To produce the power and torque that move the car, with a wide usable curve peaking between 10,000 and 14,000 rpm, reliably enough to finish endurance.
A 2008 Yamaha YZF-R6: 599 cc inline four, 13.1:1 compression ratio, naturally aspirated, 16,000 rpm maximum engine speed, 135 lb wet, running 100 octane gasoline. CR26I produced 36.8 lb-ft peak torque at 8,600 rpm and 84 hp peak power at 13,500 rpm, against CR25's 36.5 lb-ft at 11,300 rpm and 79.5 hp at 11,500 rpm. The engine assembly as costed includes the engine itself, the engine mounts and engine pins that locate it in the frame, and the modifications made to it: EGR blockoff and PCV plate.
Keep the engine, improve everything around it. The justification is explicit and is re-argued every year: six years of knowledge and experience, an engine test stand designed and built around this engine, vehicle and test stand instrumentation harnesses designed for it, three functional assembled engines already owned, and an iterative year-to-year design process that only works if the engine stays constant. The downsides are stated honestly rather than argued away: it is the heaviest engine configuration commonly used by FSAE teams, it puts higher loads on the cooling system because power is only accessible at high engine speeds, and it is less efficient than a single or twin. The cost to change is quantified: roughly 720 hours and $3,200 to redesign the test stand, plus the cost of the new engine and its parts. 1. Characterise the engine experimentally rather than from published data. Intake port geometry captured by pouring 2-part casting silicone into the ports, then 3D scanning and post-processing the molds. Port flow measured on a flow bench with valve lift controlled by fine-pitch fasteners threaded into a plate bolted to the head, read on dial indicators, with an individually characterised bell mouth adapted to the port inlet. 2. Measure camshaft geometry with a dial indicator rigidly mounted to the head probing the lobe surface, combined with lifter geometry to get the effective lift profile. CR26I: exhaust 180 deg ECD at 0.050 in lift, 7.95 mm max lift at 245 deg ATDC; intake 200 deg ECD, 8.67 mm max lift at 475 deg ATDC; 115 deg LSA, 150 deg overlap. 3. Measure valve spring force-displacement on an MTS Exceed, averaging multiple springs. Maximum displacement limited by coil bind at 0.9270 in. 4. Build the GT Suite model from those measurements and validate against dyno data. 5. Develop calibration on the engine test stand, then validate on track.
- Target peak performance between 10,000 and 14,000 rpm while remaining drivable everywhere else. - Keep the engine healthy under all testing and competition conditions. - Improve the model until it predicts what the dyno measures. - Maintain powertrain system weight.
- Weight. It is the heaviest engine configuration commonly used in FSAE, and that is accepted rather than fixed. - Cooling load. Power is only available high in the rev range, which raises the heat rejection requirement. - Efficiency relative to single and twin cylinder alternatives. - Model limitations. Power and torque outputs depend on combustion equations with assumed values for flame front speed and in-cylinder pressure, plus input flow bench data and discharge coefficients. Converge coupling and in-cylinder pressure measurement with a Kistler 6054C are the planned fixes.
GT Suite 2024 with GEM3D. AC motor engine dyno with National Instruments RIO hardware and LabVIEW for high-speed acquisition, independent coolant and oil temperature control, ambient air temperature control, and adjustable 12V system voltage. Flow bench for port characterisation. MTS Exceed for valve spring curves. 3D scanning of silicone port molds. Ionic current knock detection through Mitsubishi H6T60271 ignition coils with integrated IGBT and signal conditioning.