Malcolm -
>
>You can't do much more good by cranking the engine over before starting
>it, at least not much in the oil department.
>
>Even though it has a pressure, oil is an incompressible medium. If you
>circulate it using the engine combustion or the starter motor, it still
>gets squeezed about by the oil pump.
>
>The only way to get oil up to the top end of the engine is by using either
>an electric oil pump or the pressure gadget previously mentioned.
>
>Or you can peel off the dizzy every cold morning and spin the oil pump
>with an electric drill... that's what you do after an engine rebuild to
>build pressure. But it's also a bit of a chore to reset your timing ;-)
>
.. I do not quite understand.
The 'theory' is:
Oil circulates in the engine when the oil pump is running. Normally,
the oil pump is running only when the engine is running as well, i.e.
800+ rpm. When the engine has sat for a while the majority of oil is
sitting in the pan. Then I start the engine, and -as in your case- after
two revolutions it fires up and is running at 800+ rpm. Almost certainly
the oil pump has not distributed very much of the oil about during these
first two revolutions.
Let's assume now the following:
(1) The oil pump needs 100 revolutions in order to spread oil about
in sufficient quantities for proper lubrication.
(2) The engine fires up after 2 revolutions and runs at 800+ rpm.
In this case I will have 98 of the first 100 revolutions at 800+
rpm until enough oil has been distributed.
Now another scenario:
(1) The oil pump needs 100 revolutions in order to spread oil about
in sufficient quantities for proper lubrication.
(2) I turn the engine for the first 100 revolutions only with the
starter motor.
(3) The starter motor runs at 100 rpm.
In this case I will have the first 100 revolutions at 100 rpm util enough
oil has been distributed for decent lubrication. Then I activate the
ignition and fire the engine up.
The higher the speed (rpm), the higher the friction and the associated
wear. Therefore I prefer to do my first 100 revolutions
(the "lubrication cycle") at a lower rpm (i.e. 100, with the starter
motor only).
Comments please!
Cheers
Romano
'77 Spit
Oxford UK
--
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Dr. Romano T. Kroemer
Phys. & Theoret. Chem. Lab.
University of Oxford
South Parks Rd. | Tel: ++44-1865-275475
Oxford OX1 3QZ | Fax: ++44-1865-275410
England, U.K. | Email: romano@bellatrix.pcl.ox.ac.uk
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