For some people it’s about the excitement of the process as it is about the end result itself. Building a track day car can be as interesting as driving one and it is not as expensive, or as difficult as you might think. However, it’s not free either and you will need some aftermarket parts and mechanical knowledge, or help from a mechanic.
You shouldn’t just use anything you have. Having a family MPV, or an SUV is not the best option for a track day car. Even if you drive a family sedan with lots of power, you should know that cars are abused on the track and that parts on a regular car will hardly endure a day of torture. You need to have a good sports car or build one.
The very choice can differ greatly, depending on the level of upgrades, but you should go for a lightweight car that is well balanced and has strong chassis. Ease of access to parts is also important, since you are bound to change many things. As for the drive layout, engine position and gearbox, this is often a matter of preference. However, most drivers choose a RWD car with a manual. Having the engine in the middle position is the best idea for balance, but most cars have it at the front.
If you want to build a track day car, it should be just that – a TRACK day car. Comfort is irrelevant and this is even more important when you know that vast majority of comfort perks add weight and take some of the power from the engine.
The best rule for weight reduction is to get out anything you don’t need – rear seats, upholstery, much of the dashboard, spare tyre, tools… Some people go so far that they remove even the headlights. Doing that or not, weight reduction is sure to do wonders for acceleration and cornering and it is completely free.
Engine and transmission
There are loads of options here. You can swap your stock engine for a larger one, or you can improve your stock engine to give it more power. The improvements include things like increase in forced induction (provided that you have a turbo, or a supercharger), new intake and exhaust and ECU tuning. If you have a turbo, you have far more room for improvements and they are far cheaper (simple, but well done ECU tuning on a turbo engine can bring up to 20% more power without any issues or new parts), but if you don’t, you will need a lot more work to get your car to respectable power ratings.
The gearbox needs to be paired with the engine in a way that they complement each other. Moreover, depending on the level of improvements, some parts may not be able to withstand the additional pressure. Upping the power by 20% should not be a huge problem for the clutch, for example, but if you build a car with 50% more power, you might need an upgrade in that section as well.
If you aren’t upgrading a sports car, stock suspension needs to go out. Even if it is extremely reliable and well built, it is still tuned for comfort more than keeping the car in line during extreme cornering conditions, so you will need something better. The “something better” is usually installing coil overs which allow you loads of setup room, but there are also cheaper and sufficient sports shocks and springs. If your budget allows it, go for coil overs.
Brakes and tyres
Better brakes are a must. They will last longer and endure the abuse easier and they will also reduce braking times. There are loads of options and you should simply go as far as your budget will let you.
Tyres are often neglected, but they are as important as brakes. They are what keeps you connected to the road, so improving your grip is paramount. However, before you buy new tyres, you should see if you want to increase the diameter of your wheels.
If you experience lots of body roll, you should install a roll cage. This is usually not massively expensive and it will do wonders for confident cornering.
When people want to build a track day car, budget is often a limiting factor. However, it is better to make small upgrades in every of the above segments, than spend all of you money on a massively powerful engine and neglect everything else. This might actually be pretty embarrassing, as you will be faster in the straight line, but any curve will be an insurmountable challenge and losing a race to a car that has 150 hp less is not a fun thing.