Motor vehicle manufacturers are
mandated by the EPA to produce vehicles that meet specific smog standards.
To meet these standards with the current TC88 and exhaust technology, the
MoCo tunes their engines relatively lean. As a result, bikes produce less
smog, mileage is better, but lean tuning denies you max performance, and
causes excessive engine heat which, in turn, negatively affects engine
life. Tuning your bike to provide optimum fuel/air mixture provides better
performance and engine life at some loss of mileage. For carbureted
engines it's relatively simple to fix by tweaking your carb. But, fuel
injected systems have matrices stored in the Electronic Control Module
(ECM) called maps which control fuel/air and ignition timing for different
RPMs and throttle positions. To optimize your fuel/air mixture or ignition
timing you need to either remap the Electronic Control Module or provide a
downstream correction. This is especially important if you make changes to
your breather, pipes, cams or heads.

The MoCo's Solution

Harley provides two solutions for those making modifications to their
bikes- The Stage I/II/III ECM Calibrations (aka chip burn, re-flash, etc.)
which are simple solutions for re-mapping the bike's ECM for typical
configurations, while increasing idle mixture, and increasing the rev
limiter to 6200 RPM; and the Screaming Eagle ECM Race Tuner which allows
much finer control of your bike's fuel/air and ignition maps.

For most folks, a stage one upgrade (aka "The Harley Tax") means
changing to free-flowing breather and pipes. But the stage one re-flash is
not designed for a free-flowing exhaust system. Changing both the breather
and pipes provides increased air flow, and with the right fuel mixture,
provides greater performance. Doing such an upgrade with only a stage one
re-flash could create an excessively lean condition. If you perform only
the MoCo recommended Stage One mods, leaving stock pipes in place, a stage
one reflash might be acceptable.

For those performing more extensive modifications, the ECM calibration
re-flashes do not allow tweaking for specific choices of breather, pipes,
cams and heads. Since every combination is going to have different affects
on your torque and HP curves, a simple re-flash is not likely to allow a
bike modified beyond stage one to achieve its full potential. For that,
you need fine control of your fuel/air mixture maps.

It does increase the rev limiter, so if your Wide-Glide with hot cams,
SE breather kit and White Bro's 2 into 1 pipes makes its peak hp at 5600
rpm's, (higher than the stock rev limiter), the chip burn will allow you
to reach it's peak. For those into getting the last bit of performance out
of their bikes, this might be important. For cruisers, that higher rev
limit may be of little or no practical value.

To provide the racer with finer control, Harley sells the Screaming
Eagle ECM Tuner. This is a software package you load on a computer, with a
cable and a dongle that plugs into your ECM. It allows you to re-flash
your ECM with either standard calibrations, or with your own custom maps.
The calibrations that come with the system are the same as those your
dealer offers, and as of this writing, there are no custom maps available
from Harley or any third party. However, you can precisely adjust fuel/air
mixture at different rpms and throttle positions, as well as to
advance/retard ignition. It comes with directions as to how to adjust
settings based on feel, dyno runs or track runs. You can take a track run,
download performance curves from the ECM, make adjustments and upload the
new maps.

However, this amount of control comes with a price - $460, and use of
it voids any warranty. It requires a great deal of technical knowledge and
commitment. Further, the dongle is a security device that does not allow
you to use the system on more than one bike. The first time you use it on
your bike, it handshakes with the ECM and will forever only work with that
ECM. Own two fuelies? Get two systems.

Power Commander

The Dynojet Power Commander (commonly referred to as a PCIII) is a fuel
injection and ignition timing adjustment unit that plugs inline with the
bikes' stock ECM. Changes are made to the bikes fuel and ignition curves
without making any permanent changes to the bike's ECM. The PC uses
original equipment style connectors allowing you to plug it in without
splicing or cutting of the wiring harness. Removing the PC returns the
bike to its previous stock condition.

The unit comes with computer software and a USB cable that allows you
to select a specific map, upload it, or fine tune maps. The PC is
pre-loaded with a base map which generally provides an improvement for
stock bikes. Alternate maps are available for most typical configurations
(i.e. TC-88 w/ stage 1 calibration, SE Air Filter and V&H Staggered Dual
pipes). Each PC is supplied with a CD-ROM with common alternate maps. More
maps are available for download on their website.

The software provides a spreadsheet interface allowing one to make
fuel/air adjustments at specific RPM and throttle positions. The resulting
custom map can be uploaded via the USB cable.

You can also change the fuel curve with the faceplate buttons. This
adjustment moves the fuel curve richer or leaner in each area of the map.
For instance, if you're riding heavily loaded or its particularly hot
weather the PC can be temporarily adjusted at the faceplate to eliminate
the "pinging" that is so common during these conditions. If you are about
to make a long highway run, you can temporarily make the mixture more lean
for better mileage.

For some bikes, Power Commanders can also adjust the ignition curve for
increased throttle response, increased peak power, or to eliminate
detonation. On most models the ignition curve is close to optimum for
"pump" fuel.

One poster (MRBHD) had a PC installed in his 98 bagger. His Comments:
"The bike had the HD stage II and Sampson slip-ons already. On the dyno
prior to the power commander, the bike made 58 HP with about 60 ft/lbs of
torque as verified by the dyno. After the power commander the bike now
makes 76 HP with about 72 ft/lbs of torque! All of these are at about 3800
rpm due to the stage II cam. The bike now runs FANTASTIC, and it doesn't
ping!!!"

A less expensive (~$240) and a simpler solution is the device designed
by Mark Dobeck and sold by Dobeck Performance as the Techlusion Fuel
Injection (TFI), and by RevTech as the Digital Fuel Optimizer (DFO).

Like the Power Commander, they plug inline with the ECM. Adjustments to
fuel/air mixture utilizes four adjustment pots which work similar in
concept to carburetor jet and mixture screw adjustments - An idle and low
speed circuit (pilot jet\mixture screw), mid range and throttle response
circuit for acceleration (needle and slide), a main circuit for wide open
throttle and power (main jet), and a circuit which provides an adjustable
accelerator pump function that senses when you grab a handful of throttle.

They are inexpensive, easy to install and easy to tweak, They do not
require (or allow) a computer interface, downloads, extensive mapping,
etc. They only add fuel, they do not allow you to reduce it as other
solutions do, and they do not provide for changes to ignition timing.

Yup, lots of others, more coming, and they change all the time. S&S,
Daytona Twin Tech, Daytona Sensors ... Wide band systems, oxygen sensors
... This is only an overview of the issues, and the most common solutions.
See "Other Forums" below for places where you can get deeper into it, and
keep up with it all.

Will any of these void my warranty?

Maybe, probably. Especially if it can be proved your use of such a
device caused damage. (i.e. you burned up your valves by running
excessively lean). If you are concerned, check with your dealer. And if
you don't like the answer, check with other dealers in the area. OTOH, If
you're not ready to accept full responsibility for modifications you make,
maybe you should stick with what the MoCo offers or leave your bike stock.

Jeeesh, are there any other downsides . . .

Sure, if you enrich your system, fuel economy is going to suffer. When
your bike runs lean, you burn less fuel. If you make your fuel/air mixture
richer, you can expect a drop in MPG. One poster experienced a 10 MPG drop
using a standard map for his bike. Dyno tuning can provide a more optimum
map and fuel rate.

Then there's the ever-evolving issues with legality of futzing with
your systems, environmental issues, noise issues. Consult federal law,
state code, lawyers, and spiritual advisors for advice in these areas.

What to do, what to do?

If you can afford it, if you have a better than average understanding
of how to tweak maps, and if you want the finest control over your ECM,
the Screaming Eagle ECM Tuner is certainly a clean, first rate solution.

Many in this group like the PCIII and enthusiastically recommend
installing them. The TFI/DFO solution is certainly a viable alternative
for folk looking for a simpler solution.

The ongoing, raging controversy is whether to do the MoCo's ECM
calibration first or to save the ~$150 re-flash cost. The stage one setup
will enrich your idle (which neither the PC nor the TFI/DFO do) and will
increase your rev limiter to 6100 RPM (which neither device does). If your
PC/TFI/DFO craps out, and you have a stage 1 kit, you can simply unplug
the PC, reverting to the OEM system in a matter of minutes and you're back
on the road with a less than optimal, but probably not dangerously lean
condition to worry about. If you have a bike modified beyond a simple
stage one, the extra $150 might be cheap insurance. Some feel (and others
don't) that the MoCo's ECM calibration should be done regardless.

There are hundreds of messages on this topic in RMH. A Google search of
the archives will give you a wealth of experience with these issues.

Other Forums

This is bar talk, if you want a more technical discussion there are
other online forums which go into much more technical detail: