On 30 Mar 1999, aribert neumann wrote:
> after running the car, the idle oil pressure is 15 psi (approx 60 psi at
> road speed).
This sounds pretty spot-on perfect to me. Nothing to worry about.
The factory specifies a pressure between 40 and 60 psi at 2000 RPM with a
hot engine. By my reckoning, that is a simple and also very good and
relevant test.
A hot reading of 20 psi at 2000 RPM would be something to be concerned
about. If it rises to 40 psi at 4000 RPM, crankshaft/camshaft bearings are
suspect, while if it stays at 20+, the pressure regulator should be
examined.
To prolong useful crankshaft life, it might be worth while to change
crankshaft bearings when 2000 RPM pressure goes below 40.
Whatever you do: Don't worry about tick-over pressure (except is should
be above zero, and don't worry about 5 psi changes in pressure).
> I am assuming that the oil is thinning down due to excessive temps.
The oil is thinning, not due to *excessive* temps, but due to *normal*
operating temps. This is exactly like it should be.
Contrary to popular belief, oil pressure is not important for an engine
per se. It is, however, an indicator of:
* Sufficient oil flow through bearings, important for bearing
lubrication and cooling.
* Correct bearing clearances. Excessive clearances would lead to
increased wear an stress, as well as uneven distribution of oil
flow.
Engine oil is designed to perform at its best at an operating temperate
around 80 deg C, which by my guesstimate is what your are seeing.
Excessive oil pressure gives your engine no benefits - instead it will
strain internal components unnecessarily. Why do you think an engine
wears more when cold? It has much to do with the engine oil not being up
to operating temperatures.
> THerefore I plan on adding an oil cooler.
If, by actual measuring oil temperature, you detect temperatures around
the 100 deg C mark, you should consider an oil cooler.
This will depend on many factors. If you regularly drive with a heavy
load (caravan in hilly terrain), you probably need one. A GT6 with a 2.5
engine not tuned to excesses probably won't, IMHO.
Egil
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