This innovative system allows for greater low - end torque, more immediate engine response from any throttle position, and improved fuel economy under higher engine loads. (greencarcongress.com)
The sound occurs under all conditions; warm / cold engine, low / high engine load etc.. (mechanics.stackexchange.com)
Achieving low - temperature activity, while surviving the harsh conditions encountered at high engine loads, remains a formidable challenge. (science.sciencemag.org)