K24, 8000rpm and oil pump – all you need to know
There is NO NEED to swap out the oil pump, it is the same design as the K20Z3’s oil pump and that can spin to 8600 rpm’s all day long.
You will loose some low rpm/idle oil pressure(about 20%) with an A2 pump.
Here is a pic comparing the A1/A3/K24A2/A4/Z3 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 and has a much less restrictive turn 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 will be disecting a Z3 oil pump next week to see if the rotors and, or passageway’s are any different to account for the higher rev-limit. I need to find a engine block that has been destroyed, just to get the girdle to make a oilpump test bed.
I see two benefits of running the balance shaft equipped oil pumps now, more pressure at idle, and a much smoother idle(K24). On a very warm day in around town traffic the engine oil pressure will drop to about 5-7psi at the #5 cam cap with the A2 pump, not enough to protect the valvetrain with any kind of aftermarket cams.
If you will be able to drive a RSX with a K24A2 both before and after the A2 pump swap, there will be some very minor gains in top end and with quicker revs in neutral, BUT the vibes will be very noticable at idle and around town drivability suffered just like adding too light of a flywheel. So unless you are building a dedicated 1320′ car that doesnt see traffic, I would use the OEM pump and balance shafts.
Information was taken from: tsx engine swap tuning question | Acura RSX, ILX and Honda EP3 Forum (clubrsx.com)