M5x Crankcase Breather

[f0xy]

Just wondering how people with the M5x swaps run these? To clarify this is the breather/vent on the front of the rocker cover.

M52 usually runs to the PCV, then back to the inlet, with a drain to the sump, as you probably know. I've seen many people with conversions run this back to the inlet elbow (using a dual port inlet boot), without the PCV, and this is how mine is at present.

This is a new engine build, with a brand new head, and is making very good figures.

The problem I'm having is under heavy engine load - I get smoke for a split second between gear changes out the exhaust, or if I come off the throttle sharply. Driving normally, there is no issue or smoke. After driving hard (i.e track), there is evidence of oil vapour on the rear bumper, which i'm guessing is from said smoke.

I'm assuming this is being caused by said breather when the engine comes 'off load' and is drawing oil from the rocker into the inlet.

I have ran an external catch tank a good while ago, but I dont see how that would make a difference as oil would just be drawn up out of the can rather than the rocker?

Any advice is appreciated.

[JF008]

What engine oil are you using? The oil mist coming from the crankcase is minimal in my case. Maybe you are burning oil.

JF

[JF008]

You can vent to atmosphere for a bit and see if it makes a difference.

[f0xy]

I'm using 5w30. I had a look inside the intake elbow halfway through the last day and there was no excessive oil, near enough dry as you would expect. It never used fluids throughout the day and oil level remained about the same once cool on each occasion.

The motor only has about 2000 miles on it, has even compression across all cylinders and pulls hard. The M54 pistons had new rings, and the bores were checked/honed before assembly, as was everything else. Its making 250hp/250lbft, which makes me wonder - also the fact it only really does it 'off load'.

[JF008]

Off load equal higher vacuum if I'm correct. Some oil may find its way pass the stem seals or piston rings.. You could try a higher viscosity on your next oil change, I think BMW recommended 15w40 in the service manual. It may solve the smoking tailpipes issue. I've just changed from Castrol Magnatec 15w40 to Mobil1 5w30 and I now puff a bit of smoke on compression and quick starts... I know fully synthetic is no good for me, I have more then 100k on the m50 tho.

JF

[mattxr2]

I run mine to a bottle and blocked the boot off. Run on 10/40 magnatec. No issues with smoking on or off load

[DanThe]

Removing the vacuum on the crank case is bad practice, I also had a similar problem with the B30 after a day at Donnington which is a much more revvy track than Oulton for example, I refitted the oil separator but rather than use a bodge load of hoses/clips etc I just drilled a hole in the intake manifold and pushed the separator into it with its original rubber seal. Works perfectly

[f0xy]

Interesting you say that Dan, as these issues came to light yesterday at Anglesey - consistently high RPM 3rd+4th all day.

With that are you still running the drain to the sump, to the original fitting at the bottom of the dipstick? Where abouts did you end up drilling?

Its due to be mapped on standalone any week now, and I really wanted to resolve the smoking before that. Will have to dig out my M52 manifold and remove the separator from it.

[DanThe]

Yes drain to sump for obvious reasons







I was going to fit a bracket to hold it but its that tight in the rubber I cant see it moving at all TBH

[f0xy]

Cool, spot on. Will have a play about with it this weekend and see if any smoke appears when its being mapped. Cheers

[mattxr2]

Do you want to sell your ecu foxy


Iv never had an issue but it's something I'll look into, my car sits 6-7k for a few minutes at a time, I plumbed it that way after having an engine with nikasil problems

[HairyScreech]

Without the negative pressure in the crankcase the blow by from the cylinders will build up and push oil past the rings on the intake stroke (high pressure in the case and low in the cylinder).

This will be a likely culprit for your oil burning between gears as you will be coming off the throttle at high engine speed creating lots of vacuum in the cylinders.

[f0xy]

Would explain it - as I was told the smoke only appeared 50% of the time between gearchanges, not every single time. Will have to get the separator back on as above and give it a try.

[DanThe]

I remember seeing an E30 with an M20 on throttle bodies at Donnington about 8 years ago, they had the breather piped into a modified washer bottle, the shagged old engine was burning so much oil and over fuelling that much the exhaust/rear bumper set on fire at about 11am and the guy had to be flagged down by the marshals who proceeded to cover the back end of the car with extinguisher powder, funny as fook

[mattxr2]

I'll chuck mine on and see if it improves things

[mcjjordan]

So has anyone got a pic or diagram where all the pioework goes?

[f0xy]

Got round to doing this eventually.. Holesaw + new seal from BMW.



Had to clip off the two ridges as you can see for the PCV to fit properly. Ended up getting a new Febi unit as it was only 20 odd quid..





Even though it was a real tight fit and probably didn't need a bracket as Dan said, made one anyway..



Butchered some old cracked pipes for the fittings and just made up one with some proper hose (MCJJORDAN.. from rocker cover vent to the PCV valve)



Not drove it yet but off for mapping shortly so will see if its resolved the smoking!

[f0xy]

So this got mapped back in May and has been great since, no issues and no smoke 'off throttle' at two track days although the same issue (albeit a lot less) has reared its head again this weekend at Spa.

Coming off the throttle at high RPM gives out a small puff of blue/white smoke, sometimes when downshifting with heel/toe. Does not occur every time, only intermittently. Back of the car had some oil residue

I'm pretty sure the brand new CCV has not failed yet.... could it be that its not working well enough for the engine?

I had the rear view camera on, and data logging, so if needed can upload a clip with when its occurring...

[DanThe]

I think its just a high rpm issue, where there is so much oil in the head that it has nowhere else to go. Ive noticed a bit in the intake hose since refitting the separator but I've done a wet day at donington a few weeks ago and it was bone dry, will be at Oulton tomorrow so will see how it goes there, I've never had oil on the back of the car though or noticed smoke in the mirrors

[f0xy]

To be honest I would never notice myself, its only after someone mentioned it to me and I saw it on the rear camera. I had the air box off and the boot was bone dry all day... probably being caused by sustained high RPM (wide open throttle all the way uphill to the limiter in 5th on Kemmel Straight)

Been under the car today and there is a bit of box oil knocking about on the floorpan, looks like the breather has been spitting a bit out on top of the box (ZF), then its being blown to the back of the car, so that could be the stuff on the back.

I'm at Donington next week so will just see how it goes I guess! Have a good one at Oulton

[DanThe]

So I had a fantastic day at Oulton, more grip than I've ever had and going really well! Not even the slightest bit of oil in the intake hose when I removed it to check, was using 4th gear its limits too as the diff is quite long and not worth the change into 5th

How did you get on at dony?

[f0xy]

Good stuff sounds like its going well, I'm there in a few weeks - I was just about to reply in here this evening too...

Unfortunately it was a shi*e day, way too many cars on and 15-20 car queues in the pit lane to get out. I did 54 miles on track.......waste of time really! Although, the puffs of smoke are still happening.

My inlet elbow is always bone dry, same with the throttle body. Just before Donington I swapped out the breather valve + sump drain pipe as a test, but it seems to have made no difference. When I had the valve removed from the inlet, the actual inside of the manifold had a light misting of oil, which obviously isn't making its way back to the throttle body. The sump drain is working as the drain pipe had a misting inside it also.

What I did notice on the video's is it only puffs smoke the split second you go back ON the throttle after coming off it at high RPM, or thats what it looks like at least. Its like some is being drawn into the inlet, then as you go back on the throttle its being burn't and showing as smoke. This would mean the breather valve isn't really working as expected or as efficiently as it should?

[DanThe]

Yeah sounds like its dumping a bit into the manifold, I wouldn't worry about it TBH

[f0xy]

Yeah, just going to see how it goes. I didn't cover many miles so the oil level did not even change - only does it at high RPM too and not when normally driving