You always hear how you can get a
pre-programmed fuel control box for your Cat or Polaris and it will be set up to
work perfectly with YOUR engine!
Is this really the case?
Are ALL engines the same and,
therefore; require the same fueling requirements?
Is this pre-programmed (1 size
fits all type) controller really allowing to you extract the full power
potential from the expensive "kit" you just spent your hard earned money
OK, let's look at these questions in a
little more detail..
First, it would be wise to
get a few facts straight about fuel flow in these throttle body injected
power-plants we love so much..
1) Injectors operate on what is called a
"Duty Cycle". What does this mean? A Duty Cycle is the fraction of time that a
device (in this case your fuel injector) is in an "ACTIVE" state. The
injector is fed a square wave pulse (see below for a sample of a square wave
When the amplitude is at a "1" ,the
injector is active and will open and flow the fuel that is present in the fuel
rail and pumped from your fuel tank via the electric fuel pump. This fuel is
INJECTED via the injector to your engine. This is why they call it "Fuel
When the amplitude is at a "0", the
injector will close its orifice and fuel flow will stop traveling from your tank
through the injector to your engine.
This square wave signal is not necessarily
"even" in its "on" and "off" times. Meaning, the square wave will not give equal
"on" time and "off" time to the injector. The amount of "on" time is
directly controlled by your engine's electronic brain box.
2) The longer the amplitude stays at "1"
the longer and more fuel that will be injected to your engine. The reverse is
true as well.
Aftermarket fuel controllers, alter this
square wave. The injector pulse (Square Wave) is fed to the controller and the
controller will adjust its duty cycle based on the controller's programming.
This is how you add or subtract fuel to your engine. NOTE:
there are only 2 controllers that can removed fuel from your engine. ALL can add
more fuel but only 2 can subtract it.
3) The pressure present in the fuel lines
will DIRECTLY effect the amount of fuel that will be injected when the injector
is "on". The higher the fuel pressure, the more fuel that will be injected when
the injector is turned on. Conversely, the lower the fuel pump pressure, the
LESS amount of fuel will be injected when the injector is turned on. So, you
see, that the amount of fuel that is delivered, via injector, to your engine, is
NOT just related to your injector pulse duty cycle, but is also directly related
to the line pressure.
There is a very good calculator and
description of this located at:
http://www.rceng.com/technical.aspx You can play with numbers and see
directly how the fuel flow is altered. VERY good article, play with the fuel
flow calculator. Please check it out!
OK, now, you have a good understanding of
how the fuel gets from your tank to the engine on a throttle body injected
Now ask yourself: "Are ALL fuel pumps
outputting the SAME pressure?"
Are ALL fuel rail regulators outputting the
Answer: "ABSOLUTELY NOT!"
We KNOW that the fuel pump and rail
pressure directly effects the amount of fuel flow through your injectors and we
KNOW that all fuel pressures WILL vary between sleds.
Please ask yourself: "How can there be ONE
Fuel Control Box setting for, say ALL M8 sleds? All M10's? All Polaris
800's? etc. etc.
Answer: "There Can't!"
WHY? Because there is NO WAY to KNOW the
fuel flow of each and every sled. WHY? Because the fuel pressures vary! It is really that simple!
There are MANY performance enhancement kits
available that require a fuel controller to allow for better fuel flow.
These kits are supplied with a fuel controller that has pre-programmed fuel maps
that optimize the kit. These controllers are non-adjustable (one size fits all
of the same models) and are said to be adjusted , just right , to
maximize the performance enhancement kit that they are selling.
Hmmm.. how can this
be? Is the fuel flow of your injectors known? Is it the same for all engines?
Is your fuel pump's
output pressure known? Is it the same for all fuel pumps?
Are ALL regulators at
the same level?
Well.. since there are variances in the pressures, it stands to reason, that there will need to be variances in the
fuel controller's settings as well.
So, what happens when you purchase a power
enhancement kit with a non-adjustable fuel controller? Are you getting the FULL
enhancement from the kit you just laid down your hard earned $$$ to purchase? OR
are you only getting a percentage of the power that is really available due to
the fuel controller's settings NOT be optimized for your engine? Please ask
yourself this question.
What happens is that the "kit" suppliers
will pre-program the fuel controller for the lowest fuel pressure they have
seen. In this manner it will be safe for all engines. What it will NOT be is
optimum for all engines.
Since this programming is based around the
"exception" and not the "norm" if your engine falls in the "norm" category (like
most do) you will have a controller that is OVER-FUELING your engine. While this
will be "safe" , it will not produce the best power. You could be seriously down
on power (even lower than stock power outputs) because of this
In conclusion... It is nearly impossible to
have a pre-programmed fuel controller that is OPTIMUM for your engine. There are
simply WAY too many variables (fuel pump pressure, rail pressures, exhaust, riding elevation,
head, temperature etc. etc) that factor when programming ANY fuel controller.
Having said all that, fuel controllers are
a great thing.... They allow you to TUNE your engine for optimum power output!
The "key" word here is "tune" you must be able to tune your controller or you
could be missing out on a lot of hidden power simply because you are
over-fueling your engine. Fuel controllers are very easy to tune
and one should NOT shy away from running them.
I am sure you have all
witnessed or even owned a "Stock" sled that simply performs above other stock
sleds (and even some mod sleds). This "Super- Stock" sled's superior performance
can usually be traced to a better (more accurate) fuel supply. The proper
fueling of ANY engine is critical in determining the power output.. Too much..
low power, too little.. low power and low life... just right.. great power and
So, while you may feel more
confident purchasing a "kit" that has a "hands off", "Set to go" advertisement
surrounding it. Keep in mind, it may be "hands off" but it will rarely be
"optimum" and , after-all, you purchased the kit to extract more power and be
optimum. Why not get it?