Oil Control In Rb's For Circuit Drag Or Drift

[PSI Parts]

Just been thinking about solving my problem of excessive breathing and looking for a quick fix instead of dealing with the problem (blown rings) and it got me thinking about venting to the exhaust system, like the V8 boys did (using the Moroso Exhaust Nipple). There are obvious limitations depending on where you plumb it into, like clogging up o2 sensors and cat (If you actually run one). It does however have the added benefits of never needing to empty a catch can and removes gasses under vacuum.

Keen to hear pros and cons?

[Cjmartz2k]

There was a lot of talk about doing this over on the NICO forums. People seemed real pleased with the results.

[DCIEVE]

Considered doing that but it really depends on being able to guarentee the exh will be in vacuum at all times, which means big exhaust and straight through mufflers etc. And if you do it direct from the head (with no tank in between) what happens when you dump a pile of oil into the breathers?

[PSI Parts]

I was planning on running a tank with baffles and then to the exhaust.

[DCIEVE]

I assumed you weren't when you listed not having to empty a catch can as one of the benefits

[juggernaut1]

The supra boys do this mod too with a one way valve.

However, I understand that you need to measure and regulate the amount of vaccum with this setup.

Here's a link to a similar thread on freshalloy

http://www.freshalloy.com/forums/showthrea...can+cans+vacuum

Edited August 16, 2009 by juggernaut1

[simpletool]

For a very-mild RB25 GTST with occasional track use is it sufficient to just vent the sump (from the dipstick tube) and the vents from the rocker covers into a sealed catch can then into the stock intake pipe spot?

ie. Do I need to perform these mods??

I think I need to do something as after long 130kph country drives I find a light cover of all down the rear exhaust side of the block. I figure this is from excess oil pressure in the rocker covers. Perhaps another rocker cover vent at the rear?

[bradsm87]

For a very-mild RB25 GTST with occasional track use is it sufficient to just vent the sump (from the dipstick tube) and the vents from the rocker covers into a sealed catch can then into the stock intake pipe spot?

ie. Do I need to perform these mods??

I think I need to do something as after long 130kph country drives I find a light cover of all down the rear exhaust side of the block. I figure this is from excess oil pressure in the rocker covers. Perhaps another rocker cover vent at the rear?

U need a way bigger sump vent than the dipstick hole and it needs to be on the other side of the engine. It needs to be big enough so there is bugger all air blowing up the oil return galleries.

If u wanna do the minimum to it vent the intake side of the sump to the bottom of the catch can using a large hose and the 2 rocker cover breathers to the top of the catch can. put a big breather on it. That way crankcase won't be contantly blowing up the return galleries and any oil in the catch can will drain back down.

[DCIEVE]

I'm with you on venting from the sump, but I still can't see how doubling the sump vent as a drain is a good idea on a street car with 5000+k's between oil changes. Why not send it to the top of the can like the other breathers and throw out the crap that builds up in the can??

[bradsm87]

The 'crap' is pretty much just oil with a little water that'll evaporate out. Better that than losing oil to the catch can on the track and running the sump dry.

[Cjmartz2k]

What are you basing that assumption on? Even if you have had your blow by tested and it's clean, can you safely assume everybody else's is the same way? I know every single catch can I've ever seen has some nasty smelling/looking black liquid in it that I sure as hell woudln't want to put back into my motor oil. Also, if you run the catch cans the way they are designed, you don't dump anything out onto the track. The can seperates out most of the suspended liquids/condenses most of the fumes and saves them in the can for you to dump later, and the little bit of vapor that's left is supposed to be routed back into the intake and burnt in the combustion chamber. That does, however, gum up your intercooler if you have a lot of blow by. That's why the cans stared being used--to help keep the intake tract clean.

All of this worry just so you don't have to top off the oil as often.

[DCIEVE]

The 'crap' is pretty much just oil with a little water that'll evaporate out. Better that than losing oil to the catch can on the track and running the sump dry.

I was talking street car with 5000km+ between oil changes (ie 90% of people on here). If your track car breathes enough oil to affect the level in the sump then the drain might be a good idea, as well as frequent oil changes!

The crap in my can after street driving is condensation that smells like fuel and after a run on a skid pan it becomes oily water that stinks like fuel - there isn't a lot there but I'd much rather it didnt go back to the sump.

I previously ran a can that drained back into the cam cover breathers, and the oil was a fuel smelling mess before 1000km's, so I have tried it.

Edited August 22, 2009 by DCIEVE

[Swiper the Fox]

do what i do...run an intermediate small tank to catch the 'heavy' oil and run it into the sump, then vent the mist from the smaller tank to another larger oil/air separator tank that 'scrubs' the nasties from it and vent it via a filter. My small tank only ever looks like its had sump oil in it...my larger tank when drained has black watery fuelly shit in it id never want back in my engine bearings.

Edited August 22, 2009 by DiRTgarage

[shanef]

do what i do...run an intermediate small tank to catch the 'heavy' oil and run it into the sump, then vent the mist from the smaller tank to another larger oil/air separator tank that 'scrubs' the nasties from it and vent it via a filter. My small tank only ever looks like its had sump oil in it...my larger tank when drained has black watery fuelly shit in it id never want back in my engine bearings.

earlier in this thread you said the line from the bottom of your intermediate tank to sump is a sump vent?

Footnote: Not digging, have been working on a catchcan setup with dan/noel for noels car and have been reading through this thread to double check everything and my ideas

[SLAPS]

I ran a blocked rear and 1.5mm up front for some time. Im really not all that happy with how there is signs of increased wear up top.

Cold starts the reduced oil was noticeable from day 1. Back left rear there was signs of increased wear.

I've now done it properly and vented the damn sump.

If I were to do it again I definitely would not look at a single 1.5mm for a hydraulic head without VCT.

---

As for Dirt not holding grudges. yeah sure bud.. I've seen your comments a good couple years after a pm confrontation. 'grease monkey' lol.

Edited September 19, 2009 by SLAPS

[Swiper the Fox]

earlier in this thread you said the line from the bottom of your intermediate tank to sump is a sump vent?

Footnote: Not digging, have been working on a catchcan setup with dan/noel for noels car and have been reading through this thread to double check everything and my ideas

it works both ways Shane...under boost it releases pressure and if any oil needs returning it will flow down to the sump. Just get Dan/Noel to give me a call if they need a hand...im sure they know they could call me anytine anyway.

Slaps...trying to belittle people who are trying to help on here by calling them childish names does very little. Grow up.

Edited September 20, 2009 by DiRTgarage

[shanef]

it works both ways Shane...under boost it releases pressure and if any oil needs returning it will flow down to the sump. Just get Dan/Noel to give me a call if they need a hand...im sure they know they could call me anytine anyway.

Slaps...trying to belittle people who are trying to help on here by calling them childish names does very little. Grow up.

how does boost get involved? except for the extra cylinder pressure on the top of the rings. shouldnt the sump be 'venting' all the time seeing as there's not an external/secondary vacuum source involved? (your system is totally open)

on the flip side i kinda see what your saying, in that under boost the extra cylinder pressure is bypassing the rings because there is more pressure being forced down then there is vacuum acting aginst the bottom of the rings and the line from the sump to the tank removes this excess pressure. if that were the case then, wouldnt there be a greater need to increase the vacuum below the rings to stop this pressure fed cycle?

they've sorted out a system, these questions are for my understanding

[GTRPSI]

Wow, a Sunday arvo reading till page 24. LOL

I have a different attitude to the problem at hand.

We know the crankcase is pressurized due to blowby.

This pressure runs up the block, through the oil drain backs to the place of least pressure, the breather hoses.

While this air goes up, the oil is trying to go down....common sense.

Take a garden hose, put some oil in it and blow through the other end.

Larger, smoother (take note of m speeds large rear machined drains) helps the oil run back.

Its an old school hot rod trick to open all oil drain backs, but 2 schools of thought how to go about it.

1/ make them larger and mirror finish smooth to let the oil run down faster, or 2/ open them up and paint them with the idea of a rough finish helps the oil pickup heat off the head and block on the way down. The argument with 2 is paint flaking off.

The adding of a drain to the rear of the head gives another escape for blowby under pressure and oil under conditions of even pressure between the sump and cam covers.

The more venting (opening all drainbacks and adding more) means less airflow though each drain individually going from top to bottom giving the oil more of a chance to run back down.

Ideally there should have been a big 5 inch drain to reduce blowby air flow speed up the engine and give the oil a path of little resistance.

Yes restricters help reduce the amount of oil you need to get back down again, a must with high/long periods of RPM.

Just my thoughts...

Edited September 20, 2009 by GTRPSI

[T04GTR]

well this is all very interesting.

porche figured this out with the 924 turbo.. with a factory oil air seperator then off to the breather pipe. nismo has a oil air seperator for the gtr that t's into the rear turbo drain to return the oil with the air continuing on to the rear breather.

[Swiper the Fox]

how does boost get involved? except for the extra cylinder pressure on the top of the rings. shouldnt the sump be 'venting' all the time seeing as there's not an external/secondary vacuum source involved? (your system is totally open)

on the flip side i kinda see what your saying, in that under boost the extra cylinder pressure is bypassing the rings because there is more pressure being forced down then there is vacuum acting aginst the bottom of the rings and the line from the sump to the tank removes this excess pressure. if that were the case then, wouldnt there be a greater need to increase the vacuum below the rings to stop this pressure fed cycle?

they've sorted out a system, these questions are for my understanding

under boost we have seen the amount of pressure coming up the line from the sump...not even noticable at idle or low revs without boost.