Originally Posted by willwren
Andy, do your best, and post it regardless of how you feel it turned out.
Per Will'* request:
“More power!” it’* what Tim “the tool man” Taylor from TV’* Home Improvement wanted, and it is also what many car enthusiasts want. The quest to pump every ounce of horsepower and torque out of an engine has been around for well over a half of a century. Every year many people around the world spend small fortunes on making their car better. Whether it is to make it faster, more functional, or purely better looking, people love making modifications to their cars.
As far as power goes, there are two basic set ups: naturally aspirated and forced induction. Naturally aspirated, for the sake of argument, is pretty basic. Your car engine is a lot like a giant air pump. It takes air into the cylinders, reacts with the gasoline and a spark (making combustion), and then sends the wasted by-products out the exhaust. The combustion cycle of the engine is where your car derives its power.
What if I want more power though? Well then your choice of engine is going to be one with forced induction. What is this you may ask? Like the naturally aspirated system above, the car needs air to make combustion. An engine with some type of forced induction will probably either have a supercharger or a turbocharger that will compress the air before it enters the cylinder. The general rule of thumb with engines is, more air is better.
So, now that you know your options for forced induction, how do you choose one over another? Each system is unique, and has its advantages over the other. Some of the factors that come into play are: price, availability, HP, torque, and the effects on your engine.
Turbochargers, on paper, are quite easy to understand. Basically, your engine starts off normally aspirated, until you hit a certain rotation per minute (RPM). Then, as the exhaust gasses that are being sent out your exhaust, they hit a turbine. The turbine on the exhaust side spins a bearing that powers another turbine on the intake side. This intake turbine compresses the air, creating boost. OK, maybe not too easy to understand on paper, but a lot easier than it is inside the engine. When adding a turbocharger to a car, lots of steps have to be taken to insure that it will operate properly.
Some of the steps that have to be taken are, routing the exhaust to go in-line with the turbo, finding a spot for the turbocharger housing to sit, routing the intake, among others. One major advantage for turbo systems is their ability to produce very high amounts of boost at high RPM, resulting in higher horsepower ratings. Turbochargers have been known to make over 35psi of boost. The wastegate is another advantage of the turbocharger. A wastegate sets how much boost the turbo will create, if you have a controller it is easily adjustable. This is convenient if you want to run low amounts of boost around town (say 8-10psi) and higher amounts of boost at the drag strip (say 20-22psi).
There are also some drawbacks to turbo charging a car. Exhaust gasses are hot, really hot, and since these gasses are the means of powering the turbocharger some of the heat is transferred. General rule of thumb number two, heat is bad for engines. Cold air is denser and has more O2 molecules than hot air, and therefore reacts better with fuel. Turbo charging still gives you that power though, right? Yes, but not right away. The time it takes from the time you stomp on the gas and for your exhaust gasses to build up enough to spin that exhaust turbine is known as, turbo lag. In drag races, you want as much power as you can get, and you want it immediately. Waiting for your turbo to make boost, or spool up, can cost you valuable seconds in ¼ mile racing.
Supercharging gets the same thing done as a turbocharger, it just does it in a different way. There are many different types of superchargers, such as a roots type, centrifugal, and a few others. A supercharger uses your engine’* system of belts and pulleys to power it. It has its own pulley that powers a pump, all of the air that enters through the intake is sent through this pump, and in-turn, into the engine.
One of the benefits of supercharging is its readability. You do not have to wait for anything to spool up and there is no lag on it. This instant power translates into a lot of added torque, which helps at off the line acceleration. You will get horsepower with adding a supercharger, but superchargers are generally known for their ability to produce a lot of down low (RPM wise) power. The size of the pulley on the supercharger determines how much power it will make. A smaller pulley will spin faster, producing more boost. Temperatures, as far as air goes, are generally lower on a supercharger. As stated above, lower temperatures are better.
Superchargers usually do not produce as much boost as a turbocharged system will. The normal amount for a supercharger is somewhere in the range of 12psi. Yes, there are higher amounts, and yes there are lower amounts, 12psi is just a good average. Because of their nature, pulley driven, supercharges cannot be adjusted as easily as turbochargers. You have to physically go under the hood and swap out pulleys, not as easy as twisting a ****.
Both turbochargers and superchargers are effective ways to increase the horsepower and torque of your engine. Be warned though, with extra power comes extra responsibilities. If you want your engine to last, it is highly recommended that you run no lower than 92 octane in your car. All of the added boost requires a higher quality gas to run properly. Also, you will want to measure your fuel’* readings to make sure that your engine does not start running lean, as this can have permanent negative effects on your engine. Plus, your pistons, transmission, rods, and other internals, for the most part, were not designed to handle all of this extra power. Depending on how much boost you run, their lives can be short, as in minutes.
If you are safe with it, and careful, forced induction can be a lot of fun. One of your best bets as far as the whole turbo vs. supercharging argument is to simply go with both of them. New hybrid systems use the advantages of each. The hybrids use part supercharger to get boost low in the power band and switch to turbo once above a certain RPM. You have to look at the advantages and disadvantages of each system, and fully evaluate what fits your specific application best. You must ask yourself which attributes are more important, once you figure that out, then you can make your decision.
By: Andrew Ljubi