Factory supercharged cars are wonderful. More times than not, a hefty increase in power simply involves installing a smaller blower pulley to make it work harder and to match the increased, forced-inducted air with the proper amount of fuel by way of controlling the ECU. That's why we wanted to do a project on the Cooper S versus the base model-more power!
The Mini Cooper S is rated at a modest 163 bhp, but we want a reliable 200 hp at the wheels. Where most Cooper S cars are known to dyno around 145 whp, a near 40% increase in power without getting into the motor should be classified as a remarkable feat. How quick would this car be? Think about it: at 200 whp our MINI would be roughly hauling only 14.5 lb per whp, compared to our Project M3 and Project S4 cars that started life at around 15- and 16.5-lb per whp, respectively. However, so we don't get ahead of ourselves, let's see if this can be done by starting with a simple pulley, intake, software and full exhaust upgrade.
Several companies offer supercharger pulleys for this car, but we decided to try one from Mini Mania. Started by long-time Mini racer Don Racing in 1975, Mini Mania now offers a full range of products for both the classic Mini and new MINI, including motor, suspension, brake and aesthetic upgrades-everything else you can throw on these cars. It's obvious Mini Mania's roots and passion for racing are still present-by the time you read this the company would have co-hosted this year's Ultimate Mini Challenge at Laguna Seca Raceway.
For Project Mini we ordered a full Stage 2 kit from Mini Mania, comprised of a supercharger pulley, belt, heat-shielded intake system, headers with catalytic converter and a dual sequential high-flow cat-back system-all for about $1,750. We opted for the software tuning option as well, which costs an extra $745.
Starting off with the air intake kit, the system reportedly improves on existing designs for greater efficiency. It also uses the factory front grille air inlet and windshield vents to draw in air to the K&N filter.
The exhaust system is a piece of work. We ordered one with a catalytic converter connected to it; however, you can order your exhaust headers without the cat. The exhaust header system is a polished, four-into-two-into-one design. Equal-length primaries ensure flow improvements and are also threaded for the oxygen sensors. Mini Mania reports that with this system alone a significant increase in mid-range torque can be had. From there the cat-back system, also known as the Mini Mania "S Performance exhaust," uses a twin sequential exhaust system, reportedly to free up more horsepower from the supercharged motor.
The three-piece supercharger pulley has a 15% reduction in diameter compared to the factory unit, and is reportedly good for an additional 4 psi boost. This design allows installation of the pulley without a press, enabling easy pulley removal. Mini Mania rents and sells the special tool for easy stock pulley removal.
The box of cool stuff was sent to evosport along with Project Street S for installation and testing. evosport's shop in Huntington Beach makes it an easy, one-shot deal to have the parts installed and dyno-tested, and the technicians there have been helping us out with several of our project cars. The company specializes in performance upgrades, tuning, installations and service for Mercedes-Benz, BMW and Ferrari
The evosport technicians installed the Mini Mania Stage 2 kit easily, giving us plenty of time for the fun part: testing the system on evosport's 248C Dynojet dynamometer. Just to be safe, evosport went ahead and monitored the air/fuel ratio to make sure we were always under 13.0:1.
With the Stage 2 kit installed Project Street S spun the dyno rollers, registering 176.2 whp at 7000 rpm with 152.6 lb-ft of twist at 4000 rpm. Peak increases were a very significant 24.5 hp and 19.1 lb-ft of torque right where the supercharger whines the most: at 6750 rpm. Testing was done on California's 91-octane, ping-prone fuel. But the car showed only smooth pulls without any sign of knock or pre-detonation.
After hearing the news, Mini Mania was somewhat disappointed, as the company had been dynoing around 185 whp with its Stage 2 kit. But it was the software that told the story. Right at 4500 rpm the car dumps so much fuel that the modestly rich reading of a mid-11 air/fuel ratio goes down off the chart-under 10:1-and stays there through redline. It's right in this area where the torque isn't quite as flat as it could be.
When asked about this, Mini Mania's Ken Suzuki said that all of their customers had been seeing normal air/fuel ratios, with several peaking over 180 whp. After being asked to put around 50 more miles on the car, Project Street S's new dyno runs revealed the same problem, too much fuel. At least it's not leaning out anywhere-we're definitely on the safer side of that spectrum.
Despite this, I was still excited to check it out the modifications. After warming it up properly, and within an instant of my first wide-open-throttle application, I was pleasantly amazed. The power increase was obvious throughout the entire rev range. and the car seemed to pull with total anger. The new sound of the considerably louder exhaust system and supercharger whine surely contributed to that sensation as well. Although the dyno showed the rich conditions, I couldn't detect any hesitations or sluggishness from the motor-this car hauls ass, and the motor sounds like it's still begging for more.
In the meantime, Mini Mania will be looking into the rich condition from 4500 rpm-on, which should be solved by the time you read this. So far, we are only 24 hp away from the desired 200. Perhaps some custom yet mild tweaks are in order-stay tuned to see how we getProject MINI closer to our goal.
Author's note: Special thanks to evosport for the install and dyno testing of the Mini Mania Stage2 power upgrade.