The 1990 BMW 850i automatic, as it I purchased it, had damages in the engine and gearbox, traces of numerous amateur repairs and many parts were missing. In addition to the constant parking in the open air, it was not used two years or more. The overall condition of the car was disastrous!
To make sure, that the car will look exactly like I want it, instead of buying some much better unit, I decided to do the complete restoration. I replaced all the damaged parts, repaired the automatic transmission, filled in most of the missing items. I did some external paint repairs as well, and restored the interior of the car.
On the occasion of the repairs I introduced some improvements:
instead of the standard M70B50 engine, I combined the block of 5.4-Litre M73B54 with equipment of the M70, before the final assembly, engine M73 was disassembled and cleaned, intake collectors were polished inside,
standard injectors were replaced with newer from M50B25 engine,
new sports engine software,
K&N air filter cartridges,
custom exhaust diameter 65mm,
rear differential replaced with shorter 3.91 LSD from BMW E34 M5 (standard was 3.15),
front calipers were replaced with two-piston floating calipers from BMW E32 750iL,
suspension height lowered in about 40mm,
new rims 17x8.5 (tires 234/45) in front, 17x10 (tires 255/40) rear.
Since I'm the owner, no other mechanic touched this car! I do all work myself.
The job is not yet finished. Anyway the car already has much better performance, than the standard one. Just have a look at the video clip, showing the quarter mile run side by side with stock 1991 BMW 850i automatic. The ET difference was around 0.7 sec.
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P. Zal, editor-in-chief
