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Air Filters
This hopup is often overlooked as it's perhaps one of the least glamorous in nature,
however it is an important one that does deserve a second look. An air filter's job
is simple enough in theory; it simply filters the air coming into the carburetor with the
least resistance. However the practicality of this is that air filters have one main
shortcoming that engineers have tried for years to overcome. That is, that in order
for a filter to be effective, it must finely sieve the airflow that comes in but at the
same time, not clog itself in the process. Just a slight intake resistance from a
partially clogged filter can greatly effect performance.
MotorSaver dominates the very short list of superior filter design by using a dual
filtration method. By using a dry, fine woven plastic fabric on the outside of a
basket frame and then using a conventional wet-type sponge filter in the center, the
filter is far less likely to get clogged. This is because large debris (normal dust,
dirt, sand, whatever) get deflected off the dry outer filter before they have a chance to
cling to the inner wet filter. Only the fine dust particles that make it through the
basket's filter get to pass through the wet filter... a very small percentage of the total
contaminant. The MotorSaver filter also has far more surface area exposed for
filtration. Most wet-type filters just have a single-end surface that is exposed
and take on the brunt of all the contaminants that come its way. It doesn't take
long in dusty conditions for these type of filters to get clogged. The paper
canister type filters don't attract as much dirt as to the wet type, and are often covered
in a dry sponge outer-shell, but because this outer shell fails to deflect any of the
contaminates, and because the paper canister cannot be washed, this is hardly any better
than the conventional wet types.
Summary:
Highly recommended, especially under dusty conditions.
Hop Up Meter: 8.0
Aluminum/Titanium
Parts
It's hard to find a kit or RTR these days that doesn't contain at
least some aluminum parts. This is because
aluminum is extremely heat conductive, rigid and extremely
light-weight. It makes for a far better parts material than
traditional plastic that most kits start out with. Titanium takes
things even farther with an unprecedented ability to take any abuse you
can throw at it. One of the hardest, lightest metals in existence,
it was first made popular in NASA's space program where an extreme
tolerance, light-weight, virtually indestructible
material was needed to construct the space capsules of the time.
Today, titanium is seen nearly everywhere where extreme high-demands are
in order, from high-quality watches, to tools, to precision
instruments. Because of the manufacturing process of titanium as
well as the demand, it does tend to be rather expensive, but often, well
worth the investment.
Popular R/C applications include tie-rods, ball
ends, pulley shafts, transmission gears, etc.
Summary:
Always a good idea as it will add a tremendous amount of durability to
your car/truck/buggy. Can add up in cost very quickly, so choose
parts wisely. Titanium a must for serious racers for ball ends and
tie rods.
Hop-Up Meter: 7.0-9.0
(depending on application)
Ball Bearings
Perhaps the single greatest improvement that can be made to any car or truck that uses
bushings. Because bushings are far cheaper to manufacture, they are usually found on
most entry-level kits and RTR's. They provide somewhat adequate support for a very
limited time. Usually made of either nylon or bronze, they are subject to a great
deal of friction. This causes both a serious performance drag on the car or truck as
a whole and tend to wear out rather quickly, especially in high-speed/powered
vehicles. Ball bearings are designed so that the inner hub and outer hub roll past
each other by use of small steel balls that roll on track that is machined on the inner
surfaces. This completely eliminates any "rubbing" that is inherent in
bushings.
Summary:
Definite must-have! Will give the greatest performance boost.
Hop Up Meter: 9.0
Belt Tensioners
These are perhaps more of an esthetic
enhancement as well as a
belt-saver than a real performance hopup. Belt tensioners
simply take up the slack
that tends to develop as belts stretch from normal use. By helping to prevent the
belt from slapping around you can actually enhance overall efficiently
in some cases and
increase the life of the belt by allowing it to properly seat on the pulleys.
Belts are typically only used on either 4-wheel drive on-road
sedans and some rally type cars. Often the belt that drives the front wheels is the
longest and gets the most benefit from a belt tensioner.
Summary:
Not usually a must have, but does clean up the esthetic
quality of the overall machine. Hop
Up Meter: 4.0
Heads
This one is fairly simple. The performance difference between one head and
another is it's ability to dissipate heat. The more air surface that is exposed, the
better it will cool. Most (or all) are made of aluminum which conducts and
dissipates heat very rapidly. Since these engines are not liquid cooled, the
majority of engine cooling is performed by the head, so this is an extremely important
item on your engine. These are considered hopups because a cooler running engine
runs more efficiently and therefore can put out more horsepower. Not to mention that
a cooler engine equates to longer engine life! The O'Donnell head is your best
bet for .12 to .15 engines as they are easy to install, tough as nails, dissipate heat
extremely well and come in a rainbow of different colors to match your body or chassis.
Summary:
Well worth the investment. Increases horsepower while keeping your engine
cooler; adds to lifespan of your engine.
Hop Up Meter: 6.0
Shocks
The purpose of shocks are
two-fold. To absorb the shock of bumps and dips in whatever track you
run on and to stabilize the chassis bounce that normally accompanies
handling such bumps. Keeping the tires in contact with the ground at
all times (with the exception of jumps) is a necessary demand for any car,
truck or buggy. Without proper tire contact, the vehicle would be
impossible to control. By allowing the relatively low mass of the
wheels and a-arm assembly to travel up and down to compensate for the dips
and bumps, the chassis can remain fairly stable through it's handling
phase. This all sounds more complicated than it really is. The
important thing to remember is that allowing controlled vertical travel of
the wheel assembly is the key to keeping the tire contact at it's maximum
and shocks are the main ingredient in this system. The better your
shocks, the better your handling.
Most shocks today are fluid
dampened with various grades of silicon oil that are forced through a
piston/cylinder assembly that acts to absorb the kinetic energy of
suspension flex. To main factors effect the handling characteristics
of shocks, the plunger's by-pass holes (through which the silicon fluid
passes) and the viscosity (liquid thickness) of the silicon fluid.
R/C shocks are generally single
action, that is to say that the upward and downward dampening are the same
(unlike today's advanced cars which have one dampening factor for up-thrust
and another one for down-thrust which allow more tuning flexibility).
This limitation requires experimentation to find the correct compromise
between the two. This is one of the biggest reasons you will see guys
at the track tinkering so heavily with their shock/spring setup... trying to
find that sweet spot where handling is at it's best for a particular track.
Summary:
Most kits come with silicon shocks
nowadays, but for those who don't have them yet, a definite must.
Hop Up Meter: 10
Sway
Bars
This is one of the most
controversial hopups out there. Sway bars (or actually anti-sway
bars by their proper name) are bars that run width-wise, pivoting on a
common axis and joined at both ends by the suspension control arms.
The tensile strength of the bars determine the effectiveness they have on dissuading
the natural chassis leaning factor that independent suspension produces
when a vehicle takes on a corner.
The problem with vehicles
leaning when going around a turn is it tends to compound the problems of
traction roll and reduction inside tire traction. Under severe
conditions this can lead to the vehicle flipping over when
cornering. Sway is more problematic with vehicles that have a high
center of gravity.. that is that there is more mass sitting up high on the
vehicle rather than in the preferable base. Because of the heavy
machinery of nitro cars, they tend to have a higher center of gravity than
their electric counterparts and sometimes require a countermeasure to
compensate for the excessive body roll. This is where anti-sway bars
come in. By minimalizing the independent suspension characteristics
of the chassis, body roll can be reduced. When the vehicle
goes around a corner and the outer side of the vehicle tends to lean in,
the a-arms on that side will tend to compress more than the others.
The sway bars help to artificially compress the inner a-arms while at the
same time add tensile strength to the outer arms by dissipating the
compression energy to the inner arms.
Summary:
Very useful for nitro sedans that
tend to flip excessively around turns or have severe oversteer..
Hop Up Meter: 5
Tuned Pipes
Those of you out there that have started with anything other than a tuned pipe
will know that this is one of the single most important hopup you can buy. One of
the only cons that I mentioned about the HPI RS4 was that it came with a muffler (the old
airplane canister types), and many of you out there may have gotten similar exhaust
devices in their kit or RTR.
The idea of a tuned pipe is to create sufficient back-pressure
in low RPM's to allow the engine to idle properly, but to "open up" when the
RPM's are cranked up. All the reasons for this are beyond the scope of this article,
but let's just say that the physics of 2-cycle combustion engines require this. Tuned pipes
achieve this proper back pressure by utilizing gas turbulence. Based on the design
of these pipes, slower moving gases such as with low RPM exhaust have more resistance to
vacating the pipe than gases that move at a faster pace as with higher RPMs. The
exact method varies from manufacturer to manufacturer, but the concept is the same.
Paris' ring pipe is a prime example of this technology at work. In theory the
"rings" running width wise through the pipe create turbulence which creates a
natural resistance, or backpressure.
Any of the tuned pipes out there will give you a significant
advantage over mufflers because they allow the gases to escape at a high velocity at high
RPM's where the engine power-curve is at it's maximum. Mufflers tend to do just what
their name implies...to muffle. This suffocation tends to lead to higher
engine temperatures and poor engine performance. The only advantage to mufflers is
that they tend to keep the noise down quite a bit. If you live in a neighborhood
that enforces noise ordinances you might have to consider keeping your muffler (or get
better neighbors).
CVEC and Paris seem to be the two preferred pipe manufacturers
out there. As to which is the better one... this all depends on the
application. Check with your local KNOWLEDGEABLE hobby store clerk or better yet,
ask the guys down at the track which they prefer. Mounting size, ease of
installation, back pressure requirements, and normal operating temperature all effect the
experts opinions on what pipe to use.
Summary:
Highly recommended, especially if you do any racing. Dramatically increases
engine power, especially in higher RPMs. Increases decibel level which may be a problem in
some neighborhoods.
Hop Up Meter: 9.0
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