Weight savings is not the main point in my lupo. I have only taken out weight to get better acceleration. There will come unofficial fuel economy race between my lupo and my customers Audi A2 which still has almost all the gadgets it had from factory. So comfort is not sacrificed like in my lupo.
Shortest route to great fuel consumption is good aero and small engine. That small engine can be built to have lots of power like I have done. Now OEMs are making high boost petrol engines because that is enough what market knows can be done. Now those 1.0 liter engines dont last and for some reason most owners dont mind.
If they would put small diesel engine it would get them 1 liter less fuel consumption and still almost same performance. At the moment BMW is testing their 1.5 liter 3 cylinder diesel engine and rumours say it will produce up to 180 hp. Then imagine putting that engine to car thats cd is 0.20 and body that would weight 1100 kg (which is easy) and you have a car that is as good as my lupo both performance and fuel consumption wise.
OEMs have their reasons not to build cars like that and its mainly related to reason people dont know they could build similar monster car like my lupo with same effort as they put to any of their cars design process. Other reason is BIG OIL manufacturers effect to oems...
Also some people still think its cool to own big V8 (and they seriously think they need it), I think its much cooler to kick V8 ass on the road with 3-cylinder 1.2 TDI performance and fuel consumption wise.
What comes to tunecovers price will drop when I got the ziptie plug ready for market.
What comes to legal issues I could build Lupo or similar but more efficient car to meet all regulations.