Why are we even talking about
this... "there is no replacement for displacement"
I
have been
to many web pages and forums and one question I keep seeing is "What
can I do or add to my motor to get more horsepower?" I have seen
many answers to this question, mostly in the form of lists of
parts. Before we go and spend our whole car budget on
parts, it
is a good idea to understand how the part is improving
horsepower. That way you can pick the combination of parts that
will best suit your car's application, ie you wouldn't want to
put a blower on a car that you use every day for a 60 mile commute.
There are three general ways to increase horsepower at the flywheel.
The first way
is to increase the fuel air
volume in the chamber, which correspondingly produces
more energy during combustion. This is the most straight forward
way to increase horsepower, more
CI or
fuel/air volume per cylinder = more power. However, it
comes at a
price (literally), more CI= less MPG.
The second way to
increase horsepower is to
improve
the
efficiency of the combustion so as to burn a greater % of the air
fuel mix. Other than parts, there is no added cost to doing this;
however the economic "law of deminishing returns" applies:
as more parts are added, the % of increase gets smaller and smaller as
we
move toward 100%. The
fuel is already in the chamber, we are just burning a greater % of
it. The average stock motor only burns 60% - 80% of the fuel that
passes through it. Higher
% Burn = more HP.
To understand the third
and final way to increase horsepower, you need
to know that a motor produces more horsepower
than what can be measured at the flywheel. The problem is
the motor uses those horses to run. in other words it takes HP to turn
the
cooling fan, draw in fuel/air mix, compress the mix and then push out
exhaust gasses. Less effort from the motor = more HP at the
flywheel. Like before, other than the price of parts, there
is no extra cost to freeing up these horses. There are, however,
only a limited number of horses available to be harnesed.
The following chart lists performance parts
and how they contribute to HP increases. Keep in
mind,
some parts fit in more than one category.
I generated
most of these
numbers using "Digital Dino 2000". I took a Ford 302 and built it
on
the computer completely stock. It bench tested at 167 HP. I
then added each
part by itself and recorded the gain in HP. The next step was to
build a 302
with all of the performance parts listed above, except the forced
induction and NOS and it bench tested at 417 HP. I then changed
each part
back to stock by itself and recorded the loss in HP. Some of the
items listed did not have an option on my computer, such as performance
ignition
and ram air. I found these % on line form manufacturers and took
the highs and lows. Keep in mind that parts work together, in
other words, you
will not get the full benefit of a performance motor if you are only
running a 350 cfm carb. All percentages should be taken into
consideration
with the following disclaimer:
THESE
NUMBERS
ARE THE EXTREME HIGHS AND LOWS AND WHEN
PUTTING PERFORMANCE PARTS ON A MOTOR, THERE ARE A LOT OF VARIABLES THAT
CAN INCREASE OR DECREASE THESE NUMBERS.
Use
this chart as
a jumping off point or reference to potential
gains. Don't add up the % to 100, get those parts and expect to
double your HP. It's probably not going to happen. The last
thing to consider is cost. Sure, if you want to drop $2,000 or
more,
you can go buy a blower and see some huge performance gains, but by
adding the right combination of parts, you can get almost as much power
for a lot less money.
Efficiency
Higher % Burn = more HP
Free
Horses
Less effort from the motor = more HP
Volume
More Fuel/Air per Cylinder = more HP
Hedders / Free Flowing Pipes & Mufflers
A free flowing exhaust makes for less
effort on the part of the motor in pushing out exhaust gasses.
18% to 21% HP
increase
Performance Heads / Port and Polish
Longer smoother runners allow for better air flow and air/fuel
atomization, or a more complete mix. Also, many performance
heads have a smaller combustion chamber which = a higher
compression ratio. (see below)
16% to 33% HP increase
Performance Heads / Port and Polish
A larger exhaust valve makes for less effort on the part of the motor
in pushing out exhaust gasses.
16% to 33% HP increase
Performance Heads / Port and Polish
Longer smoother
and larger runners coupled with larger valves allow
for more air flow of air/fuel mix into the chamber.
16% to 33% HP
increase
Performance Carb
A performance carb
creates a more balanced mix of fuel and air, as well as better
atomization of the mix.
1% to 25% HP increase
Performance Carb
A performance carb
provides more
fuel/air mixture than a stock one.
1% to 25% HP increase
Increased Compression Ratio
The higher the CR,
the more volatile the fuel/air mix becomes, making it burn better.
0.5% to 1% HP increase per 1:1
increase
Roller Cam
A roller cam reduces
the friction in the valve trane, reducing motor effort.
Many roller cams are performance oriented (see performance cam)
1% to 14% HP increase
Performance Cam
A performance cam
keepes the exhaust valve open longer allowing easier removal of exhaust
gasses.
1% to 25% HP increase
Performance Cam
A performance cam
keepes the intake valve open longer, allowing more fuel/air mix per
cylinder.
1% to 25% HP
increase
Hotter, Mutiple Spark, Ignition
The hotter and
longer a spark fires, the more fuel is burned.
1% to 5% HP increase
Performance Intake
The longer larger
runners allow for better atomization of the fuel/air mix .
1% to 12% HP
increase
Performance Intake
The longer larger
runners allow for less effort on the part of the motor to draw in
fuel/air mix.
1% to 12% HP increase
Performance Intake
The larger
runners allow more fuel/air mix to enter each cylinder.
1% to 12% HP increase
Electric Fan
/ Flex Fan / Clutched Fan
There is a
considerable amount of drag created by a fan, but reducing the
drag to only what is needed to effectively cool, or eliminiating the
drag all together, we reduce motor effort.
2% to 15% HP increase
Electric Waterpump / Oilpump/ Fuelpump
Mechanical parts are driven by the motor. By converting these
parts to
electric, we reduce motor effort.
Air pressure builds
up in the front of the car. By running tubes from the front of
the car to a sealed carb box, when the car is moving, fuel/air
mix is pushed into the motor rather than making the motor go through
the effort of pulling it in.
Air pressure
builds up
in the
front of the car. By running tubes from the front of the
car to a
sealed carb box, when the car is moving, fuel/air mix is pushed into
the motor rather than making the motor go through the effort of pulling
it in. This pressure increase allows for a larger volume of
fuel/air mixture to enter each cylinder. Also, the air from the
front of
the car is cooler than the air under the hood. You can
fit more cool air and fuel in a cylinder than you can warm air
and fuel
5% to 10% HP
increase
NOS
NOS
oxigenates, making the burn more complete.
12% to 30% HP
increase 2# per min N2O
flow
NOS
NOS super cools,
allowing
for more mix volume per cylinder
12% to 30% HP
increase 2#
per
min
N2O flow
Turbos / Blowers
Turbos and blowers
use
the same idea as ram air, however, they are mechanically driven and add
a
huge increase in fuel/air mix volume per cylinder.
26% to 40% HP
increase
Synthetic Oil
Synthetic oil coats
cylinder walls better and makes a better seal on the compression
stroke. This improves compression (see above)
1% to 3% HP
increase
Synthetic Oil
Synthetic oil
lubricates better, reducing friction on ALL moving parts. This
frees up more power.
1% to 3% HP increase
EFI
Electronic Fuel
Injection delivers the perfect mixture of fuel and air at the
most optimum time, creating a more efficient burn.
1% to 26% HP increase
Stroke the Motor
By increasing bore
and
stroke, we increase volume per cylinder.
You do the math
Disclaimer on Daze Tech Tips
I am not an expert
in this field. I have performed these modifications myself with very
good results. I am passing along restoration and
performance tips for the purpose of education. If you are
concerned about reliability or safety issues, I do not recommend that
you or any other individual perform these changes or attempt to modify
your cars from stock configuration except under your own
volition. I do not assume nor accept any liability for the
use of
this
information or how it is applied.