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Thread: Deep sump oil pan

  1. #1
    bunkyone
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    Deep sump oil pan

    Hey all; My '76 R90 came with an aftermarket (?) oil pan that the local dealer says is somewhat deeper then stock. My question is HOW MUCH deeper? The dip stick shows quite a bit less then two liters when filled with the proper amount of oil according to the manual. Do I (1) use extra oil to bring the level up to the two liter mark, or (2) just run the required amount of oil? Is there a extended dip stick available ? Is the deeper pan used for extra oil capacity or to keep the oil from creating extra drag on the crank? I know this may seem a bit anal, but I tend to worry about this sort of thing... Thanks in advance. Vaya con Dios Dutch

  2. #2
    RTFlyer
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    I'm going to take a stab here...

    The advantage of the deep pan is more oil in the system. FRom what I understand, this can help for those who regularly operate in heavy stop-and-go traffic or hot climates. In order to have the advantage of recirculating more oil and to still reach the sump, you fill to the correct level on the old dipstick. Or at least that's what I would do. Make sense to anyone else?

  3. #3
    --Tony AnnapolisAirhead's Avatar
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    This is another topic that comes up and is the source of a lot of debate. Here's what I've been told and what sits well in my mind.

    The area between the bottom of the crankshaft and the oil level is called ullage. Conventional wisdom what assume more oil, takes longer to heat up so fill that area up. I think that thought process is very flawed, primarily because the difference in the additional amount of oil capacity is still very small and will heat up essentially at the same rate.

    The advantage of a deep oil pan, IMO, is that you increase the ullage and therefore allow for a larger, uninterrupted surface area to let the oil cool. Without a deep sump, the ullage is very small and oil is continually sloshing up against a very hot crankshaft.

    So deep oil sumps are better, but not if you add more oil. You'll have to get a longer dipstick or read it a bit differently.

    Just my opinion, but I had the same curiousity.
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  4. #4
    bunkyone
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    Larry; That's what I have been doing, but if the pan was put on to increase performance by decreasing drag on the crank, it seems that filling to the full mark would be counterproductive. (Of course, I don't think you can ever have too much oil in an air cooled engine.) Besides, how much more extra horse power could it generate? Thank for the response. Vaya con Dios, Dutch

  5. #5
    Liaison 20774's Avatar
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    Anton Largiader has a good page on various oil pans and dipsticks:

    http://largiader.com/tech/oilpan/

    The deeper pan can serve a couple of purposes. Lower the level of oil which allows for more air volume inside the case and keeping the pressure down as the pistons come in and out. I don't think that the crankshaft actually runs in the oil or splashes in the oil...it's the job of the oil pump to pickup the oil and move it around the engine. Or it allows more oil which theoretically lets the oil run somewhat cooler, but I think it's debatable if that really happens.

    Running the original 2 liters should be OK, provided that the oil pickup has been extended (it should be). Be sure that the extension doesn't have any leaks which means it will suck air instead of oil...not good. I'd probably be included to run the oil to the regular level on the dipstick, meaning adding more oil...or at least adding more oil than the 2 liters. Get the benefit of more air volume and more oil to circulate.
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  6. #6
    Registered User skiteach's Avatar
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    It's purpose has to do with cooling. I would fill to the line on the dipstick. It also has the benefit of additional capacity. There is a current thread that addresses the cooling of our machines. I do not remeber a longer dipstick being part of the package.
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  7. #7
    IBA #44567 Ken F's Avatar
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    I've not expierence reguarding this subject on a motorcycle, however went through two years of an identical problem when building the my boat engine.

    Although Anapaolis Airhead is correct about Ulage, or the space between the crank & oil level, there is also another thing to consider. Windage. This is a tornado effect caused by the crank spinning partiallly in the oil, and partially in air. The oil in the crankcase can be sucked up into this "tornado" and aeirate the oil, causing a drop/loss in oil pressure. This is what was happening with the boat.
    It would idle at 65 psi, but oil pressure would drop off to about 5 psi once aeiration occured, which only took about 1/8 mile of 3\4 throttle.

    My problem turned out to be a poorly designed oilpan. However it took almost two years of changing oil pumps, different types of oil, increasing the size of oil passages (perticular to big block fords), and eventually a new FordMotorsports block & custom oilpan.

    I say all this to say, the advantage of a larger volume oil pan is to increase the amount of oil (which is as much of a coolant as antifreeze, water, or air) and allow more oil to cool the engine. Also, at sustained high RPM, it allows more oil in the pan as oil is being pumped at a very high rate throughout the engine, allowing the pan/pump to never run out of oil as it is circulating and draining back to the pan.

    My suggestion would be (unless you are able to find a difinative answer from someone you trust implicitly) to install a quality oil pressure guage and keep a very close eye on it through out the RPM range at various increasing levels of oil. This exact thing cost me two spun main bearings in a V8. In a 10 quart pan I'm running 8 quarts of oil which is just before aeriation occurs.

    Hope that helps some, probably not what you wanted to hear.

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  8. #8
    Of course the crankshaft doesn't dip or splash into the oil. It is located above the camshaft. And the camshaft doesn't dip or splash in the oil either.

    As for fill level, if you fill to the original level as shown on the dipstick you have exactly the same crankcase air volume as stock, but with a larger quantity of oil. Which is why they call them high capacity oil pans. The purported purpose is so the oil cools better. There was even a better system that had a spacer that went between the stock oil pan and engine case with air tubes that ran from front to back so air flowed through the tubes allowing even better cooling than the puny fins on the pan. These caused too much cooling in cold weather so we blocked the front of each tube with a cork in the winter.
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  9. #9
    IBA #44567 Ken F's Avatar
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    And there you have it.
    IBA #44567 Pres. Springfield BMW Roadriders
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  10. #10
    bunkyone
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    Hey all; Thanks to everyone who has posted here. I suppose if I had looked more closely in the Hanyes I would have realized that the crank doesn't touch the oil in the pan. I think I will continue to fill to the 2 iter line, giving a total capacity of three liters (actually quarts). As long as it isn't hurting anything, the more oil flowing through the engine the cooler it will be. Thanks again. Vaya con Dios Dutch

  11. #11
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    This is timely, because I have gotten 1981+ factory oil pans for my <1981 bikes. My Clymer manual does not differentiate the oil capacity as to the 1981 change, only as to oill cooler or not. However, Haynes does show a 250ml increased capacity for 1981 on. This corresponds pretty closely with the 300ml difference in pan volume Anton's website shows.

    The engine cases are not different, but the 1981 pan is clearly larger, so the increased oill capacity must be with the pan. From all this it seems BMW's intent with the larger pan was the oil level be the same with regards to the crank. So with an aftermarket deep pan it would make sense to follow the original dipstick lines. With the usual caveat about going to max line typically increasing blowby.

    The deeper oil pan lets you run a bit more oil, but also it would seem gives you a safety margin on runs where you might go below min.

    I would have a concern about a non-stock pan I did not personally do, if the corresponding correct pickup were also installed. People do sell deep pans with no pickup; this could be disastrous, especially if one were only using, say, Clymer capacity fill data. No good having extra oil if your motor cannot access it.

  12. #12
    --Tony AnnapolisAirhead's Avatar
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    I think if you fill it to the stock dipstick line, you've effectively negated the increased ullage, filling it with oil. As hot as these engines run, I doubt that tiny amount of additional oil keeps them noticeably cooler. I haven't checked the BMW specs on oil capacity when they went to deeper oil pans around 1981 or so, but I think it remained the same--this indicates to me that their approach was likely to increase the ullage, not the oil volume.

    Camshaft, right. Not crankshaft. (Thanks Paul...maybe I was dreaming of a /2??). Although the camshaft isn't soaking in it, it would seem that the further away from the oil level, the less likelihood of hot oil splashing up onto a hot camshaft, keeping it hot.

    The aftermarket tube coolers (I think they are called Braille) are interesting. I was told at Supertech that there were issues with them over time as the venturi effect of the air passing through the tubes caused cracks in the aluminum. Interesting concept.
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  13. #13
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    FWIW, I just swapped my 1980 (shallow pan) dipstick to my 1982 (deeper pan) bike, and they read the same level above min. It seems the levels inside the engine are to be the same.
    I suspect the factory was going for cutting down effect of sloshing of oil, increased safety margin on oil level, and a tad more cooling with the increased frontal area.
    I saw a new MAC deep pan kit, and it didn't come with an aftermarket dipstick.

  14. #14
    Nutfarm
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    There were 3 oil pans for the older twins, /5 /6, had the shalow pan, oil pickup bolted to the crankcase. /7 had a slightly deeper pan, 10mm, with 2 sheet metal baffels, a 10mm spacer for the oil pickup, and a slightly longer dip stick. Refill volume was the same, 2ltrs. 80 or 81 had another slightly deeper pan, a longer spacer for the pickup and used the same dip stick as a /7, more oil, if I remember right it was 2.4 ltrs.

    There were after market pans that were deeper yet and held more oil.

    Ken G.

  15. #15
    James.A
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    There is only one reason to use a deep sump, that is more oil in the sump. 3 quarts of oil are better than 2. Having said that, I offed my deep sump oil pans when I switched to synthetic oil.

    The more oil circulating, the better. Think about the heat generated by a motor turning 4 to 5K RPM. Would you rather have that heat dissipated by 2 quarts or 3 quarts?

    With a deep sump oil pan, fill it to the full level on the dip-stick. There is no reason to have a deep sump unless you are willing to carry more oil.

    BTW, the full mark on the dip-stick brings the oil level right up to the bottom of the oil filter cover. Ask me how I know this....

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