As beav stated, fixed displacement pumps (single or two stage are still fixed displacement gear pumps) don't put out 'pressure' they move flow by volume. Pressure is resistance to flow. With heavy load, the pressure climbs until something limits it: wood splits, engine stalls, structure breaks, hose or pump or cylinder splits open, etc. The relief valve bypasses pressure from the pressure line to tank line at some preset number to prevent broken parts. Relief valve will 'crack' at some pressure setting, then have a rise slightly as flow increases, maybe a couple hundred psi usually.
RV is usually located in the manual control valve just due to economy. Most Prince and Energy and other logsplitter valves are screw adjustable. Some industrial valves are shimmed, or sometimes the preset cartridge must be changed. You probasbly have a simple screw adjustment. Many good posts and pics about adjusting that.
A relief valve is ESSENTIAL to any hydraulic system with fixed pumps.
A two stage pump should unload at 700-900, it is not going across relief at that point. nly when it hits the higher 2500-3000 setting does it relieve, and that will be the low flow 2 to 5 gpm.
A single stage pump will relieve all its flow at the RV setting, so the differene between low idle and high idle pressure might rise a bit more..
Force on the splitter is proportional to pressure, so backing the relief down from 3000 to 2500 is a 500/3000 = 1/6 reduction in MAXIMUM force. If the wood only takes 500 oir 2400 to split you will see no difference at all. T'he RV does not affect flow, or 'create' the pressure, it just limits the maximum pressure.
All components have some safety factor built in, of course. Also, thre are NFPA and SAE pressure rating standardized tests for components, usually limited by fatigue after thousands or millions of cycles, but sometimes by seal failures or life. Not nearly as simple as the breaking point of a piece of steel or chain that would be more exact and repeatable
Anyway, I see some choices:
1. Rework the mechanicals to mount the '3000 psi rated' cylinder
2. Run the 2500 psi rated cylinder and figure it can take some overload for some unknown time.
or 3. Reset your relief valve to 2500 and save money, be safe, and probably see very little day to day performance differnce.
Get a gauge in the system. Back the RV out a couple turns, run the cylinder to full extend and stall it, and adjust the RV. Easy job if you have the gauge in place. Searchhere for other posts.
a bit off topic, but if you do the math on most purchased splitters you will see the 22 or 25 or 35 'tons' is often marketing bs, and requires 3200 to 3500 psi to reach those numbers. Most splitters are way less than advertised and they work just fine. A better measure for comparing between brands is simply the cylinder bore size (isnide diameter, not tube OD.).
kcj