine is filling the crancase with the correct amount of oil, which may NOT be anywhere near the full mark on the dipstick.

Ok, thanks, sounds reasonable, so it acts also as inlet filter, rather than outlet filter. It sounds like that the key is how this shutter is implemented and set to have the proper ventilation ratios. Yes, in the article it was mentioned almost as a root cause of blowby to be hitting by crancshaft and rods to the oil especially when engine bottoms were made shallow. It for sure contributes to crankcase pressure, but it is a bit contradictory to definition of the source of blowby. But I can relate to that that new engines with low blowby level can have higher crankcase pressures/blowby due to that.

If you need to know what is the correct amount of oil, which may not be near the full mark on the dipstick, how do you determine this amount?

I could answer how I solved that. My engine had been overhauled prior to integration on the boat and new marks on the dip stick were made in the repair shop on land. When in the boat, I was filling the oil to the top mark and engine was always "consuming" oil and I kept adding meaning that it was simply older technology, but then pretty fast I realized it is not so little amount of spent oil in the end and I decided to check if there is actually some issue. I decided to not refill and check how far will it go. It turns out it leveled at exactly the half between low and high mark and it stayed there between the oil changes. And that is the level to which I fill the oil now. My guess is that this is probably due to the engine being a bit out of normal angle compared to standing on land. But also could be an error of repair guy making the markings, which I do not believe, these are really "experts" (older team doing only that brand for the industry since the begining of careers). Not many such experts these days, they learned the causes of each issue from books and analysis, today most repair guys learn how to do replacement and detect the issue, but not much about the root cause. Of course, there are always a few enthusiasts even today. Back to the oil level though, I am not sure if this what I did would be possible with new engines which are probably much better sealed than this old engine which I have. Though, the principles of all of them are the same for decades.

 

[C. Dog]

Barry as far as I know there is no calibration of factory dip stick systems by the manufacturer, and you will find variation between similar engines. You can calibrate your dip stick after an oil change by filling with the manufacturers specified volume of oil, give it a test run then see where the oil level sits on the stick. Sometimes it is spot on, other times significantly wrong. You can actually mark a new "full" indicator on it or remember where it should be. Generally more problems occur due to over filling than the opposite, just like with the old two stroke outboards vastly more issues occurred from zealous owners adding a dash of extra oil to the fuel, thinking that they were protecting the engine; than would have happened with 30% less oil.

 

[BlueBell]

If you need to know what is the correct amount of oil, which may not be near the full mark on the dipstick, how do you determine this amount?

From the engine manufacturer.

 

[Barry]

From the engine manufacturer.

Barry as far as I know there is no calibration of factory dip stick systems by the manufacturer, and you will find variation between similar engines. You can calibrate your dip stick after an oil change by filling with the manufacturers specified volume of oil, give it a test run then see where the oil level sits on the stick. Sometimes it is spot on, other times significantly wrong. You can actually mark a new "full" indicator on it or remember where it should be. Generally more problems occur due to over filling than the opposite, just like with the old two stroke outboards vastly more issues occurred from zealous owners adding a dash of extra oil to the fuel, thinking that they were protecting the engine; than would have happened with 30% less oil.

I think that you misunderstood my query.
It appeared that KapnD had some method of determining "a proper engine level" without using the factory dip stick marking and I was just curious as to what that method was.

 

[kapnD]

I’m referring to the manufacturers recommend quantity of oil, but that may still need adjustment depending on the particulars of your installation, including installation angle, running angle and degree of roll your vessel exhibits, how hard it pounds, etc.
I use Nizdas method of filling with recommended quantity and monitoring loss to point of stabilization.
As C.Dog stated, and from my experiences, more problems occur from overfilling than under filling.
I’ve run a Cummins B motor on less than seven quarts for over 100 hours (emergency get home after an oil leak incident) with no damage, did not affect oil pressure or temperature. It normally takes twelve quarts. 1400 hours later, still fine, so I’m thinking that no long term damage occurred.

 

[C. Dog]

When the Americas Cup came to Fremantle in the mid 80s, the outfit I was working for picked up the contract for mechanical maintenance for one of the teams, America II Syndicate. They seized the 350 Chevy in the stringer mount OMC Sterndrive fitted to a ~24' Grady White boat at a time when we were on a deadline to get a couple of new surveyed boats out the door and thus decided to pull the engine and have it reconditioned elsewhere. It was eventually reinstalled and trialled on the Swan River, only for us to discover a massive engine oil leak that we had not picked up running it at the shop. Professionals never need towing right? It is never necessary (until it is) so the boss cut the top off a beer can and we used it to scoop oil from the bilge back into this newly rebuilt V8 engine and when that didn't bring the level up to the bottom of the dip stick we topped it up with auto trans hydraulic oil, which got us back to the workshop without needing external assistance. Straight on the phone to the reconditioning factory that had rebuilt it and they sent out their troubleshooter who discovered that the wrong rear main seal had been fitted. That rig never gave them an iota of grief, unlike the pair of manual tilt 90hp Johnnos that OMC had donated for their RIB chase boat when everyone else was using 200hp Mercurys and Yamahas. The manual tilt became too much and we fitted factory hydraulic units to it, then gearboxes blew up etc etc.