The Honda VTX 1800 is a cruiser-style motorcycle with a 1795 cubic-centimeter V-twin engine, designed for relaxed cruising and medium-distance touring. Although the engine has a large capacity, gains in horsepower, torque, fuel mileage and driveability often come with aftermarket parts. The easiest gains come from modifying the intake, exhaust, and/or ignition.
Any engine must breathe fresh air and expel spent air. The easier it is for the engine to suck in fresh air, the more power it can make. An air filter is necessary to keep dirt and grit form being sucked into the engine. However, most reduce air flow too much because the filtering medium is corrugated paper. High-performance free-flowing filters use oil-impregnated foam as the filtering medium which allows air to flow through more easily, while still providing adequate filtration. Since intake air flows more freely, it increases horsepower.
The VTX 1800 is a fuel-injected motorcycle. The addition of an ignition module allows the owner to tune the motorcycle's fuel map. The engine can be tuned to increase horsepower, torque, fuel mileage and even move the torque and horsepower curves for better engine response and driveability.
Just as an engine needs to intake fresh air as easily as possible, it also needs to expel spent gasses. Stock exhaust systems are often very constrictive in order to meet noise and emissions regulations. This means that the engine has to work harder than necessary to push the spent gasses out of the engine and down through the exhaust system. The stock exhaust system can be replaced with a free-flowing exhaust system that will flow gasses without slowing them down as much, freeing up horsepower. Aftemarket exhaust companies sell complete exhaust systems that increase power while still meeting noise regulations.
Although each of the above-mentioned tuning tricks increase power on their own, combining them allows you to get the most power and efficiency from your VTX 1800. For example, while an air filter helps the engine's air intake ability, that benefit increases after combustion with a free-flowing exhaust. A freer-breathing engine allows you to change the ignition or fuel delivery maps with an ignition module, to take advantage of the gains in intake and exhaust.
