ALT-5 How to Increase Horsepower
There are a number of different ways to improve your cars' HP output and these range from the cheap, to the very expensive. It all depends of course on what type of car you have and what kind of HP return you are longing for.
I drive a sporty little Toyota Starlet GT Turbo (139+ HP) and I'm quite happy with the output from this "pocket rocket", but to keep it in tip-top shape I service it often.
The cheapest way to maintain HP would be to regularly change the oil and oil filter (extremely important for turbochargers), the spark plugs, induction filter, cooling fluid, ensure wheel brakes and bearings are free-running and if possible, keep using the correct fuel grade for your vehicle. Basically, you've got to keep your engine's insides clean and lubricated and reduce unnecessary drag on the body.
I presume you could also restore your engine to almost its original HP by extracting it from your car and sending it off for a complete overhaul. This is called "reconditioning" and involves the re-honing of cylinders, replacement of seals and rings, and other bits and pieces.
Finally, you could choose another expensive option and purchase a HP/Turbo upgrade kit, available from recognised suppliers. Be sure to get one that's compatible with your make and model, otherwise you could end up fabricating extra flanges and pipes to make it fit!
These kits usually come with all the components you need to install in your engine, but beware; if you are not sure of what you are doing especially if you need to modify the engine interior - get a qualified/professional person to assist you.
Another word of warning; it's quite simple to strip an engine and all of its related components, but it's an entirely different matter if you try to rebuild it without knowing where all parts refit or if they become lost amongst the debris on an untidy garage floor! Where possible, always refer to your vehicle's manual.
If you're not into a bit of oily, hard work, and really want a car with a high performance engine, then just save up and buy an already modified one. Remember, however, that with increased HP comes greater fuel consumption and different handling qualities. The experience from driving a high-powered vehicle is an exhilarating one, so be responsible.