MINI COOPER PERFORMANCE PARTS, AN UPGRADE GUIDE FOR YOUR MINI
This is a comprehensive guide to Mini Cooper Performance Parts that will extract more performance out of your Mini Cooper. This article will focus on the 2nd generation Rxx Mini Cooper S models, but many of the principles can be applied to any MINI Cooper model. This article will cover:
- What types of upgrades are available
- Reasons for the upgrade
- What you can expect from the upgrade
Whether you are looking for improved street performance or better lap times on the track, all of the upgrades discussed below will contribute to both. Mini Cooper Performance Parts can be categorized in four main areas:
- Engine or power upgrades - more horsepower for stronger acceleration
- Drivetrain upgrades - getting more power to the road
- Suspension upgrades - better handling for lower lap times
- Brake upgrades - improve stopping performance
If your Mini is under factory warranty, always check with your Mini Service Advisor on the impact of the upgrades to the factory warranty. Warranty coverage 'may' vary from one dealer to the next.
The internal combustion engine develops power by a combination of thee basic elements: fuel, air, and ignition. In order to increase power, each of these areas can be improved individually, or combined for maximum gains.
Engine upgrades may fall under the scrutiny of emissions laws, especially in states like California where some engine upgrades require a CARB (California Air Resources Board) approval sticker. If you are in California or any state that adopted California emissions standards, you should check to make sure your upgrades will pass emissions testing BEFORE you make your purchase. Unfortunately, something that is legal today may not be legal next year and we have no way to predict future changes to the laws. Always check your current local regulations on compliance for street use BEFORE you make your purchase. We always recommend you keep your factory original parts, just in case...
As with any upgrades, we recommend you upgrade one item at a time in order to appreciate and understand how each upgrade affects the performance.
Cold Air Intake - Upgrading the restrictive stock airbox is one way to get more air into the engine. More O2 into the combustion chamber means more powerful combustion and thus more power at the wheels! This is especially true at higher rpms when the stock airbox becomes more restrictive. A side benefit is more 'sounds' from the intake, including the growl at full throttle, the whine from the turbo, and the sounds from the bypass valve when it releases boost at throttle-off. We see 'typical' gains in the 4-6 hp range with Intake upgrades (less with the K&N filter only upgrade). (See Mini Cooper Intake upgrades.)
Cat Back Exhaust - Once you improve the flow into the engine, you should upgrade the exhaust to allow better flow out of the engine. Turbochargers perform better with less back pressure, especially when you upgrade to a larger turbo. Some cat back systems connect at the flange eliminating the secondary cat and the resonator with larger diameter piping - this results in less back pressure and more flow. The other kits that splice in downstream from the cat and resonator flow better than stock due to the larger diameter pipe and free flowing mufflers. We see 'typical' gains in the 8-10 hp range with Intake upgrades. (See Mini Cooper Cat Back Exhaust Application Guide.)
Downpipe upgrade - The downpipe is the exhaust pipe that connects from the turbo outlet to the exhaust system and has an integrated catalytic converter. The upgraded downpipe improves flow by three features, larger diameter piping, larger inlet and outlet at the cat, and higher flowing catalyst inside the cat. The net result is less back pressure which allows the turbo to spool up faster minimizing the lag. Unfortunately, the federal law prohibits replacing the factory catalytic converter with a performance unit. This limits the use of any and all downpipe upgrades to off-road use and may never be used on public roads. Aftermarket downpipes will usually trigger the check engine light (CEL) so that needs to be addressed separately. (See Milltek Downpipe or NM Engineering Downpipe.)
ECU Software upgrade - The ECU software is the software inside the Minis main computer (ECU) that controls how the engine runs (among other functions). The ECU monitors sensors throughout the car and adjusts various engine parameters based on the inputs. The stock software from the factory is developed with a delicate balance between fuel economy, durability, and performance. The ECU software upgrade skews the software towards performance by manipulating parameters such as ignition timing, fuel mixture, boost pressure, just to name a few. ECU upgrades become more critical as you add more 'serious' engine upgrades such as Turbos or internal upgrades, but are also effective on a stock Mini. (See Mini Cooper ECU upgrades.)
If the ECU software upgrade sounds too intimidating, take a look at the Sprint Booster Throttle ReMap Module. This tiny module transforms the throttle response making your Mini more FUN to drive. It does not add horsepower, but the improved throttle response is very noticeable. Think of it as Sport Mode on steroids, and yes it works in conjunction with Sport Mode. This is a simple device that takes about 15 minutes to install or remove, and it comes with a 30-day money back guarantee!
Turbo upgrade - The turbocharger is a type of forced induction using exhaust gasses to spin a turbine which forces more air into the engine (boost). This means more O2 for a stronger combustion and more power! Turbocharging allows smaller displacement engines to produce power outputs similar to naturally aspirated engines of larger displacement. Many of the newer cars are turning to turbocharging for its high power output from a smaller engine producing better fuel economy.
The stock turbo on the Gen2 Mini is a K03 Borg Warner unit. Some of the aftermarket turbo upgrades are 'hybrid' K03 units that have a larger compressor section to develop more boost (and power). The upgraded K03 units maintain boost much longer than stock units (the boost with stock units fall off as you approach higher rpms). The higher horsepower units use larger K04 turbos which run higher boost and produce more power, but also comes with slightly more throttle lag. (See Mini Cooper Turbo Application Guide.)
One of the side-effect of increasing the boost is more heat. When you compress a gas (air), more heat is generated - higher boost means higher intake air temperatures (IAT). In order to reduce the intake air temperature, an air-to-air intercooler is used downstream from the turbocharger. As you increase the boost with a turbo upgrade, you should upgrade the intercooler to reduce the corresponding increase in the intake air temperature.
Intake Plumbing upgrades - In order to improve flow into the engine, there are various 'plumbing' or pipes that can be upgraded. These aftermarket pipes use larger diameter and / or less restrictive piping in order to smooth the airflow and flow more air. Although these upgrades by themselves offer only small gains, they are more effective when combined with other engine upgrades. (See the Turbo Outlet Pipe and the Turbo charge Pipe.)
Intercooler upgrades - The Intercooler is used to cool the intake charge after it has been compressed by the turbo. The Mini intercooler is an air-to-air intercooler which uses airflow to cool the intake air temperature, much like the radiator which uses air to reduce the coolant temperature. As you increase boost, the intake air temperature increases exponentially which greatly increases the combustion temperatures. If left unchecked, the computer will sense the rise in combustion temperatures and retard the timing and increase fuel to lower the combustion temperatures. This robs the engine of performance in order to safeguard against detonation which can occur when the combustion temperature gets too high. Detonation will eventually damage the engine internals. In order to avoid this, the intercooler upgrade is the best solution to reduce the higher intake air temperatures BEFORE it enters the engine. This preserves the increase in performance and safeguarding against detonation. (See Mini Cooper Intercooler upgrades.)
Engine Internal Upgrades - Internal engine upgrades are usually performed after most other engine upgrades are completed and may be prudent if you increase the horsepower beyond 250whp. Due to the complexity of the newer Mini engines, internal upgrades may be limited but there are some options. Products such as stronger Forged Pistons or Camshaft upgrades are currently available. Your local race shop should be able to port and polish the Cylinder Head, and install bigger valves. These types of upgrades are fairly expensive in terms of $$ per hp...
Drivetrain upgrades improves the components that takes the power from the engine and applies it to the wheels. The Clutch and Flywheel connects the engine output to the transmission and the differential transmits the power from the transmission to the axles. Upgrades to the clutch becomes necessary as you increase the power output of the engine and more so if the Mini is driven in a spirited manner or on the track. Otherwise the clutch will have a limited life. The Limited Slip Differential applies power to both axles regardless of the traction, something the stock open differential is unable to do.
Clutch upgrades - The Clutch is the connection between the engine and transmission. There are two basic reasons that Mini owners look for clutch upgrades: 1. Upgrade to a more durable unit than the stock. 2. Upgrade to handle the increased horsepower for street and track.
The clutch on the Mini is designed to function properly at a given horsepower figure (plus some headroom). As the Mini engine gets upgraded producing more power than stock, the increased horsepower can overpower the stock clutch's clamping force and/or the friction material on the clutch disc. This can cause excessive clutch slip and the net result is a burnt clutch making the Mini non-operational.
The Clutch Upgrade manufacturers offer their product with higher clamping force and better friction material to handle the increased horsepower. These upgraded units are designed to grab quicker with greater force for faster engagement. The problem is, this is not ideal for the street driver where slipping clutch on a hill or repeated engage / disengage in bumper to bumper traffic is common - performance clutch upgrades are not designed to slip, but to engage. For this reason, the Clutch upgrades for the street driven Mini should be limited to Stage 1 or Stage 2 unless the Mini has been modified producing higher horsepower outputs. For best results, choose an integrated clutch and flywheel package. (See Mini Cooper Clutch Kit Application Guide.)
Flywheel upgrades - The flywheel is the surface where the clutch engages and is typically designed with some mass in order to maintain momentum for easier driving. The flywheel also contains the ring gear where the starter motor engages. The newer 'dual-mass' flywheel contains a dampening system to reduce the gearbox noise and body vibrations.
The Mini Cooper Flywheel upgrades are typically single-mass units that eliminate the dual-mass dampening function in order to lighten the weight for faster throttle response. The only drawback is the lack of dampening can introduce more gearbox noise into the cabin. On some Mini models, this can sound like loose marbles in the engine.... Some would expect the rpm to drop immediately after releasing the throttle on Minis with the lightweight flywheel, but unfortunately that is controlled by the computer where it momentarily maintains the throttle after release for emissions reasons. For best results, choose an integrated clutch and flywheel package.
Limited Slip Differential - The factory differential in the Mini is an open differential where power goes to whichever axle with less traction (path of least resistance). This is why a stock Mini can spin its inside tire in a hard corner. The mechanical type limited slip differential (LSD) includes a mechanism where both axles get 'locked' to some degree so both axles get power. (Think of the old school 'posi-traction'.) There are different types of limited slip differentials including Torsen Type (Torque Sensing Differentials) where a bias can be applied to the power that goes to each axle depending on the available traction. Another type is a Clutch Type which utilize small clutch plates to lock the two axles together so power is applied to both axles. Torsen type LSD work well on street performance applications. The Clutch type seem to work more effectively and consistently on track applications.
For track driven Minis, the limited slip will allow the Mini to accelerate out of a corner without spinning the inside wheel. Newer models have an Electronic Limited Slip Differential where brakes are utilized to force more power to the axle with more traction. This can be effective for normal street applications, but the brakes can be overheated under track conditions. It can also accelerate brake wear depending on how much track driving is involved.
Suspension upgrades are designed to improve handling, or more specifically to allow the Mini to corner at higher speeds with greater control. Although a great deal of engineering went into designing the Minis suspension, it is a compromise between ride quality and sporty handling while maintaining maximum safety. Suspension upgrades are designed to improve handling with less emphasis on ride quality and more emphasis on lower lap times. As with any upgrades, we recommend you upgrade one item at a time in order to understand how each upgrade affects the handling.
Rear Anti-Sway Bar - The factory suspension is intentionally setup with understeer which happens when the car enters a corner too fast - this is where the car wants to go straight even with the wheels turned. This is a safety factor which forces the driver to reduce speed in order to navigate the corner. For the performance oriented driver, the preference is to have a more 'neutral' suspension where the car turns more easily instead of understeer. A larger rear sway bar will change the balance so the car turns more neutral or even oversteer - as preferred by some performance type driver. This allows the car to carry higher speeds in the corner and lowers the lap times on the track. Aside from taking a drivers education event at a track, we recommend the larger rear sway bar as the first suspension upgrade for improved handling.
Poly Bushings - All suspension bushings on the car are made of rubber which offers the best compromise between handling and ride quality. Rubber is an excellent material for isolating the noise, vibration, and harshness (NVH) from the chassis, offering the occupants a comfortable ride. For the performance minded driver, this is not ideal since the flex from rubber makes the car feel sloppy and does not allow the driver to feel the road as well. The Poly Bushings or polyurethane bushings are stiffer than rubber making the car handle better, at the cost of slightly elevated NVH in the cabin. (See Powerflex bushings.)
Lowering Springs - Lowering springs are designed to lower the car's center of gravity for improved handling. The lower center of gravity will improve the turn-in response, allow flatter cornering and reduce 'dive' under braking. The drawback is a reduction in ride quality and reduced clearance under the car. Since the Mini has a fairly short suspension travel, reducing the suspension travel even further with lowering springs makes the car handle better, but also makes the car ride 'stiffer'.
Racing springs are typically linear in design where the spring rate is constant throughout the compression of the spring. Most of the street performance springs are 'progressive' where the spring rate changes as the spring is compressed. The progressive springs are softer initially, and firms up as it compressed. This is done in order to preserve some of the ride quality on the street, but becomes stiffer when driven aggressively on the track. It is almost impossible to compare spring rates on progressive springs since the rates vary. The best solutions are shocks that are offered with matched springs since the functions of both interact and are dependent on each other for the net result.
Shocks - Shocks, dampers, or struts are designed to 'absorb' the road surface irregularities and provide the occupants a more comfortable ride. More importantly, the shocks are designed to keep the tires in contact with the irregular road surface for maximum control and safety. The factory shocks are designed as a compromise between ride quality and 'sporty handling' while keeping the car safe to drive under all conditions. Since the performance minded driver typically carries more speed, the shocks need to be more aggressive with less emphasis on ride quality. (See Mini Cooper Shocks & Struts Application Guide.)
Coilovers - Coilovers are products where the shocks and springs are integrated into one package. These products are typically more expensive than springs and shocks, and typically selected by those drivers that drive their Minis on the track. Some offer height adjustments where the lower spring perch can be moved up or down to vary the ride height. (Even at the highest settings, coilovers will lower the car about 1.0 - 1.25"). Some offer rebound adjustment, combined rebound and compression adjustment, or independent rebound and compression adjustments. The adjustability allows the driver to change the settings to match the type of track being driven, thus lowering their lap times. (See Mini Cooper Shocks & Struts Application Guide.)
Strut Bars - Strut Bars are designed to limit chassis flex by limiting the movement of the strut towers. Strut towers usually extend up high from the main chassis, and are subject to stresses from the front struts in a hard corner. When the strut tower moves or flexes under hard cornering, the suspension geometry changes and has a detrimental affect on the cars handling. By limiting this flex, the suspension can function as designed for precise handling.
Rear Adjustable Control Arms - The Rear Control Arms on the Mini Cooper help maintain optimal suspension geometry as the suspension reacts to the varying road surfaces. The Mini Cooper has 'fixed length' upper and lower control arms on each side of the rear axle. The length of these control arms determine the camber and toe settings. As long as the suspension or chassis is not damaged or bent, the stock control arms should set the rear camber and toe to the factory specifications. When the Mini Cooper is lowered using lowering springs or coilover shocks to improve handling or looks, the lower ride height causes a large increase in negative rear camber - the lower the car, the greater the negative camber.
The addition of the Adjustable Rear Control Arm provides the capability to correct this negative camber on cars with lowered ride height. By varying the length of the Rear Control Arms, the camber and toe of the rear wheel can be adjusted. Most Mini owners with lowered Minis simply replace the two lower control arms with adjustable units which allows the rear camber to be corrected back to factory specifications, but this also has a slight affect on the rear toe setting. For most street application, the change in toe is small enough to be inconsequential. For those Mini owners that drive on the track and need to 'dial in' the suspension for maximum improvement in handling, the best approach is to replace all 4 control arms with adjustable units. This allows independent adjustment of rear camber and rear toe. (See Mini Cooper Adjustable Rear Control Arms Application Guide.)
Front Camber Plates - The camber is a measure of how close to vertical the wheel sits from the ground. In the front suspension, the camber is set based on the position of the front strut and the camber varies as you turn the wheel in order to maintain the tire contact on the ground. The factory specification is about -0.5 degrees of camber which means the top of the tire is tilted inwards by 1/2 degree. This works fine on the street, but not so much on the track.
As speeds are increased in turns, the stock camber setting causes significant pressure on the outer edge of the tires resulting in the outer edges deteriorating rapidly. In order to avoid this, track driven cars are set with a large negative camber up front to improve turn-in response and preserve the tires. Since the stock front suspension does not allow any manipulation of the front camber, an Adjustable Front Camber Plate becomes necessary. The adjustable camber plate can be set to as much as -3.0 degrees depending on the type of springs or coilovers on the car. For the track Mini, a -2.0 to -2.3 degree camber setting may be ideal (in combination with changes to the rear suspension).
A large negative front camber is not ideal for the street as the handling may become very sensitive and the tires will wear unevenly. The adjustable camber plate allows you to adjust to track settings and restore factory settings after you are done on the track. (See Mini Cooper Camber Plates.)
Brake upgrade can mean different things to different people. For the average street driver, brake upgrades can mean better durability (more miles) and / or less brake dust. For the street performance driver, brake upgrades can mean shorter stopping distances. For the track driver, brake upgrades can mean reduced brake fade and improved brake feel in addition to shorter stopping distances.
Brake fade is a condition where the brakes respond slower when pressing the brake pedal, or the brake pedal needs to be pushed further to engage. This can happen when the brake fluid boils (vapor lock) or if the brake pads overheat and loses friction.
Aggressive track driving or even a very long downhill can cause the brake fluid to boil releasing gasses into the fluid (vapor lock). This makes the fluid compressible and reduces the hydraulic effect of braking. The net result causes the pedal to feel 'mushy' and sometimes the pedal goes all the way to the floor with greatly reduced braking effectiveness - a true pucker moment!
Continuous or repeated braking can heat the brake pads beyond its rating causing the pad material to overheat and release gasses. This creates a film or layer of gas between the pad and rotor greatly reducing the friction and braking effectiveness.
For a great majority of the Mini drivers, brake fade is not an issue. It is more about durability and shorter stopping distances. However, it is important to select the correct pad for your application. (Don't use street pads on the track and track pads on the street, unless they are rated for such.)
Brake Pads - Brake pads are available in different levels of upgrades depending on the type of friction material or combination of friction materials. They typically include one or some of the following materials: organic, semi-metallic, or ceramic. Each of the different materials contribute to the brake pad's durability (long life), abrasiveness to the rotor (won't chew up the rotors), temperature stability (reduced brake fade) and noise. There are different types of pads depending on what you are looking for in a brake pad upgrade. (See Mini Cooper EBC Brake Pad Application Guide.)
Brake Rotors - Mini recommends that you replace brake rotors any time you replace brake pads. Front rotors are always vented and the rear rotors are solid. There are rotor upgrades available that are slotted, drilled, or slotted and drilled. The slots and drilled are options that are designed for better cooling of the rotors and for expelling brake dust. These are typically not necessary for street driven Minis, but many owners like them for the looks. Keep in mind, when you have slotted and or drilled rotors, you have slightly less surface area against the pads. They also produce a little more noise and 'can' shorten the life of your pads. (See Mini Cooper Brake Rotor Upgrade Application Guide.)
Big Brake Kits - The Front Big Brake Kits are the ultimate brake upgrades for performance (and for looks if your budget allows). These are oversized brake kits that offers greatly improved braking performance in all areas including stopping distance, improved brake feel and just about no brake fade. Big brake kits offer better braking performance with:
- Larger calipers with more pistons to press the pads against the rotors
- Larger brake pads for greater pad to rotor friction area
- Larger diameter and thicker rotors for greater friction surface and better heat dissipation
- Full floating rotors where the hats are separate and of different materials to aide in heat dissipation
Since the front brake perform a great majority of the braking, a rear big brake upgrade is not necessary. A simple rear brake pad upgrade is sufficient to balance the braking between front big brake kit and rear stock brakes. The downside is the cost of the big brake kit and most stock wheels do not have enough clearance to fit over big brake kits. You will most likely need spacers or different wheels altogether. (See Mini Cooper Big Brake Kits Application Guide.)
Brake Fluids - Mini recommends you replace brake fluids ever two years. This is because brake fluid is hygroscopic or it attracts water. Water in the brake fluid will eventually damage the ABS controller, unless you change your fluid regularly. The Mini uses standard DOT4 Brake Fluid.
For track driven Minis, brake fluid can be a critical element in reducing brake fade (or vapor lock). Any time you take your Mini on the track, you should upgrade to high performance or racing brake fluid with higher boiling temperatures to delay the onset of brake fade. You should also change the brake fluid more frequently if you track your Mini. For High Performance Brake Fluids, see the following:
- Ate Performance Brake Fluid - Very Good
- Motul Racing Brake Fluid - Better
- Torque Racing Brake Fluid - Best
When considering performance upgrades, always have in mind your goals or what you wish to accomplish with the upgrades. What end results do you seek with the upgrades? If you contact us, this will help us make the best recommendations to match your goals. Your budget and application will also narrow down the choices.
Even if you purchase a 'Stage Kit' with several components, it is always best to add one item at a time. This will help you understand which upgrades made what changes to your Mini.
Performance upgrades usually involves some compromise. Engine upgrades will usually affect your fuel economy. Suspension upgrades will usually sacrifice some ride quality. Brake upgrades can increase maintenance costs. Be prepared to 'compromise' when you upgrade for performance.