[KevM2]

Originally Posted by doughboy

They do in a way - its in the cylinder head cover, cyclonic oil removal and drainage return.

It just doesn't work very well...

It gets plenty of the physical oil out of the gas stream, but not the oil vapours, mainly as the head cover is plastic and gets very hot the oil vapours don't condense so they carry on back to the intake tract / front turbo / intercooler / charge pipes / inlet manifold and condense in there instead!

A separate catch can will only catch oil mist ejected under boost conditions. Not when idling or on overun, in those cases a valve in the head cover opens and the crankcase is directly scavenged by the vacuum behind the throttle plate, so oil vapours are then sucked directly into the inlet manifold locally, bypassing any catch can etc.

There is nothing you can do to stop oil & carbon deposits getting on the valve stems and inlet tract during the idle or overun phases.

But (i'm fitting the BMS OCC) a OCC will reduce greatly the "on boost" oil vapours (of which the volume is much greater than idle vapours) and which cause the most mess going back through the turbo etc.

Love a reply from someone who knows their shit! Thanks!

[doughboy]

I went through this whole thing tuning an N54 335i in 2010, it's great to be back in a turbo 6 again!

[omasou]

Any pictures of what the OCC caught? From the posts I have seen so far there isn't much if anything to catch w/the S55.

[hlm2c]

I installed the BMS OCC on mine around 1000km. Prior to break in at ~1950 km, it was about a third full. After break in, I checked again at 4000 km and also at 6000km. Bone dry since then.

[chmura]

Any DIY on how to install the BMS OCC?

[doughboy]

It's pretty straightforward. I did mine in about 10 minutes.

I did add a piece of high density sticky foam to one of the radiator hoses where the bottom of the OCC just rubs it to avoid any possible damage to the hose.

I'm planning to remove and empty / clean it this weekend so ill get a few pics.

[KevM2]

Originally Posted by doughboy

It's pretty straightforward. I did mine in about 10 minutes.

I did add a piece of high density sticky foam to one of the radiator hoses where the bottom of the OCC just rubs it to avoid any possible damage to the hose.

I'm planning to remove and empty / clean it this weekend so ill get a few pics.

Please let us know how much it has collected and how much mileage. If it's going to be bone dry then I won't install my BMS catch can that's been sitting in my garage for the last couple of months.

[chmura]

Originally Posted by doughboy

It's pretty straightforward. I did mine in about 10 minutes.

I did add a piece of high density sticky foam to one of the radiator hoses where the bottom of the OCC just rubs it to avoid any possible damage to the hose.

I'm planning to remove and empty / clean it this weekend so ill get a few pics.

Yes please take some pics of the install and of course how much oil has collected!

[msdss]

Originally Posted by doughboy

There is nothing you can do to stop oil & carbon deposits getting on the valve stems and inlet tract during the idle or overun phases.

But (i'm fitting the BMS OCC) a OCC will reduce greatly the "on boost" oil vapours (of which the volume is much greater than idle vapours) and which cause the most mess going back through the turbo etc.

I've never heard that overrun had any negative side affects. If overrun causes an increase in oil deposits on the valves, then why do so many car manufacturers and tuners tune to include them? Sometimes excessively.

I like my stupid OEM burbles. But I can live without them if they are causing unnecessary wear.

[msdss]

Originally Posted by chmura

Yes please take some pics of the install and of course how much oil has collected!

I found a video of someone with an M2C and the BMS OCC.
TLDR: About 1/8th a cup of fluid was collected after 1 month of driving. That seems like a considerable amount for such a short time.

https://www.youtube.com/watch?v=ueQKh5ORo3g

[Got f1?]

A few things to consider with catch cans.

1 - If you daily drive in the winter, there is some risk that the liquid freezes which clogs lines and causes major issues. This happened to me on my VW Golf R. Standing in freezing temps with a blower dryer was not fun.

2 - If your driving patterns are more short trips where the engine does not run at full temp long enough to cause condensate to evaporate, there will likely be more fluid in the can.

3 - There is a lot of debate about whether or not catch cans have any impact on carbon build up on valves in direct injected engines. The location the catch cans typically connect negates much benefit from the deposits on the valves. What it will do is reduce the liquid seen in the above video and keep it from being in the oil.

[omasou]

Originally Posted by msdss

I found a video of someone with an M2C and the BMS OCC.
TLDR: About 1/8th a cup of fluid was collected after 1 month of driving. That seems like a considerable amount for such a short time.

https://www.youtube.com/watch?v=ueQKh5ORo3g

Dude need to take the camera off his head. Now, I'm motion sick, sheesh.

Looks like water not oil?

[doughboy]

Originally Posted by msdss

I've never heard that overrun had any negative side affects. If overrun causes an increase in oil deposits on the valves, then why do so many car manufacturers and tuners tune to include them? Sometimes excessively.

I like my stupid OEM burbles. But I can live without them if they are causing unnecessary wear.

No , maybe a UK terminology thing?

Overrun isn't burbles, it's the term for rolling with your foot OFF the gas. When an engine is being turned by the moving car then a vacuum is generated in the inlet manifold and the crankcase fumes then are drawn directly into the inlet manifold without passing through the inlet/turbo/intercooler route.

[Got f1?]

Originally Posted by omasou

Looks like water not oil?

Exactly. This is condensation built mostly on cold starts as I was referencing in my earlier post.

[omasou]

Originally Posted by Got f1?

Exactly. This is condensation built mostly on cold starts as I was referencing in my earlier post.

Yes, agreeing with you.

It's catching condensate that's suppose to burn off and like you mentioned could freeze if not maintained.

[doughboy]

Originally Posted by Got f1?

A few things to consider with catch cans.

1 - If you daily drive in the winter, there is some risk that the liquid freezes which clogs lines and causes major issues. This happened to me on my VW Golf R. Standing in freezing temps with a blower dryer was not fun.

2 - If your driving patterns are more short trips where the engine does not run at full temp long enough to cause condensate to evaporate, there will likely be more fluid in the can.

3 - There is a lot of debate about whether or not catch cans have any impact on carbon build up on valves in direct injected engines. The location the catch cans typically connect negates much benefit from the deposits on the valves. What it will do is reduce the liquid seen in the above video and keep it from being in the oil.

The liquid is a nasty corrosive emulsion of water, part burnt oil and fuel. It might look watery but it isn't water. You should smell it, rancid, stinks like creosote.

Normally all that would be sucked back into the inlet tract, through the turbo and intercooler and then the carbon in it burns onto the back of the hot valves.

All the carbon on valves comes from crank case vapour, nowhere else.

The liquid in an OCC if the OCC wasnt fitted would never get in the oil, not possible, it would just get passed through the intake as above.

[msdss]

Originally Posted by doughboy

No , maybe a UK terminology thing?

Overrun isn't burbles, it's the term for rolling with your foot OFF the gas. When an engine is being turned by the moving car then a vacuum is generated in the inlet manifold and the crankcase fumes then are drawn directly into the inlet manifold without passing through the inlet/turbo/intercooler route.

I suppose the burbles are a tuned in side affect of overrun then, and not the overrun itself. So burbles aren't causing any issues themselves. Gotcha. Thanks for clarifying!

[speedsnice]

Installed my BMS catch can today. I have run catch cans on most of my cars over the years.

[KevM2]

Originally Posted by speedsnice

Installed my BMS catch can today. I have run catch cans on most of my cars over the years.

Nice!! Hey did you need to remove the carbon brace to get it installed? If so, are those bolts reusable?

[speedsnice]

Originally Posted by KevM2

Nice!! Hey did you need to remove the carbon brace to get it installed? If so, are those bolts reusable?

I removed the carbon strut brace in order to install BMC drop in filters and do a charcoal filter delete. The bolts use low tightening torque and are reusable.

[doughboy]

I didn't find it necessary to take the strut brace off.

Just slipped the OCC under it and attach the bracket afterwards.

Same reverse for removal.

[KevM2]

Well, I just spent 20mins trying to pry off that damn PCV hose from the engine without any success. I know there are tabs you gotta use a screw driver to press as you wiggle the hose off but there are 5 tabs all around and there's also that plastic thing onto which the engine cover sits on that's in the way and makes it super hard to get to the tabs on one side. Any advice?

UPDATE: went at it again with more force and managed to get the damn thing off but in the process some of the small tabs broke but I don't believe there is another way around this. I don't think those smaller tabs are needed anyways. Here's the pic of the small tab I'm talking about: