Learn How to Build a Turbo Kit
Welcome to the Learn how to Build Turbo Kits web site. This site teaches you everything you need to know about building turbo kits for almost any fuel injected engine. The web site is intended to educate the reader in
all aspects of turbocharging for extreme horsepower.
This website contains pages of information about turbocharging, so scroll down below the table of contents and start learning. Please share our site with the turbo community and on turbo forums. We would love to see turbo kits being built in garages around the world because of this web site!
The
knowledge gained from reading this information should help you to make
informative decisions concerning turbocharger selection, engine build
configuration, fuel system upgrades, PCV solutions, PCM tuning and upgrades,
turbocharger system fabrication and much more.
If you
intend to turbocharge your vehicle by means of an off-the-shelf kit, or by
fabricating your own system, this web site
will provide you with a wealth of knowledge that will help you obtain your
goals.
Please
note that all material contained on this web site are copyrighted. Any unauthorized use of the information
provided on this site will be considered copyright infringement, and an
injunction will be filed.
This website covers the following turbocharging topics. Scroll past the table of contents to begin chapter 1.
Chapter 1: Basic
Turbo charging Concepts
Chapter 2:
Selecting a Turbocharger
Chapter 3:
Turbocharger Systems and Components
Turbo chargers
Waste gates
BOV
Headers
Boost Control
Chapter 4: Intercooling
Air to Air Intercooling
Air to Water Intercooling
Alky Injection
Chapter 5:
The Hot Side
Manifolds
Stock Manifolds
Log Style Turbo Manifolds
Custom Tubular Headers for Turbos
Turbo Downpipes
Chapter 6:
Turbo Oiling Systems
Turbo Oil Feed
Turbo Oil Return
Tapping the Oil Pan for Turbo drain tube
Scavenge Pumps
Sumps
Chapter 7: Fuel
Systems
Stock Fuel System Limits
Fuel Pumps
Fuel Injectors
Return Type System
Chapter 8: PCM Tuning
Dyno Tune
Software
Standalones
Piggy Backs
Speed Density
MAF Limitations
Tuning
Basics
Chapter 9: Internal
Engine Modification
Camshaft
Cylinder Heads
Pistons
Crank/Rods
Intake Manifold
Chapter 10:
PCV Systems
Modifying the PCV System for Boosted
Applications
Chapter 11:
Turbocharger Mounting Locations
Conventional Mounting
Rear Mounting
Chapter 12:
Keeping an Eye on Things (Gauges)
AFR Air Fuel Ratio
Boost
EGT Exhaust Gas Temperature
Fuel Pressure
Chapter
1 -Basic Turbocharger Concepts
Here are
some basic concepts and formulae that you should know before delving into your turbo
project.
Selecting
a turbo size to match your engine is not at all difficult. You need to find a
few things about your engine, decide how much boost you want to use, and then
plot the information against a turbocharger's compressor map. There is a little
bit of math involved, but it’s easy.
First you need to know the CFM of your engine when running naturally aspirated.
You can find this by using the following formula:
volume of air (cfm) = engine rpm x engine cid
3456
So, an example engine with 350 cubic inches of displacement would look like
this:
volume of air (cfm) = 6000 x 350 = 2100000 = 607.639
3456 3456
The engine in this example needs about 600cfm of air at 6000 RPM naturally
aspirated. Now we know our NA cfm requirements, but in order to read a
compressor map we'll need to figure out the airflow in pounds per minute
(lb/min) required by our engine under boost. For our example, let's use a boost
pressure of 10psi.
At this point it is important to talk about the difference between absolute
pressure (psia) and gauge pressure. The boost level that you read on your boost
gauge is really called psig or pounds per square inch gauge. The absolute
pressure is 14.7 + psig. The 14.7 comes from the pressure of air at sea level.
So 10psig = 24.7psia.
We can find our engine's requirements by plugging our numbers into the ideal
gas law. The ideal gas law relates volume, pressure, temperature and mass of
air. It is:
PV = nRT
Where
P = absolute pressure, V = volume cfm, n relates to mass, R is a constant and T
is the air temperature in Rankine.
Let's
simplify the ideal gas law to find our engine's required airflow in lb/min with
10psi boost. We will need to know the temperature of the compressed air coming
out of the turbo. Let's assume an intercooled intake air temperature of about 130F.
Turbo cars that do not have an intercooler can see intake air temperatures
around 250F. To get the temperature in Rankine, simply add 460 to the air
temperature in F.
n(lb/min) = (14.7 + psig) x V cfm x 29
10.73 x T deg R
n(lb/min) =(14.7 + 10) x 600 x 29 = 24.7 x 600 x 29 = 429780 = 67.888 lb/min
10.73 x (130 + 460)R 10.73 x 590R 6330.7
We find that ideally, our engine will require 67.9 lb/min of air under 10psi
boost at 6000RPM. I say ideally because that assumes our engine has a
volumetric efficiency of 100%. We'll assume that our engines have a volumetric
efficiency of about 85%. Now we can correct our airflow.
67.9 x .85 = 57.7 lb/min
By the way, as a rule of thumb, horsepower can be found by the following:
Hp = airflow lb/min x 10 = 57.7 x 10 = 577
Now that we know our required airflow in lb/min, we need to find something
called a pressure ratio. This is the ratio between the inlet and outlet
pressure of the turbo's compressor. Inlet pressure is usually 14.7psi.
(standard barometric pressure at sea level) The outlet pressure is 14.7psi +
boost pressure. Take the ratio of the two and you get:
Pressure Ratio = 14.7 + boost
14.7
We decided to run our project at 10psig. That gives us:
Pressure Ratio = 14.7 + 10 = 24.7 = 1.68
14.7 14.7
We now have all the of the information that we need to read a compressor map.
Let's take a glance at a few and see what compressor will work best with our
application.
The
maps show both efficiency and RPM curves for the compressor.
In order to read the maps, simply find the pressure ratio on the y-axis and
follow the map over to where the airflow meets the engine airflow.
The
map above is for a Garret T04E compressor in 60 trim (we'll talk about trim
later). Notice the islands on the graph that look like ripples on water. Those
are efficiency islands. It is desirable to have our point plotted right in the
middle of the graph, although anything down to about 60% efficiency will work.
Notice that our point is way off the map for this turbo. The turbo will still
make boost, but will not be efficient. This is a bad selection for our project.
Our point is off the map to the right. What if our point fell in the surge
limit area to the left? That would be very bad. In fact, it would surely cause
damage to the compressor. In this area, the air flow is unpredictable and
changes direction.
Let's
look at another turbo compressor map.
This is a map from a T76 compressor. Notice that the point lands right in the
70% efficiency island. This would be a perfect turbo for our example project.
But there are other things to consider when sizing a turbocharger for your
engine.
We've
talked a lot about the compressor side of the turbo, now let's turn to the
turbine side. We've shown that a T76 will work for our project, but will spool?
That depends on the area ratio (A/R) of the turbine housing, and the turbine
size. A larger turbine wheel will spool slower than a small one. A larger
turbine will make more power, but it will come on later, maybe when the race is
over.
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