When it comes to modifying a road car, the mods come under two categories – styling or go faster (even if that means going slower – like braking). There are one or two mods that sit between the two, but that’s the simplest way of breaking them down.
I’ve assumed that you have some mechanical know-how and the tools to go with that. But, I’m not talking about full engine rebuilds or bare shell restoration work. These are simple(ish), cheap mods that you can do in your yard or garage – not a race-equipped workshop.
Let’s start with the basics.
Before deciding to mod your car, you should make sure that it’s in good working order. Regular service should take care of regular issues – new sparking plugs, filters, oil, maybe some HT leads. You may as well start with what the factory intended from new. Same for the chassis. Ensure that your shocks aren’t leaking, brake pads & discs are usable, tires are within safe limits.
You should also consider mileage. If you’re looking at introducing lots more power, a 150,000-mile beater is only going to wear out faster.
One final point. You may sink some serious money in mods into your car. However, if you’re intending on selling it soon after, you won’t get your money back. In fact, you may even find it harder to sell.
So your car is mechanically OK, you’re ready to get busy.
And that’s a great place to start – a performance air filter. There are a number of well-known brands producing them. Perhaps the most popular is K&N. Although they’re at the higher end of the price range, they can be cleaned and reused time and again.
Fitting a typical air filter usually requires little to no tools, maybe the odd screw or Torx driver. Unclip the filter housing and swap the filters over, it really is that simple. You can expect gains of anywhere between 3 – 5 horsepower. However, I’ve seen some anomalies where the vehicle finds 10+ bhp.
Of course, some cars have their filters buried under the front fender, behind the headlight, or what have you. If you’re not sure of the location, either a quick internet search or call to a dealer will help.
This is slightly tricky. Performance oils can be a good thing, but they can also ruin your engine. If your engine has run on mineral or semi-synthetic all of its life and is high mileage, then doing an oil change for something like Mobil 1 will ‘glaze’ the bores. That means that the oil will just work its way past the piston rings and burn in the cylinder, leaving you smoking like a coal fire.
For what it’s worth, unless your working with a fresh engine, I’d stick to the manufacturer’s stated preference. However, it may be possible to find a performance variant of that.
The cooler you can get air going into the motor, the more power you can make. Depending on the car (mainly the popularity with aftermarket tuners), it may be possible to buy an off-the-shelf solution to cooling the air. Look for something that moves the intake box away from the heat of the engine or an insulation kit to reflect the heat.
Getting slightly more technical, it’s possible to buy thermal insulation plates that fit between the engine plenum and intake manifold. This does, of course, require the very top of the engine to be stripped off. Typical gains are around 5 hp.
If there’s no regular kit, or you can’t find a thermal spacer, then try wrapping the intake box with a reflective insulating material.
Gadgets, Gizmos, Gimmicks, and Trash
In my thirty or so years in automotive engineering, I’ve seen everything from a ‘fan’ that fits inside the intake pipe to chemistry-defying additives and electronic thingamajigs that are sold under the pretense of either improving fuel economy or improving power.
It’s true that manufacturers need to tune their fuel-injection system to cater for a hundred different markets or events. It’s also true that they need to err on the side of caution rather than horsepower. Today’s cars, in particular, are super tight on emissions.
However, to make a gain from that artificially imposed restriction takes more than adding an extra resistor to the air-temperature sender, or giving the air a bit more ‘swirl’. It can only really be done by changing the tuned state of the car. It’s most commonly done through agents that can remap the engine, or by purchasing a performance ECU (Electronic Control Unit) that can be fitted at home.
In days gone by, the exhaust system was one of the easiest upgrades to make to any car – more often than not, the manifold would be a heavy, cast-iron lump that roughly followed an exhaust shape, the main pipe would be made of heavier-gauge steel and the backbox was just a mess of design – so long as it fitted where it needed to.
Today, things are different because of the ever-increasing drive for fuel economy. While still keeping a decent level of power, the big brands spend more on exhaust design than ever before. Even the smallest of compacts typically has a well-designed, individual branched manifold, usually made from stainless steel.
Not much improvement to be had there. Yes, you can upgrade, you may find a little extra power, but it’s expensive.
With that said, if you look at the other end, things are generally better. Car makers want their standard cars to be an old plain Jane with nothing standing out to make them lose sales (it’s a super competitive market.) This means they’re quiet – plenty of baffling, max noise reduction, max strangulation.
Replacing a standard exhaust for something with a little more zip is relatively straightforward, even more so if you’re just losing the box at the back. Better still, depending on state regulations, it’s possible to fit a ‘de-cat’ or cat-bypass pipe which could free up quite a few ponies – anywhere between 5 – 10%.
We’ve dealt with some minor engine upgrades, which if done correctly could see quite an improvement in power over a standard car. My thoughts would now turn to transferring that power to the road, or coping with it. Next, I’d focus on chassis, suspension and handling mods.
Most standard brakes fitted to cars will cope with quite a bit of extra power – especially with a competent driver that’s looking forward rather than just in front of the car, so a brake upgrade isn’t necessarily crucial, but if you’re looking for track use, then it’s a must.
You can have all the power in the world, but if you can’t slow your car enough for corners then it’s to no advantage whatsoever. There are three components to consider when upgrading your brakes.
A disc upgrade can be many things – larger diameter, thicker, vented, grooved; perhaps even all four. Larger discs apply more force to actually slowing the car down. It’s usually in conjunction with a different caliper (which in itself can be an upgrade.) The grooves and vents help to keep the discs cooler for longer. This means that brake fade shouldn’t be quite so prevalent.
If you’re intending on swapping the calipers, you may find that they have bigger pistons, or even just more of them – either way, it results in a higher clamping force. A word of caution, though. Increasing the diameter of your discs may mean a change in wheel size to accommodate the bigger discs.
Standard road pads are designed to work in all conditions, come rain, snow or ‘shine, they’re also made to offer greater comfort levels – aka, reduced noise. Fitting harder pads could result in better braking. They often work at higher temperatures and are more abrasive. But, that does have a cost.
Being more abrasive means that they’ll be harder on the disc. There’s a good chance that they’ll be noisy. Perhaps even ‘ringing’ or squealing until fully-warmed up.
This is an easy and relatively cheap upgrade. It’s only really worth doing if you’re intending on doing some hard track-driving. If you’ve ever noticed your brakes fading under hard use, the chances are that it’s down to the fluid boiling. This means less pressure exerted on the pads.
A higher specification brake fluid will stop that happening, but the nature of brake fluid is ‘hygroscopic’. This means that it takes in moisture from the atmosphere. A higher-spec fluid will need replacing on a regular basis to stop that happening.
I briefly mentioned wheels when talking about brakes, but even if your upgraded brakes fit inside a standard wheel, there’s a good argument for changing them.
First up, and perhaps the most important – choosing the right aftermarket wheel will of course significantly change the look of the car, but more importantly, your goal is to lose weight – wheels, tires, and brakes are what’s called ‘unsprung weight’. The lighter you can get it (within reason), the better your car will handle, stop, turn, and brake.
Secondly, changing the wheel size could give you a better choice of tire. We’re talking about higher speed rating, better grip, seasonal, etc. It’s just another small modification that you can make that will change the nature of the car.
A decent set of tires can quite literally transform a car. I’ve driven cars back-to-back where the only difference has been standard tires vs. road-legal but sticky tires. You could almost be fooled into thinking it’s a different car. The transformation was vast.
For a number of people, investing in some grippy tires is a no-brainer. Others will always find an excuse not to. After all, tires aren’t cheap and they’ll only wear out. My last hyperbike was fitted with a rear tire that would last for around 700-miles of hard riding.
The choice really comes down to just how far you want to go with the mods. If you’re looking for ultimate performance, then sticky tires are a must.
Adjustable suspension is an absolute must if you’re serious about performance mods, that doesn’t necessarily mean a full-on, super brand like Ohlins. Many of the lower end shocks perform well, at least better than standard, and of course, they have the added bonus of being adjustable, both in terms of how stiff they are (bump & rebound) and ride height.
There are other toys that can be fitted also – things like a modified strut-brace for example, or stiffer anti-roll bars. This really will depend on the car though.
My choice would be to go for some mid-level shock absorbers and have a full (and professional) geometry set up to maximize the benefit. I wouldn’t personally take up too much time with corner-weighting and the like, unless you really are doing a lot of track driving, with a known setup and weight.
The final tool in the armory of the home modifier is weight loss (or at least when it comes to performance). There are no hard and fast rules, no formula (that XX weight is equal to XX hp), but it’s relatively straightforward to work out how much weight-loss you’d need for the equivalent horsepower.
Imagine a car weighing 3,000 lbs., with 300 hp – this means it makes 1 hp to 10 lbs. in weight. What if you lost 100 lbs. of weight? 2,900 lbs. / 300 hp = 1 hp to 9.66 lbs. of weight (going in the right direction), so without losing that 100 lbs. in weight, we’d need to understand how much extra power we’d need to get a similar figure, in this case, it’s around 10 hp:
3,000 lbs. / 310 hp = 1 hp to 9.67 lbs., so we can conclude that losing 100 lbs. in weight would make it feel like a 10 hp increase in power.
Vehicle weight / horsepower = lbs. per hp
Styling it Out
We’ve dealt with pretty much all of the simple mechanical mods you can do, the rest is just styling mainly. I perhaps may be in the minority, but I’m not a fan of adding rear-wings or as many (incorrectly) call them, a spoiler for ‘added downforce’, here’s why:
At the type of speeds you’ll be driving on the road, you don’t have any extra downforce, nor will they really create much downforce, but they’ll ruin your fuel economy. Also, unless you do have a set of adjustable shocks on the car, which can take advantage of the extra downforce, then all you’re doing is ruining the handling.
If you’re looking for performance, then it’s without the wing, but if you’re looking for the ‘Too fast, too furious’ look, then knock your socks off.
For everything else styling-wise, it’s entirely down to personal preference. You want a list of ‘sponsors’ on the rear of the fender, go for it. Tints? Why not? The single blade windshield wiper in the middle of the screen, ala every enclosed racecar, yup.
For me, modifying a car is about making it go faster, stop better and get round turns like no other. I totally get that there’s a huge market that’s dedicated to making a car look like a racecar, even if it’s completely standard underneath – whatever floats your boat.