Porsche Boxster (986)

The Engine

The Boxster's 2.5-liter M96 f1lat-six ushered in a new series of volume production Porsche powerplants and shared many components with the larger 3.4-liter version that powered the 996-gen 911 of 1999. It must be stated that the initial M96 engines were never intended by Porsche to be turbocharged or used for racing purposes, so some compromises were made in terms of cost savings and improved packaging.

The M96 engine used a pair of cylinder block castings (each with three cylinders) that resembled the design of the 944 block in that the free-standing cylinders were integral to the castings, with "open deck" water jackets around the tops of the cylinders. This reduced the casting costs compared to a more complex "closed deck" design while allowing better cylinder cooling. Porsche's supplier had some well-documented casting issues with early M96 engines, including porosity and cracked cylinders, but the vast majority of these failures occurred during the warranty period.

The M96 used a thoroughly modern cylinder head design with pent-roof combustion chambers and four valves per cylinder, driven by dual overhead camshafts. The M96 engine adapted the 968's VarioCam system to broaden the torque curve by varying the intake cam timing by up to 15 degrees relative to the crankshaft. Unlike the air-cooled 911 and like the 944 and 928, the M96 used a less complex and less expensive "wet sump" oiling system. However, Porsche referred to the lubrication system as an integrated dry sump": while the M96 had a traditional oil pan/sump at the bottom of the engine instead of a separate reservoir, a scavenge pump at the non-drive end of each cylinder head served to evacuate oil from the heads and return it to the sump.

The 2000 model year saw the 986 Boxster's engine displacement increase to 2.7 liters (via the 996 crankshaft with a 78 mm stroke), and the previous cable-operated throttle body was updated to an electronically-controlled enabled operation of the optional Porsche Stability Management system. The bigger change for the 2000 model year was the introduction of the more powerful Boxster S model with 252 hp, which was achieved by using the 996 crankshaft with a 93 mm bore to displace 3.2 liters.

The Transmission

For manually-shifted versions, the Boxster's engine transmitted torque via a dual-mass flywheel to an Audi-based five-speed transaxle, which saw Porsche's first use of cable-operated shifting instead of a rod linkage. The pair of shift cables provided not only better packaging but arguably better shifter feel and action than any of Porsche's previous designs.

A ZF-based five-speed Tiptronic automatic transaxle was an option from the beginning of 986 production. This was a similar concept to the previous 993 version with shifter buttons on the steering wheel. Still, the shifts were firmer and quicker, and the driver could tenmporarily over-ride the shift program in automatic mode by activating the upshift or downshift buttons.

The Boxster S featured an upgraded six-speed manual transaxle supplied by Getrag, similar to the one in the 996. This was a much beefier unit than the base five-speed, with larger gears and larger bearings for the shafts. The axle shafts and CV joints of the 986 S were also similarly up-sized to 996 specifications.

The Body

The Boxster debuted in 1996 as a 1997 model year car and, at the time, it was Porsche's first clean-sheet design in over two decades. To make the project viable to the cash-strapped Porsche of the early 1990s, the 986 Boxster and upcoming 996-gen 911 replacement had to share : many components as possible. Therefore much of the front end structure was shared between the 986 and 996, along with the doors, front trunk lid, headlights, and most of the front chassis and suspension components. The 986 featured unibody construction composed of various grades of steel. High-strength steel was used in key sections of the floor, rocker/sill areas, and frame horns, while ultra-high-strength, boron-enriched steel tubing was used in the windshield frame and rollover hoops. The result was remarkable rigidity in torsion and bending for an open-topped roadster, which was key to the 986 Boxster's refinement and handling prowess. The Boxster featured a slick, lightweight power convertible top mechanism that folded under a steel tonneau cover. A removable hardtop with a heated rear window was an option. Early 986 Boxsters had a plastic rear window, with the face-lifted 2003 models receiving a heated glass rear window. The tight packaging of the 986 left no space for a conventional engine lid or hatch--the top had to be opened into a "service position" and some insulation and a cover had to be removed to access the top of the engine.

Suspension & Brakes

The 986 used the tried-and-true MacPherson strut front suspension to maximize packaging efficiency, with each strut located by a pair of interlinked lower control arms. The mid-engine layout made it difficult to fit a multi-link suspension as used in the 993 and subsequent 996, so Porsche engineers devised a similar three-link design as used in the front of the 986. To save manufacturing costs, the same basic upright/hub carrier casting was used at all four corners, which enabled the use of the same lateral lower control arms for each corner.

The ideal weight balance and centralization of mass of the Boxster's mid-engine platform (47 percent front/53 percent rear for manual transmission models, 45/55 with Tiptronic) enhanced traction and enabled a low polar movement of inertia for quick turn-in and agile handling.

However, this increased rate of rotation could be dangerous for an unskilled driver, so Porsche designed the suspension geometry and calibrated bushing compliance to induce gentle understeer in most situations, which enabled the confidence-inspiring handling that the Boxster platform is known for today.

The 986 Boxster was the first Porsche to use monoblock brake calipers, a joint development with Italian supplier Brembo. The single casting for the brake caliper reduces weight by about six percent while providing increased caliper rigidity and better brake pedal feel. All subsequent Porsche sports car brake calipers have used this monoblock design, including the 986 S, which featured larger four-piston front and rear calipers clamping larger cross-drilled and ventilated rotors.