RX-8 OMP Lab

An interactive companion to my Series 1 OMP guide: see how engine speed, load and coolant temperature change the commanded step, and replay the start-up checks and switch faults.

I built this as an interactive companion to my Series 1 OMP guide. It runs entirely in your browser: there’s no account, nothing is uploaded and nothing is stored.

It covers the stock Series 1 oil metering pump only, not the Series 2 system or an electric replacement, and it’s modelled on a 2005 UK Series 1 (231 PS, six-port, manual).

Reference calibration / provisional model. I use community-decoded six-port ROM data for the reference step tables. I haven’t verified an exact match to my 2005 UK ECU, so these illustrate the control behaviour rather than reproduce my car’s calibration exactly. The oil-delivery figures are my own estimates from published teardown geometry, not measurements, and the start-up timings are illustrative.

Open the lab in a new tab →

What to try

• Explore OMP. Drag the engine speed slider (700 to 9,000 rpm) and switch between a warm engine under light load, a warm engine under high load and a cold example. The graph keeps its full curve and only the marker moves, so you can see that the same RPM can ask for quite different steps. The cold example is higher because of the coolant-temperature minimum, not because of engine speed.
• Startup & checks. Pick an example and press play. The stepper homes to zero with 60 reverse commands, and then, only when a position check is due, sweeps towards step 60 while the binary switch changes to On. Try the three switch-feedback faults and the jammed mechanism, and compare what the controller thinks with where the mechanism actually is.

What it’s meant to show

1. Engine rotation drives the pumping.
2. The stepper adjusts the stroke.
3. Oil demand depends on operating conditions, not RPM alone.
4. Startup establishes a position reference, and sometimes a separate position check.
5. The positioning switch is binary: it can’t tell you how much oil is flowing.
6. A fault can leave the controller’s idea of the position different from the physical position.

The mechanical background is in how the OMP works.

What’s documented, decoded and estimated

• Documented: how the pump is built and controlled, the start-up homing and position check, the fault-code conditions and the electrical values come from Mazda’s service information.
• Decoded: the reference commanded-step tables are community-decoded ROM data, used as published.
• My own formula: the way those tables are combined into one commanded step is a provisional formula of mine, because the factory logic isn’t published.
• Estimated: oil delivery is calculated from published teardown geometry. I don’t infer it from the step tables, because they describe a different quantity, and it isn’t a measurement.
• Illustrative: the start-up timings, diagnostic windows, switch threshold and operating-condition presets are teaching values.

The lab’s own Model notes and sources section lists every source and the ROM details. The approximate step and flow figures I logged on my own engine, on the engine running data page, are a relative characterisation rather than a calibrated map, so I haven’t used them to set any of the lab’s defaults.

Related Pages

• Series 1 OMP guide: the full set of OMP pages.
• How the OMP works: drive, stroke control, initial-set and monitoring.
• Diagnostics & testing: practical checks and fault codes.
• 13B-MSP engine running data: my logged oil pressure, temperature and OMP data.
• EnduraOMP: my MEng project, a closed-loop replacement for this system.