[93fim5]

Tulok, noticed your thread here and a couple on bimmerforums and I think its cool to see someone trying to improve fuel efficiency on the 540i, Im working toward the same goal but on my daily E36 325i auto. Personally Im trying to pick the low hanging fuel efficiency fruit, mainly on parts of the car that need maintenance first and that have big payoffs with low cost. First on my list are some low rolling resistance tires in a 1.2" narrower tread width, and less weight than whats currently on mainly because I need new tires lol. Next for me is fixing up the OEM underbody paneling and working on streamlining the underbody further especially in the rear. After that Im working on a M52 intake manifold to try and move the power band a little lower in the rpm range (longer narrower runners to promote cylinder filling at lower rpm), may work may not but its a cheap mod to try. Id suggest you think about tires as an option if youre just using the E34 as a daily driver and arent worried about losing performance when the going gets twisty. Also underbody streamlining would definitely be a good idea as the E34 tends to be a little dirty aero wise (planning on some panels on my M). As far as a grille block on the E34 since its a fairly blunt nosed vehicle Id think more about controlling the airs exit from the radiator/trapped hood area vs blocking it, you'll need to find a low pressure area for the exit. The vortex generators are a neat idea but they are more than likely going to be a negligible gain and quite tricky to get right and may even increase drag. Wheel covers are another idea and Id be willing to work with you on that a little since we could use the M-System as a basis as it has mounting provisions for all sorts of covers. Is your car a manual or automatic as a gearing change might be a pretty easy option for you. Luckily the E34 has the econometer (lack of a better term) which really helps when you are trying to watch your right foot. Anyways good luck and I'll be posting my work soon as well!

BTW most importantly is make sure you don't have any vacuum leaks or any other maintenance issues, you really need a solid car to start with.