Increase Your Car's Horsepower!!

1. Reduce the cars weight. Do not store anything in trunk, change your steel hood to an aluminum one (if available), or better yet a carbon fiber hood. If these are not an option, you can excise some extra metal underneath the hood.Using lighter aluminum rims instead of steels one will help as well. 

2. Change that exhaust system. Any leaks in the exhaust will reduce horsepower. 
Removing the catalytic converter and straigh piping the exhaust will increase the horsepower of your vehicle. Replace or modify the exhaust header. If you need more horsepower above 6000 rpm, an aftermarket header can provide another 3-4 peak HP. Useless unless cat-back exhaust upgrade done first. 

3. Change that stock air filter to a perfomance air filter such as K&N. 
Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Some newer cars are using polished intake manifolds toeliminate air resistance there. Bigger air filters and reduced intake piping can also improve air flow. 

4. Reprogramming the ECU. You can also add a chip. Some people 
have argued that the horsepower chip does not increase HP, but others 
have said they have had remarkable results with these chips. 

5. Boost your octane. 

6. Change your engine timing. 

7. Replace the flowmeter in the intake tract. If you will be using the motor above 6000 rpm frequently this can provide another 5 or so peak HP. 

The flowmeter is very restrictive and limits HP above 6000 rpm, replacing it eliminates the bottleneck. The OEM flowmeter flows 165 CFM while a bone stock 1.6 motor at 7200 rpm flows 178 CFM, this means that the OEM unit is undersized for high rpm usage, the change probably won't be noticed below 6000 rpm. 

8. Shaving the head. Compression = power. Shaving the head .010" will increase the compression ratio about a /4 point. I dyno'd this and it was good for about 4 HP and 4 ft lbs of low rpm torque. It is very noticeable across the entire rpm range. I don't know what the shaving limit is but I have not heard of anyone going beyond .025". 

FYI, the shop manual limit is .008" for 1.6 and .004" for the 1.8. As long as you have the head off you might as well R&R the valve seats too. 

9. Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (prior to the spark plug igniting it). Higher octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high octane gasoline - their engines are using higher compression ratios to get more power. 

10. Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger. 

11. Change Underdrive pullies - Usually consist of crankshaft and alternator pullies. These increase horsepower by reducing accessory drag. Pullies can benefit almost any engine, large or small. Installation is a snap, but there are a few disadvantages to underdrive pullies. Because the alternator is turning slower, it won't be able to produce the current needed to keep the battery charged when running at idle. If you leave your truck on idle for extended periods of time, you may want to only install the crankshaft pulley. An underdrive pulley set can add up to 15 horsepowerto your engine and can also improve fuel economy.

Any car that you buy today from a normal automobile manufacturer has a number of compromises built into it. These compromises are caused by several factors: 

The attempt to fit the car into a certain price range 
The need to meet emissions standards 
The desire to provide maximum life and reliability 

These compromises often give you lots of room for improvement in terms of performance! There are many different ways to create more horsepower from a stock engine. Here are several examples (generally in order from least to most difficult/expensive): 

Change your computer chip -- sometimes, but certainly not always, you can change a car's performance by changing the ROM chip in the engine control unit (ECU). You usually buy these chips from aftermarket performance dealers. It is valuable to read an independent review of the chip you are contemplating, because some chips are all hype and no performance. 

Let air come in more easily - As a piston moves down in the intake stroke, air resistance can rob power from the engine. Some newer cars are using polished intake manifolds to eliminate air resistance there. Bigger air filters and reduced intake piping can also improve air flow. 

Let exhaust exit more easily - If air resistance or back-pressure makes it hard for exhaust to exit a cylinder, it robs the engine of power. If the exhaust pipe is too small or the muffler has a lot of air resistance then this can cause back-pressure. High-performance exhaust systems use headers, big tail pipes and free-flowing mufflers to eliminate back-pressure in the exhaust system. 

Change the heads and cams -- Many stock engines have one intake valve and one exhaust valve. Buying a new head that has four valves per cylinder will dramatically improve airflow in and out of the engine and this can improve power. Using performance cams can also make a big difference. 

Stuff more into each cylinder - If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder (in the same way that you would by increasing the size of the cylinder). Turbo chargers and super chargers pressurize the incoming air to effectively cram more air into a cylinder. Many manufacturers make aftermarket turbos and super chargers for many different cars. 

Cool the incoming air - Compressing air raises its temperature. You would like to have the coolest air possible in the cylinder because the hotter the air is the less it will expand when combustion takes place. Therefore many turbo charged and super charged cars have an intercooler. An intercooler is a special radiator through which the compressed air passes to cool it off before it enters the cylinder. 

Make everything lighter - Lightweight parts help the engine perform better. Each time a piston changes direction it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes. Lighter parts also allow the engine to rev faster, giving it more horsepower. 

Increase the compression ratio - Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (prior to the spark plug igniting it). Higher octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high octane gasoline - their engines are using higher compression ratios to get more power. 

Increase displacement - More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger. 

As soon as you start to try increasing displacement, you might consider the economics of buying a new high-performance engine and trying to fit it into your car -- it may be easier and cheaper! 

**Info taken from a source**

1. Change the Ingition systems- Ignition Systems are also another source of added power. A performance iginition control can increase spark output over the whole power range. A complete ignition system upgrade should include new wires, and the spark plug gap may need to be increased to take advantage of performance ignition system. Older trucks usually benefit more than newer trucks. Although some truck owners experiemce little or no difference with a new ignition system, others find mild gains in fuel economy and power. 

2. Turbo And Super Charger - To get maximum horsepower out of almost any engine, a supercharger or even a turbocharger system can be bolted on for an easy 40-50% increase in power, often adding 100 or more horsepower to a V8 engine. 

3. Nitrous Oxide System - Nitrous oxide works by delivering high amounts of oxygen to your engine. Nitrous oxide is stored in high pressure tank at about 900 psi. At this pressure, nitrous oxide is in a liquid form. When it is released into an intake manifold at atmospheric pressure, it changes to a gas and expands, giving off high amounts of oxygen. As you add this boost of oxygen, you also get a lower manifold temperature because of the phase change of the nitrous oxide from a liquid to a gas. But too much oxygen can become a problem. High levels of oxygen alone will cause detonation and engine damage. To keep things safe, the ratio of air/fuel must be kept in check, so additional fuel must be delivered when the nitrous system is running. To keep enough fuel running into the engine, 3/8-inch fuel lines are a minimum, and a high-output fuel pump is also necessary.

Can you also give the details of the cost and the time taken for installing it?

cost and time varies from person to person and place to place