you, in order to be getting the correct, diffused combustion.” Long term, Alpha-Otto plans to use machine learning (ML), given the relative ease in having a ML architecture (such as a transformer neural network) study and learn how different permutations of engine-sensor data could be indicative of successful diffused combustion, and refining it over time to eliminate false positives and false negatives. “We can’t just use basic physics calculations and try to compute all of this on the fly. It’s just too much data to crunch. But we can monitor the pressure profile in many different ways,” Krzeminski explains. “For example, you can measure ΔP across the cylinder, like I mentioned, with fairly inexpensive instruments, or just put a cylinder pressure transducer in – the latter is what we use in testing. Granted, we don’t want to do that in operation; we want to use proxies for what’s going on in the combustion chamber. “Big picture: we want to identify and understand diffused combustion traces and back-calculate via ML where pressure, temperature, spark timing, exhaust valve timing and ΔP all need to be to reach that perfect profile for LTC. “That will enable us to maintain peak efficiency for cruise or range extension work. But, with real, ML-powered understanding of those traces, we’ll also be able to move the boundary conditions and adjust the ECU’s outputs as needed to move in a stable way towards either peak power or maximum continuous output. “It would be a lot like how conventional engines today use an O2 sensor, but instead of looking at oxygen we will be looking at combustion and toggling engine parameters to get it to where we want it to be.” While this will take more r&d, AlphaOtto is prepared to supply engines running on the Cosworth ECU, embedded with a prototype version of its map-based combustion control strategy, which it could update over the air in future. Holistic adjustment In addition to offering a fine-tuned ECU in future, Alpha-Otto has been testing a shaft-mounted, axial-flux motor generator with dimensions of about 30 cm x 10 cm, and large enough to turn the REV Force’s full shaft horsepower into electric current, or drive the shaft to double its output (drawing upon battery energy to do so). “Axial-flux tech, in general, works very synergistically with spark-ignited engines. Traditional radial-flux alternators upwards of 100 kW have massive magnets and can’t generate power at extreme speeds of 5000-6000 rpm or higher; instead being better suited to 1800-2600 rpm,” Krzeminski says. “There are certainly electric motors that can output power at higher speeds than that, but in terms of power generation our axial-flux supplier’s [name withheld due to NDA] technology has proven incredibly efficient at 50006000 rpm, so it matches nicely with our engine.” Should collaboration with its partner continue well into the future, Alpha-Otto envisions integrating the motor-generator system more tightly with REV Force and any future versions of the engine that may follow. This may include combined oil management and thermal management (including heat recycling from the motor-generator to the engine to complement the EGR). “Some of your readers might know how Wankel rotary engines suffer a particular challenge of cooling their internal rotor. Big electric motors have a similar problem in that their stator can be pumped with water pretty easily, but their rotors aren’t so easy to cool, but pump oil through its shaft and suddenly it becomes incredibly cooled and efficient,” Krzeminski says. “Combine that with an engine and suddenly you can develop a combined cooling strategy for both the e-motor and the ICE. Just as with the subsystems and stages of our LTC, there are huge efficiencies to be gained from integrating systems together and having them work holistically.” Going forwards, Alpha-Otto plans to continue optimising the electrical and electronic aspects of its engine, and it is open to new potential suppliers, partners or other contributors whose specific insights and applications may provide valuable – and fascinating (to Krzeminski and his industrious colleagues) – directions in which to hone the REV Force technology for meaningful ends. 79 Uncrewed Systems Technology | April/May 2025 REV Force Inline two-cylinder Two-stroke Spark-ignited Gasolines, kerosenes, biofuels, hydrogens Supercharged Liquid-cooled Crossflow porting Weight: 48 kg Maximum power output: 127 kW Maximum torque: 160 Nm Maximum speed: 8000 rpm Bore: 74.8 mm Stroke: 65.8 mm Displacement: 578 cc BMEP: 17 bar TBO: 2000 hours confirmed (higher expected, pending future testing) Some key suppliers ECUs: Cosworth Throttle: Bosch Superchargers: Sprintex Fuel injectors: Bosch Fuel injectors: Magneti Marelli Coatings: Line2Line Coatings Bearings: NTN Bearings Reed valves: Boyesen Cylinder sleeves: In-house Key specifications
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