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Dry Sump Designs

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Re: Dry Sump Designs

Post by kevhaywire on Thu Feb 17, 2011 6:57 am

Interesting stuff!

So if there's no oil in the pan (hate that word, makes me think of toilets), sorry, sump, that means the PCV gases coming out would be cleaner? An age old problem with forced induction.....oil coated intercoolers and intakes.

I guess hot oil sloshing about in the sump vaporises and gets mixed in with the blow by gases.

I can't picture a crank with no sump for some reason. Where does all the oil go once it's passed through the bearings and up the head etc? There's always pools of oil in heads etc, not to mention cylinder spray jets etc, where does it all residual oil end up? I'm trying to figure out the complete circuit as it where.

I'm also thinking of the good old days when engines relied on oil splashed up onto the bores from the crank for lubrication. How would you dry sump such a beast? Very Happy

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Re: Dry Sump Designs

Post by Yandards on Thu Feb 17, 2011 9:53 am

Panda, CC on the nugget is down in the wheel arch area, pretty much in the stock intercooler location.

Just run a standardish FMIC on the 16vG60.

A high cylinderical tank would work nicely, should be able to tuck it down out of the way somwhere in the wheel arch area.

Kev, there are separate oil pathways in the block and head for both supply and return, just consider the block and head oil system as a coolant system but all internally contained.

Ultimately if you think about a normal running engine there must always be a sufficient supply of oil within the sump to provide oil to the pump under normal operation. If you take the oil sump to be a store of oil for the pump then all you are doing is moving that store to another location on the car external to the engine.

As Panda has already mentioned, by doing this you get several gains in engine design as wet sumps are designed to prevent the crank thrashing through the oil in the 'store'.

You would not be able to dry sump and engine that uses a conrod style 'flicker' system without a complete redesign of the block - lawnmower engines use this type of system because it's cheap.

Finally, as for oil coating in coolers etc from FI, you will still get oil vapour and mist into the intercoolers etc but there would be a lot less than a wet sumped design - I would expect to see more power output as a result of that rather than the crankcase loses TBH.

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Re: Dry Sump Designs

Post by boost panda on Fri Feb 18, 2011 12:52 am

Hey guys, thanks for keeping my thread alive Razz

I'm just off to uni but will be free around 10:30 so will happily provide some infor and answers to questions!
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Re: Dry Sump Designs

Post by kevhaywire on Fri Feb 18, 2011 6:55 am

Cool, good explanation Yan, cheers Smile

My R32 sump has a windage / baffle tray in it, which should stop the oil > crank lobe interface? Then again, I'm not sure the standard steel sump has such a high oil level that the crank hits it anyway. There's probably at least a litre flowing around the engine whilst it's running, so I don't 5 litres in the pan is going to be a big obstruction for the crank tbh.

Having said that, I've seen PTFE crank scrapers for the VR.

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Re: Dry Sump Designs

Post by Yandards on Fri Feb 18, 2011 9:56 am

kevhaywire wrote:Cool, good explanation Yan, cheers Smile

My R32 sump has a windage / baffle tray in it, which should stop the oil > crank lobe interface? Then again, I'm not sure the standard steel sump has such a high oil level that the crank hits it anyway. There's probably at least a litre flowing around the engine whilst it's running, so I don't 5 litres in the pan is going to be a big obstruction for the crank tbh.

Having said that, I've seen PTFE crank scrapers for the VR.

It all heads back to oil mist and the parasitic loses that occur as a result of that; the problem I always have to overcome in my head is the speed at which everything is happening inside an engine and that's where it makes the difference. Even an engine idle of 600 RPM means the crank is firing round at a rate of 10 times a second, wind that up to 6000 RPM with 100 revolutions per second and you can see why the loses through an oil mist in the crank area start to have an effect. Then factor in that oil in the sump is not static, it is constantly flowing and returning to the sump, throw a few bumps in the road in there and its a big oily slop fest.

Again oil mist is not something most folks ever see, thanks to the medium of hydraulic systems failure (300b operating pressure) the way oil interacts with air at high pressure (which is what you are generating by flicking the crank through the oil) it really is a thick vapour, more like paint from a rattle can than oil or air.

A windage tray will help prevent oil being picked up by the crank through bumps etc but once again an extra weight or work the crank has to do to rotate will result in power loss, you don't need oil on the crank lobes but it will sit on them and continue to fire oil mist all over the bottom of the engine area - this is not a required design feature given the bearings and pistons have dedicated oil points.

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Re: Dry Sump Designs

Post by boost panda on Sat Feb 19, 2011 11:57 am

mrbeige wrote:Why are the 7-tooth gears more efficient? Is it down to how much tooth is in contact with another at any one time?

I think so yeah. You really only need the teeth which are pushing the oil through the gap to be meshed, the others are just wasting energy really. I think the pumping loss goes up with more teeth, as they are interacting much more but as they're not all usefully pushing the oil through then they're just making it more turbulent which makes it harder for it to flow where you want, or worst case scenario they may beging to cause cavitation.

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Re: Dry Sump Designs

Post by boost panda on Sat Feb 19, 2011 12:06 pm

kevhaywire wrote:Interesting stuff!

So if there's no oil in the pan (hate that word, makes me think of toilets), sorry, sump, that means the PCV gases coming out would be cleaner? An age old problem with forced induction.....oil coated intercoolers and intakes.

I guess hot oil sloshing about in the sump vaporises and gets mixed in with the blow by gases.

I can't picture a crank with no sump for some reason. Where does all the oil go once it's passed through the bearings and up the head etc? There's always pools of oil in heads etc, not to mention cylinder spray jets etc, where does it all residual oil end up? I'm trying to figure out the complete circuit as it where.

I'm also thinking of the good old days when engines relied on oil splashed up onto the bores from the crank for lubrication. How would you dry sump such a beast? Very Happy

Yeah, that's right. Because the PCV gases are at high temperatures they can dissolve into the oil which means that the PCV valve is returning oily air to the intake as you know, and also contaminates the oil with things like Hydrocarbons and NOx. PCV is a great system, and IIRC was introduced in the 60s/70s to drastically reduce emissions when the first realisations of smog (or smoky fog) were being generated, specifically in California (hence their "don't fart near a car on test" attitude to emissions analysis)

Dry sumping won't reduce the pooling of oil in the head I don't think. There will always be head webbing or structure in the way which means some oil gets caught down by the valve stem seals with no seeming way back to the sump. Tbh, the VR6 relies a fair amount on splash lubrication. To that end, It would be possible to engineer the lubrication system to allow for higher clearances on the crank bearings to allow a higher amount of oil to be expelled from them which would be caught on the rotating counterweights and hopefully flung back up the bores under the piston. It's a theory and by no means a proven method (although I haven't fully researched this area).
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Re: Dry Sump Designs

Post by boost panda on Sat Feb 19, 2011 12:11 pm

Yandards wrote:Panda, CC on the nugget is down in the wheel arch area, pretty much in the stock intercooler location.

Just run a standardish FMIC on the 16vG60.

A high cylinderical tank would work nicely, should be able to tuck it down out of the way somewhere in the wheel arch area.


Nice, I like the idea with the CC. OEM location so it gets all the flow that their R&D will prove, but significantly increased cooling Very Happy I wonder, do you have a pressure guage at the supercharger and another at the manifold? I would be interested on how much pressure drop, or thermodynamic head, is generated through the piping. I'm not expecting much through the Bahn Brenner system though.
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Re: Dry Sump Designs

Post by Yandards on Sun Feb 20, 2011 1:00 am

boost panda wrote:
Yandards wrote:Panda, CC on the nugget is down in the wheel arch area, pretty much in the stock intercooler location.

Just run a standardish FMIC on the 16vG60.

A high cylinderical tank would work nicely, should be able to tuck it down out of the way somewhere in the wheel arch area.


Nice, I like the idea with the CC. OEM location so it gets all the flow that their R&D will prove, but significantly increased cooling Very Happy I wonder, do you have a pressure guage at the supercharger and another at the manifold? I would be interested on how much pressure drop, or thermodynamic head, is generated through the piping. I'm not expecting much through the Bahn Brenner system though.

No I haven't but the max boost figure for a standard charger is 0.7b according to design specs (that's at the charger) so if I am making 0.7b at the manifold I think I can assume that given I have a stock charger with a stock pulley it is making design specs. It would also mean tapping an air take off point at some point near the charger, whilst I would like to get the numbers its a hole I don't need to put in my boost plumbing so it's not going to happen anytime soon. Smile

As for the chargercooler, the radiator for it sits in front of the main radiator, the chargercooler module is down in the arch because I didn't want it to be obviously charge cooled, the PWR unit is very shinny. The pump is a very small Bosch unit designed for chargecooling the Elise IIRC.

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Re: Dry Sump Designs

Post by boost panda on Sun Feb 20, 2011 1:26 am

If you made 0.7b at the manifold, wouldn't that mean that all your intake piping etc is 100% efficient as it won't have lost any pressure at all? Yeah, it would be a hole and it would need to be made airtight so that's fair enough. A sensor wouldn't have to stick a long way into the piping though, like some people who think a lambda needs to be 2" long and almost cross the exhaust pipe!

Cool, the CC setup sounds good Very Happy Is the coolant you use a separate system or part of the main one?
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Re: Dry Sump Designs

Post by boost panda on Sun Feb 20, 2011 1:33 am

[You must be registered and logged in to see this image.]

Back on topic, here's what I'm looking at now. You can see the meshing pattern on the left is far better, with surfaces staying in contatc for longer. Also smaller size means less packaging (size overall) and cheaper material and labour cost.
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Re: Dry Sump Designs

Post by boost panda on Mon Feb 21, 2011 12:13 pm

I looked into and designed a keyway drive system today to hold the gears onto the shafts. I think that is probably the best way to do it. A groove in each part, same size and depth, then a piece made up to fit the two together (replacing removed material but also slightly larger to allow for interference fit). Put the key into the keyway on the shaft and then slide the gear onto it.

I also realised some good and bad things about using aluminium for the casings.

Good - I don't need to use bearings as the gearshafts can run in the holes in the spacer plates on a thin film of oil Very Happy

Bad - the ally will expand faster than the gears will (steel I'm thinking) so there will be a bigger clearance around the outside of the gears (set to 0.5mm or 20 thou in smaller casing pictured above). Apparently this is a known issue, and the common fix is just to allow for this when calculating flow rates and ensure that it flows enough when the oil is hot (and subsequently the ally expands). The expansion shouldn't cause any other problems I am aware of.
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Re: Dry Sump Designs

Post by Yandards on Tue Feb 22, 2011 2:35 am

boost panda wrote:I looked into and designed a keyway drive system today to hold the gears onto the shafts. I think that is probably the best way to do it. A groove in each part, same size and depth, then a piece made up to fit the two together (replacing removed material but also slightly larger to allow for interference fit). Put the key into the keyway on the shaft and then slide the gear onto it.

I also realised some good and bad things about using aluminium for the casings.

Good - I don't need to use bearings as the gearshafts can run in the holes in the spacer plates on a thin film of oil Very Happy

Bad - the ally will expand faster than the gears will (steel I'm thinking) so there will be a bigger clearance around the outside of the gears (set to 0.5mm or 20 thou in smaller casing pictured above). Apparently this is a known issue, and the common fix is just to allow for this when calculating flow rates and ensure that it flows enough when the oil is hot (and subsequently the ally expands). The expansion shouldn't cause any other problems I am aware of.

That's the way a standard oil pump is on a 4 cylinder, alloy housing with steel gears.

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Re: Dry Sump Designs

Post by boost panda on Tue Feb 22, 2011 2:59 am

Ah thanks Yan, good to know I'm not talking buzzcocks Very Happy

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Re: Dry Sump Designs

Post by boost panda on Wed Mar 02, 2011 8:37 am

for all of you VR owners, how close does the Oil filter come to other objects (front cross members, radiator, etc) in situ?

I'm planning to relocate the filter and use it as the high pressure in line from the dry sump pump. I'm also thinking of designing a plate which retains the OEM filter whilst allowing me to pass high pressure oil from the pump directly nto the block at this location. This would obviously change the location of the filter and I need to work out where there would be space/restrictions. I don't really want to use a custom/inline filter if I can help it as it increases costs.


Should I just buy a crappy Corrado VR6 and measure it up myself?!
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Re: Dry Sump Designs

Post by boost panda on Wed Mar 02, 2011 9:53 am

I'm thinking I may buy an engine. Then I can use it to measure all the things I need to know like crank throw below the bottom deck plane, oil pump stuff, how the filter is housed (seems to be a cotton one in a plastic case!) and get dimensions from everything for modelling.
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Re: Dry Sump Designs

Post by Yandards on Wed Mar 02, 2011 10:03 am

boost panda wrote:I'm thinking I may buy an engine. Then I can use it to measure all the things I need to know like crank throw below the bottom deck plane, oil pump stuff, how the filter is housed (seems to be a cotton one in a plastic case!) and get dimensions from everything for modelling.

Sensible, best way to play around mocking stuff up too.

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Re: Dry Sump Designs

Post by boost panda on Thu Mar 03, 2011 2:02 am

The other benefit I completely forgot was that it improves your emissions.

Because the air from the crankcase can be routed through the standalone oil tank and vented to atmosphere, it is not going back into your intake to be burnt off (which increases the Hydrocarbons in your exhaust).

See, there's more and more benefits each time you look! Very Happy
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Re: Dry Sump Designs

Post by boost panda on Sat Mar 12, 2011 11:04 am

I took delivery of my engine stand and the VR6 block today (with crank, pump and filter housing).

It's quite an interesting block. The webbings/counterweights on the crank don't come up past the lower deck (the sump gasket surface) anywhere near as far as I thought. In fact the crank position sensor trigger wheel is probably the largest protrusion by about half an inch.

This is good because it means the sump design that I had made which is about 80mm deep, when actually I could make it half that depth or less. :-)

It's an AAA block which I think is the 2.8 Golf engine. I'm going to take the oil pump apart tonight and compare the gear tooth profiles with those that I have designed. Mine should have a higher rate of flow, have less backlash and subsequently less noise.

I am still working on how and where the pump will mount to the block. As my engine has no ancilliaries (or even that long silver bracketry which I'm guessing has the PAS/Alt/ etc bolting on to it) I am unsure where would be a good location. Perhaps I could make a simple bracket coming off the pump and then adapt it to fit the engine with another bracket.

I have taken off the oil filter housing and am a little puzzled by the triangular bolt pattern mounting, and also which of the two oil pipes is inlet/outlet I know one goes into the middle of the filter and the other goes to the other side of the gauze, but does the oil get pumped through the middle of the filter, and then the line back into the engine is from the space between filter and housing or is it the other way around? I haven't found any helpful flow arrows yet!

To this end, and because of the VR's design where the oil cooler is separate from the filter mounting position, I am much more keen to make this my high pressure line in to the engine from the pump. Anyone running a dry sump system no doubt is considering a separate oil cooler anyways, so this could be the perfect place to introduce my high pressure oil into the system. This retains the OEM filter and housing which keeps costs down by being able to use OEM oil filters instead of bespoke/custom items and having to find somewhere else in the engine bay to properly mount this hardware.

Just my thoughts from tonight, all comments welcome Very Happy
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Re: Dry Sump Designs

Post by Yandards on Sun Mar 13, 2011 7:12 am

Use the aircon mounting points on the long bracket for the pump mounting; should be easy enough to work out what needs to go where and it gives you the option of going belt driven with ease too.

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Re: Dry Sump Designs

Post by boost panda on Sun Mar 13, 2011 12:54 pm

Cheers Yan.

I've got the pump with me, partly disassembled and have a vernier too. I'm hoping to take some measurements and use the Stokes flow rate equations to find out how much better (or worse!) my pump will flow based on the gear design and rpm etc.

My block doesn't have the silver bracketry on unfortunately, I just have a pic from someone else's block that does. But yeah, I'm sure if someone is running a dry sump then they are probably hapy to do without mod cons such as air con Very Happy

Been at uni all day today, did another 2000 words, mostly on the pump. Probs overkill, but when I get everything written I can start editing etc which will be good.

I'll upload it when I'm all done :-)
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Re: Dry Sump Designs

Post by boost panda on Sun Mar 13, 2011 2:38 pm

Also, I'm wondering whether I need to include a pressure relief valve into my dry sump pump. Any thoughts?

I guess if I don't I need some very careful calculations that the system won't overpressurise or attempt to supply too much oil at top end.
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Re: Dry Sump Designs

Post by Yandards on Tue Mar 15, 2011 4:53 am

boost panda wrote:Also, I'm wondering whether I need to include a pressure relief valve into my dry sump pump. Any thoughts?

I guess if I don't I need some very careful calculations that the system won't overpressurise or attempt to supply too much oil at top end.

Always build in a PRV, you have to account for partial line/pipe blockages that was cause pressure spikes, better to have a slightly starved oil supply system than a pile of gasket pieces around the engine bay!

IIRC the stock VR6 PRV is rated at 5.5b so you have plenty of head room within factory limits.

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Re: Dry Sump Designs

Post by kevhaywire on Wed Mar 16, 2011 9:55 am

How does the PRV work then? VR6 oil pressure easily exceeds 8 bar when cold. If the relief valve is set for 5.5 bar, how is 8 bar+ cold pressure achieved? And why is so much pressure required to stop a few metal parts welding themselves together? Laughing Do crank journals really need THAT much pressure to form an oil film? I guess they do, lol!

I must confess, there are some aspects of cars I just have zero interest in. Gearboxes and oil are 2 such areas Laughing

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Re: Dry Sump Designs

Post by Yandards on Wed Mar 16, 2011 2:59 pm

kevhaywire wrote:How does the PRV work then? VR6 oil pressure easily exceeds 8 bar when cold. If the relief valve is set for 5.5 bar, how is 8 bar+ cold pressure achieved? And why is so much pressure required to stop a few metal parts welding themselves together? Laughing Do crank journals really need THAT much pressure to form an oil film? I guess they do, lol!

I must confess, there are some aspects of cars I just have zero interest in. Gearboxes and oil are 2 such areas Laughing

Humn, fluid and pressure cimbined with area make for wierd maths, thankfully I have spent some time recently on oil systems when I was doing my engine Q for the Tornado, the SPS (secondary power systems) or gearbox oil system is something else!

There is a 5.5b PRV built into the oil pump, this is an area of high flow (in fact a spur gear pump does not produce any pressure it just produces flow - trust me on this one) pressure increases as you force more oil through smaller holes - consider a 3 lane motorway going down to 2 lanes, to maintain the same flow of traffic you need higher speed or more pressure.

The point of measuring the pressure also has an impact, hence the low and high oil pressure switches on the oil filter housing, this is also why you see 8b on start up. I have no idea what sort of blockage would be needed for the oil pump PRV to operate nor do I know the flow rate in litres /minute of the pump @ x revolutions but it all adds up.

As for the crank journal, you have to consider the oil as an uncompressable liquid (it's not but never mind) and that the film of oil is, in fact, more a river of oil being supplied at a constant pressure. Then think of the oil film as a constant solid object between the bearing surfaces - this is what is actually happening in the engine to prevent metal to metal contact. Again the vast majority of bearing wear is during start-up due to low oil pressure, once the flow is established then all is ok. You still have massive amounts of heat being generated due to the forces involved, the flow of oil ensures that this is circulated around the engine and disappated.

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