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mmmmmmmmmm thanks - might try find someone local to help as i cant weld lol - i have a 25/30 going in soon so would like something like this done - as i dont think oil restriction is very good (i think)

Only just read your post as font was so tiny! Oil restrictors are the bottom line basis for any oil control system. They are designed to reduce the chance of your emptying the sump of oil.

So if one is to block one of the the oil and put a restricter on the other. Has anyone experienced more wear on the cam journals,lifters etc.<br /><br />Also the head drain mod. that is to drain oil correct? Not used as a blowby oil pressure relief system. With oil back up to the head through the drain hasn't anyone used a one way valve to stop oil from the sump being pumped into the cylinder head

So if one is to block one of the the oil and put a restricter on the other. Has anyone experienced more wear on the cam journals,lifters etc.<br /><br />Also the head drain mod. that is to drain oil correct? Not used as a blowby oil pressure relief system. With oil back up to the head through the drain hasn't anyone used a one way valve to stop oil from the sump being pumped into the cylinder head

Extra external vent lines are installed to provide a path for gases to flow up (other than through the existing in block oil drains). The in block oil drains are opened up to increase cross sectional area (if you like). The total increase in connection area between bottom of engine and top of engine is the secret to allowing enough oil to get back down - simply by decreasing the velocity of the gas coming back up.

yeah rear is restricted front aint - but engine is together so i will be restricting the vct the best i can and having a custom catch can done with drains and vents in sump and accusump set up -

if i really have to and is an affordable option ill get the head taken off and another restrictor in -

im still learning - lot of people on SAU have been helpful explaining things and helping me learn (thanks)

Only just read your post as font was so tiny! Oil restrictors are the bottom line basis for any oil control system. They are designed to reduce the chance of your emptying the sump of oil.

So if one is to block one of the the oil and put a restricter on the other. Has anyone experienced more wear on the cam journals,lifters etc.<br /><br />Also the head drain mod. that is to drain oil correct? Not used as a blowby oil pressure relief system. With oil back up to the head through the drain hasn't anyone used a one way valve to stop oil from the sump being pumped into the cylinder head

In regards to more wear on the cams etc. I dont think there will be an issue. I pulled my oil cap off the other day and theres plenty of oil splashing around in the head. I have the middle feed blocked and a 1.5mm restrictor in the rear I think. and this was up the front of the engine. Looks like plenty of oil getting around

Plenty of other people have done the same thing anyway with no issues

  • 4 weeks later...

Actually reading back to front I figured I might find evolved information but it had all got a little confusing.

If I may ask, can anyone recommend the best way I can go about this that is most suited to my particular RB?

Have bought a smashed R34 (neo turbo auto)

Putting it into my S15 with a 33 manual box, engine is mint and legit 55,000k stock non modified.

Whilst I have the engine out I'm in the best position to sort out the oil system.

Originally the fist mod I ever did to the SR was a Tomei sump and I'd like to go the same route.

So can anyone suggest a great sump for the 25?

And given I've got a neo version, what is the best path for oil control mods that I can do?

Very much appreciated thank you in advance

Drain is easy. If paranoia about windage takes possession of your brain, just put the bottom end lower than the oil level. There isn't actual positive pressure in the sump that pushes oil up a drain into a catch can. If the catch can is up high enough then there is a head of oil to push it back down into the sump. That's kind of the point.<br /> <br />Too many people imagine too much half arsed physics when thinking about this stuff.

<br /><br />Haven't actually calculated the head due to height at the highest possible location in an RB enginebay. Do you think that head force is enough to keep the oil down in a sump. Not sure how you would also measure the pressure in the sump.

It's all about providing enough open area to permit gases to move upwards at the same time as liquids are moving down. So what I said earlier, that you quoted above, is not strictly true. IF you do not have enough open area then the oil will hang up above the gas, blocking the flow channels, and then pressure WILL rise in the sump. And then you get bubbles erupting up into the top half of the engine carrying oil back up and that's when you get oil control problems.

But.....IF you do the things that you should do, which are 1) restrict oil supply to the top end and 2) provide enough flow area by way of extra breather channels, then you should be hard pressed to get into too much trouble until you're in the territory where G forces affect sump design and so on.

  • Like 1

Okay this may be annoying as I know I did when I read the same questions over and over, but I have read through and there are a hell of a lot confusion. Just to clear it up I understand the table fine and all the drilling of the oil returns and the die grinding a shamfer on the return holes as well. But I have read post contradicting each other in returns to which side the rear he'd drain goes on to. Some say intake side and some say exhaust because of crank windage. It would be easier if someone just said inlet or exhaust rather then left or right lol.

Also the diagram that has the hoses going from inlet side to a catch can with a vented filter then from bottom of catch can into the exhaust side of the sump, is that any good? As I've also read that the moisture content isn't good for putting it back into the sump? Also read guys have both of those hoses going to the inlet. Example hose coming from inlet then returning into inlet from bottom of catch can rather then back into exhaust. What would be the best option to stop the head filling up and or catch cans over filling and for the motor to just be sweet under big boost. Other then restrictors and oil return drilled and chamfered.

My eyes are bleeding and my head is spinning from reading 54 pages of this. I plan on doing both rear drain and catch can from sump but should I return from catch can or what's the go? Some simple and straight to the point advice or help would be awesome haha. Cheers guys

Okay this may be annoying as I know I did when I read the same questions over and over, but I have read through and there are a hell of a lot confusion. Just to clear it up I understand the table fine and all the drilling of the oil returns and the die grinding a shamfer on the return holes as well. But I have read post contradicting each other in returns to which side the rear he'd drain goes on to. Some say intake side and some say exhaust because of crank windage. It would be easier if someone just said inlet or exhaust rather then left or right lol.

Also the diagram that has the hoses going from inlet side to a catch can with a vented filter then from bottom of catch can into the exhaust side of the sump, is that any good? As I've also read that the moisture content isn't good for putting it back into the sump? Also read guys have both of those hoses going to the inlet. Example hose coming from inlet then returning into inlet from bottom of catch can rather then back into exhaust. What would be the best option to stop the head filling up and or catch cans over filling and for the motor to just be sweet under big boost. Other then restrictors and oil return drilled and chamfered.

My eyes are bleeding and my head is spinning from reading 54 pages of this. I plan on doing both rear drain and catch can from sump but should I return from catch can or what's the go? Some simple and straight to the point advice or help would be awesome haha. Cheers guys

The main things are

  • Increased sump capacity
  • Smaller oil restrictors
  • Lines from head to catch can, and catch can to sump (above oil level).

    This is to reduce/equalise crankcase and head pressure so that the oil can more easily flow down the returns that are already there.

    You can also put in the "drain" at the back of the block, but this is effectively just equalising the pressure so that the existing returns are used more effectively.

Remember crankcase pressure is due to blow by, not windage.

This is what is stopping the existing drains from being used.

If you can reduce this pressure then everything will be fine!

And the catch can shouldn't really get any oil in it, especially with smaller restrictors, if it is you need to improve the baffles in the valve covers.

Hope that makes sense!

Edited by Jazzadub
  • Like 1

Depending on your setup (street), Gtsboy explained a bit better. If you do the first two mods and make your sump bigger with fittings for future use incase you really need to do the headdrain. You should be alright provided the track is street use and sees the track now and then without pulling crazy fighter pilot gforces. When you open up the oil drain holes you also help oil go down easily while also venting crankcase pressure. Stand to be corrected if I doesnt make sense.

Baffling the sump should also be done imo it's a relatively cheap mod that can be done while increasing capacity.

  • Like 1

The main things are

  • Increased sump capacity
  • Smaller oil restrictors
  • Lines from head to catch can, and catch can to sump (above oil level).

    This is to reduce/equalise crankcase and head pressure so that the oil can more easily flow down the returns that are already there.

    You can also put in the "drain" at the back of the block, but this is effectively just equalising the pressure so that the existing returns are used more effectively.

Remember crankcase pressure is due to blow by, not windage.

This is what is stopping the existing drains from being used.

If you can reduce this pressure then everything will be fine!

And the catch can shouldn't really get any oil in it, especially with smaller restrictors, if it is you need to improve the baffles in the valve covers.

Hope that makes sense!

Yes thank you. I have sent a pm if you don't mind so I don't spam up this post

What sump are people using these days?

I played with a Moroso sump and swapped to a Tomei for the long term on an SR but I don't know a lot about RB's.

I've Googled and found some mixed results, some even leading back here to playing the idea down and just adding extra oil (ha) but I want to increase capacity and have baffles or at least gates like my last one.

High energy was mentioned?

Nothing coming up on FR Sport or even Ebay?

Kind regards

Thanks lots for the replies :)

Scoured the turbo Calais forums as well after Google led me there and I've found the other popular option is a spool imports modified sump pan.

Anyone have any first hand results with their modified change over product?

Really think I'll go with the ASR however

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