E39 General Performance
Performance Stages
Street
Stage (SS): increased responsiveness from engine and suspension without major
expense or compromise to ride quality
Street
& Track Stage (STS): further increases in all aspects of performance,
compromises in ride quality and comfort are acceptable at this stage. Still
streetable---good driver school cars are at this stage.
Track
and Race Stage (RS): all possible modifications are acceptable and desirable at
this stage; still possibly streetable, but only by fanatics
Engine
Power:
BMW engines are highly evolved and efficient as they
come to us from the factory. It is virtually impossible to find substantial
horsepower or torque improvements through minor manipulations of a healthy,
well tuned BMW engine. Big changes can only come through big effort, big money,
or both.
Minor improvements can be achieved through changes
to the engine management software---by reprogramming the “chip”.
Some engines benefit from installation of low restriction air filter housings, especially in combination with some device which assures that only cold air and not engine-heated air enters the engine.
See your specific car page for more specific recommendations.
NOTE: the simplest way to get a major increase in PERCEIVED torque is through a change in the differential ratio---again see the specific car pages for specifics.
Exhaust Systems
Stock exhaust: not bad, probably perfectly fine for most performance applications.
Mufflers: performance exhaust systems are free flowing and not restrictive. Factory exhaust parts fit very well and last a pretty long time. They are hard to beat. Less restrictive systems are available, but are usually louder than stock.
Street
Stage:
E39s
respond very well to minor and relatively inexpensive changes to the
suspension.
Sway bars—changing the stock sway bars
to larger diameter bars with urethane bushings produces a car that corners
flatter and feels more stable; you’ll wonder why they didn’t come that way from
the factory. No loss of ride quality; fits with AC.
Shocks---installation of Bilstein
shocks makes a world of difference in
the way the car handles. Keeping the tires in firm contact with the pavement is
the way to make the car handle well; Bilstein shocks do this best.
Tires and wheels---modern premium
tires on alloy instead of steel wheels will improve the appearance of the car,
but, more importantly, will also make the car stick to the road like it never
could years ago when it was new. This is both a matter of performance and
safety, wet and dry.
Brakes
Stainless
Steel Braided Aircraft Brake Lines
Replace rubber flexible brake hoses
with Teflon lined aircraft hoses to get the firm pedal needed for performance
driving.
Brake
Fluid
Flush brake fluid COMPLETELY at least
annually, but better yet, before each track event. For ordinary use we
recommend Castrol LMA DOT 4 fluid. For even more severe use, we recommend ATE
Blue Racing Fluid. We keep pressure bleeders charged with both types.
Brake
pads
Currently,
the best pads available are the factory original pads. At some time more
options will become available. Stay tuned for updates.