Automation Earth Day Special: Designing an Engine for Efficiency

Automation Earth Day Special: Designing an Engine for Efficiency

In celebration of Earth Day, I have chosen to create a new post specifically with environmental awareness in mind. For this I have chosen to show an example of an engine configured for high fuel efficiency and low emissions. In particular, I will share how I achieved both of those objectives. But before that, I will go into why I built the car which is powered by that engine.

A few weeks ago, I found a contest on the Automation forums that required entrants to build an economy car for a buyer whose previous car had been destroyed in a crash. Given my expertise in optimizing an engine for high efficiency, entering this challenge (which would easily have been a round of CSR if not for its creator not having won the most recent round) was a no-brainer. So, after a few hours, I came up with this:

The Zorg ZV2 1.7 AWD: Designed for economy at a reasonable price

My entry, the Zorg ZV2 1.7 AWD, looked like a normal, if small, three-box sedan from the outside, but with all-wheel-drive, fully independent suspension at each corner and alloy panels on a high-strength steel chassis, it was a technically advanced offering. It was also practical and affordable enough to be a sensible daily driver. However, the real genius lay under the hood.

Top to bottom: Internals and variant capacity, cam profiles and compression, turbocharger setup, fuel system configuration, and technical overview of the 1.7-liter straight four in the Zorg ZV2 1.7

In an attempt to extract as much efficiency from the engine as possible given the limited budget, I settled on low-friction pistons (which provide a significant increase in efficiency), a shorter stroke (to prevent the redline from restricting power outputs too much), mild cam profiles (which ensures that the valves are open for a shorter time) and a lean air/fuel ratio (again, providing sizable economy gains). The most significant work, however, was tuning the turbocharger for increased fuel economy. For this application, small compressors and turbines with modest boost and a low AR ratio were a necessity, and I did not hesitate to apply my expertise here.

The end result was an efficiency rating of 32% - an impressive figure given the tight budget. As installed in the ZV2, it provided excellent fuel economy figures (although in a lighter car, it would have yielded even better results) - high-40s to low-50s US MPG on the combined cycle - and very low emissions. Speaking of which, hypereutectic pistons actually reduce emissions even further than low-friction pistons, but aren't as useful in economy-oriented applications due to their increased friction, although they are strong enough to withstand higher redlines. For the next post, I will kick off my series of CSR retrospectives... by stepping back 30 years.