Modify with a Turbocharger?

This article is a basic introduction to the turbocharger. Next to an engine swap, the turbocharger is the most wanted mod for most tuners. Turbos, like a nitrous setup represents simple, raw power. With this power comes attention, respect, and covetousness, or in other words, you will be envied.

You plan to get a turbo when you can swing the cash. However, the thing that you should ask yourself is: what should you know about them before you get one? So you go to the nearest speed shop to ask this question and you get bombarded with all the hella-big turbos that you can order for your car. They tell you that it is ok if you just want to get the turbo without upgrading anything else.

Of course you would like to be able to do all of the additional upgrades, but because that turbo is expensive, who the heck can afford anything else. The labor for getting it installed is steep, too.

You go to your local shade tree mechanic and he knows what a turbo is, but has never installed one. He reassures you that he's been working on cars for years, mostly domestics from 1950-1980, though. You hand him back your empty Bud can and thank him for his time.

You go online to sites that sell turbochargers and again get bombarded with why their products are the best. They show you graphs with strange numbers and curves. They use language that Einstein himself could not understand.

The sad thing is...you still don't know jack about turbos.

The first thing you should ask yourself is: besides the social advantages, what do you want the turbo to ultimately accomplish?

Of course you want to go faster, but are you using the car to race, or as a daily driver? How much money can you AFFORD to spend? This question is different from can you PAY for it. In other words, let's say that you go out and pay for a Toyota Sequoia today. Could you afford the cost of upkeep, insurance, gas, etc? Having the ability to PAY for something is different than being able to AFFORD it. Being able to afford something means that there is little downside to buying the thing that you want. This is true whether you want to buy a house, a car, an outfit, or a piece of bubble gum.

You also need a basic understanding of what happens in your stock engine's combustion chamber.

How does the turbo fit into this equation?

First of all, what IS a turbocharger? A turbocharger is an air pump that uses the exhaust coming from your engine to work. Engines that are turbocharged are often called force-induction engines because air is forced into the combustion chamber.

These are the basic sections of a turbo:

I. Turbine Section
II. Center Section
III. Compressor Section

How do these three sections of the turbo work together?

Do you remember the pinwheels that you made in arts and crafts class when you were a kid? For those of you who do not remember, they are those shiny, fan-like toys that spends on a stick when you blow them.

Imagine a horizontal stick passing through the center of two pinwheels place on opposite ends of the stick. So our pieces will be call Pinwheel 1, Stick, and Pinwheel 2. Now we have our makeshift turbo.

The exhaust coming from your engine enters the turbo and spins Pinwheel 1, or the Turbine. This causes the Stick, or Shaft, to spin or 'spool up,' which in turn spins Pinwheel 2, or the Compressor. The Compressor compresses the air coming through the Turbine (Pinwheel 1), then sends it into you combustion chamber.

The typical components for your turbo setup are:

I. The turbo wastegate
II. The turbo blow-off valve or bypass valve
III. The turbo oil lines for oil supply and oil return
IV. The turbo intercooler

The turbo wastegate

Boost is the increased pressure in the intake manifold that is created by the intake side of the turbo section. The intake manifold provides the fuel and air mixture. Boost, just like everything else in the system, has to be controlled to prevent overboost which will cause engine damage. This is where the wastegate comes in. The wastegate is a large valve that, when open, causes the exhaust gases to bypass the turbine (Pinwheel 1) instead of going through it.

The turbo blow-off valve or turbo bypass valve

Chances are, you have heard the term 'blow-off valve' or 'bypass valve' when referring to turbochargers. The blow-off valve does two things:

1. it vents or blows off any overboost that the wastegate can not handle

2. it prevents pressure spikes. Pressure spikes occur between the turbo and the throttle body when you let off the gas pedal to shift, or when you slow down. The throttle body controls the amount of air that is going into your engine when you press and let up on the gas pedal.

In other words, imagine you turbo is doing its job and the air is flowing in the correct direction, consistency, and speed.

It is not easy to stop this in an instant, so when the throttle body suddenly closes, the flow becomes turbulent and the pressure spikes.

The blow-off valves kicks in to release the pressure. If it does not, the turbo will stall and have to 'spool up' or speed up all over again when the throttle body reopens. This produces turbo lag and hesitation. The blow-off valve helps to decrease wear, tear, and damage to the turbo and your engine.

The turbo oil lines for oil supply and oil return

Oil is essential to you turbo because it:

1. allows the shaft to spin without friction

2. cools the shaft, or Stick (from the pinwheel example), as it spins several thousand rpms or revolutions per minute.

An oil supply line AND and oil return line are usually the best scenario.

The turbo intercooler

Now we get to the intercooler. There is so much hype about these things isn't there? Some will tell you that they are optional to your turbo set up, some will say they are essential. Well, read on and decide for yourself.

As you remember, from science class, when air is compressed, it heats up and expands. If the compressed air in your combustion chamber gets too hot and ignites the fuel before your sparkplugs fire, knocking occurs.

This means that in regards to your turbo, the ideal situation would be to have the air that is compressed and sent to your combustion chamber, to be much cooler than the several hundred degrees that the compression creates.

Back to science class, when air is cooled, it contracts or in other words, its packed tighter.

Back to your turbo, if the hot compressed air coming out of the turbo is cooled down considerably before it enters your combustion chamber, it allows more air to fit inside. This is what you want. You want the temperature to be cooled down to as close to ambient air (outside air), or even below.

So to put it in a nutshell, the intercooler resembles a radiator and its job is to cool the compressed air coming out of the compressor side of the turbo before it goes into your combustion chamber. Intercoolers are also called heat exchangers, charge coolers, or less common, aftercoolers.

Types of turbo intecoolers

The two types of intercoolers are air-to-air intercoolers and air-to-water intercoolers.

With air-to-air intercoolers, the intake air passes through and around its fins, which cools the intercooler itself.

With air-to-water intercoolers, the intercooler itself is cooled by water or a water/antifreeze mixture. This mixture uses its own radiator which is placed in the path of the airflow. This mixture is circulated through the intercooler which is connected to the radiator by a hose.

The air-to-air intercoolers are the most common for stock engines, as well as aftermarket engines. They are less expensive, may require more tubing to ensure that it is placed in good airflow, and are often large.

The air-to-water intercoolers can have shorter tubing because it can be placed where there is no airflow. Its water or water/antifreeze mixture is what cools it. The air-to-water intercoolers are often used in drag racing vehicles.

What is turbo lag?

One of the main complaints you have heard about turbos is turbo lag. Turbo lag is the delay between pressing the gas pedal and feeling the turbo kick in.

Decreasing turbo lag with turbo design

You could also use a smaller turbocharger. As a general rule, small turbo = quicker boost at lower speeds. The downside to this is that the smaller turbo may get overwhelmed at higher speeds when more air is attempting to move through it, thus decreasing boost.

As another general rules, large turbo = quicker boost at higher speeds. The downside to this is that a large turbo may create more turbo lag because its large turbine (Pinwheel 1) and compressor (Pinwheel 2) takes longer to spool up, or spin.

Some possible ways to reduce turbo lag is to use lighter parts for the turbo. You could also use a ceramic turbo because they are lighter than the typical steel blades. However, they can shatter if put under too much strain.

Often, an O2 sensor is used to help regulate fuel/air mixture. There are also additional ways to increase your car's horsepower.

Now you know the basics of turbochargers. As you can see, there is a lot to think about when you are considering a turbocharger. Just go slow, do your research, and don't get blinded by the hype!

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