i have built a 785cc V8 engine, with over 100kw/L, and the economy is over 33%! And this is a N/A engine. I think this is the extreme in reality.
Thats actually pretty good. Only thing I’d comment is that if you dropped the performance intake for a standard it would cut a great chunk off the service costs.
The problem with the 400cc engine is the durability (MFTB - 0), and the thousands of hours to build it.
Coni, if the mtbf shows 0 build a car with a high enough cooling and take a picture from the car editor choose engine, revise engine screen. That will show its actual number.