How to Improve Thermal Efficiency?

[ThomasAnn]

Using CVVD technology provides an opportunity to increase the maximum thermal efficiency of these engines to over 50%. CVVD (Continuously Variable Valve Duration) technology is an engine technology developed by Hyundai Motor to balance fuel consumption, performance, and environmental requirements.

[AlexanderFitz]

I think improving engine thermal efficiency requires focusing on fundamental design. For instance, increasing the compression ratio, like Mazda's Skyactiv technology, which pushes gasoline engine compression ratios up to 14:1. Ensuring faster and more uniform air-fuel mixing is also crucial—nowadays, 350-bar high-pressure direct injection is mainstream, with injector nozzles as fine as a strand of hair. I remember disassembling a new engine recently and noticing how meticulously designed the piston crown was to guide flame propagation. The timing of exhaust valve opening is also critical—retaining high-temperature exhaust gases in the cylinder can help push the piston further. Additionally, recirculating cooled exhaust gases back into the cylinder reduces knocking and fuel consumption. Thermal management must keep pace too—some new engines even apply thermal insulation coatings on cylinder walls. Combining these methods, achieving over 40% thermal efficiency is no longer uncommon these days.

[DerekMarie]

Improving thermal efficiency is inseparable from heat recovery. I've driven a car with an electric turbocharger, where the exhaust gas flow is captured by a small turbine generator to convert it into electricity. Cold starts consume the most fuel, right? The current solution from manufacturers is a double-layer exhaust pipe design, where the inner pipe quickly preheats the catalytic converter. It's even more cost-effective in hybrid systems, where the engine operates solely in the most fuel-efficient range, storing excess energy in the battery. Even the air conditioning compressor has been switched to electric drive, significantly reducing the load on the belt pulley. Last time I looked at a German car design, even the transmission oil temperature was integrated into the thermal management system for unified regulation. When these peripheral technologies are well integrated, it can save 0.5 liters of fuel per 100 kilometers.

[OLogan]

From a material perspective, replacing the piston with forged aluminum alloy can reduce weight by 30%. Using ultra-thin low-tension piston rings to minimize friction, and applying a plasma-sprayed iron alloy coating on the cylinder walls. The crankshaft bearings are coated with physical vapor deposition, and the engine oil is switched to 0W-16 low viscosity. The water pump is upgraded to an electronically controlled variable type, completely stopping when the engine is cold. The variable displacement oil pump is also quite intelligent, delivering only the required pressure. The alternator is modified to a clutch-type, activating kinetic energy recovery during braking. These seemingly minor improvements, when combined, can reduce mechanical losses by 15%.