Thanks for the replys. I don't have any RT fuel economy instrumentation yet, but when i start modding, I will use the Torque app on my android. With the torque app, I can also keep an eye on voltage and temperatures, so that i know if i'm running safe.
I don't think that there are any LiFePo4 car starter batteries available for the public yet. The battery in the Mii is only a 44 or 47 amp battery, so my plan is to get hold of a shorai LFX36, or maybe two LFX24 in parallel. The engine is only a 0.999 3 cylinder, far smaller than the motorcycle engines those batteries were designed for. My most prudent concern is, that the continous electrical draw is far greater in a car than on a motorbike. For those interested, here' a paper on the benefits of using Lithium Ion batteries in cars
http://info.a123systems.com/Portals/...y-advances.pdf (NOTE: Done by A123 Systems, maker of lithium ion batteries.
I've noticed the lack of engine isulation too, but i'm not sure if i'm going to do anything about it. The engine heats up pretty quickly, aparently because "The cylinder head has an integrated exhaust manifold, the engines reach their optimal operating temperature faster with this technical layout."
I'm pretty impressed with the FE figures we are getting already. It looks like 4,1L/100km is doable, even without any mods.