Crankcase vacuum solution?

[dsobering47]

I'm struggling to find a solution to having proper crankcase vacuum for my e30 m52 swapped track car. I'm looking for a non-factory solution, as I hate all the plastic components of the stock system, and how they will inevitably fail. I have a JEGS exhaust check valve that pulls barely enough to equalize the pressure/vacuum from the engine, but not enough to actually have consistent vacuum.

Has anybody come up with a viable solution to maintaining proper crankcase vacuum? A vacuum pump with catch can is my next setup...

[TobyB]

Unless you get tricky with exhaust porting, I'd think the roundy- round vacuum pumps would be about the easiest...

t

[djjerme]

I don't know if it's still done, but people used to grab the old GM vacuum pumps from the 70's and early 80's to use for CV systems. They were actually pretty light, and easy to adapt/plum.

[dsobering47]

Well, my exhaust solution now currently has the pressure/vac equalized, but still no vacuum. I've checked with a homemade manometer via the dipstick tube....

I think my M52 would be happy with up to 4-5 in of vacuum during operation....I've seen the domestic belt-driven vacuum pumps go up to 25 in vac, which is too much IMO. A lot of people seem to use smog, secondary air, or what-have-you air pumps, and reverse the polarity to produce vacuum. Problem with that is the moisture/oil in the air will eventually cause the unsealed air pump to fail. Short of running an oil/air seperator between the pump/valve cover, I'm not sure how to combat that problem...

[jlevie]

The only reason for vacuum in the engine is to pull the oil vapors and blowby into the intake. On a track car feed the engine vent into a catch tan and then through a filter to atmosphere. Or better yet, incorporate a coalescing filter in the catch tank. The system will be essentially maintenance free if the catch tank drains back into the sump.

[dsobering47]

Nah, its to help pull the rings against the cylinder walls, aiding compression/power (reducing blowby), and no have pressure pushing oil out of all your gaskets. The reason bmw engineers ran it through the intake is for emissions purposes. I dont want oil/oil vapor on my brand new rebuilt head/valves so I'm pulling vacuum from exhaust, but its not enough.

Having vacuum on the crankcase is a proven performance and reliable engine mod. Doesnt matter if its domestic or import, its known to aide in all aspects of engine operation. I'm not going to vent to atmosphere when I know of a better solution, for a little work.

[jlevie]

Nah, its to help pull the rings against the cylinder walls, aiding compression/power (reducing blowby), and no have pressure pushing oil out of all your gaskets. The reason bmw engineers ran it through the intake is for emissions purposes. I dont want oil/oil vapor on my brand new rebuilt head/valves so I'm pulling vacuum from exhaust, but its not enough.

Having vacuum on the crankcase is a proven performance and reliable engine mod. Doesnt matter if its domestic or import, its known to aide in all aspects of engine operation. I'm not going to vent to atmosphere when I know of a better solution, for a little work.

Never heard that one before and I've doubts as to the logic.

Typical crank case pressures are 4-6" of water, which is a pressure of -.217psi. A piston ring has a very area (~.1.3sqin on an M20) and the total pressure acting on the ring would be at most .28lb. That is inconsequential compared to the spring pressure of the rings. Negative pressure in the crank case does help prevent oil from seeping past worn seals that aren't pressurized with oil on the inside. But then seals in good condition don't seep. Likewise for gaskets.

I've seen a number of professionally prepared race cars (including some built by BMW) and all of them use catch tanks for crank case oil control. If there was a performance advantage you can bet they'd not be using catch tanks.

Before emissions were a concern the crank case was vented directly to atmosphere. To control emissions engines were fitted with positive crank case ventilation systems that maintained a slightly negative crank case pressure and then burned the blowby and oil vapor.

[dirtbag30]

im also trying to figure this out on my m52, basically the last thing i need to do to achieve peak reliability. i wonder if this check valve would be any better then the JEGS one you have

http://www.trmtuning.com/?product=trm-crankcase-evacuation-kit

[burkey001]

Run a dry sump? :)

[TobyB]

Nascar is pretty convinced the drag of running a pump is outweighed by the reduction
in pumping losses. Nascar might not like brie, but them boys always did know a thing or 2.

t
Smokey Yunik liked it in Power Secrets, and that was a good while back.

[dsobering47]

JLevie- Not here to argue the benefits of having vacuum in the crankcase. I, too, have seen different crankcase oil seperators/fluid accumulators/catch tanks and they can vary. Per BMW TIS specs, most all BMW engines like to have vacuum (to varying degrees) on the crankcase. I will run vacuum in my crankcase. My question was to whether or not anybody has done so in this setup before and what sort of performance they were getting.

dirtbag30- The TRM kit is nearly identical to the one sold by JEGS. Same check valve and everything. I had almost 6 in of pressure in my crankcase before that kit and now its nearly equal (but not in vacuum). I'd say it works OK but I'm trying to grab a few in of vacuum while I'm at it.

[Northern]

Mahle provent and run the stock plumbing?

[djjerme]

Another though is that it is actually used in some applications to prevent the crankcase pressure from building up and blowing out the pan gasket, seals, etc..

Reading material:

http://www.dragstuff.com/techarticles/vacuum-pumps.html

http://www.dragzine.com/tech-stories/engine/tech-how-external-vacuum-pumps-free-up-horsepower/

http://nutterracingengines.com/racing_oil_pumps/crankcase_vacuum_facts.html

Getcha some..

[TheTacoMan]

I recently listened to podcast with the owner of Dinan, and he said that he runs a small unit running off the belt that provides vacuum to his race cars. Its like a small supercharged specifically for vacuum in the crank case.

[whodwho]

...

I've seen a number of professionally prepared race cars (including some built by BMW) and all of them use catch tanks for crank case oil control. If there was a performance advantage you can bet they'd not be using catch tanks.

...

And they are probably all running a dry sump system and the scavenging is where they are getting the crankcase vacuum from.