Lets dive into some oil pump tech!
Most people just shim their oil pumps as a way to cheaply and as easily as adding a washer to the bypass spring. This is like like trying to force a ping pong ball through a garden hose. Yes there will be increased pressure but liquids do not like to be compressed. With pressure comes heat and causes the oil to break down and thin out faster. The other down side to this with this increased pressure and ineffective housing shaping a large amount of oil has to hit pipe plug make a 180* turn then enter the block. This causes a traffic jam situation where the oil doesn’t have an easy route into the block. This means that there is more oil going through the bypass being “recycled” without ever making it into the motor. The oil gets aerated and beaten up by the pump gears yet again. This causes the oil to break down and lose viscosity much faster than you would normally see, as well as an increased oil temp.
Here is an OEM Y8 Yamada pump for reference
Pump exit diameter
Next Lets look at where the pump meets the block
D16Z6 Block 
.760″~ Measured diameter 
Even with out measuring you can see that the oil pump exit is significantly smaller than the entrance where it mates on the block.
Where the pump mates to the block is a .760″ diameter hole. The standard pump outlet is .480″~ diameter (MEANING THE PUMP EXIT MUST BE INCREASED BY 37% TO MATCH THE BLOCK!). In addition where this .480″ inch hole is the oil still has to hit pipe plug to make the 180* turn then enter the block!
Now lets look at the OEM gears
We have the OEM on the left and our over sized on the right, our hd gear set comes in at a full 1 oz heavier.
Here is the over size gears in a stock oem pump housing
Now if you increase the size of the housing as well as fit larger diameter gears you are now able to move a larger net volume through it at the same or lower pressure rating with out causing as much heat and pumping inefficiencies.
The next question I head alot is “If you port the oil pump, you lose oil pressure” this is just wrong in every sense of the word. They usually justify this view by saying “The holes are bigger that means there will be less pressure”. This is why the oil pumps have a bypass spring, the spring and plunger set up is what REGULATES THE PRESSURE. Customers have reported an increase of pressure after porting, without increasing the bypass spring pressure. This is simply achieved by creating a more efficient flow path for the oil.
Here is an example of one of our CNC ported Y generation oem pumps.
With the cnc porting there is a great deal of smoothing, straightening, and over-sizing the pump passages as well as where it mates to the block is going to increase the volumetric pump efficiency. Moving a larger amount of oil at the same pressure, simply because there is less internal resistance, less wasted energy. Next the ported pump has a smooth radius-ed and unshrouded 90* turn to enter the block with no steps in size variance to over come. The 90* transition is achieved by tapping the pipe plug deeper into the housing and “sinking it”.
Here are some pictures of our 5 axis CNC over size gear oil pumps
Cnc pump exit
This it why you will see and increase of oil volume through the block and an increased pressure at your sending unit.
They have a larger pump gear set than oem, weighing 1oz more than oem, and featuring thicker pump fins and larger diameter they are ready for abuse, as well as stiffer bypass spring and of course these are the first and only 5 axis cnc ported honda pumps available.
Our Big gear pump has been tested by Tommy @ Honda Pro parts in Puerto Rico, they had a result of 822 WHP and spinning 10000 RPM, without issue. as of 4/15/20 They have the quickest and fastest D16a6 motor in the world. 
Thanks for reading!
-SohCole
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