K20A3,K24A1/2/4 oil pump vrs the K20A2 and K20Z3

[talonXracer]

Here is a pic comparing the A1/3 oil pump and the A2 pump. Notice that they use the same exact inner and outer rotors with the same exact oil pressure relief piston and spring.
There is more of a reservoir for the oil after it has left the rotor of the A1/3 pump as it has to travel back across the pump housing before entering the block.

The only major difference is that the A1/3 pump is driven at exactly 2x crank rpm(due to balance shaft requirements), while the A2 spins at approx 1.62X crank rpm. The crank sprocket has 34 teeth and the A1/3 pump has a 17 tooth sprocket while the A2 has 21 teeth.
So when the A2 engine is at 9500 rpms the pump is spinning at 15,390rpms which is slightly above max for the A2 pump without some mods. The A1/3 pump on the other hand has a oil pump speed of 15,600rpms when the engine is only at 7800rpm's. This is the point that everyone says gives the A2 pump the edge, but I do believe that the balance shaft equipped oil pumps can spin at higher RPM's before excessive cavitation occurs because of the passageway design and pump exit being at less of an angle.

The A2 pump is on the bottom


So the balance shaft equipped pump provides MORE pressure at idle and low rpm's.

I see two benefits of running the balance shaft equipped oil pumps now, more pressure at idle, and a much smoother idle(K24)


There are significant differences in the pump rotor both inner and outer between the A2 and Z3 oil pumps. The Z3 has a larger dia, with 8 paddles vrs the A2's 6.



There is also alot of difference in the pressure relief, Z3 on the bottom. The A2 spring is longer and requires alot of effort to push in while installing the cap, but the Z3 spring is shorter and is almost effortless to install the cap.


The rotor housing has different porting and passage design.
Z3 on top, notice it is already "notched" for the 8mm deeper girdle of the Z3/K24A2/A4


The Z3 oil pickup is also significantly deeper than the A1/2/3/4
The RBC has a different pump inlet design.


K24A1 on the left and A2 on the right




Here is the Z3 housing cover showing the areas that need to have material removed as it is hit by the K24 balance shaft weights.


Here is a pic showing the two different oilpump covers. The Z3 pump is enclosed so that drainback oil doesnt get whipped up. And it is already "notched" to fit the K24A2/A4 8mm high step on the girdle.

[oldschoolimport]

link added to the engine sticky. thanks again doug!

[talonXracer]

I had a chance to disassemble a S2K pump yesterday and it appears to have the same pump rotors as the Z3.