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Thread: Install larger 1981 oil pan on 1980 R65 ?

  1. #16
    VANZEN
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    missing the point by a 1/4 cup

    Quote Originally Posted by shire2000 View Post
    For further clarification.
    In the 1981 models the pan was made larger partially due to a change in the pickup heads. They went to a cast head that incorporated the spacer as part of the casting. The new cast unit has a spacer of approx. 15mm in length while the original stamped steel head used a 10 or 12mm spacer. Not a big difference, but enough that a deeper sump was required. This allowed for a whopping big 250cc more oil in the sump (about 1/4 cup)....
    Once again:
    the MAJOR benefit of a larger sump volume
    is not the "whopping 250cc" difference,
    or even the 946.352946 cc difference of some after-market pans,
    and will NOT be realized in either case if the increased volume is filled up with more oil.

    Any advantage that might be provided by a greater quantity of oil
    PALES in comparison
    to the fact that a horizontally opposed twin,
    by virtue of it's large displacement and the design of BOTH pistons moving inward and then outward simultaneously,
    generates SIGNIFICANT and UNDUE pressure differentials within the crankcase (esp. at upper RPMs) ...
    and engine performance / efficiency suffers as a result.

    A larger (and unfilled) sump volume
    increases crankcase air volume.
    That additional air volume reduces pumping losses for the engine,
    and the lower crankcase pressure reduces blowby

    to result in a more efficient engine.

    This will be the reasoning behind BMWs changes.

    A revised pick-up & extension would not even be a production consideration
    if the deep sump weren't a part of that plan.

    Historical note:
    The 1976 R90S Superbike generated SO MUCH crankcase pressure –
    that the resulting force was known to blow it's cylinders apart from the case !!!

    And a practical note:
    Cranckase pressure is the reason that so many Type-247s are prone to weep oil at the cylinder base ...
    and foul the right carb of early models with oil.
    Last edited by vanzen; 08-22-2009 at 12:17 AM.

  2. #17
    shire2000
    Guest
    Sorry Vanzen, I feel that there is a fly in that ointment.

    The reason for the deeper sump was definitely not to reduce the "SIGNIFICANT and UNDUE pressure in the crank case". That is what the Pressure-relief valve and oil filter bypass valve are for. The engineers built that into the engine right from the start. The oil pump will pump more oil than the engine can use, so there is a valve mounted on the front of the engine (at the top of the front main bearing carrier) which dumps excess oil out onto the timing chain. At the bottom of the filter housing is a spring-loaded ball valve which allows oil to bypass the filter if the pressure gets too high. In this case, unfiltered oil will be sent to the engine. When the engine is cold, oil will normally flow through this bypass. If the bypass valve breaks, oil will flow through here when the engine is warm also. There is also that little valve on the top of the engine that is quite often missed called a Positive Crankcase Ventilation valve. It is also used to reduce pressure in the engine case.

    For the 1981 and later engines the crankcase and front main bearing were modified to provide an oil feed directly to the crankshaft front main bearing. A modified oil pan was required to accommodate this. There just was not enough room at the front of the pan to fit the modified front main bearing. They also included a baffle in the pan to help eliminate any possibility of oil starvation for the oil pump. With the larger oil pan (deeper) they then required the change in the pickup to a deeper one.

    The recommended oil capacities for all models were also changed at the same time. The following is for all models except the enduro models, i.e. R80G/S which continued with the Pre 1980 capacities until 1991

    For an oil change including filter:
    All models without an oil cooler prior to 1980 - 2.38 U.S. Quarts.
    All models up to 1980 with an oil cooler - 2.64 U.S. Quarts.
    For all models from 1981 on without an oil cooler - 2.64 U.S. Quarts.
    For all models from 1981 on with and oil cooler - 2.91 U.S. Quarts.
    Remember that these are only recommendations, your fills may vary.

    This seems to imply that when they made the change to the larger oil pan, they recommended more oil to fill them. So for a stock engine, that is not being highly stressed in racing type conditions, I would go with what the engineers recommended.

    For racing conditions, all bets are off. Many modifications have been made to help keep racing engines together. Deeper oil pans along with large oil coolers would be almost "standard equipment" for any race engine, no matter what configuration the engine is.

  3. #18
    Administrator 20774's Avatar
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    Hey guys, aren't we straying a bit much from the original post? He just wanted to know if there were going to be any "issues" with the larger sump.

    While I personally see good supporting information for both sides being presented, I don't think we can KNOW what BMW was doing when they made their changes. We can only look at some facts and back into the answer. My 0.02.

    But in the end, does it really make any difference? I think the original poster has two options, either of which will be just fine in the long run with the deeper pan:

    1) use longer dipstick, oil pickup extension and use the same amount of oil to fill before he installed in the deep sump

    2) use the same dipstick and fill the oil to the higher volume.

    Seems like either will get the job done with little chance of doing any real harm to the bike.
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    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #19
    . AntonLargiader's Avatar
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    Quote Originally Posted by shire2000 View Post
    For further clarification.
    In the 1981 models the pan was made larger partially due to a change in the pickup heads.
    You really think they needed the pickup head to be a certain way and designed the pan to match it? I sure don't.

    And if you're going to copy and repost info from someone else's website (like mine) please attribute it. Otherwise people think it's your own knowledge, which isn't the case.

    The reason for the deeper sump was definitely not to reduce the "SIGNIFICANT and UNDUE pressure in the crank case". That is what the Pressure-relief valve and oil filter bypass valve are for.
    I think you are unfamiliar with what Vanzen is describing. Vanzen knows what he's talking about.

    For the 1981 and later engines the crankcase and front main bearing were modified to provide an oil feed directly to the crankshaft front main bearing. A modified oil pan was required to accommodate this. There just was not enough room at the front of the pan to fit the modified front main bearing.
    I think you are unfamiliar with the construction of the type 247 motor. The bearing carrier is nowhere near the pan.
    Anton Largiader 72724
    largiader.com bmwra.org

  5. #20
    shire2000
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    I am sorry Mr. Largiader that I did not give you credit for the information that I posted from your web page. If there is a next time, I will definitely do so. The reason I used your info is because it was readily available. There are many other sources also available with the same information, just not necessarily in the exact same wording. Yours just happens to be put forth in as a simple explanaition that most should be able to understand.

    As to the pan being made larger due to the pickup being a certain way, I said it is a partial reason. I do not feel that any one reason was the cause. As with most developments of anything, it takes more than one small thing to cause a large change.

    As to Vanzen knowing what he is talking about, that I cannot dispute either way. I do not know this person other than his comments on here.

    As to being unfamiliar with the 247 motor, that is something that you cannot dispute either way due to your limited knowledge of me.

    As to the real reasons why BMW changed the design, that we will never really know unless we can talk directly to the engineers that developed the changes. All we can do is take what information is already available, add in what knowledge we can glean from numerous sources (both personal and otherwise), mix well and then try to understad what comes out in the end.

    Let people believe what they want. Lets just leave it at that.

  6. #21
    seniorasi
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    Quote Originally Posted by shire2000 View Post
    I am sorry Mr. Largiader that I did not give you credit for the information that I posted from your web page. If there is a next time, I will definitely do so. The reason I used your info is because it was readily available. There are many other sources also available with the same information, just not necessarily in the exact same wording. Yours just happens to be put forth in as a simple explanaition that most should be able to understand.

    As to the pan being made larger due to the pickup being a certain way, I said it is a partial reason. I do not feel that any one reason was the cause. As with most developments of anything, it takes more than one small thing to cause a large change.

    As to Vanzen knowing what he is talking about, that I cannot dispute either way. I do not know this person other than his comments on here.

    As to being unfamiliar with the 247 motor, that is something that you cannot dispute either way due to your limited knowledge of me.

    As to the real reasons why BMW changed the design, that we will never really know unless we can talk directly to the engineers that developed the changes. All we can do is take what information is already available, add in what knowledge we can glean from numerous sources (both personal and otherwise), mix well and then try to understad what comes out in the end.

    Let people believe what they want. Lets just leave it at that.

    Dude...you've been totally shredded and still have the nads to dis a highly respected BMW mechanic AND the material you ripped off from his website??? Incredible!!!!!

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