In plain and simple English.
Dont you hate tech articles that confuse you more than help you understand the true
concepts of things. Tell me if this sounds familiar. You see a tech article in a magazine
and are interested in learning about the topic, but after reading it half way through you
become frustrated and move on to something else. Its like the tech article was too
technical. All the high tech mumbo jumbo (which is often inaccurate) did not help much
either. Well here is my crack at turbo basics, in plain and simple English for the
everyday racer who is far from being an engineering graduate and being a turbo techno
Why do people turbocharge their cars? Why do people drive well over 100
mph when a signs says that the limit is 65? It is simply for the thrill and the rush. For
the love and need of SPEED and POWER. Power that is always there at the tip of your toes
twenty four hours a day seven days a week. Turbocharging your car can net a 50% increase
in horsepower if not more. Ive seen Honda Civic coupes (which have 125hp stock)
double its horsepower output by turbocharging. But be warned any plan to increase
horsepower over 50% of the stock power will definitely need some bottom end build up and
engine management controls. If you are planning to turbocharge your car, here is some
advice. Take your time, "do your homework", ask a lot of questions(to the right
qualified people), and do it the right way the first time around. Believe me, their is
nothing like the power of a turbo and the fun factor drivability is beyond awesome.
How does it work? Well here is a general bare bones run down of how a
turbocharger system works. The engine produces exhaust gases that exit via the exhaust
ports of the cylinder head. These exhaust gases flow through turbo manifold ( just like it
would through a DC header) into a turbocharger unit. As the exhaust gases enters the
turbine housing the velocity of the exhaust gas "spools" (spins) a propeller
bladed type wheel called the "turbine wheel". As this turbine wheel begins to
spin, it turns and drives a common shaft. This shaft has another propeller type wheel
called the "compressor wheel" on the other end. The compressor stage of the
turbo begins to suck air in as the "compressor wheel" begins to spool. The
"compressor wheel" spools faster and faster and the air becomes "compressed
charged air"(its like a hair dryer in your engine bay). The faster the wheels
spin, the faster the shaft speed, and thus the greater the pressure. From the compressor
stage of the turbine the "charged air" exits at a great velocity and makes its
way to the intercooler. The intercooler is a huge heat exchanger (which is like a radiator
but for air). It cools down the temperature of the "charged air". From the
intercooler the air travels to the throttle body and back into the motor. As more air is
force fed into the motor, an additional amount of fuel must also be added. The amount of
fuel must be proportionate with the amount of air that is supplied to the motor. Bottom
line - more air and more fuel equals more power.
Turbo boost! A turbocharged engine revolves around one central idea and
that is boost. Boost is defined as the increase in manifold pressure above atmospheric
pressure. Boost is a gauge measurement of turbocharger compressor discharged pressure. So
what the hell does that mean? Basically boost is the value (amount) of "charge
pressurized air" coming out of the turbocharger. In general the higher the boost, the
more air will be force fed to the motor, and more horsepower will be made. Boost is
usually measure in PSI (pounds per square inch) or bar (inches in mercury level).
The basic components
Turbocharger - The turbocharger is an exhaust driven compressor. It has 3 main
1- The turbine stage (which drives the compressor stage) is the side connected to the
2- A center section (CHRA) which houses the common "shaft". The center section
is also were oil and water flow to keep the temperature of the turbocharger down.
3- Then there is the compressor stage from which the "charged air" is created
The turbo has two propeller type wheels connected by the common "shaft". The
"turbine wheel" and the "compressor wheel" which both spool up to
create the "charged air".
Exhaust manifold - The exhaust manifold holds the turbocharger and mounts it to
the motor. The exhaust manifold directs the exhaust gases from the exhaust ports to the
turbocharger inlet. It is typically made in cast iron, mild steel, or stainless steel.
Down pipe - the down pipe is connected to the side of the turbine stage of the
turbocharger and it directs all exhaust gases from the housing into the exhaust system.
When turbocharging a car, it is often a rule of thumb to run the least restrictive type of
exhaust available to keep back pressure to a minimum.
Intercooler - the intercooler is a giant heat exchanger that cools down the
temperature of the "charged air". Usually when "charged air" is
created it is very very hot, so it must be cooled down. The colder the air (making the air
more dense) is when it enters the motor, the easier it will combust and at most times the
more power it will make. Not all turbo systems use intercoolers but it is always better to
Blow-off valve - a blow off valve is a spring loaded valve usually placed on the
pipe between the intercooler and throttle body and it is used to prevent "compressor
surge". Basically it helps the turbocharger unit last longer and increase
responsiveness. Blow-off valves give off a distinct yet impressive hissing sound.
Its the sound that screams "Im turbo and if your not, than you better
think twice before you try to run me!!!"
High flow fuel pump - At many times the stock fuel pump cannot supply ample fuel
that a turbocharged engine needs. For this reason a high flow fuel pump must be added.
What this does is raise the fuel pressure so when the additional fuel is needed the
capacity for it is there.
Boost dependent fuel regulator - As we stated before as the more air goes into
the motor the more fuel is needed. A boost dependent fuel regulator regulates the amount
of fuel that goes to the injectors. As the turbo begins to spool, boost pressure builds up
and as the boost pressure increases the boost dependent fuel regulator pushes more fuel to
the injectors which is sprayed into the motor.
Wastegate - The wastegate primarily controls boost pressure. It is an exhaust by
pass valve that opens and closes to let out or keep exhaust gases. It maintains the
turbochargers shaft speed by this open and close action. When it opens exhaust gases
leave via the downpipe and then through the exhaust system thus the shaft speed is slowed
down. When it stays shut the exhaust gases increase shaft speed by spooling the turbine
As stated before any increase of horsepower output over 50% will most probably require
bottom end build up and fuel and engine management controls. If you plan to turbocharge
your vehicle, be sure to get all the necessary parts or youll be towing your ride
home real quick. Air filters are important. They help keep dirt and other things out of a
turbo, so be sure to have one. Also maintain a clean oil supply. This means that you will
have to change oil more often but it will help for durability sake.
Well that about sums it up. I hope that I have helped you understand some of the basics
of turbochargers. The only thing left to do is for you is to go out and experience the
thrill. Its like jumping in your very own roller coaster ride. The fun factor
drivability exceeds a 10+ (on a 1-10 rating scale). Dont take my word for it. Get
out there and experience BOOST. Your life may never be the same.