Original Nissan QG oil pumps for the US domestic market are made in Mexico. At least that's what the casting on the front cover tells me.
Picture below of the oil pump front cover (inner side), inner cover, rotor gears and pressure relief/regulator valve.
WPC treatment dimples the surface on a microscopic level to help maintain a good oil film for better lubrication. It also creates a hard yet smooth and silky feeling surface. This helps to reduce friction and eliminate galling. WPC treatment results in a more efficient and cooler running oil pump. You can read up more on what an oil pump does, how it works and the merits of WPC treatment over @ MotoIQ. MotoIQ also has an article on how WPC works. You can read it here.
Picture below of the inner cover (inner side). You can see how smooth and silky the surface is.
Picture of the Gerotor inner and outer rotor gears and pressure relief/regulator valve.
WPC uses a different treatment on the gears to impart more fatigue strength and lubricity than the softer aluminium housings. WPC treatment will harden the gears and greatly improve it's fatigue strength. This will make the gears more resistant to breaking under harmonic stress. Close up of the rotors. Zip tie is to hold the gears in place during shipping.
Total cost came up to:
- Brand new original Nissan QG18DE oil pump - US$ 211.69
- WPC Treatment - US$ 100
Picture below of the fasteners required to assemble back the oil pump. Also in the picture is the spring, washer and plug for the pressure relief/regulator valve. To slightly increase maximum oil pressure, a 2-3mm shim can be placed between the spring and the plug.
The countersunk bolts are M6 x 12mm in length while the hex head bolts are M6 x 35mm. I measured coz I am thinking to replace them with titanium versions. Unfortunately Pro-Bolt only do M6 x 15mm for the countersunk bolts and want me to order 25 bolts when I only need 4 just to have 3mm shorter bolts. Excuse was due to machining set up time and cost of production. Bummer!!! Another supplier in Germany does m6 x 10mm but wouldn't ship to Bolehland. Bro Mugil, need your help!
One of the weaknesses of the QG engine is the oil pump which does not produce competitive pressure unlike other performance oriented engines. This is the reason why I do not run an oil cooler for Sharkie as an oil cooler will further lessen the already not so good oil pressure. Hotter oil is better than insufficient oil pressure. Hopefully WPC treatment will slightly increase the pressure during all engine revs and not just max pressure. We shall see as I can compare the oil pressure readouts on my dash pre and post WPC treatment and blueprinting of the oil pump. The WPC treated oil pump will be installed during my next service and oil change