Re:oil cooler

[bearbvd@domain.elided (Greg Hermann)]

At 8:56 PM 1/4/00, yaron sadot wrote:
>water cools the oil
>
>thats why the hose is there

It also can warm it, as when the coolant warms up much faster than the oil
from a cold start.

Actually--the ideal coolant temp is about 195=B0 F, at its maximum (going to
the radiator), ideal oil temp is about 180=B0 F. at its minimum (going to th=
e
galleries). With normal flow rates for each, the minimum temperature
(leaving the radiator) for the coolant is about 20=B0 F lower than its
maximum (at maximum engine power output), and the maximum oil temperature
is 210=B0 or 220=B0 F., leaving the bearings, also at maximum engine power
output level.

Heavy trucks even use a "shutter" on the air intake to the radiator. The
shutter closes at light engine loads or in cold weather so as to not let
coolant exit the radiator at anything less than about 175=B0 F. This avoids
any tendency to "shock" (thermally distort or stress) the engine block or
heads with too cold coolant coming back from the radiator.

It is wise to minimize the amount of time the oil spends at a temperature
less than 180=B0 F, as keeping it warm helps to keep it dry (otherwise, it
will accumulate water, which is one of the natural products of the
combustion process).

A coolant to oil heat exchanger is an excellent way to warm the oil up more
quickly from a cold start, and a properly designed one can also remove
about 1/2 or 2/3 of the accumulating heat from the oil in a fully loaded
engine. An oil to air cooler (smaller than what would be required with no
oil to coolant heat exchanger) is still necessary in order to cool the oil
down to 180=B0 F. after the coolant HX , but before it is fed to the
galleries in the engine. Use of an oil thermostat to bypass the oil to air
cooler so as not to cool the oil below 180=B0 F. at light engine loads or in
cold weather is also a prudent move.

It always takes more detail and more $$$ to do things RIGHT!

Regards, Greg

>yaron

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End of alfa-digest V7 #1261
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