Performance Q&A’s
By: Clark Hemrick
Will upgrading the
camshaft make the engine noisy?
Yes, depending on the lift and duration of the camshaft that
is chosen. The higher lift / shorter
duration cams have a tendency to have a ticking noise more than the stock cams. These camshafts produce more torque in the
lower RPM range.
Do I need a dyno tune
even though I only added pipes and air filter upgrade?
In most cases, yes.
Bikes with the factory O2 sensors can adjust the mixture in a safe Air
Fuel Ratio range, but the O2 sensors are turned off by the ECM in heavy
throttle positions such as 60% - 100% throttle.
The AFR ratio is usually dangerously lean in these areas.
I had a set of
performance pipes installed and dyno tuned.
Now I changes the pipes to a different brand and style. Will the bike need to be dyno tuned again?
The AFR is affected anytime that you change the induction
and exhaust systems. Some exhaust
changes will affect the AFR more than
others. It would be wise to have the AFR
checked on a dyno to determine if it is safe.
Will performance
upgrades increase my fuel consumption?
Fuel consumption
increases or decreases, depending on the type of performance upgrade that you
are looking for. If you build the engine
for lower end torque, then your fuel mileage
will usually increase (depending on the way that it is tuned).
Think of it this way.
The engine usually has the highest “VE” (Volumetric Efficiency) around
peak torque. This means that the engine
is more efficient (makes the most of what fuel is given) at the area around
peak torque. You consume more fuel the
further the throttle is opened and the higher the engine revs. If the torque is in the lower RPM band, (where
the higher VE is located) then you don’t have to open the throttle as much and
you can keep the RPMs down, resulting in decreased fuel consumption (better
fuel mileage). If the peak torque is
located in the upper RPM range, then you have to apply more throttle until you
arrive at the highest VE area of the RPM range.
This means more throttle is being use and higher RPMs are being used
which results in high fuel consumption.
Which performance
components should I start with?
It is important to start with the correct base (foundation)
to build on. The exhaust is the most
important component. If you are looking
for power, I suggest that you start with a good 2 into 1 exhaust. Remember to consult your builder before
purchasing parts that you think will make the power that you are wanting. Just because your buddy has a certain pipe
and cam combination, it doesn’t mean that it will perform the same in your
bike. Slight changes in the bends,
length, and diameter of a pipe can dramatically affect the power of your
bike. Example: If you used a particular pipe and cam
combination on a Softail, then used the same combination on a touring bike, you will have different power results. Ask for advise from a tuner or a builder that
has had extensive experience in experimenting with multiple cams and exhaust systems
on the dynamometer.
The air filter design will also affect the power of your build. Again, the length bends, and diameter of an
air filter system (just like the exhaust system) can increase or decrease the
power output. Unfortunately, there are
not a lot of tunable induction designs on the market to experiment with.