Had you bought a 1993 BMW 850Ci - thinking of it as the best Autobahnstorming luxury coupe available in the U.S. - you have reason to be peeved: BMW now builds an even better Bahnstormer, the potent 850CSi.
What to do?
Before trading in your car on a new 850Csi, the folks at Autothority Performance Engineering [(703) 323-0919] in Fairfax, Virginia, would like to offer you a couple of performance-enhancing alternatives.
The first is the installation of Autothority's E-PROM chip, an engine-management bit that reshapes the horsepower and torque curves of your 850's sohc 5.0-liter v-12 by remapping the fuel-injection and ignition timing at various rpm. While other firms program (or "burn") their own chips APE says its chips are superior because much development work is done on the road, where the engine experiences real-world loads and throttle openings.
The chip by itself, says Autothority, bumps the 850's power output by some 60bhp, and torque increases by about 13 percent below 2500 rpm. More noteworthy, though, is that this $495 chip, a 15-minute installation, passes emissions tests in all 50 states.
However, if the chip isn't enough and you crave an 850 that'll devour a new CSi (and perhaps even the Euro-market Alpina B12 5.7), Autothority builds such a car. And it's also 50-state legal. I had the thrill of driving the car, and while my roads weren't Autobahnen, the two lanes of Virginia horse country proved to be a great playground.
With 475 naturally aspirated horsepower beneath its hood, you'd think the Autothority 850 would be a high-strung steed with a temper. Not so. It's more of a dignified race horse, the one that casually walks up to the start without giving his jockey a bit of trouble, then bolts out of the gate with reckless adandon.
The engine's smooth idle, the faultless clutch-work and overall ease of driving speak volumes about the refinement of Autothority's work. You really don't sense that this 850 has been tweaked until you dip your foot into the throttle and feel the healthy thrust.
Engine modifications begin with a billet crankshaft that increases displacement to 5.5 liters, specially coated 10.0:1 pistons, larger valves, ported intake manifolds and a better-breathing header system. Of note, the valves, piston crowns and the combustion chambers are all ceramic-coated for better heat resistance. And because the Autothority 850 is a 50-state car, the stock catalytic converters are used, feeding a high-flow exhaust.
Power reaches the massive rear wheels via the 850's stock 6-speed manual transmission and the lower 2.93:1 rear end of a European-market 850. As a result, off-the-line performance has been greatly enhanced, but most of the pleasure comes from a particularly stout midrange that doesn't seem to fall flat, even at redline.
Eidbach springs at each corner lower the Autothority 850 by ¾ in., and the 18-in. 5-spoke allow wheels shod with 245/40ZRs in front and 295/35ZRs out back give the car an especially menacing stance. The rest of the look comes courtesy of Racing Dynamics, an Italian company that has shown tasteful restraint in its nose, tail, wing, wheels and rocker-panel treatment.
Overall, the Autothority 850 is an impressive package, sort of an Alpina B12 5.7 that's available to Americans. The price of admission is not cheap: $31,000 for the engine modifications alone, or $46,500 for the entire treatment.
