The JCW "Works" Cooper S has been a long time in the making. In fact, it is almost exactly one year to the day since I drove its mildly tuned normally aspirated Cooper.
Because of its "officially approved" connection, the John Cooper Garages "Works" had its Cooper S already running in prototype form back then. But, as the months slipped by and the standard S was launched to the dealer network, John Cooper Garages, in conjunction with BMW, was developing and subjecting prototypes to the same thorough test regime every standard BMW model has to endure.

Hot- and cold-weather testing means being driven flat out in the most extreme weather conditions on the good and bad quality of fuel available in the markets where the car is sold. That complete test program is the difference between a factory-approved car and an aftermarket tuner product. It means that BMW will stand behind the car 100% should there be a problem, so the warranty remains intact.

The result is a car that feels different from the other tuned Cooper S cars I have driven. The John Cooper Works car is homologated at a genuine 200 bhp and is by far the most expensive of all the conversions we have tried. But when you see the extra work involved and then drive the car, you realize why it has been done this way.

Out of the box, the factory Cooper S shares a problem with its normally aspirated brother--lack of low-speed torque. Despite its six-speed, close-ratio gearbox, it does not really get up and go until you have around 3500 rpm on the rev counter, and it seems lethargic compared to other supercharged cars I have driven.

After a few hundred feet and a couple of gearchanges, I knew the Works Cooper S was something special. The engine revs faster and more smoothly than stock, and at the top end of the scale, where the stock engine's power is tailing off, the Works car just keeps on pulling hard. It screams to 7000 rpm in the intermediate gears with a vigor and smoothness missing from the standard unit, and it has the power to make sense of the tall fifth and sixth gears on the autobahn.

It feels as though the new supercharger has a lot less internal friction and pumping losses in the system. And where the stock motor is lethargic below 3000 rpm, the Works motor is already up and charging. Pulling from low speeds in a high gear is no chore, and this supercharged 1.6-liter engine now truly behaves like a 2.5-liter normally aspirated motor. This means you can stay in a higher gear in normal driving, which is good for fuel economy. With less backpressure in the system, throttle response is keener, the revs rising and falling more quickly when you blip the loud pedal. At last it feels like whatever is strangling the stock motor has been removed, and it can fill its lungs properly and run like an Olympic athlete.

And boy does it run. When all is said and done, the car now makes 200 bhp at 6950 rpm with torque up from 210Nm (155 lb-ft) to 240Nm (177 lb-ft) at the same 4000 rpm. The fact that the car shaves a whole second off the 0 to 60 mph time, bringing it down to 6.7 sec., is almost a moot point. The 0 to 100 mph (160km/h) time of 17.2 sec. is pretty rapid for a hot hatch, and top speed is 136 mph (218km/h), so the Works car really is a giant killer, able to give a Golf R32 a good run for its money.

"When we started the 'Works' program on the Mini Cooper back in 2000, we went along the lines of what we knew best--conventional tuning to the cylinder head, inlet, exhaust and ECU re-calibration," explained Mike Cooper. "The supercharged Cooper S was a different kettle of fish altogether, and we knew early on that, for cost and volume reasons, the bulk of the aftermarket tuners would be taking the easy way out. That means just replacing the supercharger pulley with a smaller one to raise speed and boost and recalibrating the ECU. "While we agree that is fine for, say, 20 bhp extra, our target was 200 bhp with total reliability. Because of this, we did things the hard way," Mike explained. "Forced aspiration produces a lot of heat, and when you increase the charger speed and boost, you get even more heat."

Heat is the thing that destroys engines if the intercooler and radiator are not up to the job, and the other problem is the poor fuel quality in some countries, which means the engine is running into detonation and will destroy itself if you are not careful. "The BMW test regime also included running the test cars flat out for 35,000km on race tracks like the Nuerburgring and Hockenheim," Mike explained. "As the official factory-approved Mini tuner, we had to do a thorough job that BMW would be willing to put their name behind.

"When we had the engine on the dyno, we quickly realized that the factory supercharger was on the limit at just over 200 bhp, so we made the decision to change the unit. Our supercharger has an abradable rotor coating with ceramic particles so that as it beds in it creates a better seal. The pulley is smaller than standard, so boost pressure is up from 0.7 bar to 1.0 bar. We also gasflow the cylinder head, and flow through the head is improved by up to 15%. The spark plugs are changed for colder range ones and the ECU re-programmed. "Our objectives apart from the extra power and torque were efficiency, driveability and fuel economy," Mike continued. "In normal driving, there is a 10% improvement in fuel economy over the standard car despite the extra power!"

The Works stainless-steel exhaust system is new from the catalyst back and lowers backpressure, a very important thing for forced aspirated engines. It also makes a deeper, more purposeful noise while meeting all European drive-by noise regulations.

"The other aspect was that the kit had to be easily fitted by any BMW dealer around the world," said Mike. "A customer can either have it shipped to his local dealer or, if he is so inclined, can book his car in with us and have the work done at John Cooper Garages. Either way, he or she will be fully covered by the BMW warranty."

There are more JC "Works" goodies on the way. Our test car was Mike Cooper's personal Cooper S, and this has the prototype sports seats that will be on sale soon. Made by Sparco, these leather-covered seats answer all the criticisms leveled at the stock items.

It is a tribute to the standard chassis that the extra power and torque overwhelm neither suspension nor brakes. Having said that, ride is a weak point of the standard car. On the 17-in. wheels especially, things can get very choppy on badly surfaced roads.

"We have developed a suspension kit that delivers better handling and more comfort than the standard set-up," said Mike. "We worked with Bilstein on this, and the dampers are the new dual-valve variety as used on the recently facelifted Lotus Elise. This design enables you to set bounce and rebound rates independently, so you can optimize both ride and handling without compromising either.

"BMW has proven that the standard brakes will cope with the 200 bhp," said Mike. "But we have many customers who want bigger brakes, some only for the looks. There are a few big-brake kits on the market already, but they require you to fit bigger wheels. We are developing a kit that will fit behind all the standard factory wheels."

At this point, Mike explained a point that could cause confusion to customers. "I have to differentiate between John Cooper Works and John Cooper Motorsport parts," he said. The former are the tuning kits and parts that have been sanctioned as BMW-approved products. The latter are the parts that we developed ourselves for the racers and for road use but which we sell ourselves. The suspension and brake kits fall into the latter category."

When we drove the Cooper "Works" car last year, Mike had fully expected takeup to be modest compared to the Cooper S kit. "In fact, we have been pleasantly surprised at the sales figures for the 131-bhp Cooper conversion," he said. "I thought we would sell 3,000 Cooper S kits and 300 Cooper kits in 2003, but in the first three months we had already sold 300 Cooper conversions. It just goes to show that there are still many enthusiasts out there who prefer conventionally tuned, naturally aspirated engines!"