25 Years of Boxster Evolution

We look at how Porsche’s popular roadster has advanced over the last two-and-a-half decades.

Photo: 25 Years of Boxster Evolution 1
July 1, 2021

It has been a quarter of a century since the introduction of Porsche’s entry-level mid-engined roadster. Thanks to strong initial sales of its Boxster, Porsche was able to survive its 1990s financial crisis, and the company has flourished ever since. Perhaps more significant than the car itself was the sea change within Porsche in terms of manufacturing and supply chains. The concept of sharing parts amongst different Porsche model lines remains to this day.

1997-2004 986

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 as 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.

As discussed in the #255/June 2018 tech feature about body construction, 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 (#261/February 2019) 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.

Engine

The Boxster’s 2.5-liter M96 flat-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.

Photo: 25 Years of Boxster Evolution 2

M96 engine

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 (#260/December 2018).

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 version—this enabled operation of the optional Porsche Stability Management system (PSM; #233/December 2015). 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.

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.

Photo: 25 Years of Boxster Evolution 3

Many of the 987’s underpinnings were based on the 986-gen cars.

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 temporarily 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.

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 (#238/August 2016). 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.

Photo: 25 Years of Boxster Evolution 4

The 987s got large aerodynamic undertrays.

2005-2008 987.1

The second-generation 987-gen Boxster shared many components with its 997-gen 911 sibling, but it had distinctive front styling with different triangular headlights and a unique front fascia. Higher-strength steel in the cowl area and improved spot-welding and adhesive bonding techniques resulted in a body shell that was four percent more torsionally rigid than the 986 and 14 percent stiffer in bending. Aluminum front and rear trunk lids saved weight. The 987 underbody received a much more comprehensive package of plastic undertrays that reduced the aerodynamic drag coefficient (Cd) from 0.31 to 0.29 (#256/August 2018).

The 987 base 2.7-liter engine and 3.2 Boxster S were largely carried over from the late 986, but a 12 lb weight savings was realized by eliminating the cast-iron bearing girdle inserts. During the 2006 model year, Porsche incorporated a larger ball bearing for the support of the intermediate shaft at the flywheel end, which mostly mitigated the infamous intermediate shaft (IMS) bearing issues that plagued the M96 series.

The 2007 Boxster received engine updates to match those of its hardtop Cayman stablemate. This consisted of the VarioCam Plus two-stage intake valve lift to both the base and S versions. The latter received a 3.0 mm increase in bore to achieve 3.4 liters, plus revised cylinder heads from the base 997 Carrera to achieve 295 hp.

The 987 manual transaxles featured closer ratios for both the five- and six-speed versions, with carbon-faced synchronizers and a revised shift mechanism with a gearbox-mounted flywheel mechanism improving the shift feel. The base five-speed manual was no longer Audi-based but made by Japanese supplier Aisin; the Boxster S six-speed retained the Getrag unit. Both the manual transaxles and the five-speed Tiptronic S featured shorter final drive ratios to compensate for the larger-diameter wheels featured across the 987 range (17-inch wheels were standard on the base Boxster, 18-inch rollers were standard on the S, and 19-inch alloys were optional).

Photo: 25 Years of Boxster Evolution 5

Monoblock calipers were first seen on the 986.

The 987’s suspension was mostly unchanged from the 986. However, many detail improvements were made, such as stiffer and lighter castings for the aluminum uprights/wheel carriers and larger wheel bearings with embedded magnets, which replaced the separate tone rings for the ABS wheel speed sensors.

The 987 also featured variable-ratio steering for its hydraulically-assisted rack and pinion gear; the steering ratio was 17.1:1 turns on center but increased to 13.8:1 once turned past 30 degrees, which reduced the lock-to-lock turns of the steering wheel from 3.0 to 2.6. Porsche’s Porsche Stability Management (PSM) system was now standard across the 987 range and offered more precise controls, which allowed the driver greater freedom before PSM intervention.

2009-2012 987.2

Porsche introduced the face-lifted 987 for the 2009 model year, in parallel with a 997.2-gen 911. The updated Boxster featured a family of all-new engines with an MA1 designation (the part numbers of components for these engines began with 9A1). The MA1 had a much more rigid two-piece crankcase/block assembly made entirely of silicon-impregnated aluminum alloy (Alusil), which was much more rigid than the previous M96 and M97 engines and dispensed with the separate crankshaft main bearing girdle. The cylinders were reinforced and were a closed-deck design to minimize cylinder distortion; this was important as the MA1 crankcase/block configuration was to form the basis of all future turbocharged engines, as well as the street and racing versions of the high-revving GT3.

Porsche engineers had gained enough confidence in contemporary timing chain technology to eliminate the separate intermediate shaft of previous flat-six engines and drive the camshafts directly via a pair of long chains and generous supporting ramps. The oil pump was driven via a separate chain. The pump itself was demand-controlled by the DME control unit to supply only the necessary amount of oil for the engine running conditions, which saved energy.

Photo: 25 Years of Boxster Evolution 6

The 981’s body shell was lighter and stiffer than the 987’s.

The revised cylinder heads had separate bearing caps for the camshafts instead of the M96/97 design with integral bearing caps in the camshaft covers. Otherwise, VarioCam and VarioCam plus systems remained in a similar configuration as the preceding engines. The other big news for the MA1 engine series was direct fuel injection (DFI) for the 3.4-liter S versions of the 987.2 and for all 997.2s (#223/November 2014); the base model 2.9-liter 987.2 had port fuel injection.

The other major change for the 987.2 was the replacement of the optional torque converter-equipped Tiptronic automatic transaxle with a dual-clutch automated transaxle that Porsche dubbed PDK. You can find a brief history of the PDK and a detailed description of its operation in the #225/April 2015 PDK tech article. Still, in short, the quick-shifting PDK quickly became the transmission of choice for most buyers, eventually achieving a nearly 90 percent take rate among buyers of Porsche sports cars.

2013-2016 981

The next generation of Boxster was the 2013 981 generation. The body shell of the 981 was 17 percent lighter than that of the 987 thanks to an increased usage of aluminum construction, along with strategic use of high-strength steel in key areas. This kept the curb weight to around 3,000 lbs, despite being a larger car than its predecessor. Porsche aerodynamicists kept the 981’s Cd at 0.30, which is exceptional for a wide-tracked roadster.

The 981 Boxster had a fully automatic top; the driver no longer had to manually latch or unlatch the convertible top from the windshield header as in the 986 and 987. The lightweight top was composed of magnesium panels, aluminum and steel frame bows, and plastic covers. Its compact folding pattern no longer required a separate tonneau cover panel. Alas, the slick packaging of the 981 top made engine access more difficult than in the 986/987.

Engine

The 981 was powered by the MA1-series flat-six, which were quite similar to those used in the 987.2. The base engine’s displacement was actually reduced by 200cc to 2.7 liters, but this was more than made up for by replacing the base 987.2’s port fuel injection system with DFI, which allowed a higher compression ratio of 12.5:1, which was the same as the 3.4-liter engine of the Boxster S.

Photo: 25 Years of Boxster Evolution 7

Porsche’s PDK dual-clutch transmission debuted in the Boxster in 2009 and has been a strong seller since.

Otherwise, the 981 powerplants had the same features as the big brother 991.1-gen 911, with assembled camshafts, a thermal management system of vacuum-operated switches and valves to help optimize engine warmup and cooling system management. The engine management system was used in concert with the electrical gateway system control unit to orchestrate the operation of the oft-maligned auto stop/start system.

Transmission

A six-speed manual was standard on both the base car and the Boxster S, with slightly different gear ratios and an improved torque capacity for the latter. The optional “Sport Chrono” package added dynamic transmission mounts, which functioned similarly to the optional magnetorheological mounts used on the engine side of the rear-engined 991. The mounts automatically stiffened as necessary by varying electrical current through a fluid containing magnetic particles.

The optional PDK gearbox continued on similar internals as its predecessor, but some new features such as a fuel-saving “coasting” mode and the ability to select neutral by engaging both shift paddles.

Chassis

The 981’s chassis and suspension were similar to the 991, with a 60 mm longer wheelbase and increased front track by 36-48 mm depending on front wheel offset. The front suspension geometry was revised to increase its resistance to braking dive, and the rear suspension had much greater resistance to dynamic toe changes than did that of the 987.

Chassis control electronics also evolved, with the ninth generation of Porsche Stability Management offering enhanced functions such as holding the vehicle on a steep incline to aid hill starts, improved Porsche Active Suspension Management (PASM), and optional Porsche Torque Vectoring (PTV). PTV actively braked the inside rear wheel during cornering, which enhanced turn-in and agility. The steering itself was the same as the 991, with an electronically assisted power steering rack featuring revised steering geometry to allow a tighter turning radius of 10.36 meters.

2017-Present 982

Ever-stringent government fuel economy and CO2 emissions standards forced Porsche to downsize and turbocharge its entire range of engines. This meant that the marketing department leaned on the flat-four heritage of the 550 Spyder and 718 race cars, dubbing the internally-designated 982 Boxster and Cayman models as the 718.

The MA2-based (see the #244/April 2017 tech feature for more info) flat-fours of the base and S versions of the Boxster had more varied specifications than any of their predecessors. The 2.0-liter MA2/20 of the base model had a turbocharger with a conventional internal wastegate for boost control, while the 2.5-liter, 350-hp MA2/22 of the Boxster S had a variable turbine geometry (VTG; #273/June 2020) turbocharger in addition to a conventional internal wastegate to reduce exhaust backpressure.

Porsche fans who missed the howl of a flat-six in a new mid-engined roadster collectively rejoiced with the introduction of the 2019 Boxster Spyder, which featured an MA2-derived, naturally aspirated 4.0-liter flat-six, which generated 414 hp and revved to 8,000 rpm. This drivetrain reverted to the three-point mounting system of previous six-cylinder Boxsters.

Chassis

Porsche chassis engineers always find incremental improvements between generations of model lines, and the 982 was no exception. While the 982 was an evolution of the 981 design and shared most of its body and chassis construction and layout with its predecessor, there were optimizations in every area of the suspension system to improve response and feel.

The 982 retained the three-link strut rear suspension design, which has been cited by the erstwhile Porsche engineer and  718/982 project manager August Achleitner as one of the main engineering reasons that Porsche has never produced a true 911 rival based on the current mid-engine platform—there simply isn’t room for a proper multi-link rear suspension design.

The Future

It will be interesting to see what the future holds for Porsche’s mid-engine sports car; as of this writing, it may convert to an all-electric design, which, if anything else, would leave plenty of space for optimal suspension layout and geometry!

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