Improving Vehicle Performance: Modifications for Better Acceleration

Automotive customization has become very popular in recent years, but it has a history as old as the car itself. Even with the advanced stage that car design has reached, many consumers still feel the desire to improve upon the manufacturer's product. Some want better fuel economy, some want improved acceleration and handling, and others want a smoother, quieter ride.

In this article, we are going to focus on improving acceleration. Some of these vehicle modifications can actually improve fuel economy as well. This article is intended for people who own 'average' cars and economy cars. If you are looking to improve your Corvette or Porsche, your best bet is to go to a speed shop and seek professional guidance, as those types of vehicles are already tuned for high performance, and replacing stock parts with just any performance parts will probably not give you much, if any performance increase.

A good rule of thumb when adding performance parts is to start from the outside, and work your way in. This means that you should start by replacing the intake and the muffler, reducing airflow restrictions from the extremities of the intake and exhaust systems before replacing parts that are closer to the engine. This is where planning comes into play- if you just want a little gas mileage improvement, or a minor acceleration boost, simply upgrading the muffler and adding a performance intake will do.

Choosing a muffler- for commuters who want a simple MPG increase, a performance muffler may do you some good, but you may want to shop around for one that has good airflow characteristics without making too much noise. For those who intend on making larger horsepower increases, you're going to need to decide just how big the exhaust pipes will need to be. For turbo and supercharging applications, a very large muffler will be desirable, and you'll want to start with a large muffler so that you don't need to buy a new one later. In fact, you should probably start by buying a cat-back system to save yourself some time and effort. If you insist on having a custom exhaust system, the fewer turns in the piping, the better, and larger is not always better. Determining the right size depends on the size of the engine and other factors. It's best to do a little research to find out what is right for your application.

The next components to replace are the exhaust manifold and the throttle body (or carburetor). There are many exhaust manifold options- including different designs and finishes. For four cylinder engines, 4-2-1 and 4-1 designs both have different performance characteristics, and a little research will help you decide which is best for your needs. A larger throttle body may or may not be commercially available for your vehicle. If you cannot find one, a little research might reveal that a throttle body from a different car will fit yours.

If you intend on adding turbo or supercharging your engine, I recommend that you do not do it to an older, high mileage engine, and you should also have your engine rebuilt with this application in mind, or it may not last long.

Underdrive pulleys are a popular way to improve performance. Basically, your original pulleys are replaced with lighter and smaller parts. There are pulleys available that bolt on to your existing ones as well. The belt driven components of your engine get turned more slowly with this modification, so you need to do a little research to make sure that this is not going to hurt your engine, as the water pump or oil pump could run from these belts. This can result in a few horsepower at the wheels if you're lucky.

Weight reduction does wonders for both fuel economy and acceleration. Losing 100 pounds results in about .1 faster 1/4 mile times. It's up to you what you want to get rid of- depending on your goal, you could get rid of most of the seats, replace the windows with lighter plastic or plexiglass, cut out body parts, tear out the dash and door panels, etc. Be careful that you don't weaken the structure of your vehicle, and make sure that these modifications are legal in your area. In extreme cases, a rollcage is recommended.

Any drivetrain parts that can be replaced with lighter versions will also help- moving parts cost twice their weight in terms of energy loss- not only does it take energy to get the part moving, but the vehicle has to haul the part around as well. Light weight tires and wheels will help make your vehicle faster, too. For cars equipped with manual transmissions, a lightweight flywheel can help with acceleration. Replacing the clutch with a performance part is recommended if you're going to do this. Labor-wise, it's almost the same job.

In general, lower gear ratios result in better acceleration. Of course there's a point of diminishing returns. Finding a close gear ratio transmission for your economy car may prove difficult and the part is probably very expensive as well. Slightly shorter tires can help in this area- but a little goes a long way: about %3 smaller than stock should do the trick. Keep in mind that with different sized tires, your speedometer will read differently. I've read somewhere that speedometers are usually off by about 5 mph from the factory to reduce speeding anyway.

Having your intake manifold polished (sand-blasted) can improve airflow, resulting in some performance increase. You can actually make the passageways slightly larger by doing this.

A performance computer can make significant improvements in engine performance, but be careful, as you can damage your engine with the wrong settings.

Performance fuel injectors can make a significant improvement in horsepower when used in conjunction with a high flow intake and exhaust system. You may want to look into performance electrical components (coil, wires, plugs) to go with these mods as well.

Timing adjustments can yield an improvement in acceleration when used with high performance fuel, but then you'll risk damaging your motor if you use lower grade gas.

On some vehicles, you can replace the cooling fans with electrical fans, and you can also replace the water pump with an electrical pump as well.

Some engines can handle displacement modifications, which include having the cylinders bored, and having the pistons replaced with larger ones. Another option is finding a larger engine altogether. There are a few popular engine swaps for different cars, and a quick search of vehicle-specific forums should reveal what options are available on your particular car.

As you can see, there are many, many options available to someone with enough time and money on their hands. How far you want to take it is up to the individual. It's been said that with enough time and money, anything can is possible.