Turbochargers
Turbochargers
Turbochargers are a type of
Forced Induction.
Turbos are just another form of a Supercharger. The major difference is how they make the power and where they make it(as in rpm). A turbo uses the exhaust in a car, while a supercharger is run by an accessory belt connected to the engines pulley system. Superchargers will add power and totally change the power band of your car, as a turbo will only increase the top end portion of its power band. Both are further explained in the articles.
Parts
A Turbo has 2 fan-like propellers on the opposite ends of a small light shaft. The shaft runs on a fluid bearings. The turbo has two shell-like metal casings that enclose the fans. The exhaust shell and side of the turbo is called the turbine and the intake shell and side is called the compressor. The turbo has to be placed where both the exhaust and intake pipes are located so that the turbine can spin the compressor wheel without having a long shaft in between.
How it works
The exhaust gases push the exhaust turbine. The blades spin a rod in the center of the turbo which spins the compressor wheel on the other side. The compressor wheel while spinning, forces air into a small channel on the sides of the compressor shell. As the air gets closer to the discharge port and/or intake pipe its space gets smaller and smaller, compressing the air. The air is then shot into the intake manifold where it is force into the cylinders by biult up pressure. By pressurizing the air it makes it possible to fit more air into the cylinder. By putting more air in the cylinder you can put more fuel. More fuel will give you a larger exploison and therefore more horsepower.
When it makes power
The compressor blades need to spin at very high rpm to produce boost, which is also know as psi. Turbos, like centrifugal superchargers, start to make boost at about 30,000 to 40,000 rpm. Some turbos can spin at over 100,000 rpm. That is why regular ball bearings won't work. They cause to much friction, which in turn makes heat. Liquid bearings are most common in turbos. A special type of ball bearings are sometimes used but are a lot more expensive. They are super-precise bearings that are made of specially disigned materials to handle the speeds and temperatures of the turbocharger. With the ball bearings a lighter shaft can be used making the turbo even more efficient.
Another thing to consider. Depending on how much boost and the size of the turbo can effect the output power of the turbo and power range. More boost means bigger turbo and usually more turbo lag. Turbo lag is the period of time that it takes the turbo blades to speed up. The normal psi of a normally aspirated engine at sea level is 14.7 psi. With turbos most people usually make between 7 and 14 psi.
Since the turbo will only make power at very high rpm(30,000+ rpm), it needs a huge amount of exhaust to push the turbine enough. This is one of the flaws of the turbo. At lower rpm there simple is not enough exhaust to spin the turbo fast enough. When it gets higher in rpm though its power output spikes. A turbo will only increase and magnify the top end of the engines power band. It's power increases exponetially with engine speed. Its powerband should look something like this:
Accesories and other things to consider
Turbochargers might require other components depending on how big they are but accessories can make them to run smoother and more efficiantly.
Waste Gate and Boost Controller
When you have a turbo and you want to make a certain boost you need to buy a boost controller. Along with this you need a waste gate. A waste gate will allow you to regulate the amount of air going through your turbo. Its place on the exhaust pipe before it goes into the turbo. The waste gate will open and let air out when you have reached the appropriate boost level.
Fuel Injectors
Most turbo kits will come with new fuel injectors, but if it doesn't it is a must. The only way your turbo will make more power is if there is more fuel injected into the cylinders with the extra air. Fuel injectors, if you get an electronic one, will change the amount of fuel incerted to go along with the air. They are also adjustable from the cockpit of a car.
Ball bearings
Ball bearings designed for turbos are very presice. They are made to make the least friction and withstand the speeds and temperatures produce by a turbo. With them lighter shafts can be used making a more efficient turbo. Since the lighter shaft allows the turbines to spin faster it reduces turbo lag. Turbos with ball bearings are a lot more expensive then regular turbos, but maybe worth it to an automotive enthusiast.
Intercooler
The air your turbo compresses heats up quickly when being compressed. If you want to make even more air go into the cylinders you can lower its temperature where it is will be more dense. For more on Intercoolers.
Sequential Turbochargers
Some cars have 2 turbos. One is smaller and is used at lower rpms because it spools up quickly. After the engine gets to a higher rpm, where the smaller turbos boost would slow, the larger turbo kicks in and makes the power.
Ceramic Turbine Blades
Ceramic turbine blades are a lot lighter then the stock steel blades. This allows for a faster spin. Turbo lag is also reduced.
For Larger Turbos
Larger turbos might require you change a few things such as: the compression ratio; Stronger pistons; Stronger piston rings; Stronger plumbing; Igntition retarder.
ADVANTAGES
Turbos, especially big turbos, produce huge amounts of hp at higher rpms. They do not drain any power from the engine like superchargers do which may turn off some people. They are the cheapest parts for the most horsepower. Turbos usually come in kits so buying different additional accessories is not always needed. Many people would also say the best part of the turbo are its sounds, plus the massive amounts of power they make.
DISADVANTAGES
There are a lot of disadvantages to turbos but the good overweigh them. (Big)Turbos make very low hp at low rpms, so accelerating off the line you might not have the power needed. Sometimes at lower rpms exhaust gases backflow when they hit the impellers, causing bad combustions. Installation requires a lot of work. If using larger turbos wear and tear can be a concern on many of the engines parts.
Conclusion
Turbochargers are good for high end hp and are one of the cheapest($1500-$4000) things you can buy for the amount of hp you get. Nothing can give you the power that a Turbocharger gives for its price.
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