Our team decided last year to start developing a unique telemetry system for the Bosch MS4 Sport motor controller we use. The system was designed entirely according to our needs, so it was realized with a very low budget. In the first generation, the wireless transmission of the 15 engine parameters dictated by the construction was solved (speed, injection, ignition, battery voltage, various temperature and pressure values, etc.). The hardware itself enables the implementation of additional functions, as it contains additional circuit units, so in the future we will expand the capabilities of our telemetry system through software. The diagram below shows how it works:
The system consists of two separate units: Telemetry circuit (Transmitter) and Bridge (Receiver – Gateway). The transmitter communicates with the engine controller via the CAN bus and saves the necessary engine parameters from the data stream it sends. It organizes these into packets and then transmits them wirelessly to the receiver. Radio transmission is currently one-way. The receiver forwards the received data to an Ethernet network, which thus reaches all endpoints. Our team is currently developing a computer program that enables real-time display and logging of data.
Based on preliminary measurements, the range reaches 1000 meters in open terrain.
The most important element of the cooling circuit is the pump, which is a Davies Craig EWP80 electronically driven and controlled model. With this solution, the pump does not take power from the engine’s crankshaft, but from the battery. The control electronics delivers at the most appropriate speed for the engine’s operating state, thus optimizing cooling. The cooling radiator has a unique construction, its cooling surface is 200×300 mm, the thickness of the element is 40 mm.
The oil circuit of the Evo 2 engine, like the Evo 1, has a dry sump system. The external oil tank remained the same, but a custom-designed four-stage pump was installed instead of the factory pump. In the case of the Evo 1 engine, the foaming of the engine oil was a problem, which is a fault of the lubrication system. The suction capacity of the uniquely designed four-stage pump is proportionally greater than that of the factory pump, thus eliminating the problem of oil accumulating in the crankcase. It also prevents oil foaming. The planned pump has a pressure branch that delivers the oil to the crankshaft, to the control, and to the piston cooling nozzles. The task of the remaining three pump sections is to suck the oil collected in the crankcase and from the bottom of the deck covering the control.
We quickly set the goals for the development of the EVO II engine. These were weight reduction, easier installation, cost efficiency and a more compact design. We have changed the geometry, the most significant and noticeable change is the ribs used to stiffen the bearing areas. These are the results of a finite element analysis and the subsequent topological optimization. The result was very noticeable and led to a 30% weight reduction.
It is important to note that we also tried new materials with the EVO II. Furthermore, as a result of a lot of consultation and research work, we changed the previous metal side cover to fiber-reinforced plastic. Since the density of this special plastic is much lower than that of aluminum, this step also freed the crankcase from a lot of excess weight. Although the strength of plastic is lower than that of aluminum, this part was not exposed to load, which is why we decided on polyamide.
At the same time, we have also made many minor changes, improving the fitment, the efficiency of the lubrication system and, last but not least, the safety. As a result of consultations with manufacturing companies, we designed the new crankcase in such a way that production factors and possible costs were also taken into account. This achieves a cost-effective and low-mass construction. Overall, it can be said that our EVO II engine is more compact, lighter and easier to assemble than its predecessor, which are important features in the Formula Student racing series.
EVO II made of deckli fiber-reinforced plastic and aluminum
Assembled EVO II crankcase
When designing the EVO 2 crankshaft, we kept the split, three-part design. The primary consideration in the design was the further reduction of rotating masses. This was achieved most spectacularly around the crank pin. In order to reduce ventilation losses, we created a conical geometry on the counterweights, and from the point of view of rigidity and installation, two ‘ears’ were designed on each side. The tungsten carbide rods used for the remaining EVO 1 were used for mass balance due to cost reduction, however, there are not three identical rods, but one large and four smaller rods per side. Our bearings are cylindrical roller bearings that are also used in the series. We paid a lot of attention to the exact calculation of the stresses, the various simulation programs (AVL Excite Designer, AVL Power Unit) provided a huge help in this, for which we received a lot of help from our sponsors. The main advantages of the EVO 2 crankshaft are the reduction in weight, voltage and size.
New, further ground valve springs were added to the EVO 2, which did not have enough space for the valve springs, so the upper surface, together with the camshafts, was moved 1 mm higher. Thanks to the redesign of the camshafts, the second generation cylinder head became lighter by more than 150 grams. New cams were designed for mass-optimized camshafts, so the valve control of the engine became more optimal in terms of consumption and performance. It also required the design of a new camshaft and new clamps, which further reduced weight. The sprockets of the camshafts have changed in the chain drive. In addition, a new valve cover and a new oil delivery pipe were designed.
Compared to the first generation, the intake system of our second-generation engine underwent a weight reduction of about 50%, while serving the charge exchange processes significantly more efficiently. The system starts with an AT power-brand intake manifold, specially developed for the Formula Student racing series, which includes a 19/20 mm restrictor and throttle. The next element is the airbox, which we optimized for our engine, so its volume became 3.5 l, which is about half the volume of the airbox of the first generation engine. The biggest weight reduction was achieved by improving this component.
The intake pipe is connected to the airbox, which is also made of carbon instead of aluminum, which is why the weight has been greatly reduced here as well. An important aspect in the design of the intake pipe was the use of gas dynamic effects, these thermodynamic simulations were carried out with the AVL Boost software. The injector holding element is connected to the intake pipe, the primary consideration during the design of which was optimal injection. The use of gas swings and the smallest possible weight were also primary considerations in the design of the exhaust system. The engine is supplied with fuel by an external electric AC pump with a pressure-regulated fuel bridge.