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Oil Control In Rb's For Circuit Drag Or Drift


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Yeh, but I think it is pretty widely accepted that the rear head drain doesn't act as a drain, it's a vent. 

 

But I find it interesting that in 82 pages of discussion and the general consensus being to drill out the oil returns to 10mm, nobody has mentioned weakening the block by doing so. But any engine builder or machinist I speak to is hesitant to drill out the returns. One said he might do 7mm, but certainly not 10mm. And I believe CRD also say don't touch them, leave them standard size. 

 

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Cause this thread was started by circuit racers who only had 300-350rwkw back in the day

e85 bumped that up to 400rwkw

noW all the drag kids with 700-1000hp(that converts to 1000-1400hp in trump land) are on board and Reading info from circuit guys from 20 years ago

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I'd be surprised if drilling the drains out would significantly weaken the block. Yeah, sure, when pushing to really big power figures you probably need every little bit of material you can get, but by then I'm sure you're in need of a half grout fill and so on anyway.

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Yeh that was sort of my suspicion. I know a lot of these guys are building 1000hp+ engines, so it doesn't surprise me that they are thinking of block strength. But it was something I considered interesting enough to ask the question. 

I'm currently building my motor with a goal of 450rwkw so nothing crazy, but it is for a dedicated time attack car, so I want to get the oil control right (in Perth though, so our track is going to be pretty forgiving with no fast left-handers). My block is currently with my machinist, and he is happy to drill out the returns to 7mm and chamfer them, although he said it looks like the gasket might cover some of that anyway and isn't really sure there's any point. I'm sure I saw a picture in this thread of how the gasket sits with the enlarged return, but I can't find it now.

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I'm at 500kw at the hubs and use for circuit, and Tarmac Rally.

 

1 hour ago, Unzipped Composites said:

Yeh that was sort of my suspicion. I know a lot of these guys are building 1000hp+ engines, so it doesn't surprise me that they are thinking of block strength. But it was something I considered interesting enough to ask the question. 

I'm currently building my motor with a goal of 450rwkw so nothing crazy, but it is for a dedicated time attack car, so I want to get the oil control right (in Perth though, so our track is going to be pretty forgiving with no fast left-handers). My block is currently with my machinist, and he is happy to drill out the returns to 7mm and chamfer them, although he said it looks like the gasket might cover some of that anyway and isn't really sure there's any point. I'm sure I saw a picture in this thread of how the gasket sits with the enlarged return, but I can't find it now.

I'm in Perth too.   If you go to Collie (and you definitely should) it will be all left handers.   Come do a Rally Sprint and watch your oil logs go nuts even with all the wet sump mods.

If you're building a serious time attack car go dry sump and don't stuff around ever again with it.  

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28 minutes ago, R32 TT said:

I'm at 500kw at the hubs and use for circuit, and Tarmac Rally.

 

I'm in Perth too.   If you go to Collie (and you definitely should) it will be all left handers.   Come do a Rally Sprint and watch your oil logs go nuts even with all the wet sump mods.

If you're building a serious time attack car go dry sump and don't stuff around ever again with it.  

 

It isn't what I would consider a 'serious' time attack car. It's a development car for my business, so will primarily be used for developing and collecting real world data on aero and other carbon fibre components that I build. I already build half the field in Racer class, as well as sponsoring two of the cars in that class - so I don't really want to try to compete with those guys, that isn't in my interests. 

 

That said, I still intend to compete in the secondary Tuner Class, so I am aiming for the 61 second bracket around Barbs. Which is no 55/56 second car, but it is still very very quick for a RWD front-engine car. The engine is going to have to be capable to do it. But dry sump is not part of the equation.

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You will almost certainly have oil surge problems doing 61's at Barbagallo in my opinion.  Even with all of the Wet Sump mods in these preceding pages.

Maybe consider adding an Accumulator as a band-aid.

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1 hour ago, Ben C34 said:

You would have to think Venting the sump properly pretty much cancels out the need to drill the returns.

 

Yeh I would have thought it would help for sure, and I do intend to vent the sump properly. 

I'm really just going off the info in this thread vs what experienced builders are telling me. This is a pretty respected thread, and there seems to be a pretty widely accepted summary of feed restrictors, vented/extended/baffled sump, drilled oil returns, no rear head vent. So I just wonder where the discrepancy comes in between that consensus, and what engine builders/machinists say is the way to do it. Is this thread out-dated? Or are the engine builders?

 

 

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7 minutes ago, R32 TT said:

You will almost certainly have oil surge problems doing 61's at Barbagallo in my opinion.  Even with all of the Wet Sump mods in these preceding pages.

Maybe consider adding an Accumulator as a band-aid.

 

Yeh I sort of expect to, which is why I want to get it right. However there are a few cars in Racer that are going under the 60.0 bracket, none of them are dry sump (Laine and Simon are the two that come to mind, though perhaps I'm forgetting if Simon has gone dry sump - I'm quite sure he hasn't) and not having crazy oil control issues. So I'm sure it can be done.

 

Oil accumulator I am sort of planning on. Perhaps not initially, but I do feel it is affordable insurance, so I think it will happen.

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34 minutes ago, Unzipped Composites said:

Is this thread out-dated? Or are the engine builders?

The thread may well be outdated relative to stupid power levels. The engine builders would rather an engine that has oil breathing problems than one that cracks the block, so are being (possibly excessively) conservative.

The simple fact remains that more open area is required for gases to go up and oil to go down. However you achieve that is however you achieve that. I have no doubt that many have implemented the vents without drilling the block, which may well prove that you don't need to drill the returns.

I don't have much skin in the game, but I think if I was building a moderately serious engine, I would drill the returns out as much as I thought they could take, and put stiffness back in via other means if I was aiming for more power than is actually useful.

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13 minutes ago, GTSBoy said:

I don't have much skin in the game, but I think if I was building a moderately serious engine, I would drill the returns out as much as I thought they could take, and put stiffness back in via other means if I was aiming for more power than is actually useful.

No you wouldn't..     you'd dry sump it.   Look within - you know you would.  ;)

Just a completely side question for the engineers here.  Has anyone thought about 'rifling' the oil drains?  Essentially like making a keyway down that hole?   May not be easy to do I am not machinist.   But I have a faint memory from physics days that this may actually be more effective than drilling out by breaking the surface tension and allowing a pathway for air to travel up alongside the oil trying to get back down..   ?    having a perfectly round hole promotes the oil to keep the hole 'blocked' so to speak.

Thoughts?   Or am I talking rubbish?

Edited by R32 TT
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8 minutes ago, R32 TT said:

No you wouldn't..     you'd dry sump it.   Look within - you know you would.  ;)

Just a completely side question for the engineers here.  Has anyone thought about 'rifling' the oil drains?  Essentially like making a keyway down that hole?   May not be easy to do I am not machinist.   But I have a faint memory from physics days that this may actually be more effective than drilling out by breaking the surface tension and allowing a pathway for air to travel up alongside the oil trying to get back down..   ?    having a perfectly round hole promotes the oil to keep the hole 'blocked' so to speak.

Thoughts?   Or am I talking rubbish?

 

Haha, you and my machinist would get on well I feel. He also isn't one to do things by halves, and over the years has tried to talk me into dry sump/Motec/PDM/sell the Skyline and buy a Lamborghini if you actually want to go fast, etc.

 

I'll ask him what he thinks of your keyhole suggestion, I feel his response will be something along the lines of it being practically too difficult to do vs the theoretical advantages of it.

 

GTSBoy, I feel you've nailed the answer to my question, thank you.

 

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7 minutes ago, R32 TT said:

No you wouldn't..     you'd dry sump it.   Look within - you know you would. 

Well, for a circuit engine, you're probably right.

8 minutes ago, R32 TT said:

Just a completely side question for the engineers here.  Has anyone thought about 'rifling' the oil drains?

Uh. maybe. But probably not. If you want to try to use rotation to generate centrifugal forces to keep the oil on the outer and gas up the centre then you'd really need to get the oil spinning before it enters the drain hole. Like a cyclone (you know, particle or droplet separator). That way the oil will spin out against the side and sort of stay there.

But I doubt that there's a lot of benefit. Certainly not gunna be easy to do either, given cast iron, etc etc. Better to just do all the actually easy stuff.

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Wasn't so much about spinning or centifugal forces.  I probably shouldn't have used the word rifling. 

More about breaking up the uniformity of the hole by having a channel to one side of it.   If you pour oil down it, the majority will go down the larger portion of that hole and air will come up the channel.     So the theory is to promote this action and perhaps have faster oil return..     I'll have to find a youtube on it to explain it better..      but yes, you're right at the end of the day probably too hard to pull off vs the benefit.

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21 minutes ago, R32 TT said:

Wasn't so much about spinning or centifugal forces.  I probably shouldn't have used the word rifling. 

More about breaking up the uniformity of the hole by having a channel to one side of it.   If you pour oil down it, the majority will go down the larger portion of that hole and air will come up the channel.     So the theory is to promote this action and perhaps have faster oil return..     I'll have to find a youtube on it to explain it better..      but yes, you're right at the end of the day probably too hard to pull off vs the benefit.

Please try it and report back (although success may be hard to measure!).  The purpose of the sump breathers going to catch can(s) and eventually the turbo intake is to generate negative pressure in the crank case (or at least to reduce the positive pressure) to facilitate oil return.

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2 hours ago, R32 TT said:

Wasn't so much about spinning or centifugal forces.  I probably shouldn't have used the word rifling. 

More about breaking up the uniformity of the hole by having a channel to one side of it.   If you pour oil down it, the majority will go down the larger portion of that hole and air will come up the channel.     So the theory is to promote this action and perhaps have faster oil return..     I'll have to find a youtube on it to explain it better..      but yes, you're right at the end of the day probably too hard to pull off vs the benefit.

Yeah, once I heard rifling I assumed that the spiral shape was important to your thinking.

The three big issues at hand are;

  • oil viscosity/surface tension,
  • qty of oil that needs to go down,
  • qty of gas that needs to come up.

I strongly suspect that cross sectional area is the king, assuming that the three main factors are essentially fixed for any given engine & operation thereof. Therefore I wouldn't expect to be able to pull too many tricks with the shape of the hole (which is essentially what any little keyway/slot runnign down one side of it would be). And further, narrow slots don't play well with movement of oil. Surface tension will hold a liquid in a narrow slot against gravity. So t probably wouldn't drain any better anyway. And then, if you just make the slot "not narrow", ie make it a bloody great wide slot, then it just comes back to extra cross sectional area. And possibly with the bad addition of sharp corners to create stress raisers.

We're probably better off just agreeing to add big fat sump breathers and drill out the oil drains only if forced to (although, it's a bit late once the engine is running!)

Edited by GTSBoy
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22 hours ago, Unzipped Composites said:

Yeh I sort of expect to, which is why I want to get it right. However there are a few cars in Racer that are going under the 60.0 bracket, none of them are dry sump (Laine and Simon are the two that come to mind, though perhaps I'm forgetting if Simon has gone dry sump - I'm quite sure he hasn't) and not having crazy oil control issues. So I'm sure it can be done.

 

Oil accumulator I am sort of planning on. Perhaps not initially, but I do feel it is affordable insurance, so I think it will happen.

I don't have a dry sump but I probably should. If I cared more about the engine I probably would but it's a bottom of the ocean junker so it's not a huge concern. I get some concerns with pressure, it always stays above 50psi so at least there is oil there.

22 hours ago, R32 TT said:

If you're building a serious time attack car go dry sump and don't stuff around ever again with it.  

Is it too soon to bring up dry sumps being a stuff around in the first place :P

Edited by SimonR32
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1 minute ago, SimonR32 said:

Is it too soon to bring up dry sumps being a stuff around in the first place :P

lol - probably - but not from you..  ?

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