oil pressure with 15w50

Damn! Someone has done their homework ! One thing that you may have missed is Fittings inside the diameters ! Your oil pump passageways are 19 mm ? ( filter housing ID 17 mm) AN 12 HOSE ID diameter is 17,5 mm. Now flow area is reduced from 19mm to 17,5 mm and AN 12 Fittings ID is 15,5 mm ! That means 34 % smaller flow area. Overall most of the NSX speed part suppliers AN 10 hose is too small for NSX !

To any of you guys in the colder climates who track and are thinking about 15/50 I tried it for one summer in Pa and the morning temps can still be in the 50's-60's and the car ran rough and was hard to start....not worth it imo.

I had 15w50 in the car when I got it. The engine had weird oil pressure readings when cold.

Changed to 5w40 and immediately the oil pressure was like it should be.

15w50 is too thick for our engine. I think Honda had their reason why they recommend a 10w30 in 1990 which was quite ahead that time ...

Bernhard

Operator said:

Damn! Someone has done their homework ! One thing that you may have missed is Fittings inside the diameters ! Your oil pump passageways are 19 mm ? ( filter housing ID 17 mm) AN 12 HOSE ID diameter is 17,5 mm. Now flow area is reduced from 19mm to 17,5 mm and AN 12 Fittings ID is 15,5 mm ! That means 34 % smaller flow area. Overall most of the NSX speed part suppliers AN 10 hose is too small for NSX !

Click to expand...

Good point - All of the sudden expansion and contractions going from hose to fittings is also a loss, obviously besides the smaller fitting diameters themselves. All of the extra stuff adds up... extra oil coolers, their fittings, the hose losses, etc. It makes a difference too whether you use an elbow or a smoother radius on your fittings.

The good news is that most of these extra losses are just a small fraction of the total pumping power required for the oil pressure orifices and losses through the engine bearing journals. Also, your pump is positive-displacement so it will always put out the same volumetric flow at a given RPM... whether you add more restriction downstream or not (for the sake of this discussion at least). All you are doing is requiring more of your engine power to turn the pump. However, like the original poster of this thread, if you add too much restriction by way of an extra oil cooler and switching to heavier oils at the same time, then your oil pressure as measured in the heads will be less at ~6k or higher RPM due to bypassing through the untouched relief valve that was sized for OEM oil and restrictions.

That's why his idle and cruising oil pressures were the same, yet higher RPM oil pressures dropped... he was bypassing more oil through the OEM pump relief valve.

Dave