Joel Artursson profile picture Joel Artursson 2 years ago 3

Porting the oil pump on a Saab.

Saab - Porting the oil pump on a Saab. - DIY

Decided to port the oil pump in order to get better oil pressure control and get rid of the in-pump cavitation(air bubbles).

All the places where there are ridges and bumps that make sudden changes increases the chances of creating a cavitation environment in the oil pump.

Different sizes in the piping before the oil pump is the biggest cause, there is a suction of oil and then a sudden expansion of the piping happens. Then there will be a vacuum at that expansion point which releases air trapped within the oil.

The last pic of the inlet inside the oil pump near the pump gear. That is what should be done to eliminate all cavitation problems in the pump. I am thinking about getting it welded and gonna re-do the inlet at work with a die sink and die grinder to get it perfect. Like I painted the pic. Since I am going to rev it to 8000rpm.

As you guys can see the oil pressure relief valve is much like a wastegate. Except this one is originally recirculating directly in to the pump gears again as many other stock oil pumps do. There is a problem with it building pressure endlessly with the rpm and not reliefing the oil pressure like it should when you get past 6000rpm. This causes tremendous stresses on the oil pump gears and housing since it gets fed by pressurized oil again, raising the oil pressure even further. This helps increasing the chances of cavitation because the pressurized oil speeds up the oil also getting sucked in causing a slight vacuum.
The oil pressure should always be steady after reaching a certain rpm, too much oil pressure causes friction instead of decreasing friction.
My fix is basically welding the recirculation shut and open up a drain on the back side and letting it drain down in the crankcase instead. There are several other ways to do this aswell even externally.

Hopefully this works well otherwisr it is back to drawboard and make a external solution of oil pump and pressure relief.