E38 Performance General
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.
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.
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:
E38s 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.
Springs---the stock springs do a fine job of keeping the body of the car off the pavement but for higher performance we want the car lower and stiffer so that the driver’s input is translated to vehicle response as rapidly as possible. Shorter and stiffer springs are available from a number of manufacturers---we commonly use Ireland Engineering, Dinan, Suspension Techniques, H&R, and others (wherever best pricing can be found). Note: try to choose springs and shocks together since installation labor overlaps and sometimes shorter springs require shorter shocks.
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.
Street
and Track Stage:
Sway bars---Bigger sway bars are the
mandatory on serious performance cars.
Modern adjustable bars are
sometimes also available, either conventional bars that mount in the usual
location, or special hollow tubular bars with custom aluminum mounting brackets.
Shocks---Bilstein Sport shocks are the
answer here. Very firm control, great when driven hard. Often used in conjunction
with fixed negative camber plates at top.
Suspension bushings---should be replaced
with polyurethane bushings at all suspension pivot points, both front and
rear.
Tires and wheels---V- or Z-rated tires
on larger diameter wheels
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.
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
Stock brake pads are the only pads available at this time.