Under what circumstances are they effective? Disadvantages?
Under what circumstances are they effective? Disadvantages?
In reply to stroker :
My 911 is dry sump from factory. As I understand it the oil pump feeds off of a tank rather than an oil pan Which on hard cornering can cause l o s s of oil supply and pressure. Additionally eliminating an oil pan sump allows the engine to be mounted lower reducing cg. FWIW my sump carries about 12 litres of oil making oil changes an occasion for trip to my credit union.
Oil is pumped from 'the pan' back to a tall vertical tank which holds a crapload of oil and feeds oil back to the engine from the bottom. So, it's basically a really fancy way to keep from losing oil pressure while turning the vehicle hard.
stroker said:Under what circumstances are they effective? Disadvantages?
They are good anytime you have high accelerations the push oil away from the pump....like ALL racing.
The disadvantage is cost and complexity.
Aside from the above mentioned, they are also good for cutting windage losses by making sure the crank isn't whipping up a bowl of oil, and by extension, making sure that you have 70psi of solid oil and not foam, aided by the nice deaerator tank.
You can use them to pull a vacuum in the crankcase, which is good for ring seal (and allows the use of lighter tension rings), but there are ways to do this without a dry sump setup.
They are also good for engines that end up with blowby issues, or rather that have oil entrainment in the blowby due to whatever internal geometries make this a problem.
They are ALSO good for doing an end run around oil pump problems on engines with crank snout driven oil pumps. Crank harmonics at high power and/or RPM can turn the oil pumps into shrapnel.
Additional advantages are:
You can also sometimes run the crank centerline closer to the ground (either by lowering the whole car or by lowering the engine in the car)
Having the ability to store the oil somewhere other than in the oil pan can help with weight distribution. The oil tank in my Camaro is where the rear seat used to be.
Additional dis-advantages are:
More weight. The pump is heavier and there's the weight of the tank and additional oil.
There are more opportunities for leaks.
In general I think the advantages outweigh the disadvantages. If the rules and budget allow I always dry sump.
Vigo said:Oil is pumped from 'the pan' back to a tall vertical tank which holds a crapload of oil and feeds oil back to the engine from the bottom. So, it's basically a really fancy way to keep from losing oil pressure while turning the vehicle hard.
Is this also what an Accusump does?
paranoid_android said:Vigo said:Oil is pumped from 'the pan' back to a tall vertical tank which holds a crapload of oil and feeds oil back to the engine from the bottom. So, it's basically a really fancy way to keep from losing oil pressure while turning the vehicle hard.
Is this also what an Accusump does?
Sort of. An Accusump is a reservoir that stores additional oil when there's oil pressure and dumps it into the engine when there isn't. They can be a great solution in some applications. It does have some shortcomings compared to a dry sump.
If you loose oil pressure due to the oil sloshing away from the pickup that oil is still in the engine. When the Accussump discharges you end up with a couple of extra quarts of oil in the engine until it pumps back out. This can cause oil aeration (and a subsequent lack of oil pressure) and/or oil being pushed out of the breathers.
They're of limited capacity so you can still loose oil pressure on long corners.
Billzilla made a 2 stage dry sump pump from two SBC oil pumps hooked together and driven off a V belt.
Is this also what an Accusump does?
Well first of all I agree with what APEowner said. The thing about an accusump is that it's attainable on a budget. It has some serious limitations compared to a real dry sump. If dry sump conversions were cheap and easy, the accusump approach would be silly. But, the dry sump approach is NOT cheap or easy.
Also, accusump systems are very sensitive to being applied imperfectly, from capacity to orientation to plumbing to solenoids blah blah blah. You can design one that works like a dream or slap one in that barely helps at all. In contrast to that, most dry sump systems in existence are OEM designs that work like a dream. So, in practice a dry sump tends to be way better than an accusump mostly because there's a high chance it was designed by a bigass company that had to warranty the engine it was attached to, while accusumps are usually imperfect patch jobs applied by hobbyists. Some tiny fraction of them will be amazing, the rest will be.. hopefully good enough most of the time.
We also used A/C commercial sized coolent tubing to run the oil Back to the resivour About 1/2" ID hole and Cooling fins down the Legnth of it,
The Rules here allowed for the Crankshaft CL to be only 10" from the ground
Vigo said:
...most dry sump systems in existence are OEM designs that work like a dream. So, in practice a dry sump tends to be way better than an accusump mostly because there's a high chance it was designed by a bigass company that had to warranty the engine it was attached to...
Can you elaborate on this? Other than Porsche 911s, the Z06 LS7 and some exotics, I can't think of another OEM dry sump system. I'm not trying to be argumentative. I'm genuinely curious if there are applications I'm not aware of. My experience with dry sump systems is mostly American V8s in circle track and road race cars that were converted from the original wet sump so when I think of dry sump I think aftermarket.
In reply to APEowner :
And there are probably more dry sumped 911s than other dry sump engines combined.
I still think the only reasons Porsche did it were so they could run a huge cooler up front, and that it was the only effective way to oil and scavenge a SOHC aircooled flat six. No easy way to do drillings, so you'd have a nest of plumbing anyway, so may as well just have an external tank.
308/328 engines, transverse engines, have a huge problem with oil pressure in corners. The pan is wide and keeping oil in the middle is hard. The euro engines got a dry sump but the US a cheaper wet sump.
Boxer engines, like the 911 have a similar issue as it's not so easy to to keep oil out of the cylinders.
....factories add cost only when they need to.
Knurled. said:In reply to APEowner :
And there are probably more dry sumped 911s than other dry sump engines combined.
That may be what Vigo was thinking of but one of the things that I like about this board is that there are many people here with backgrounds different than mine who know things I don't, hence the question.
mke said:308/328 engines, transverse engines, have a huge problem with oil pressure in corners. The pan is wide and keeping oil in the middle is hard. The euro engines got a dry sump but the US a cheaper wet sump.
Boxer engines, like the 911 have a similar issue as it's not so easy to to keep oil out of the cylinders.
....factories add cost only when they need to.
Some more modern Ferraris like the 458 for example also run a dry sump. I guess what I'm really wondering is if there's something less exotic or more common that uses one. Something from Japan for example. I know very little about Japanese cars.
In reply to APEowner :
All the ferraris 348 up are dry sump I believe.....but it adds cost and is only needed for real track use so it generally doesn't make sense as an OEM feature. I think the 911 is about the least exotic to get it and that's not exactly non-exotic. Great system, if you need it and are willing to add it. I added it on my frankenferrari and I think it cost me about $500-$600 so it can be done at a not horrible price.
Other than Porsche 911s, the Z06 LS7 and some exotics, I can't think of another OEM dry sump system.
Well, that's the kind of stuff i was thinking of. I still think there are more factory applications than aftermarket on race cars (could be wrong!!), but if you spend a lot of time at tracks you'll run into all the aftermarket ones. I can't remember the last time I saw one in person that wasn't on a corvette.
Early Esprits were dry sump.
MYear VW Phaetons went to dry sump IIRC
Ovid_and_Flem said:MYear VW Phaetons went to dry sump IIRC
Ugh. WHY??? if true.
New GT40 are dry sump.
In reply to stroker : Brakes!!
Oil will slide forward under heavy braking ( and you can stop harder than you can corner)
but yes a dry dump will also help in cornering and acceleration. Anything that will throw the oil away from the oil pickup.
I had to design my own dry dump system on my Jaguar, because of the big bearings I was forced to go to a three stage system.
Stock a Jaguar can use up to 22 quarts. my system used 48 quarts plus 2 oil filters, and all the oil in the lines etc.
The advantage is my bearings lasted decades of racing when before I was lucky to get one weekend before needing to replace them
In reply to Vigo :
I have only seen one on a Corvette because I try not to look at them On the other hand every Formula Ford, F5000, Can-Am,Trans-Am, Sports2000, F2000 car I have ever seen or worked on has a dry sump from the original manufacturer.
In reply to frenchyd :
I might be able to slow down harder than I can corner but I can corner a lot longer than I can slow down. I'm not going to hurt the engine (much) braking for 2 or 3 seconds, it's 10+ seconds in a sweeper with the engine under load that will hurt.
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