340i

Hello everyone!

I'm running an n/a LS7 engine converted to a wet sump system (LS3 oil pump), installed an oil catch can (it has vent filter on top and 2 inlet ports for hoses)...

Althrough it has an LS7 valley cover (LS3's doesn't fit the block) with 1 outlet near the throttle body and taller valve covers (red ones with LSX tags from Summit) with 1 outlet on drivers's side and one on passenger's side - like stock LS3 covers has I guess.

Also installed a "FAST LSXR 102mm" intake mani (it has 2 inlets) with 102 TB DBW.

The question is: how should I connect the hoses for the crankcase vent system to make them run in my oil catch can and then just outside of it (via filter) but not back into the engine?

Found a lot of pics but it seems like everyone has a "return" line after a catch can back into manifold...

Thx in advance!

tech@WS6store

iTrader: (2)

If your catch can has a breather but no valve to regulate where the air goes then you should not put it into the manifold.
The valley tube goes to the pass side of intake.
The valve cover/s should go to either a port on the tb if there is one (cable tbs have them) or to a port in the intake tract after the maf. The driver side port is for evap and should be capped if not used for evap, it should not be used for catch can routing.

SoFla01SSLookinstok

I'm thinking you don't want the oil fumes back into your intake?

If you don't use your engine to evacuate the crank case you will just have to vent to the atmosphere. Or get a vacuum pump. With just thinking of venting crank case pressure I would bring both valve cover ports to the vented catch can. I would also maybe run a line from the valley cover port over to the catch can & maybe splice it in. This giving three places where the pressures can vent from the engine. Also the bigger the ID on the hoses the better. More area for less pressure/resistance. Cap off the ports on intake manifold & TB.

I didn't want oil fumes/puddles in my intake anymore. Went with a vacuum pump. Very happy.

Just my thoughts.

tech@WS6store

iTrader: (2)

A vacuum pump is completely different. The vapors wont vent if atm pressure is higher than internal pressure venting them. Plus you have a potential fire hazzard just venting it. Ive literally seen a few blow oil out of those vent filters. why make a mess or cause an issue when a properly operating pcv system is what works best? If you have a huge blowby/pcv issue, a catch can is only a bandaid.

SoFla01SSLookinstok

Yes a vacuum pump is different. You have to buy one & install it. It also gives you crankcase vacuum at high rpm/load. Something no pcv system can do.

Your definitely right.

I know pcv systems are the legal/clean way. Getting you puddles of oil in the intake. Maybe this is a race car or something. Just gave an idea.

tech@WS6store

iTrader: (2)

The clean air side does basically pull the air out of the crankcase even at high rpm. it may not make a vacuum but it does relieve the pressure.
A pcv system will not always leave a puddle of oil in your intake either. if you engine has excessive pcv or blowby issues or low tension oil rings then yes it can, but those arent the pcv systems fault.
Installing a filter (basically what a catch can is) is the best way to combat it short term, but addressing the actual issue is the only real solution but not always the affordable or easy one though.
Sucking all of that oil mist etc through a vacuum pump isnt very good either unless you have an air oil separator/catch can before it also.

SoFla01SSLookinstok

I thought it was more like.. at manifold vacuum the pcv is operating, using the vacuum to evac the crankcase. At WOT you lose manifold vacuum & crank case pressure goes up. Now all lines connected to crankcase, even the clean air line, are now just vents for the pressure to go. Why sometimes people talk about seeing oil in the clean air line. I pulled my ls6 intake off, all stock motor, under 50k miles, & there were puddles of oil.

The maker of my vacuum pump actually wants some oil mist to go through it. Lubricating the vanes.

tech@WS6store

iTrader: (2)

The air rushing past the small tube still creates a low pressure area whether in the intake or on tb or in intake tract. The clean air line isnt a one way valve. More pressure in the engine than atm the air wilk come out normally, more pressure outside it would stay in the crankcase.
Basically the same as a bead blaster with a syphon system on it. Air flowing fast enough past a small tube that is perpendicular (or angular) to airflow will suck the sand..or air...out. Otherwise the pressure will push itself out. If the air flows into the clean side at wot also it stops the advent of a vacuum in the crankcase with clean air in and dirty air out.

A little yes, but excessive oil wouldn't be good.

SoFla01SSLookinstok

I understand what you're saying about the air going past small tube. The clean air line has no valve true. The only time pressures would be even, outside/crankcase, is when the engine is off. Now the last sentance you wrote. First off why would you want to stop crankcase vacuum at WOT? Even if it could appear somehow. At WOT every port attached to the crank case becomes a vent tube for pressures. All engines have blow by & create crank case pressure.

Yep. Oil mist or fumes.

tech@WS6store

iTrader: (2)

I didn't say stop vacuum at wot.
The clean air tube literally introduces clean air. Trying to suck air through a straw with your finger nearly covering the end is alot harder than half way etc. IF the pcv system was not intentionally metered it could pull alot more air, but also alot more oil mist possibly.
The way the system operates changes with airflow and pressure differential changes.
If you want to split hairs yes all engines have "blowby" so to speak, but where do you think crankcase pressure comes from? def NOT primarily from blowby.

I meant a little oil would be ok on the pump but excessive oil no.

SoFla01SSLookinstok

As I have a vacuum gauge connected to my crankcase I know where it primarily comes from. In my engine anyway lol. When driving in vacuum it will drop under WOT. It's linear to the gas pedal. That says crankcase pressure comes from blowby.

tech@WS6store

iTrader: (2)

Yours yes, but not all.

kingtal0n

iTrader: (1)

Pressure passes the rings into the crankcase- that is how crankcase pressure goes up. Yeah, its "blow by", check yourself. Where else has a higher than atmospheric pressure been created? The only thing on an engine doing compression is the piston. And a/c compressor I guess. And PS pump. And tiny spaces between gears of the trans and diff I suppose. But none of those things are tied to the engine crank case? Oil pump isn't pumping any air around so....


If you are looking for a non-contaminating intake air path driven PCV solution for WOT that still drives low pressure signal for evacuation (race car stuff) you either use a vacuum pump, OR an exhaust driven venturi.

IF the engine is healthy, properly assembled for cleanliness and reliability, there is no reason you can't design a nice internal air-path solution, off the post air filter tract. As you adjust air-filter flow resistance (think of it clogging up or getting smaller) the pressure drops behind it, robbing the engine of power but increasing the low pressure supplied to the crankcase, which means cleaner oil and longer healthier engine life in most cases. OEM paper air filter tracts are designed with a bit of both intentionally (reasonable flow and reasonable pressure drop for PCV system)- it helps that paper filters tend to clog quickly. I only will use a paper filter on the street, if given the choice.

340i

Yeah - it's a racecar and the reason I don't want a return line back into my intake is just because at WOT there will be oil 100%.
Engine was completely reassembled with all new internals and runs great (already 460rwhp at the dyno and not done yet - had to fix some issues) and a catch can has been installed to prevent oil into actually clean and nice intake manifold

So I'm actually need to vent it into atmosphere and not worry about cleaning a mess inside of the engine.

BTW no valve on a catch can - just a 2" filter on top of it and 2 inlet ports (and a drain line at the bottom of course )

340i

Did I got it right:
1) I should connect the valley tube to inlet on my manifold (there's a port on pass side just after the TB)
2) If both valve covers should be connected to an intake after the MAF then what should I connect to a catch can? )

And you're right - there's a breather on top of my can and 2 inlet ports as I've mentioned earlier but no return lines - the only way out of it is through a breather filter...

tech@WS6store

iTrader: (2)

Normally valley cover tube goes to catch can then to intake. you can y valve covers together and go into intake tract or into 2nd catch can then into intake tract.

340i

But can I route valley cover tube and both valve covers into a catch can and just cap off the inlets on manifold and TB?

I guess the only reason why it should be routed back is because of 'already calculated' air that went through the MAF?

I'm goint to dyno it (not myself but the professional tuner guy) and could make some corrections with HPtuners - just don't like the idea of purging the engine with oil vapors )))
There's no O2 anyway...

tech@WS6store

iTrader: (2)

If you are running 1 tube from any part of the engine and to the intake and the others are exposed to air outside it wouldnt be a good idea. vent all to atm or run the pcv right those are the best ways. The air after the maf is metered yes which allows easier tuning than adding another source of fresh air.

340i

Well in that case I will get a higher idle RPMs along with wrong A/F ratio and actually there'll be a simple air "leak" inside of the engine that MAF can't "count"? You mean that?
So can I connect a valley cover tube direct to the 1st inlet of my catch can and "Y" both tubes from the valve covers and connect them to the 2nd one AND just cap off the inlets on a manifold and TB?
It will be vented through the breather filter to amtosphere, there will be no "return" line into my intake so I'll get a clean intake in any cases?

I've made the same thing on BMW's V8 (m60b40) - just connected the tube from the engine (there's one like a valley cover tube on LS engines) to a catch can and it vents to amt, all the "return" inlets are capped off - still the same 650 RPMs at idle and maybe 1 time of 20 engine may shut down then TB is wide open and then suddenly closed but it's no big deal because racecar - there's almost no moments then you need an idle RPMs at the race track.

tech@WS6store

iTrader: (2)

Correct