Digi-Tec M Coupe
Ariel Atom
This car is based on a 1999 M Coupe, which normally has 321 bhp. In its modified state, the motor produces a healthy 385 bhp at 8000 rpm with 295 lb-ft (400Nm) of torque between 3900 and 7200 rpm. Digi-Tec founder, Michael Pollmuller, explained how his engineers had achieved these numbers.
"We start with a special airbox system and free-flow air-cleaner. Then we remove the restriction of the factory airflow meter, substituting our Alpha N system, which uses the parameters of throttle position, Lambda, ignition and engine revs. It took us a whole year to develop the Alpha N system, but the result is a lot more power and torque and added smoothness."
This engine also benefits from a pair of high-lift cams, stronger valve springs, free-flow exhaust manifold, stainless-steel sports exhaust, 100-cell free-flow catalytic converter and finally, the reprogrammed ECU.
"The Siemens-made ECU also controls the VANOS system, and you can alter all the other parameters and delete the top-speed limiter, just as our competitors did. We realized they didn't change the information for the VANOS, so when the engine reaches 7400 rpm at 168 mph, the VANOS closes down and the car cannot go any faster, even downhill. Because we modify the VANOS controls as well, the system continues working up to the 8000-rpm limit, allowing our car to reach 179 mph."
Helping the motor to spin more freely is a Group A flywheel, which tips the scales a whopping 30-percent lighter than stock. The total weight of the beefed-up twin-plate clutch and flywheel is now just 8.5kg (18.7 lb), so the motor revs like a motorbike!
The suspension is a combination of H&R springs and Bilstein dampers. The system is height adjustable with a maximum drop of 50mm from standard, although you could not sensibly run on the street with such a low ride height. "We also offer a Nuerburgring suspension kit." The suspension top mounts are solid, with a suspension tower brace in front.
Brembo makes the uprated brakes, which use 325- and 304mm vented discs, front and rear, clamped by big four-pot calipers. Pad material is Pagid RS14 ceramic alloy in front and Pagid Blue at the rear. There is also an on/off switch for the ABS system. BBS alloy wheels, 8.5J and 10.5Jx18-in. are shod with 225/40ZR18 and 265/35ZR18 tires for street use and 255/35ZR18 and 285/30ZR18 in serious track trim.
The lowered ride height and big wheels and spoilers served to emphasize the brutal appearance of the standard car. The M Coupe has a pretty substantial front air dam and spoilers out of the box, and Digi-Tec augments the downforce with a pair of spoiler lips made from either carbon or GRP. Alternatively, you can buy a complete, new lightweight bumper/spoiler section with the same look, but molded in one piece from either carbon or GRP. The front wings and doors are also made from carbon and the car weighs 1,220kg (2,689 lb), 160kg (352 lb) less than Euro stock.
The aerodynamics of the car are drastically altered by the new spoilers. "The diffuser between the exhausts works really well," Michael said. "Apart from creating downforce at speed, the rear window now stays clear in the rain on the move."
The spectacular looking rear wing on the roof is three-position adjustable and creates further downforce. "You really need it at the Nuerburgring," said Michael. "There is one fast sweeper which you can take flat in fourth at over 140 mph with the wing in the high position. Without it, you will be sideways at 120 mph. Of course, the wing creates drag, slicing 19 mph off the top speed.
Digi-Tec offers three rear differentials for the M Coupe, short, medium and long, with an oil cooler in the rear diffuser for track work. With the tallest differential, 0 to 60 mph takes 4.4 sec., and top speed is 181 mph. On slicks with the shortest differential, it will get to 60 mph in 3.9 sec. with top speed an adequate 146 mph.
Digi-Tec has shown just how much potential there is in the M Coupe with a devastatingly fast road car that can produce near racecar lap times on the track.
Hamann Motorsport M Coupe
A great driver's car is made even faster
The car which gave Hamann the inspiration to so radically change the detailing on the M Roadster and M Coupe was Porsche's 356. Its smooth, rounded look appealed to Richard Hamann, so he set to work cleaning up the flanks of the BMW to give it a similar dolphin-smooth look. Stability in high-speed autobahn testing proved to be an issue, and Hamann's racing heritage inspired the DTM-style aerodynamic addenda.
The changes start right at the nose, where the chromed BMW "cornbeef tin" grille is given the Hamann Shadowline treatment. The already deep front half spoilers receive a full-width extension that takes the bodywork even closer to terra firma. Below the front bumper, new bigger air intakes house Hella DE foglights.
In fact, with a height-adjustable sports suspension kit that starts off 20mm lower than stock front and rear, and can drop a further 40mm at the front, you really have to be careful of large bumps in the road. Because of this, Hamann modifies the engine oil sump for more ground clearance.
Small DTM-style fillets were added to the front and rear ends of the sills. Come to think of it, they are reminiscent of the wings on the feet of some mythical Greek god, but thankfully they have the opposite effect and instead help to keep the car on the ground! High up along the flanks, the more obvious tweaks are the new, rounded door mirrors, the cleaner bonnet side scoops and that rather sexy race-style aluminum fuel filler cap.
Under the tail, a three-piece wing channels air between itself and the bodywork to clean up the airflow as it leaves the car. In the near future, a rooftop spoiler will be added for more downforce. On the M Roadster, and indeed any Z3, Hamann can replace the taillights with its unique four-round light units. This does not apply to the Z3 Coupe, which has a completely different taillight assembly, but Hamann is working on something special for this car.
The wheels and tires on this car are simply enormous. Modular three-piece Hamann PG1 wheels made for Hamann by OZ Racing, they are 8.5Jx18 with 235/40ZR18 tires in front and 11Jx18 with 285/30ZR18s at the rear! A more modest alternative for the back axle is to use just 10Jx18s with 265/35ZR18 rubber.
For those who prefer a smaller contact patch, the one-piece five-spoke Hamann HM2 wheel of 8.5Jx18-in. size in front and at the rear will be just fine. These can be used with 5mm spacers as an option for that macho arch filling look. The other extreme is 8.5Jx19 and 10Jx19 with 235/35ZR19 and 265/30ZR19 rubber. An alloy strut brace between the front shock towers to keep body movement in check when exploiting the grip of these gumball tires is an option for the serious driver.
Through the spokes of these big wheels, you can make out the uprated brake kit in front. This uses massive 330mm cross-drilled discs and Hamann's four-pot calipers stuffed full of fast road pads. As most of the braking effort is done on the front, the rear brakes are left alone.
We've saved the best bit for last. As if the 321-hp DOHC, double VANOS motor was not powerful enough, Hamann have given it its standard M3 Evo upgrade. This consists of a huge carbon-fiber airbox, which works in conjunction with the removal of the stock airflow meter and the substitution of a throttle position device that feeds its angle directly to the modified ECU. With a freer flowing exhaust manifold and Hamann's sports rear silencers with their four huge 76mm DTM-style outlets, this results in a 29-hp gain, better throttle response and an even healthier induction and exhaust symphony.
Hamann's program has adopted the British-made Race Logic traction control and Launch Control. With the system, the already good handling of the M Coupe can now be exploited in the wet within sensible limits without fear of the car disappearing into the undergrowth. At the same time, the multi-position selector of the traction control system means that you can dial in varying degrees of oversteer when you do want to play. More importantly, for those who simply use the cars as transport, simple tasks like getting away from the lights or T-junctions is not accompanied by lots of unwanted drama.
There are small but significant changes to the cozy cabin. The leather-bound sports steering wheel helps you keep a firm grip on the proceedings, although it has to be said that the factory one is excellent anyway. But the stubby short-shift alloy gearlever takes shift precision to another plane. The aluminum pedals and footrest are matching touches as are the Hamann floormats. Instrument faces in carbon-look or color-coded to match the body (as with this car) are a Hamann speciality.
Buying an M Coupe already marks you out as an enthusiast and someone who appreciates the cutting edge of BMW's car-making abilities. The Hamann Motorsport interpretation of BMW's best two-seater takes this whole argument of excellence and individuality one step beyond.
Intrax BMW M Coupe
An even better driving machine
With one throttle per cylinder in race style, the M Coupe Euro engine delivers a crisper, more immediate answer to every question asked at the right pedal. The U.S. version is more muted in that respect as you would expect of an engine with a single throttle bolted to a plenum. In essence, it is a more muscular version of the normal BMW six with a sportier exhaust note.
With these power delivery characteristics in mind, the U.S. version is a good base for a supercharger conversion which adds significant power and torque without spoiling refinement. That is what Intrax, a Los Angeles-based tuner, wanted to achieve in the first instance, and it ended up with a car that is not only devastatingly fast on the road but also quick enough to be effective in street-legal production sports car racing.
"The supercharger components come from Bullet Performance Engineering in Costa Mesa," explained Fabryce Kutyba of Motorsports West (www.motorsportswest.com), which did the engine conversion work. "The first time you attempt the installation it will take around 15 hours, but once you get the hang of it, 8 hours is a realistic time frame. One advantage of this Vortech supercharger conversion is that it is bolt-on. You don't need to open the engine and lower the compression ratio, so you can easily return the car to stock when it coms time to sell it."
The kit itself uses Dinan components and is the latest version for cars with the U.S.-mandatory OBD-II system. "We did a car with the older OBD-I system and got 380 bhp on 10 lb of boost," Fabryce explained. "The problem on later cars is while we fit larger fuel injectors, the fuel pumps are controlled by the OBD-II system, which has more restrictive parameters. Even so, with 6 lb of boost for road use, we are getting 354 bhp at the flywheel or 298 bhp at the wheels at 7200 rpm."
One of the advantages of forced aspiration is the enhanced torque: The engine now makes 360 lb-ft at 4500 rpm. This is over 100 lb-ft more than even the Euro-spec M3 motor, and makes it near the torque of an AMG E55 5.5-liter V8! With a perfect launch, 0 to 60 mph is a tad under 5.0 sec. bracket; top speed is close to 170 mph once the limiter is disabled.
The quality and fit of the parts is spectacularly good. All the mounting brackets and ancillary hardware are either die-cast or machined from solid billet to race-car quality, and the finished product looks like it left the factory this way. The Remus exhaust silencers look and sound good with a deep note under acceleration. They also release a few more horses thanks to reduced backpressure, but it's as quiet as the standard exhaust when cruising.
Apart from the lower ride height and subtle rooftop spoiler with high-level brake-light, the most obvious visual change is the huge 19-in. wheels. These are the C5 style from a Japanese company called Racing Hart, and are 8.5J and 10Jx19-in. with 245/35ZR19 and 275/30ZR19 Pirelli P-Zero Asimmetrico rubber. They look great, filling out the big wheel arches very effectively. They are right on the edge of ride/handling acceptability on California's rapidly deteriorating road surfaces, so a switch to 18-in. wheels as a better compromise for daily use seems to be in the cards.
Intrax makes the shorter uprated springs, which can also be used with the standard dampers. On this car, they are matched to Koni adjustable dampers. Intrax also makes the anti-roll bars, which are 28mm front and 21mm rear. These raise roll stiffness by 40 percent over the stock bars, giving the M Coupe equal roll stiffness at both axles for progressive and balanced handling.
With good low-speed torque in standard form, the supercharged M3 motor becomes a real powerhouse. The numbers are impressive, but the real test is how the car feels on the road. Power delivery is smooth and consistent, but there is just so much of it, accompanied by a huge wave of torque, that all thoughts of a 3.2-liter six go out the window. The engine now pulls like a small-block V8 through the rev range, and you don't need to drop a gear to go. There is so much low-down grunt that so long as you have 1500 rpm on the clock, you can get meaningful acceleration in any gear. From 2500 rpm, the motor is pulling hard, and by the time the rev counter is reading 4000 rpm, you are really flying.
Because of this, the modified M Coupe is even easier to drive around town than the stock version. And where the power of the U.S.-spec 3.2 begins to tail off at 6500 rpm, the supercharged engine keeps pulling hard to just over 7000 rpm. The engine is responsive and lag-free, but, of course, it is never going to match the single-throttle-per-cylinder Euro M3 motor for sharp throttle response. When you consider the superior numbers against the stopwatch, however, that becomes a secondary consideration.
Another mechanical difference between the European and U.S. M Coupes is the latter has conventional 315mm and 312mm vented discs in place of the M3-style compound brakes. These are fine for the 240-bhp motor and less demanding American driving conditions, but they are nowhere near able to handle the velocities achievable by the Intrax car, especially on the track.
The cure is a set of 14-in.-diameter Brembo vented discs in front with four-pot calipers. With comparatively less weight on the back, the stock rear brakes with slightly harder pads are fine. The combination gives good pedal feel and strong retardation from three-figure speeds.
If the driving experience comes first on your list, then the fact this car goes like the clappers and handles like a dream is a very persuasive argument.