Oil pressure question
 

I'm almost certain I know who the answer to this will come from, but here goes anyway.


I'm in the process of having my oil cooler repaired off of my Monster 620 and the repairer asked me a question which made me look a bit of a numpty as I had no reply to it, other than to shrug my shoulders.

"What sort of pressure does the oil run at through the cooler ?"

His interest is in being able to supply a cheap alternative, but obviously needs some idea of capacities and pressures.

Does anyone have any idea or have a mathematic formula for calculating flow and pressure ?

Oil Pressure increases as the engine rpm, and consequently the oil pump rpm, increases. The oil pressure also increases under all conditions if you use a higher viscosity oil. Conversely, oil pressure decreases with engine rpm and oil viscosity, which in turn decreases with temperature.

So the lowest oil pressure will be at idle when the engine is hot and should be at least 16 psi. This number will above 36 psi when the engine is cold and be 60–80 psi around 4,000 rpm.

Taken from the workshop Manual

Of course these figures are only relevant when the bike is the right way up Mark -)

As the return pipe from the cooler just returns the oil back to the sump with no restriction the pressure is at atmospheric i.e 14.7 psi. As RPM increases flow increases through the cooler.

Yes there may be a slight pressure increase due to the restrictive passages of the cooler but nothing like the pressure that the engine is running at.

Thanks for the replies guys. (Apart from Brian's)

So, the upshot of this is that I'm now confused even more.

I'm under the impression that the max pressure the cooler needs to be able to cope with is around 80psi, as its not particularly pressurised but merely a passage way back to a pressurised crank case ?

Maybe I should have paid attention more at school !

Worst case scenario is you have a blockage on the return resulting in the cooler getting exposed to the maximum pressure at high revs.
Must be a rare occurance as I can't recall a specific case of this happening

Several suitable Ducati oil coolers on Ebay for a round £70, so what is the repair cost and what would the cheaper alternative cost

I recall someone using a 749 oil cooler, think it was Rattler
But it now £50
http://www.ebay.co.uk/itm/DUCATI-749...em23243 c75f5

or bid from £30
http://www.ebay.co.uk/itm/Ducati-Gen...em1e76a 14e06

New 7-Row Mocal Oil coolers cost about £60, but then you need to sort out the hoses with the correct fittings

The pressure going in to the cooler will be much less than 80psi due to an open return back to the crankcase, and crankcase is not under pressure, if it was it would blow a seal, hence the breather at the rear.hope this helps

Just sold one for £30 on ebay

That does it for me, thank you.

That is most certainly the sort of "lay mans terms" I understand !;)

Also, cheers to Kev (again) for the input, I'll let you know on the costs, etc once I've spoken to him.

Cheers fella's.