02GF74
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| posted on 18/10/06 at 08:38 AM |
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another oil/sump related question
I've been thinking about sumps and oils recently, as one does 
I am trying to get a feel of what is the minimum amount of oil needed for an engine to run.
Now bear with me.
The oil pump pushes up oil into the engine and it is a fair assumption that the engine designers made it so that there is more than enough oil flow to
lubricate and cool the engine. The pump provides the folw of oil upwards.
The flow down is due to gravity and the amount of oil in the sump is chosen so that there is some reserve when the amount of oil dripping downwards
is less than that pushed up.
Two cases where I can think that happening:
a) at cold start up - all the oil will have dripped into the sump so there will be a short length of time whilst the oil is being pushed up before the
flow down is equal to the going up. Oil being cold taking longer to flow down due to increased viscousity.
b) sudden increase in engine revs.
Now by knowing capacity of the oil pump the flow of oil can be computed and an estimate for the time where oil up > oil down can be
made/computed.
This would give the minimum amount of oil required in the engine. (ok, it is not that simple since the pick up needs to be immersed in oil and
surging.)
Ok, so where is this heading?
Firstly how much can a sump be chopped to reduce oil capacity before it becomes a problem, assuming baffles are in place to prevent surge (probably
not possible).
As an aside, I have seen sumps shortened on here and then have wings added and thnking is that necessary as the oil capacity can be maintained by say
an oil cooler or tank?
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jollygreengiant
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| posted on 18/10/06 at 05:21 PM |
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Don't forget to allow in the calculation for the amount of oil in suspension for mist lubrication by the thrashing around of the crankshaft when
running. manufacturers still rely on this for a fair bit of the lubrication.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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