22 vs. 28 GPM Log Splitter Pumps (Cycle Time Test)
A 28-GPM pump has 27.3% more stated flow than a 22-GPM pump, but that does not guarantee a faster split. In an ideal constant-flow test, its full cylinder cycle would take about 21.4% less time. Real results depend on pump stage, engine power, cylinder size, valve and hose capacity, oil temperature, and load. Test both under matched conditions.
A pump change can look like a simple bolt-on job, but a higher-flow unit may overwhelm parts that were sized for the original pump. Before removing anything, confirm the engine speed, valve and hose ratings, suction plumbing, and cylinder match the pump. That check is often easier and less costly than troubleshooting heat, noise, or poor cycle performance after installation.
For a useful comparison, separate two questions: how fast does the ram move without a log, and how long does a complete cycle take while splitting? The first can show whether the system reaches its expected flow. The second tells you more about working performance, but only if the test load and conditions are consistent.
Equipment Setup, Pump Matching & Safety Prep
A pump’s GPM rating describes flow under specified conditions, not guaranteed flow at every pressure. Before comparing pumps, record the ratings for the pump, engine, control valve, hoses, and cylinder, then check that the whole hydraulic system can handle the selected pump’s flow and pressure.
Start by recording the pump model, rated flow, pressure limit, and required engine RPM. Note the engine’s usable power at that speed, plus the cylinder bore, rod diameter, and stroke. Check the valve and hose flow and pressure ratings, the suction-line size and condition, and the fluid type specified in the manual.
A higher-flow pump does not automatically raise the splitter’s safe working pressure. The relief valve and every connected part still matter. Do not increase pressure settings to chase faster splitting. If a component’s rating is unknown, find its specification or ask the equipment maker before running the new pump.
Power is a key limit. Hydraulic horsepower is calculated as:
Hydraulic hp = PSI × GPM ÷ 1,714
At 3,000 PSI, 22 GPM requires about 38.5 hydraulic hp, while 28 GPM requires about 49.0 hydraulic hp. These figures do not include drive losses. Confirm the engine can supply the needed power at the pump’s specified RPM; do not assume a small engine can sustain full flow and pressure at once.
| Check before choosing a pump | What to confirm |
|---|---|
| Pump | Flow, pressure limit, and engine RPM |
| Engine | Usable power at the required governed speed |
| Valve and hoses | Flow and pressure ratings meet the pump’s needs |
| Cylinder | Bore, rod diameter, stroke, and pressure compatibility |
| Suction line and reservoir | Correct size, sound connections, and manual requirements |
Inspect for leaks, damaged hoses, loose fittings, and missing guards. Work on stable, level ground with a clear ram and log path. Wear eye or face, hearing, hand, and foot protection suited to the machine, and keep bystanders away.
Controlled Field Cycle-Time Test & Log-Splitting Operation
A cycle-time test measures how long the ram takes to extend and retract. For a fair pump comparison, use the same splitter, cylinder, engine speed, oil temperature, and test method. Record several cycles, not just the quickest run, and report both the median and the range.
The basic timing equation is seconds = 60 × fluid volume in gallons ÷ flow in GPM. A full cylinder cycle uses the extend-side volume plus the rod-side, or annular, volume. To calculate these volumes, you need the cylinder bore, rod diameter, and stroke.
For an illustrative 4-inch-bore, 2-inch-rod cylinder with a 24-inch stroke, the extend side holds about 1.31 gallons. The retract side holds about 0.98 gallon, so total full-cycle volume is about 2.29 gallons. At constant flow, the theoretical cycle is about 6.25 seconds at 22 GPM and 4.91 seconds at 28 GPM.
These are calculated examples, not universal splitter times. A common two-stage pump provides high flow at low pressure, then shifts to lower flow as pressure rises. So a “22 GPM” or “28 GPM” label does not tell you the flow during a hard split. Engine limits, valve capacity, and load also change the result.
| Comparison | 22-GPM rating | 28-GPM rating |
|---|---|---|
| Flow ratio | Baseline | 28 ÷ 22 = 1.273 |
| Ideal constant-flow cycle time | Baseline | 21.4% shorter |
| Example full cycle, constant flow | 6.25 sec | 4.91 sec |
| At 3,000 PSI, hydraulic power required | 38.5 hp | 49.0 hp |
How to run the test
- Check the oil level and condition as directed in the manual. Make sure the suction line is clear and connections are secure.
- Start and warm the engine and hydraulic system as the maker directs. Use the pump’s specified RPM.
- With the work zone clear and the operator at the controls, time at least five complete extend-and-retract cycles. Keep the same timing points each time.
- Test unloaded first. If you need working-cycle data, use a consistent, safely positioned test load and do not force a stalled split.
- Record each time. Report the median and range, and note oil temperature or other changes that could affect the result.
For instance, if a compatible splitter is being considered for a 28-GPM replacement, first check the engine and valve ratings rather than relying on a faster unloaded ram as proof that the upgrade works under load. If the existing engine cannot supply the required power, the higher rating may not produce the expected working speed. These are test scenarios, not measured field results.
Hydraulic-System Inspection & Preventive Maintenance
A cycle-time change can point to more than pump flow. Low or inconsistent speed may come from a restricted suction line, low or unsuitable fluid, air in the system, a worn pump, or a control valve or engine that cannot support the operating conditions. Compare the system’s condition before blaming the pump alone.
Before and after a test, check the oil level and appearance according to the manual. Look over hoses, fittings, the reservoir, and the suction side for leaks or damage. Listen for abnormal noise and watch for unusual heat, but stop the test if the system behaves differently from normal.
Never search for a pinhole leak with your hand. High-pressure oil can pierce skin and cause severe internal injury, even when the puncture looks small. If injection is suspected, seek emergency surgical care immediately. Shut down and depressurize the system as the manufacturer directs before inspection or service.
Avoid holding the ram against its end stop. Do not repeatedly force a stalled split, and do not make adjustments to pressure controls unless the manual authorizes the procedure. A pump, valve, or hose that is too small for the flow can contribute to overheating, cavitation, component failure, or loss of control.
Shutdown, Fluid Care & Seasonal Storage
Good shutdown practice protects people and helps preserve a reliable seasonal start. After testing, return the control to neutral, shut the engine down, and relieve stored hydraulic pressure as instructed by the maker. Let hot parts cool before service, then inspect for leaks or damage.
Clean the machine and store it according to the manual. Follow its instructions for hydraulic fluid, filter service, and seasonal storage; do not guess at fluid type or add a different oil without checking compatibility. Record the pump rating, engine RPM, oil condition, and test results so you can compare performance later.
If cycle time changes from one test to the next, compare test conditions first. A different warm-up, engine speed, or load can make the result misleading. Repeat the test under matched conditions before deciding that the pump or another part needs replacement.
FAQ: 22-GPM and 28-GPM Pump Cycle Tests
These answers cover the main limits of a pump-flow comparison: what the ratings mean, how to time a full cycle, and what must match for results to be useful. Use the equipment manual and component ratings for decisions about installation, pressure, fluid, and safe operation.
Is a 28-GPM pump 27% faster than a 22-GPM pump?
No. It has 27.3% more rated flow, but that does not mean a splitter completes a loaded cycle 27.3% faster. Under ideal constant-flow conditions, the cycle would be about 21.4% shorter. Real cycle time depends on load, pump stage, engine power, and system capacity.
How do I calculate full cylinder cycle time?
Add the fluid volume needed to extend the cylinder to the volume needed to retract it. Multiply that total in gallons by 60, then divide by flow in GPM. This is a theoretical estimate when flow stays constant.
Why can the loaded cycle be slower than the unloaded cycle?
Splitting wood raises hydraulic pressure. Many log-splitter pumps shift from high flow at low pressure to lower flow at higher pressure, so the pump may not deliver its nameplate flow during a hard split.
What measurements do I need for the cylinder calculation?
You need the cylinder bore, rod diameter, and stroke. Bore size determines extend-side area; the rod reduces the working area on retraction.
Can I install a 28-GPM pump on a splitter built for 22 GPM?
Only after verifying engine power and speed, pump compatibility, valve and hose ratings, suction plumbing, reservoir requirements, and cylinder compatibility. Do not install a higher-flow pump based on the old pump’s fit alone.
How many cycles should I time?
Time at least five complete extend-and-retract cycles. Record every result and report the median and range, with test conditions noted.
Should I time unloaded or loaded cycles?
Both can be useful. Unloaded timing checks ram movement under light demand. A consistent, safe test load better reflects work, but do not force a stalled split.
What should I do if the pump makes unusual noise or the system heats up?
Stop the test and inspect only after shutdown and pressure relief as directed by the manual. Check fluid level, suction plumbing, leaks, and component ratings. Do not keep running a system that shows abnormal heat or noise.
Is a suspected hydraulic injection injury an emergency?
Yes. High-pressure fluid under the skin can cause severe damage even if the wound looks minor. Seek emergency surgical care immediately, and tell medical staff that hydraulic fluid injection is suspected.
(This article was written by one of our staff writers, Harrison Croft. Visit our Meet the Team page.)
