The Basics of Internal Combustion in the MINI Cooper

Let’s start at the beginning. Your MINI Cooper is powered by an internal combustion engine. Aside from some electric cars, nearly all cars on the road have IC engines. All this means is that the power is produced by an explosion—combustion— that happens inside—internal to—the engine.

In contrast, in an electric car the combustion happened somewhere else, at a power plant or in the sun. The resulting energy was sent over the electric power grid to be stored in the car’s battery and then used by the car’s motor to produce power.

With a hybrid car, the power still comes from internal combustion within the car’s engine. However, what makes the car a hybrid is that it also has an electric motor that can be used as both to produce power and to generate power. Normally the car is driven by the IC engine, and any excess power is used to make the electric motor generate electricity, which can be stored and used by itself, or in conjunction with the IC engine. But we digress.

In an internal combustion engine, the power is produced by the interaction of three forces. Air is pulled into the engine, is mixed with gasoline, and then the mixture is compressed by the cylinder and ignited by a spark to produce an explosion which pushes the cylinder down, turning the crank, and producing power. Air, fuel, and spark. Once the explosion occurs, the only remaining task is to get the resulting smoke out of the engine as quickly and efficiently as possible, so a fourth factor, the exhaust, enters the equation.

In modern automobiles, to provide the fine-tuning needed to maintain performance while meeting emission regulations, the air/fuel/spark equation is controlled by an engine control unit (an ECU)—a computer which controls basic engine operations like fuel mixture and spark timing— linked electronically to the throttle pedal and to several sensors that measure engine performance.

The S Stands for Supercharger

In the MINI Cooper S, the engineers added another component, the Mini Cooper Supercharger, which is only used on high-performance cars. It is used on Jaguars and Bentleys, for example, but on few cars as inexpensive as the MINI. The presence of the supercharger is one of the few major differences between the MINI Cooper and the MINI Cooper S

The supercharger is worth a few words on its own. As we mentioned, in order for the fuel to burn, we need air. If we want more powerful combustion, then we need more air.

This principle first became an issue back in the days when all airplanes used IC engines and the designers wanted their craft to fly higher. However, the higher the airplanes flew, the thinner the air became. With less air, there was less power produced by the engine. So engineers came up with the idea of using a little component with spinning blades, powered off the engine, to compress the air coming into the engine. With more air being forced into the engine, more power could be produced. They called it “supercharging” the engine.

It wasn’t long before automobile designers were using the same invention on the ground to make race engines run faster without having to get bigger. Remember the “Blower Bentleys” that were raced at LeMans in the early 1930s? You probably don’t, unless you’re an auto history buff. They were probably the earliest well-known application of a supercharger in a racing car. But if you want to impress your car buff friends, just tell them you have a “blown” MINI and refer to your supercharger as the “blower.”

It’s that same principle we find in the MINI Cooper S today. A small turbine between the air intake and the engine is driven off the main driveshaft by a pulley and belt to compress air coming into the engine. More air means that more fuel can be added, and more power will be produced.

Incidentally, engines in some other makes of cars address the same problem of compressing the intake air by using turbochargers. The difference between a supercharger and a turbocharger is how the little vanes in the turbine are powered. In a supercharger, the power comes directly off the driveshaft, connected to the supercharger pulley by the main engine belt. In a turbocharger, there are two sets of vanes, connected by a shaft. Exhaust gas coming out of the engine spins one set of vanes, which in turn push the other vanes that push air into the engine.

The problem with a turbocharger is that you’ve got to wait for the engine to build up some exhaust pressure before the turbo kicks in—what the gearheads call “turbo lag”—which means that the added power isn’t immediately available. With a supercharged engine, the supercharger spins faster as the engine gains speed, so the added power is always on tap and ready for use.

Improving Your MINI Cooper

You’ve probably already been impressed by how good the MINI Cooper is at what it does. It’s quick off the mark, fast on the highway, and can zip around corners at an enviable clip with almost no body sway or looseness.

What’s to Improve?

To be more specific, the stock MINI Cooper S can get from zero to 60 in just under seven seconds, which puts it easily in the middle of the pack of what are called “performance cars.” Top speed is north of 130 miles an hour, which also makes the car quite respectable in the sports car league. That speed is much faster than most of us should be driving, even on a closed course, though it does mean that at normal highway speeds the engine is right in the middle of its power band with lots of reserve power when needed.

Cornering is where the car really excels. BMW has a well-deserved reputation for suspension engineering, and it is really reflected in this car. Compared to even the best of the performance cars, this car chews up corners without looking back, leaving most of the rest of the pack at its rear.

However, there are still areas where the MINI’s performance can be improved. That’s not surprising, of course, since the design and development of a modern car is a balancing act. A wide variety of vehicle specifications are affected by laws and regulations. Fuel economy, smog emissions, and crashworthiness requirements all challenge designers by adding weight and putting limits on engine performance.

Designers also have the problem of deciding what the market actually wants in a car. Most auto journalists and some potential customers want a car to be fast off the mark, capable of high speeds, and able to corner without body sway. At the same time other buyers simply want a car that is quiet, comfortable, and smooth-riding.

And all of this regulation-following and customer-pleasing has to be put together into a car at a price that will be competitive in the marketplace and still produce a reasonable profit. So automobile designers and engineers have to make compromises.

The great thing about the MINI is that the basic platform is well-designed and very well put together. So once you’ve decided what kind of a MINI owner you want to be, you can make the changes you want so that your car won’t be just some product planner’s package of compromises. And with some knowledge and care, you can make your changes without having any bad effects on the overall quality and reliability of the car.

So if you will all take your seats, we’ll start the first class in “Maximizing Your MINI 101.” In this first class, we’re going to focus on the principles of making the MINI make more power. We can do that because the steering, handling, and braking are all well above average, so we can save those factors for a later class.

Join Your Many MINI Friends

Sure your MINI will be great for all the normal stuff, getting to work and out in the evenings, transporting you and your luggage on trips, or moving furniture, plants, or whatever else has to be moved from one place to another on the weekends. But there’s no substitute for just taking the car out on a weekend for the sheer pleasure of driving.

If you can combine that with some friendly comaraderie, all the better. And there is where the MINI will excel. When Minis were first introduced in the sixties, their owners immediately recognized that they were a special group of people, able to appreciate the finer things in automobiling, and Mini clubs rapidly grew up all over the world.

Those clubs remained active throughout the dark years when Minis weren’t even sold in the United States, and were a ready-made network of friendship and support when the new MINIs were first introduced. Recognizing the common appeal of old and new Minis, the club members were among the first to line up to try and buy the new MINIs, and the clubs welcomed the new owners with open arms.

Today, any assembly of club members will still include a few of the old classics, but the majority of the members will be driving new MINIs. It’s easy to become one of those members.

All clubs arrange frequent tours to allow members to get their cars out on the good roads in their areas, as well as organizing social and charitable activities around their cars. You’ll be surprised at how many activities are available.

You’ll also probably be surprised at the wide range of backgrounds and interests represented by people who have been drawn together by the attraction of this new car. Membership in most of these clubs will span every age, from new drivers to old veterans, and their day jobs will cover every occupation and endeavor.

The nice thing is that, regardless of how much different the members are from one another, you’ll all have one common interest in your MINI, which means there will always be something to talk about as you get to know one another. As one member said recently, “I was surprised at how many friends I had that I hadn’t even met yet.”

In the appendix to this book, we’ve listed the contacts for as many of the clubs as we could find at press time. For current information, check with your local MINI dealer, who will know if there is a MINI club in your area, and it won’t take you long with an internet browser to find a current list of clubs.

If you can’t find a local MINI club, maybe now is the time for you to start one. It won’t take much effort. Find a local restaurant or pizza parlor with a back room you can reserve, make up some flyers announcing a meeting in a month or so, then stick them on any MINIs you see. Offer to work with your MINI dealer to start a club. In no time, you can have your own local club.