Why do you only recommend the 15% reduction supercharger pulley?

My thoughts on appropriate pulley reduction are based on a lot of time spent on the subject - including track testing with real-time data gathering of manifold inlet, supercharger outlet and water temps, long engineering discussions with Eaton (the manufacturer of our supercharger), and plenty of dyno testing.

We started developing the supercharger pulleys in the US before most all of the aftermarket, including the "factory" aftermarket - John Cooper Works. I started with a 10%, 12%, 15% and 18% reduction from stock. What we came up with after all that testing was that the 15% is the optimum reduction based on several factors. Remember that the goal of all of this is to have the highest DENSITY air parcel at the inlet port to the combustion chamber. Density is directly proportional to pressure and indirectly proportional to temperature, or D=p/t .

That makes the most significant performance factor the adiabatic efficiency rate of the Eaton supercharger at increased RPM. In short, it isn't great. The forte of the Roots type supercharger (which includes the Eaton) is high efficiency at low boost - giving rapid response without "lag". The faster you spin the rotors, the more you compress the air going through it - however, you are also increasing the heat (remember that from physics - anytime you compress you also heat). Some rotor designs minimize the effect of this, but the Roots does not. All of that means that while you are increasing pressure, at some point the heat you generate with additional compression will outweigh the pressure increase, and that point is with a 15% at about 5400RPM and higher. You also need to outweigh the fact that you are causing additional drag on the crank pulley by spinning at a higher resistance when you are forcing a higher parcel compression.

The other factors are more reliability based. The most significant of these is belt life. No matter which belt we try to use, they all fail with anything greater than a 15% reduction pulley on the track. I have three cars we have used on the street and track with higher reductions than 15% for data gathering, and even on the street it is a 50/50 on the belt failing. We have tried literally every belt on the market, and the issue is not corrected.

Also related to reliability, but much less of an issue, is the water pump speed. We didn't think this was an issue at first, until we started monitoring oil temp as well as coolant temp. On the track, we noticed elevated oil temps that we didn't see with 15% pulleys. It took a bit to figure this one out, but if the pump is cavitating, it will show first on oil temp. The reason behind it has to do with the volume of water and its movement through the entire head versus through the oil cooler. On the MINI, the oil is cooled with a water-oil exchanger. The water volume is great enough in the entire system that a small flow change does not effect coolant temp at the coolant temp sensor, but with the small volume in the oil cooler, the oil is not cooled as efficiently if the flow is decreased even a small amount, resulting in higher oil temps. This seems only to be an issue with the 19% reduction pulley at sustained high RPM.

I have personally installed over 400 15% reduction pulleys, and have not had a single issue with any of them. I have installed 4 pulleys greater than 15% reductions, and have had issues with all of them. Based on this, the preliminary testing we did, manufacturer discussions, and the fact that a few months after we came out with a 15% reduction recommendation John Cooper Works came out with a pulley on their supercharger that was within .03" of a 15% reduction, I can confidently say that the 15% reduction pulley is the best choice for not only performance, but reliability as well.

What engine performance modifications do you recommend to start with?

This is a question that really depends on what your plans are, and what your concerns are. Simply recommending based on the best combination of factors, I would recommend - in order - the supercharger pulley (and a colder heat range spark plug to go with it), the Alta air intake, a cat-back exhaust, and the ECU. To gain power from that point starts costing serious money. The intercooler and header would be the next two items, followed by the throttle body. Finally, go internal and do the head and cam - again expensive. The nice thing about the MINI is that each of these mods can be done singularly. I build cars using a "whole package" concept - making sure that the parts work in harmony. With the MINI, nothing is taken away from drivability, safety or performance if each part is done in conjunction with the others or separately.

The biggest issue with most folks is always the warranty. The pulley will be the most common concern for most dealerships in regard to warranty. The Moss-Magnuson Act protects the owner from dealers not wanting to honor warranty claims on a modified car. Very basically, it states that the aftermarket part has to be directly responsible for the failure in order not to be covered by warranty. So, in literal translation, the pulley should only void the warranty on the supercharger. We have never had a supercharger failure outside of the test regime. Webb Motorsports also carries a 2 year/24,000 mile warranty to protect you against possible issues.

What handling improvements should I make?

I recommend the H-Sport, Alta or RSpeed rear swaybar, Webb Motorsports front camber plates, sticky tires with some light wheels, the H-Sport springs, and H-Sport or Alta lower control arms/camber links. What size wheel and tires is dependent on what you are doing with the car and what is legal for the class you are running. For autocrossing without worrying about specific rules, the smaller the diameter the better - so we use 15x7" wheels. The common size tire for that wheel is a 205/50-15, and it works well on the MINI with no rubbing issues. For road racing, I use a 17" wheel, 7, 7.5 or 8" in width depending on how many concessions you are willing to make (spacers, clearancing fenders and liners, clearancing bodywork). The 17" wheel allows for a shorter sidewall and therefore gives less deformation to the contact patch. On a 17" wheel, you can use a 215/40-17, a 215/45-17 for better ride, and with many concessions, a 235/40-17. There are several great tires out there. Some of the common tires we use are the Toyo T1-S, the Bridgestone S03, the Kumho Ecsta MX, the Yokohama AVS ES100, and the Falken Azenis.

The next step would be to change the rebound and compression rates of the shock - which is good to start with. The advantage of having changeable rates does provide for different set ups based on use. For instance, you can make the car oversteer a bit by going firmer in the rear and softer in the front, but this wouldn't be the set up for rain, or high speed track work. These settings can be changed using simple shock replacements with adjustable rebound, and can even be built into "double-adjustable", which means rebound and compression. I use the Koni yellows to accomplish this, and they are direct replacements, meaning you can use the H-Sport springs with them, or even stock springs if you are in an SCCA stock class.

You may notice that I didn't recommend installing coilovers. While the ultimate in handling can be had with coilovers, the truth is that they are bigtime overkill for 95% of MINI drivers. The biggest advantage of coilovers is corner-weighing the car. You can manage load by transferring weight from one corner to another to better balance the handling of the car. Most folks with coilovers don't even have this done, completely defeating the purpose. The MINI has great shocks stock - good compression and rebound rates. One of the other advantages of coilovers is changing that rate, and since the MINI is good in OEM form, it really doesn't prove to be as big an advantage on our cars. With a coilover kit the spring rates can be changed as well. The final trick with coilovers is that you can adjust the ride height. These two last positives for coilovers can be done with springs as well, and the H-Sport springs have the rates and ride heights nailed.

Which exhaust do you recommend?

This is a question I hear a lot, and there isn't an easy answer because many variables play into the question.

There is an easy filter up front - which year is your car? In '04, MINI changed the orientation of the rear exhaust hangers. That made most of the aftermarket exhaust systems non-compatible with the newer cars. Since then, several manufacturers have caught up to the change, and the '05 cars use the same system. Here are the systems currently compatible with the ‘04+ cars:

• Borla
• Milltek
• UUC

I start by asking what kind of volume you are willing to accept, or may even want. If loud is your bag, than the Magnaflow or Borla Sport is the system for you. The UUC sneaks in on being a bit louder, but it ranks below these two thunderers. The Borla Street and the Milltek are both conservative noise-wise, and make fine daily driver systems. Of these two, the Milltek gives the more authoratative sound, with the Borla being a tad raspier. The UUC gives a sound that is again between the two extremes.

I don't like the single sided muffler systems as much - the Alta, the Mania NRP, the Quicksilver - for a couple of reasons. They don't split the flow, which is more restrictive, and you just can't get the things to hang right! They melt the rear valance and rattle at idle as they hit it. They are usually non-offensive in sound, and they are definitely lighter than the twin muffler systems, so they are not all bad.

Based on power as the major consideration, the Magnaflow and the Borla Race are at the top of the heap. Based on torque, the Milltek is the champion. So again it boils down to what you want out of the system.

All around, I think the Milltek is the best choice based on the non-intrusive sound that still emits a deep note and the highest torque available. It is only two horsepower down on the big boys for horsepower as well, and the price point is smack dab in the middle.

Which swaybar do you recommend?

I think all three of the pieces I offer have their place in the market.

The RSpeed is the strongest bar on the market, as it is solid forged steel. It uses collars on each side to prevent lateral movement, so you can adjust if need be to different suspension clearance issues. It has a special crinkle finish that keeps the grease from leaving the bushing, and all of the brackets are black - making it very stealthy. There are also three adjustment positions.

The H-Sport is the lightest bar, as it is tubular steel with forged ends. The bend schedule keeps the bar from moving laterally, just like the factory bar. Unlike the original H-Sport bars, the newest units are black - keeping them unnoticed. The H-Sport has three positions for adjustment. Perhaps the coolest part of this bar, and one that helps give it a nudge for favorite, is the grease fitting that is part of each bushing carrier. This makes it very easy to regrease the bar, and the bushings are grooved to keep this from being an often necessary ordeal.

I only recommend doing the rear swaybar. The purpose behind the rear swaybar is to dial out the inherent understeer, which most new cars are programmed with. Why? Because if you enter a turn too hot, the car goes straight when you turn the wheel - the tendency then is to lift the throttle, which transfers more weight to the front and gives more coefficient of friction to the front contact patch, letting the car turn in. It isn't the fastest way through a turn, and it certainly isn't the most fun way through a turn. That's where the rear bar comes in. Thinking on a twisting body model, if you apply force to the outside, or loaded wheel, and you have a stiffer rear bar, it will do two things: first, it will lift the inside rear wheel, reducing the rear coefficient of friction, and second, it will transfer load diagonally to the inside front wheel. This makes the car neutral. It has a secondary benefit of acting like a cheap limited slip differential if the unloaded front wheel is the power driven wheel.

If you change both the front and rear swaybars, the car will still understeer, but it will handle flatter - less body roll. That's the reason I don't recommend doing both the front and rear swaybar - the most dramatic thing you can do to the car is make it neutral, not flat.

Which springs do you recommend?

This one is a no brainer. I love the H-Sport springs for several reasons.

The MINI has precious little front suspension travel. What this means to a suspension tuner is that you can't lower the car too much in the front, or you will always be bump stopping - hitting the bump stop at the end of the shock travel. This causes your spring rate to go to infinity, and the car handles worse than stock.

To avoid this, H-Sport took two unique steps. The first is easy to see, and I honestly wonder why more spring manufacturers don't use it - they only lower the car 1" in the front. Many of the other spring manufacturers lower the car 1.3" - even 1.5". The other is unique to H-Sport - they include new, shorter, polyurethane bushings for bump stops, which gives you back the travel you lost in lowering the car.

The other solution that separates the H-Sports is the spring rate. Adhering to the same basic suspension tuning philosophy as swaybar tuning, stiffer rear rates will solve understeer issues. H-Sport uses a progressive rate that is actually softer than stock in the front, and stiffer in the rear. This split rate solves some of the inherent understeer the MINI exhibits at the limit.

There is another option, which is similar to the approach the H-Sports use as far as rate split goes, but the winding is such that the ride is even softer than stock. Those are the M7 springs. These are also a great option, but don't include the new bump stops, and because of the softer ride, take some of the edge out of the MINI (which I like!). I think the M7 is the only other feasable choice for springs, and should be used for those more interested in ride quality than handling (not that the M7 springs don't make the car handle better - they do).

Why do you only use headers that have a catalytic converter?

Because I care for the environment - just kidding (not that there's anything wrong with that).

This question goes to how the MINI determines the A/F (Air/Fuel) ratio. There are two basic functional modes the ECU: open loop and closed loop. Closed loop is your friend, as it uses real time, actual fuel burn to determine the A/F ratio. This is determined through the O2 sensors, located in the header. The spent combustiable mixture passes out of the cylinder head and into the exhaust system. The O2 sensors can tell the ECU what the fuel ratio was, and the ECU trims accordingly to maintain the desired ratio. OBDII (On Board Diagnostics II) uses the O2 sensors to monitor catalyst efficiency.

Open loop is used when the O2 sensors can no longer handle the flow rate. This is pretty acuurately described as a "best guess" A/F determination. It is a very accurate guess, but real time data is always the best.

The MINI has two O2 sensors, one pre-cat and one post-cat. The sensors measure the temp difference and convert it to voltage, which is monitored by the ECU. Because of the OBDII, it needs to be sure the cat is functional. If there is no change in voltage, the O2 sensor assumes it has failed and the ECU functions in open loop.

So, the reason I use only cat-equipped headers is so I don't lose the accurate closed loop ECU function.