Apr 2

Apr 2 Guide: the M3 goes Club Sport - a Historical & Technical Appraisal of the BMW E92 M3 GTS

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BACKGROUND

For the 2009 season, BMW embarked on a GT racing programme with the critically acclaimed E92 M3 Coupe. Initial outings focused on the American Le Mans Series where GT2 spec. machines were campaigned by the factory-supported Rahal Letterman Racing squad. That year, the quasi-works outfit finished third in the GT2 standings behind the Porsche 911 GT3 RSR of Flying Lizard Motorsports and the Ferrari F430 GT of Risi Competizione.

Despite posting just another solitary class win the following year (once again at Road America), consistent podium finishes throughout the season saw Rahal Letterman claim the re-classified 2010 ALMS GT title for Teams. Meanwhile, over in Europe, BMW Motorsport made a triumphant return to the Nurburgring 24 Hours when Augusto Farfus, Uwe Alzen, Jorg Muller and Pedro Lamy claimed victory in the 2010 contest driving their Schnitzer-prepared machine (BMW’s 19th victory in the event).

Six months prior to that famous win at the Nurburgring (in November 2009), the company released details of a hardcore track-focused E92 M3 Coupe to be produced in a limited run of no more than 150 units. Conceived to celebrate BMW’s ongoing success in GT racing, the resultant M3 GTS most notably featured an enlarged 4.4-litre long-stroke high output V8, an adjustable aero kit, uprated suspension and brakes plus an array of weight-saving measures to include a racey stripped-out interior.

BMW publicly announced the green light had been given for GTS production the day before that successful outing at the Nurburgring in May 2010.

Priced at more than twice the cost of a standard E92 M3 Coupe, the GTS was a direct rival to the Porsche 911 GT3 and Ferrari F430 that it routinely went up against on track. Unfortunately though, the GTS was outlawed from sale in the USA on account of its extreme specification for which BMW did not bother to seek DOT type approval.

Whereas the regular M3 was manufactured at BMW’s Regensburg factory 125km north of Munich, GTS production saw partially assembled body-in-whites sent 120km south to the BMW Motorsport facility in Garching where assembly took place in batches over the course of an 18 month period.

CHASSIS

Each M3 GTS started life as a standard E92 M3 Coupe pressed steel monocoque.

The M3’s custom front subframe and thrust plate were also carried over along with the 63-litre fuel tank from the regular E92 which was mounted underneath the rear seat zone. Uniquely, a smaller battery was added to save a little weight.

Suspension-wise, the GTS retained the MacPherson strut / multi-link arrangement of the normal M3 plus most of the usual goodies like reinforced front struts, stiffer bushings, forged alloy control arms, camber struts and wishbones and re-rated anti-roll bars.

Significantly though, the GTS came with two-way adjustable KW coil-over shocks and there was also a now rigidly bolted height-adjustable rear subframe. This enabled ride height to be reduced by up to 16mm at the front and 12mm at the rear while camber settings could similarly be tailored to the driver’s requirements.

Whereas the regular M3 came with cross-drilled and vented brake discs of 360mm diameter up front and 350mm at the rear, for the GTS these were respectively switched to 378mm and 380mm items. Also, the original single-piston calipers were exchanged for beefier six-piston front calipers and four-piston items at the rear.

Stainless steel Stahlflex brake lines were another GTS-specific feature.

Standard issue wheels for the GTS were the normally optional 19-inch diameter Y-spoke Style 359M alloy wheels (9 and 10-inches wide front-to-rear). These were originally painted matt black and shod with Pirelli P Zero Corsa tyres (255/35 ZR19 and 285/30 ZR19 respectively).

Imported without further modification was the regular M3’s quicker-than-normal variable assistance Servotronic steering.

ENGINE / TRANSMISSION

In the GTS engine bay was an enlarged version of the S65 B40 engine found in the regular M3.

For this application, the size of the cylinder bores was kept at 92mm, but stroke was lengthened from 75.2mm to 82mm (a gain of 6.8mm). As a consequence, overall displacement went from 3999cc to 4361cc which represented an increase of 362cc.

In addition, the GTS motor was given a Fire Orange cam cover and a lightweight free-flow exhaust with titanium silencers and trick catalytic converters.

As a result, peak output went from 414bhp to 444bhp at an unchanged 8300rpm and from 295lb-ft at 3900rpm to 325lb-ft at 3750rpm.

Aside from these upgrades, the rest of the existing S65 B40’s characteristics were carried over; these were essentially eight cylinder versions of the F1-inspired normally aspirated V10 motors used by the contemporary M5 and M6.

They featured an all-alloy construction, 90° vee angle, dual overhead camshafts per bank and four valves per cylinder. A split two-piece crankcase was also used along with a forged five-bearing crankshaft, cast aluminium crankshaft and pistons, a semi-dry-sump lubrication system, high-pressure double VANOS variable valve timing plus lightweight valves and hollow camshafts.

To maximise the engine’s responsiveness, simultaneously actuated and electronically-controlled individual throttle assemblies were installed for each cylinder.

Compression was kept at 12.0:1 and engine management was via an MSS60 system powered by a trio of 32-bit microprocessors.

Whereas the regular M3 could be configured with a ZF six-speed manual gearbox, the GTS was offered exclusively with BMW’s M Double Clutch Transmission (M-DCT) produced in collaboration with Getrag. In manual mode, gear shifts were carried out via F1-style shift paddles located behind the steering wheel. Shift speed could be adjusted via a button on the transmission tunnel.

Uniquely, the M-DCT set-up for the GTS was modified with increased oil capacity and specific software calibration.

Also present was BMW’s Variable M Differential Lock - effectively a more advanced version of a traditional limited-slip differential. It activated when a difference in rotational speed between the rear wheels pressurised a viscous silicon fluid which in turn operated a multi-disc clutch that directed extra power to the wheel with the greatest traction.

For the GTS, the M3’s Dynamic Stability Control system (DSC) was specially adapted to make allowances for the extreme high performance nature of this latest variant.

DSC (which could be disabled if desired) was able to reduce engine power and in addition (or independently) apply brake force to any single wheel. DSC also incorporated a Brake Standby facility that anticipated hard braking by pressuring the brake pad up against the disc when the driver abruptly reduced throttle. Other features included Brake Drying (which pressured the pad up against the disc when the rain sensor detected moisture) and Start-Off Assistant (which kept the brakes applied for one second after the driver's foot was removed from the brake pedal in uphill conditions).

BODYWORK

Externally, the M3 GTS was immediately identifiable on account of its new front splitter and rear wing, both of which were adjustable and finished in matt black. The rear spoiler was itself imported from the 320 Si as raced in the World Touring Car Championship.

To reduce weight, the usually glass rear screen and rear side windows were switched to Polycarbonate.

Officially, BMW offered the M3 GTS in just one colour scheme: Fire Orange with the normally optional black chrome metal effect kidney grilles and side gills fitted as standard. However, two cars reputedly left Garching painted Alpine White.

Like the standard E92 M3 Coupe, the GTS was equipped with an exposed carbonfibre central roof panel. With the exception of the bumpers, sills and mirror casings (manufactured from Olefin Thermoplastic), the rest of the body panels were fashioned from steel as per the series production M3.

INTERIOR

Although the chassis, engine and body modifications were not insignificant, the most dramatic changes made to the GTS were found in the cockpit.

In the interest of weight reduction, sound insulation was much-reduced and the rear seats were junked along with the audio system and air-conditioning. To further this agenda, the door panels and centre console were simplified and now partially trimmed in alcantara. More alcantara was used to upholster the steering wheel rim and much of the rear quarters.

Instead of the regular electrically-operated and leather-trimmed M sport seats fitted to the regular M3 Coupe, the GTS came with manually-adustable Recaro Profi SPG buckets covered in fireproof black fabric. Standard inertia-reel seatbelts were retained, but each car was also supplied with pair of six-point Schroth harnesses. Like the fire extinguishing system, the harnesses were included with every car but not automatically installed.

Bolted in place behind the seats was a lightweight half roll cage painted Fire Orange.

Located on the passenger-side of the exposed carbonfibre dash insert was a GTS insignia with chequered flag motif and each car’s individual serial number.

Door sill plates with an M3 logo and chequered flag motif were also fitted.

In the trunk was a tool kit with everything necessary to adjust the cars suspension and aero.

As usual, instrumentation comprised a 330kph / 200mph speedometer and a 9000rpm rev counter inset with fuel and oil temperature read outs respectively.

Electric windows, electric mirrors, Anthracite headliner and exposed carbonfibre cockpit inserts were fitted as standard.

OPTIONS

The only optional extras available for the M3 GTS were air-conditioning, a full roll cage and an audio system. If an audio system was specified, the normally Polycarbonate rear screen and rear side windows were switched to glass.

WEIGHT / PERFORMANCE

Despite the addition of its half cage and fire system, BMW quoted the GTS at 70kg less than an M-DCT-equipped 2010 model year M3 Coupe: 1530kg as opposed to 1600kg.

As a consequence of its additional engine output, reduced weight and re-calibrated gearbox software, the 0-62mph time dropped from 4.9 to 4.4 seconds.

Top speed went from an electronically limited 155mph to 189mph.