Does the N54/55 engine run a vacuum?

Racing engines run a vacuum, something to do with oil lubrication + horsepower gain, but I don't understand why, or whether the N54/55 runs a vacuum.

Suspect they do, as the dipstick, a potentially large leak, has been scotched.

Some engines have vacuum pumps.

BMW mechanics, what can you tell us?
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Sounds like you're speaking of crankcase vacuum.

If so, this is an old old trick. It's used to alleviate the pretty nasty parasitic horsepower loss due to oil "windage", or oil being whipped up into long ropey strands that tangle up with very fast-spinning crankshaft when the engine is running at high RPMs.

Decent oil control + little/no air = little or no windage.

its a forced induction engine....

Here you go Cal:

http://nutterracingengines.com/racin...uum_facts.html

They talk about what you were asking about.

Originally Posted by galahad05

Sounds like you're speaking of crankcase vacuum.

If so, this is an old old trick. It's used to alleviate the pretty nasty parasitic horsepower loss due to oil "windage", or oil being whipped up into long ropey strands that tangle up with very fast-spinning crankshaft when the engine is running at high RPMs.

Decent oil control + little/no air = little or no windage.

Originally Posted by Orient330iNYC

its a forced induction engine....

Forced induction, yes, but here we're concerned about crankcase vacuum.

Somehow BMW moves air + fumes from the crankcase to incoming air [crankcase ventilation]. A centrifugal separator's built into the engine to pevent oil from leaving the crankcase and

1) coking incoming air valves at the cylinders
2) burning oil

So, how is crankcase gas made to move?

when the engine is under boost, the crankcase is pressurized. vacuum for the brakes is provided by an aux pump.

see here:
http://www.n54tech.com/forums/showpo...80&postcount=1

If I remember correctly, the crankcase is not under vacuum and the dipstick has nothing to do with BMW removing it. The 335d has a dipstick, does it not?

Originally Posted by galahad05

Here you go Cal:

http://nutterracingengines.com/racin...uum_facts.html

They talk about what you were asking about.

Thx galahad!

N54/55 operates @ what pressure? Anyone?

Honestly, I don't believe BMW uses this trick with the N54 or N55. I doubt they even use a windage tray.

So, to answer your question CAL....I think 1 atmosphere, or about 15 inches of mercury.

Originally Posted by galahad05

Honestly, I don't believe BMW uses this trick with the N54 or N55. I doubt they even use a windage tray.

So, to answer your question CAL....I think 1 atmosphere, or about 15 inches of mercury.

If so, they depend on their mechanical [passive] separator to keep crankcase vent gas clean.

But what if boost is generally higher than normal - read just about any 335i tune? Not heavily modded - those engines are known to have intake valve coking / crankcase vent blow-by issues. Talkin' average schmos w/JB3/4....?

Of interest, believe Audi supercharged engines were known to coke valves. Maybe that's solved? Westy-West?

Here's what Terry says @ N54Tech.com yesterday, post #15, high noon, regarding vacuum and crankcase ventilation:

IMHO there is no reason to expect massive amounts of blow by unless there is a ring sealing problem.

But we did a BETA test awhile back with a breather connected to #2 which worked quite well although there was some odor that went with it. What we used to do with domestic motors was vent to the exhaust using a check valve / Venturi effect. Maybe doing that post turbo could be done if you wanted a little vacuum.

Terry's no poseur - over 20K posts there!

Wait, I think we (you vs everyone else) are talking at cross-purposes here.

I (we?) were talking about using crankcase vacuum to gain horsepower. You're talking about ways to minimize oil contamination on the intake valves/combustion chambers.....


The N54 guys worried about the latter usually use a catch can.

Originally Posted by galahad05

Wait, I think we (you vs everyone else) are talking at cross-purposes here.

I (we?) were talking about using crankcase vacuum to gain horsepower. You're talking about ways to minimize oil contamination on the intake valves/combustion chambers.....


The N54 guys worried about the latter usually use a catch can.

Both as they're related.

An engine using centrifugal separation of liquid [oil]/gas needs gas exiting the engine @ some velocity, provided how?

If blowby's minimal, then is gas extracted, creating negative crankcase pressure? Blowby + extraction?
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