If you’re anything like the countless youths and youths-at-heart learning about how to make their cars accelerate faster, stop quicker, and corner harder, you may have come across some mods that don’t quite live up to the hype—because they don’t actually do anything. Here are five of the worst offenders.

5. Test Pipe

If you were picketing VW’s headquarters with snarky homemade signs the day after Dieselgate broke, then you may want to skip this particular morsel of information. As it turns out, there are people in the world that don’t care about the level of emissions their car puts out and simply want the most performance that the engine can produce. One of the most widely accepted on-road mods that is legally for off-road use ONLY is called a test pipe, or a catalytic converter delete.

For those that don’t know what a catalytic converter does, it essentially houses an element that burns off the bad gases coming out of your engine. It does this by having the escaping gas go through a filter, with the gas on the other end being considerable safer to ingest by you and the entire reticulated chipmunk population. A test pipe replaces this system with a straight-through pipe, with the idea that a more direct flow increases power to the engine.

While this may be the case with some older turbocharged and supercharged engines, where there is a benefit to freeing up the extremely restrictive exhaust, most exhaust systems on newer engines don’t suffer from being catastrophically restrictive, and most stock engine computers certainly can’t account for the change in exhaust flow on the fly.


Not only will no respectable shop install this for you since they could incur a federal fine for screwing with a manufacturer’s emissions system, but it won’t do a damn thing for your engine’s performance, you’ll likely get a Check Engine light, and you’ll be on Al Gore’s hit list - and I hear he’s surgical with a rifle.

If you’re concerned about flow, pick up a quality high flow catalytic converter instead, with an increased diameter exhaust, coupled with a tune of your car’s engine management system. You’ll at least get some measurable gains without any of the headache associated with knowing that you single-handedly caused the next ice age.

4. Race Fuel


Don’t get me wrong - race fuel does make power in that it creates an environment where detonation (meaning premature combustion) is very unlikely, and therefore you can crank up the boost, nitrous, or timing. However, if you have car that isn’t heavily mechanically modified, race fuel will do absolutely jack shit.

It may even make things considerably worse, as most race fuels are leaded, unlike the unleaded fuel that comes out of a regular gas station, meaning the fuel is incompatible with your catalytic converter and will clog it up in short order, and brings with it the possibility of fouling your oxygen sensors after continued use. In a race car with engine tuning maps and hardware specifically made for it, race fuel makes sense.

For your consumer-grade car taking a track pass on Sunday and driving to work on Monday, race fuel won’t do anything.


3. Adjustable Lowering Springs


From the factory, there’s a trade-off between handling and comfort when it comes to a car’s suspension. The more of one you have, the more of the other you lose. That’s why the most comfortable cars are often the ones that can’t take a turn without involuntarily going for the car flip world record and the ones poised for track times make their drivers four inches shorter after every race.

However, if you’re just after performance and willing to ignore the comfort consequences, the aftermarket will allow you to tip the scales in your favor. One of the most effective ways you can make your car handle better is to install a good set of struts and lowered springs, or a tailor-made adjustable coilover suspension system. What these do is make the car stiffer, allow it to handle more predictably, and lower the car’s center of gravity, making it less likely to pitch and roll on spleen-compressing right handers.

Having said that, one of the easiest ways to screw up your car’s handling is with a set of universal adjustable lowering springs.


In order to have a car handle well, the springs and struts must be dialed in, which means that the spring rates of each axle should be matched to the weight balance of the car, depending on what kind of setup and ride quality you’d like to have. Also, the strut or shock absorber needs to be stout in order to take the stresses of a firmer system. With a cheaply made pseudo-universal system like the one pictured above, not only do you not have any indicator as to what the spring rates are, but if you put a drastically lowered, likely super-stiff spring onto a stock strut or shock, you’ll kill any semblance of ride quality, bottom out your suspension and blow your shock absorber with unparalleled quickness. Instead, get a set of struts and matched springs from a reputable manufacturer, or an adjustable coilover setup that doesn’t require assembly. Your passengers will thank you.

2. Short Ram Air Intake


First off, the name “short ram” is a misnomer. Ram Air, no matter what your Trans-Am owning uncle says, doesn’t actually cram any extra air in the cylinder past what a traditional cold-air intake would do. The theory, in a nutshell, is that if you place your air intake path on the car in such a way that it takes advantage of the moving air flowing over the car, it’ll use the car’s momentum to pack all that air in the engine, making for a bigger bang and more power. SCIENCE!

The problem is that in order to have this happen with any sort of reasonable efficiency, you have to be traveling orders of magnitude faster than any speed limit in the country. But even if, for the sake of argument, ram air on consumer-grade cars worked, a short ram air intake system wouldn’t.

While it does shorten and smoothen the intake stream over whatever stock airbox and resonator assembly comes in cars nowadays, allowing the air a more direct path to the combustion cycle, it does so by being placed in the extremely hot engine bay, where air pressure is often lower than it is outside, which is a no-no for power.


This sort of intake configuration, in naturally aspirated cars, is particularly susceptible to heat soak and can let a considerable amount of ponies out of the stable, never to return. Sure, the setup makes an interesting induction noise but not much else. You’re better off buying a good panel filter for your stock airbox or, at most, a well-engineered cold air intake that takes air from outside the engine bay which is colder and thus more dense.

1. Spark Plugs


If anyone ever tries to sell you an aftermarket spark plug with promises of horsepower gains, they’re one of two things: stupid, or a liar. All spark plugs do is start the combustion cycle, with two possible modes: on and off. Like an HDMI cable, either the signal gets there or it doesn’t. The only gains you would ever get is when you replace badly worn plugs that are no longer efficient.

Hell, here’s spark plug giant NGK with an explainer if you don’t believe me:

A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle’s computer can make adjustments so that vehicle operation seems smoother and more seamless.

Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don’t understand is that most newer car engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can’t burn more fuel because there is no more fuel to burn.

When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.


However, that doesn’t mean all spark plugs are created equal.

You may have heard the term “hotter” or “colder” plugs. This refers to the spark plug’s heat range, which dictates the temperature at which the spark plug is most efficient. That’s why naturally aspirated cars, which tend to have leaner burns and produce higher combustion temperatures, would require a hotter plug. Turbocharged and supercharged cars would have a more rich air/fuel mixture, and thus would likely require colder plugs.

The center electrode may also be made of various conductive elements, like copper, platinum and iridium, but the only thing they’re distinguishing is the longevity of the electrode before it needs replacing. Copper tends to be cheapest and wear out the longest, then platinum, then Iridium. No performance gains can be had from any spark plug. Whatever the manufacturer recommends will work just fine for any car that’s more or less stock.


There, I just saved you some cash and hopefully didn’t burst too many bubbles. If you want to know a few mods that do transform the way your car drives for low cash, take a gander at this.

Tavarish is the founder of APiDA Online and writes and makes videos about buying and selling cool cars on the internet. You can also follow him on Twitter and Facebook. He won’t mind.