Cheap way to add horsepower – Exhaust

When you are trying to get more horsepower out of your engine there is one key thing to remember. More air = More power. Your engine takes in air and fuel then uses a fixed percent of air to fuel ratio combustion which give you power to crank up. There are several ways to add more power to your engine that I already talk about. The next thing I would like to share is the exhaust modification.


Exhaust system include headers, catalytic converter, exhaust and mufflers. Each part plays an important role in performance. Air resistance or backpressure makes it hard for exhaust fumes to exit a cylinder, and it robs your engine of potential power. When an exhaust pipe is too small or a muffler has a lot of air resistance, this can cause nasty backpressure. So, when you upgrade your entire exhaust system to one with larger pipes, you can eliminate this backpressure, therefore allowing air to exit more easily, and giving your ride a big boost in power.

Picture3 exhaust-system

It is very good if you can start with a good quality muffler. One of the easiest things you can do is to get rid of your power robbing stock muffler. Stock mufflers are designed to be as quiet as possible at the expense of horsepower. They are filled with twists and turns that the air has to go through that make them not straight through and awfully restrictive. Plus, they muffle the exhaust too much, and you don’t get the true performance sound from your car. A good quality pair of performance mufflers may set you back just under $500, but this is still a rather inexpensive way to add a noticeable gain in power.

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Next to the muffler, the catalytic converter is the next biggest item on the exhaust that creates the most restriction. The stock catalytic converter is designed to catch as much of the exhaust as possible to ensure that as it flows through the catalytic converter that it trims all of the toxins as it exits. This is good for the environment and to keep smog pollution down, so replacing the catalytic converter can be done in two ways. The first way would be to replace it with a straight pipe. This simply gets rid of it all together. The other way would be to replace it with a high flow catalytic converter.

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Aftermarket headers also have to do with reducing the back pressure of the exhaust. If you already have a cold air intake and an aftermarket cat-back exhaust system then you will feel the power this gives to you.

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Using under-drive pulley to save gas and boost power

Using under-drive pulley to save gas and boost power

A pulley is a wheel on an axle that is designed to support movement of a cable or belt along its circumference. A belt and pulley system is characterized by two or more pulleys in common to a belt. In the car engine, a serpentine belt used to drive multiple peripheral devices in an automotive engine by driving the pulley on each device, such as an alternator, power steering pump, water pump, air conditioning compressor, air pump, etc. This allows for mechanical power, torque, and speed to be transmitted across axles. If the pulleys are of differing diameters, a mechanical advantage is realized.

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An underdrive pulley refers to an aftermarket crankshaft or accessory pulley (such as an alternator pulley) that is designed to drive a vehicle’s accessories at a slower rate than stock parts. Underdrive pulleys usually are marketed as a performance enhancing item that increases the torque and horsepower output of an engine by reducing parasitic drag caused by belt-driven accessories, but more importantly by reducing the moment of inertia


Underdrive pulleys can raise fuel mileage by decreasing load on an engine. An underdrive pulley is a pulley that has a smaller diameter than a car’s stock pulley. These pulleys reduce load on a motor. Specifically, they decrease resistance on the accessory drive belt which is connected to the crankshaft via the crank pulley. By reducing load on the crankshaft the pistons are free to move up and down with less resistance. This means it takes lesser amount of fuel to travel the same distance because you have freed up power in the motor. Usually underdrive pulleys are sold in kits of 2 or 3 pulleys including a new crankshaft pulley and alternator pulley.


All parts should be very easy to assemble and it only required minimum of knowledge about engine. There are many companies out there that sell pulleys made specifically for your car. You need to pick the right one and put it on with our any other turning. Some company claimed for up to 4% gas mileage.

On the other hand, underdrive pulleys are also a relatively cheap way to gain horsepower as well. Underdrive pulleys usually represent smaller diameter alternator, crankshaft, and other engine pulleys that are installed in place of stock diameter pulleys. Independent dynamometer tests have shown up to 15hp increase at the wheels after installing an underdrive pulley. With the size change of pulleys, each accessories runs slower than stock witch take less power from the engine. So “gain” horsepower output is actually means “recover” those engine output.


There are some drawbacks to the underdrive pulleys. When each accessory is not spinning fast enough, it leads to dips in alternator voltage, power assist, and air conditioning effectiveness, especially when idling. A crankshaft or accessory pulley that is not machined or balanced properly can cause severe damage to the engine. As I normally said, be smart to choose those aftermarket parts because you are the one to take the risk.






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Strut bar

Today I would like to talk about the strut bar. Strut bar can also be called strut brace, or strut tower brace (STB). It is very common suspension accessory for the aftermarket vehicles. It usually used in conjunction with MacPherson struts on monocoque or unibody chassis to provide extra stiffness between the strut towers.

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It is my belief that a strut bar definitely does help.  And during the explanation that follows I will try to provide a convincing argument for this.

A strut bar is designed to reduce this strut tower flex by tying two parallel strut towers together. This transmits the load of each strut tower during cornering which ties the two towers together and reduces chassis flex. To accomplish this effectively (especially on MacPherson strut suspensions), the bar must be rigid throughout its length.


Figure 1 shows the forces of interest in a strut bar analysis.  For this calculation only horizontal forces need be considered.  There are of course vertical forces, but since the sum of forces must independently equal zero in both the horizontal and vertical directions, we can concentrate on just the horizontal forces in this analysis.

What a strut bar does is tie the two strut towers together so that they share the load applied at the outer tower.  This gives you twice as much material to deal with the same cornering force and helps reduce fatigue stress in this area.


Many manufacturers have fitted strut braces to performance models as standard or optional equipment. But it is also very easy to add on your car by yourself. With approximate 8 bolts you can add the strut bar on top of the suspension. Although it will void the manufacture warranty, but it should be very easy to remove before you go to the dealer. In addition, as usual you need to take your own risk to modify your car. So please do it smart before you make the decision.

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Timing chain vs. timing belt

In my previous post I simply illustrate the importance of change the timing belt. It is such a pain in the neck that we need to pay over one grand to change timing belt because it is critical. It cost time and money. Certainly you can absolute do it yourself, however miss-timing will caused a catastrophically failure. Many of us would thing why we did not “invent” a non- maintenance timing belt or some equivalent thing so we can save some bucks. Actually before timing belt become popular in 70’s-80’s, most car manufacture use timing chain instead.


Timing chains have been widely used before timing belts popularity explosion in 70’s-80’s.Timing chains look just like the chain on a bicycle, but much greaser. The beauty of the timing chain is that they typically last a very long time. A few car manufacturers recommend replacing them at certain mileage or time intervals, while others claim that the chain is good for the life of the automobile. It really depends on the make and model of the car or truck. The downfall of timing chains is that they are heavier, generally known to be noisier, and if they do break, it is usually catastrophic to all of the surrounding engine parts.

Much like automotive timing belts, timing chains also have tensioners that keep the chain from flopping around. The difference is that timing chain tensioners are nearly always controlled with engine oil pressure. As you can imagine, if the engine oil pressure becomes low for whatever reason, the oil driven timing chain tensioners will lose pressure, and the mechanical engine timing becomes extremely erratic. This will cause poor engine performance and give the chain the opportunity to fail in grand fashion. The other benefit to timing chains is that they rarely have anything to do with the water pump. So replacing them at the same time isn’t nearly as necessary as it is with a timing belt.


Facts of timing belt and chain

– Timing chain requires a quieting shoe. In many cases one of them may serve both roles and two tensioner/quieter shoes could be used.

– Chain is usually heavier per inch length than belt and therefore require stronger infrastructure to hold it in place. In case chain get stretched over time and go above tensioner’s adjustment capability things could go hairy fast. Engine’s timing may become erratic.

– Timing chain in general is very reliable and requires only every so often check-ups.

– Timing chain usually enclosed within an engine case and constantly lubricated.

– Timing belt drive usually quieter than a chain drive. Since belt is lighter it requires lighter support structures and does not need a calming shoe.

– As a result SOHC/DOHC engines could have higher RPMs without worry of an added chain momentum.

– Timing belt must be changed every 50-75 thousand miles along with the tensioner and a water pump if one driven by the timing belt.


It is hard to say which one has the absolute advantage than the other. We know the in 2009 model year trend of car manufacturers moving back to timing chain engine design. Many of them rely on a service data and price/performance evaluation for the size of the vehicle. It is unlikely that general public will know exact figures on timing belt/chain price/performance comparison but we all have our own preferences and that may become a driving force for the future engine models.


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Why we need to change timing belt

Why we need to change timing belt
Timing belt, or cam belt (informal usage), is a part of an internal combustion engine that controls the timing of the engine’s valves. It connects the crankshaft to the camshaft(s), which in turn control the opening and closing of the engine’s valves. As most vehicles on the road have 4-stroke gas engines. During one complete 4-stroke process, the crankshaft rotates twice, and the camshaft(s) will spin once. “Mechanical timing” is what we call the relationship between the crankshaft and camshaft(s) rotation. This, in turn, is really just controlling the movement of the valves and pistons inside the cylinders. The timing belt has teeth to turn the camshaft(s) synchronized with the crankshaft and it’s frequently snake through a series of pulleys and has mechanical or self-contained hydraulic timing tensioners to keep the proper tension on the belt throughout the entire rpm range. These mechanical and hydraulic tensioners and pulleys should always be replaced at the same time as the belt.

Obviously, this is bad news for vehicle maintenance as this internal collision can cause destruction fair amount of engine damage, especially in interference engines. The most common failure will be valve bent by collision with a piston after timing belt breakage. The higher RPM it happens, the more damage your engine will get. Therefore, it’s important to stay ahead of your belt’s lifespan — traditionally replacing it every four years or 60,000 miles (96,561 kilometers) or, in newer vehicles, every 100,000 miles (160,934 kilometers). Mechanical and hydraulic tensioners and pulleys should always be replaced at the same time as the belt. They are all the same age with the same mileage, so replacing them is a great habit and great insurance.

Along with pulleys and belt tensioners, water pumps are often replaced at the same time as timing belts. This is for two reasons. Some water pumps are actually driven by the timing belt itself, and therefore a liability if they are old and worn out. The other reason is because many water pumps, especially on newer vehicles, are tucked behind the timing belt due to packaging constraints. You wouldn’t want to replace the timing belt and then have to take it off again later when your old water pump fails.

As conclusion, it is critical to change timing belt. If your car reach that mileage, go get a new belt kit.

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Worth to install a Cold-air intake?

For different reasons people want to do something on their cars. Maybe their propose is to improve the gas mileage, or they probably want better performance. In this bad economic, I think most people want them both. As the cost of gas going higher, people want “cheap speed” with less gas consumption. Honestly speaking, to me in United States the major cost to a car upgrade is not the parts itself but labor. One of the first choice for an inexpensive Do-It-yourself upgrade part that will cranks more horses with better fuel efficiency is the cold intake. A well-made cold air intake should give you additional 5-10% of output increase.


The principle behind a cold air intake is pretty simple. The cooler air has a higher density, thus containing more oxygen per volume unit than warmer air. But warm air will make engine start better only when engine is cold. Therefore vehicles manufactured since the mid-1970s have thermostatic air intake systems that regulate the temperature of the air entering which providing warm air when the engine is cold and cold air when the engine is warm to maximize performance, efficiency, and fuel economy. It is obviously better to sucks cool air coming through the grill or front fender of the car which is a more appealing option than grabbing warm air from under the hood.


Other design strategies include increasing the diameter of the intake for increased flow, smoothing the interior of the intake to reduce air resistance, tuning the length of the intake to work best at certain engine speeds, and using a more efficient, less restricting air filter. All of these methods are precisely engineered to supply maximum oxygen to get the most out of your engine.

Generally the cold intake can feature:

  • Reworking parts of the intake that create turbulence to reduce air resistance
  • Providing a more direct route to the air intake by eliminating muffling devices
  • Shortening the length of the intake
  • Placing the intake duct so as to use the ram-air effect to give positive pressure at speed

However aftermarket cold air intakes can pose a risk of damage to the vehicle.

  • Hydro locks – The intake opening may be closer to the street than an original-equipment air intake, and more likely to introduce water into the engine when fording streams or flooded roads.
  • Noise – Stock air filtration systems usually include resonator-based muffling tubes. Removing them reduces pumping losses but increases noise.


Back to the question does it worth to install cold air intake. It really depend on your propose. If you primarily think you want to save gas money then I would say don’t buy it. How to save gas is really mattered on your driving habits. When it comes to increasing the mileage of your car, the basic problem you will encounter is how you maintain your car and your driving habits without a cool air intake. Also cold air intake will cost you couple hundred dollars. You might need over 6 years to get your invest back. If you’re cold air intake did not filter out water. It will damage your engine badly.

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The rotary engine

The Wankel rotary engine is a fascinating beast that features a very clever rearrangement that using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. It was developed and gets its named by Felix Wankel in the 1950s.

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In the Wankel Engine, a triangular rotor incorporating a central ring gear is driven around a fixed pinion within an oblong chamber. That’s how Wankel engine as get name as Rotatry engine or Renesis.

The shape of the rotor of Wankel engine are often confused with a Reuleaux triangle, a three-pointed curve of constant width, but with the bulge in the middle of each side a bit more flattened. In other word the rotor of the Wankel engine is curved sides are somewhat flatter than those of a Reuleaux triangle and so it does not have constant width.


The most famous application is Mazda 787B, it is the only Japanese car and the only team use a Rotatry engine to win Le Mans 24 hours Endurance. In additoin, Mazda is pretty specialized in Rotary engine and is bulit Rx-7 FD, FC and RX-8.

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Since Wankel and very compact compare to four-stroke reciprocating engine, it can produce very smooth power output at higher RPM.

Each revolution of the rotor Wankel engine produce three full works which making a significant advantage compared with the general four-stroke engine which produce one work on every two revolutions. the entire engine has only two moving parts, while four-stroke reciprocating engine has more than 20 moving parts, a much simplified structure of the engine can reduced the volume, weight as well as the failure rate. Furthermore, rotory engine have a special characteristics on the motion in axial direction, it does not require a precise balance of the crankshaft and able to reach a higher RPM easily. Also it takes much less of time to crank up than reciprocating engines.

The rotor circulated motion run more smoothly and occur less vibration and noise than reciprocating engine’s linear motion. Since the volume of the engine is small and circulated motion is the smoothest motion in the world, it emitted fewer hydrocarbons in high RPM,

In addition, the Wankel engine does not use valves to control the opening and closing of the intake and exhaust gate, it does not produce any mechanical loss. Therefore there will be no catastrophic failure caused by mis-shift or other wrong operations.


The concept to increase the power output for reciprocating engine is very simple. You cannot change the valve timing or change the angle of Camshaft on Wankel engine because those parts never exist on Wankel engine. Also we cannot simple adjust the compression ratio because the engine will not take more air, in another word, if we want to increase the peak horsepower we have to sacrificed the torque in low RPM range.

Since the combustion time is short as it is hard to make the air and fuel fully mixed, fuel consumption will be 02% higher than reciprocating engine. As I said it emitted fewer hydrocarbons in high RPM, however Wankel engine will produce almost double of hydrocarbons in idling or low RPM range.

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