Rb26 Head Rear Oil Drain

[legzy86]

Im currently in the process of rebuilding my 26 and converting to single turbo. I've decided to fit a Spool oil drain kit and have noticed every drain kit I have seen installed goes to the sump. Is there any reason why that I can't use the now redundant rear turbo drain to return the oil too. Obviously it still goes to the sump but just makes the whole installation a bit neater.

Cheers Simon.

Edited August 4, 2013 by legzy86

[drag-on silvia]

alot of people do. in fact im certain the nismo catch can actually has a y-pipe that t's it into the rear turbo drain. same shit, draining oil back to the sump

[R31Nismoid]

Do it right the first time you won't need the external drain.

[KiwiRS4T]

Just forget the rear head "drain".If you need to ventilate the sump do it from the intake side and run the hoses to a catch can.

Im currently in the process of rebuilding my 26 and converting to single turbo. I've decided to fit a Spool oil drain kit and have noticed every drain kit I have seen installed goes to the sump. Is there any reason why that I can't use the now redundant rear turbo drain to return the oil too. Obviously it still goes to the sump but just makes the whole installation a bit neater.

Cheers Simon.

[legzy86]

Do it right the first time you won't need the external drain.

What do you mean by this? So many mixed reports on this forum as on oil control. Currently running a Nitto oil pump, 1.2 mm oil restrictor and modified oil return galleries.

[Shoota_77]

He means wait till you spin a bearing or blow up an oil pump (which WILL happen...) pull the engine out, send off the sump to be extended and have additional -10an fittings welded on for venting to catch can.

[legzy86]

He means wait till you spin a bearing or blow up an oil pump (which WILL happen...) pull the engine out, send off the sump to be extended and have additional -10an fittings welded on for venting to catch can.

Well if you had read the first post and my last post you would have noticed that the engine is already out and I already have a nitto oil pump. Some people really need to read before they start writing their useless comments.

[Shoota_77]

Strong words from a faceless clown.....

Don't be so defensive bloke. I was offering assistance. If you don't want help, don't ask.

[GTSBoy]

Well, they're not useless comments, because the now accepted wisdom is that external drains are unnecessary.

[legzy86]

Well you obviously didnt read anything before you decided to write your comment mate. Honestly cant see how draining the catch can back to sump any different.

[Shoota_77]

You're partially correct. I read some of your comments. Most of them weren't worth reading...

The hose from the sump to the catch can is not a drain, it's a breather or "pressure equaliser"....

[legzy86]

Seems like the drain kit would do the same as well as the PCV valve..

[KiwiRS4T]

What R31 Nismoid is saying is that if your piston and ring clearances etc are spot on you shouldn't have significant blowby although RB30s seem to manage to generate excess pressure in the sump anyway. if you read say the last ten pages of this thread:<br />http://www.skylinesaustralia.com/forums/topic/110680-oil-control-in-rbs-for-circuit-drag-or-drift/?hl=sk%20oil%20control<br />you will find the real world solutions that people have come up with and a fitting at the back of the head is not one of them. Relieved oil drains and restrictors are good but if you have the engine out consider also an enlarged and baffled sump and take the opportunity to put a couple of 20mm outlets at the top of the sump. if you need to ventilate the sump you don't want the pressure going in to the cam covers but out to a catch can. The solutions from people who have fixed their oil problems (including me) are there to be read.

[R31Nismoid]

^ pretty much this.

External drains are a by and large, band aid fixes to a problem not correctly addressed during the initial build.

Granted some circumstances require them, they are few and far between.

[Shoota_77]

If the pressure in the sump is going into the catch can then inadvertantly it's going to feed back into the cam covers as it's all linked. The pressure doesn't disappear when it gets to the catch can, it has to go somewhere unless the cam covers are in permanent vacuum which I believe them to only be during closed throttle decelleration.

I think having feeds to the head and to a catch can would be beneficial as it should help to create a nice balance of pressures between all sectors of the engine (cam covers, crankcase positive side, crankcase 'vaccum side' (or just lower pressure side if not actual vacuum)). Having a 'balanced' vacuum/pressure situation in the engine should be beneficial as there is reduced pressure in the crankcase causing less oil to be pressurised past the rings and less vacuum in the cam covers which reduces oil draw down passed the valve stem seals on deceleration.

This is just my understanding of it and happy to be proven wrong but it makes sense to me! At the end of the day overkill is better than underdoing it. If the hose to the back of the engine does no harm and may help, why not do it?

If the engine is built properly and all the failsafes are done then it should be right.

It would be interesting to have pressure sensors placed in the three sectors of the engine to see what they're doing under certain circumstances. This would be the only way to 100% understand what is happening. However through a lot of trial and effort by everyone on this site the answers are pretty much discovered anyway.

[GTSBoy]

The mistake you are making is saying "the catch can". With the emphasis on the the word "the". If you do this stuff properly, you will have a catch can attached to the cam covers and possibly vented via a second catch can into the turbo intake. You will also have a sump vent up to a separate catch can which will need to be separately connected to the turbo intake. Whatever the pressure situation inside the crankcase/cam cover (which should be approximately the same) you have your vents connected to a decent source of suction (or vented to atmosphere if race car).

Variations on this scheme (probably more accurate, given they reflect peoples' actual setups) have been discussed in the oil control thread and a couple of other places lately.

[Shoota_77]

You're right, we should transfer this discussion to the oil control thread.

[legzy86]

Ok this is some good stuff thanks!. I have already extended the sump and have installed the tomei sump baffle which I had to extend slightly to match the extended sump. I already have the head rear drain kit so I will be installing it as I can't see it being a bad thing. I just have to weld a fitting onto the sump to breathe back to the catch can. At the end of the day this car will be built for the drag strip with the odd street use so I shouldn't have the problem that is seen with circuit use as long everything else is in check which it will be.

[portaz]

My rear head drain was originally connected to the turbo side if sump, I took my tuners advise and welded a fitting on intake side of sump as apparently the direction of rotation has a large part to play in this. So far my engine hardly breaths at all. About 8 hours on dyno and catch can Is dry , we do have other issues though and are installing a second and possibly 3 rd catch can just in case. Just try to get the fitting above the oil line in the sump. Pm me if I can help you in any way.

Scott

[G37Sam]

Do you guys drain your oil catch back to the sump? My mechanic left it wiggle in open air as he believes hooking it into the sump will force oil in the wrong direction.

Or should I just block it off and fit a small filter on it?

Edited August 5, 2013 by G37Sam