Every car that’s ever left the showroom floor has been compromised in some way. Manufacturers have to jump through all kinds of different hoops to make their cars comply with emissions regulations, crash safety standards and the day-to-day reliability and usability expectations of the average motorist, so it’s impossible to create a road-legal vehicle that’s truly without compromise.

Perhaps the most extreme road-legal car out there right now, the Aston Martin Valkyrie, still had to be dialled back from a performance standpoint to meet legislative requirements. That’s why there’s a separate track-only version, the AMR Pro, which doesn’t have to meet any rules at all (apart from track day noise restrictions). It’ll lap a given circuit several seconds faster than the road car as a result.

Why does all of this matter? The point is that every car leaves something on the table in terms of performance. While the manufacturer was restricted by legislation, you aren’t. So, if you want to boost your car’s performance - even if it means sacrificing a little of the standard car’s reliability and refinement - there are plenty of options available to help you.

If you’re bored of your car’s current power output and feel the time is right to upgrade, this is the guide for you. Below, we’re going to explain how you can boost your car’s power output and which mods you should focus on, starting with more budget-friendly options and ramping all the way up to extreme, money-no-object re-engineering projects.

How to increase the horsepower of your engine

Before we get into the specifics and cover which mods you should be adding to your shopping list, let’s first talk about how those engine mods work.

As you’re probably aware, a petrol-powered internal combustion engine draws in air, mixes this with fuel in the combustion chamber and adds a spark to create a small explosion, which in turn pushes the pistons up and down and turns the crankshaft, which (cutting a long story short) then transmits power to the wheels via the gearbox, differential and axles.

The more ferocious each of those little explosions are, the more horsepower and torque your engine will produce. Sounds simple, doesn’t it? Broadly speaking, every engine mod you carry out to increase horsepower will fall into one of three categories:

• Air: Anything that helps the engine breathe air in and ‘exhale’ it more efficiently. Think induction kits, air filters and exhaust systems.
• Fuel: Any part that can introduce more fuel into the cylinders, like an uprated fuel pump or larger injectors.
• Ignition: A component that creates a bigger spark in the cylinders, thereby enhancing the efficiency of the combustion cycle. Ignition upgrades can include aftermarket coilpacks and high performance spark plugs.

The only notable exception to this rule is ECU (Engine Control Unit) tuning, because it kind of falls into all three categories at the same time. By tweaking the software inside your ECU, you can alter the engine’s air-fuel ratio (AFR) and ignition timing, optimising every aspect of the combustion cycle to make the engine work harder and produce more power and torque.

On modern vehicles, simply remapping the ECU (without even installing any aftermarket parts) can deliver significant performance gains. This applies particularly to turbocharged performance cars like the BMW M2 and Audi RS3, both of which can see gains of 50bhp or more just from software changes alone.

The best mods to increase horsepower

Now you understand how performance engine parts work and which categories they fall into, let’s take a closer look at which parts are available and what they do.

Bolt-on breathing mods

In terms of engine mods, these are usually the first things that people upgrade. By breathing mods, we mean air filters or induction kits and exhaust parts, including performance manifolds, sports catalytic converters and straight-through back boxes.

Relatively affordable and simple to install, breathing mods are produced for a wide variety of cars and can deliver significant power gains, particularly when paired with an ECU remap (more on those in just a moment).

The performance enhancements these mods deliver is just one of the reasons why they're so popular. Induction kits and free-flowing air filters not only improve the look of your engine bay, they make your engine’s induction sound louder and more exciting, amplifying the sound you hear in the cabin. If your car is turbocharged, fitting an induction kit will mean you can hear more turbo noise when you let off the throttle - and trust us, that never gets old.

The same applies to exhaust upgrades. With an aftermarket exhaust fitted, your car will sound a lot more aggressive and exciting under acceleration, making every drive that bit more fun.

Fuel system upgrades

Although they’re a little more involved to install, fuel system upgrades are another cost-effective way to increase the potential of your engine. Installing a high-performance fuel pump or injectors will give you additional headroom to turn up the boost while maintaining a safe AFR, although you’ll likely need a remap once you’ve altered the fuel system to prevent the engine running rich.

ECU remaps

ECU remapping has been a cornerstone of the tuning world since the 1990s, when fuel injection became the norm. As we’ve already mentioned, ECU tuning can make a real difference to your car’s performance when it’s done right, and for comparatively little money.

When you take your car to an ECU tuning specialist, they’ll hook your car’s ECU up to a laptop and make changes to your engine’s fuelling and ignition timing, optimising its performance throughout the rev range. If your car is turbocharged, they may also be able to increase the boost level for even more performance.

Combine some breathing mods with an uprated fuel pump or injectors, fresh spark plugs and a remap, and you could see significant power gains.

Forced induction upgrades

If your car is already turbocharged, fitting a bigger turbo would be the next step on your quest for more power, assuming you’ve already added breathing mods, fueling upgrades and had the ECU remapped. A bigger, aftermarket turbo can push far more air than its smaller stock counterpart, delivering a whole lot more power and torque. You will notice a little more turbo lag, however.

If your car is naturally-aspirated, you can add a turbo kit to it - but this is a risky move in most cases, and could severely impact the car’s reliability if it’s not done correctly.

Internal engine changes

Once you upgrade your turbo (or install one), you’ll likely be nearing the limits of what your engine’s internal components can handle. Standard conrods, pistons and other components all have safe power and torque limits, so rebuilding the engine using lighter, stronger components will be necessary if you’re shooting for even more power.

Complete engine swaps

Still not got enough power? There’s no mod more drastic than a complete engine swap. From rotary engines in Corvettes to V8s in MX-5s, we’ve seen all kinds of crazy concoctions over the years. In theory, pretty much anything is possible if you have the budget and engineering know-how to get it done!

Some cars have more tuning potential than others

Bear in mind that the availability of aftermarket engine components will vary significantly depending on the car you drive. Some cars have a whole lot more tuning potential than others, and it’s the cars with plenty of potential that you’ll see most companies producing parts for.

In terms of German cars, it’s machines like the M2 and RS3 we mentioned earlier that have the most aftermarket support. Other notable models include performance Ford models like the Fiesta ST and Focus ST and RS, as well as Japanese sports cars like the Nissan Skyline, Silvia and Toyota Supra.

You’ll notice that all of these cars have one thing in common: they’re turbocharged. It’s much easier to squeeze extra power out of a turbocharged engine than it is a naturally aspirated one; adding a selection of bolt-on parts, upping the boost pressure and carrying out an ECU remap is enough to deliver gains of 50-100bhp on many of these models.

If you drive a naturally-aspirated car, don’t expect to be able to extract much extra power from it without carrying out serious engine work. We’re talking high-lift cams, lightened, forged internals, independent throttle bodies, a standalone ECU… mods that will set you back thousands.

So, if you’re looking to buy a car you can upgrade and extract more power from, choose wisely. Unless you’re ambitious (and deep-pocketed) enough to carry out an engine rebuild or aspiration conversion, sticking with a factory turbocharged engine is your best bet.

Get your first engine mods here at LK Performance

Ready to get started and upgrade your engine? LK Performance is one of the UK’s leading suppliers of performance parts, stocking everything from alloy wheels through to coilover kits, engine upgrades and styling accessories.

Here, you’ll find everything you need to get started on your quest for more horsepower, from induction kits through to complete exhaust systems. Check out our range of engine tuning parts today, or get in touch with our team of experts for advice - we’re always here to help you get the parts that are right for you.