Issue 37 Unmanned Systems Technology April/May 2021 Einride next-gen Pod l Battery technology l Dive Technologies AUV-Kit l UGVs insight l Vanguard EFI/ETC vee twins l Icarus Swarms l Transponders l Sonobot 5 l IDEX 2021 report

62 Dossier | Briggs & Stratton Vanguard EFI/ETC vee twins can plug into the ECU and use our in- house diagnostics software to identify and fix whatever might be wrong.” The ECU also enables flexibility for future engine development. Re-mapping the ECU or changing a few software settings to run a different engine configuration is relatively simple compared with redesigning mechanical systems. “For example, right now the Small Block uses a single throttle body injector,” says Pomeroy. “But if we find in the future that having two injectors has advantages we need to offer, the ECU can easily be set up to drive them.” The 23 bhp EFI/ETC system uses as few sensors as possible to minimise the overall current draw required to start the engine. A straightforward speed density strategy is therefore embedded into the ECU, along with a TMAP (temperature and manifold absolute pressure) sensor. There are no dedicated sensors for O 2 , throttle position or speed; speed readings from the ignition coils are sufficient to precisely adjust the ignition timing, fuel injection and throttle width as defined by the engine mapping. “Having a low number of sensors and wires is useful for UAV operations, since it reduces weight and potential failure points by having fewer connections,” Ihrig adds. “We can also carry out special calibrations for different UAVs, such as setting lower idling speeds for logistics UASs that may spend a lot of time taxiing on the ground. That reduces the burden on the brakes and fuel.” The ECU itself is mounted atop the engine, to one side of the stepper motor, for throttle control. The motor sits roughly in the middle of the vee of the cylinders, between the intake manifold and throttle- injector assembly. “While automotive EFI systems typically use tank-mounted high-pressure fuel pumps, utility engine customers prefer not to customise their fuel tanks for EFI,” Bruener says. “To accommodate them, we therefore mount a high-pressure fuel pump module on the engine. “So our module acts similarly to a carburettor bowl – it contains a float and a vapour separator, with a high-pressure fuel pump down at the bottom to deliver fuel to the injector according to the ECU’s mapped requirement. We couple the fuel module with a simple and reliable pulse-type lift pump to draw fuel from the customer’s fuel tank.” The Big Block has a similar sensor and pump architecture but the ECU – along with the throttle body, ETC assembly and TMAP sensor – are supplied by Continental subsidiary Vitesco Technologies. Duch adds that because of the ECU’s position next to the throttle body, it is designed on the 40 bhp engine to contain a throttle position sensor and mass airflow sensor as well, to make packaging easier and reduce the wiring needed. As a result, the bigger engine also tracks throttle position as a key control input, to enable quicker responses in injection timing and quantity relative to throttle changes. With different ways to sense load available, alternative engine management strategies could be implemented if desired. “From a practical standpoint, the TPS and TMAP sensors are both basically telling you what load the engine’s under, they’re just doing it from different angles,” Duch comments. “So by using both on the bigger engine we also get a form of redundancy. The TMAP gives consistent information on fuel requirements during routine cruise, while the TPS helps a bit more during transient stages of operation.” April/May 2021 | Unmanned Systems Technology The camshafts are die-cast from iron, and feature four lobes for the four valves Our high-pressure fuel pump module acts similarly to a carburettor bowl. We couple it with a simple pulse-type lift pump to draw fuel from the tank