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How
to Make More Horsepower - Part II
Last
month we discussed how to get more air into your
engine. This month we will discuss how to get
all that air out. Remember what I said last month,
an engine is nothing more than a big air pump.
So as important as it is to get air into the engine,
it is equally important to get the air out. So
on to the exhaust system.
We
will start at the beginning of the exhaust system,
the exhaust manifolds. The exhaust manifolds are
the first source of a restrictive exhaust system.
Most factory exhaust manifolds do not have enough
room to allow efficient scavenging of exhaust
gases. This causes the cylinders to fight each
other when pushing the exhaust gases out of the
engine at a higher RPM. Replacing the factory
exhaust manifolds with headers will give you much
less restriction and more power. The headers work
by giving each cylinder an equal length of tube
so they to don’t have to fight each other.
There
are two different types of headers, short tube
or “shorties” and long tube. Short
tube headers will give you more torque and more
horsepower in the low RPM range. Long tube headers
are designed for higher RPM use. So depending
on your vehicle’s application, you may want
to look for a particular style.
One
other option for headers is to have them thermal
coated. Thermal coating does a couple of things.
First, it keeps the heat in the header. This allows
for better exhaust gas scavenging inside the header
and keeps under hood temperatures lower. Second,
it protects the header. There are several companies
that offer thermal coating. You can also get it
direct from some header manufacturers.
The
next item to consider is the catalytic converter.
The factory catalytic converter is not designed
for performance in mind. It is designed to do
its job of reducing emissions cheaply. Meaning
the factory has built this as cheap as they can,
but still maintaining its designed function. There
are several companies offering performance catalytic
converters now. These are designed to allow far
better flow, but still maintain their function.
These are usually made out of more expensive catalyst
then what the vehicle manufacturer would use.
You get better flow and still remain legal.
Our
next step in the exhaust system is the muffler.
Factory mufflers are designed for one thing and
one thing only, noise reduction. A stock muffler
is the most restrictive part of the exhaust system.
So replacing your factory muffler with a performance
muffler will benefit you by giving you less restriction.
Also, don’t forget that a performance muffler
will give you a much better sound.
The
last step in the exhaust consideration is pipe
size. When it comes to the exhaust pipe, bigger
is not always better. You have to take in to consideration
in what RPM ranges will your vehicle operate.
The bigger the exhaust pipe, the less low end
torque you will have. Remember unless your engine
will be used for all out racing, it will still
need some back pressure.
There
are several manufacturers that offer complete
exhaust system replacements. Some offer everything
from the engine back, while others only offer
cat-back exhaust systems. You choices are abundant.
You can buy a pre-made exhaust system or have
a good exhaust shop custom bend one just for you.
Next
month we will discuss ignition systems. As always,
if you have any questions or comments, please
send them to sales@kmwperformance.com.
You can also check us out online at www.kmwperformance.com.
Vincent Wright
sales@kmwperformance.com
http://www.kmwperformance.com
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