What is Data?
Data is defined as a collection of facts from which conclusions
may be drawn. When speaking of engines, a tuning decision
(e.g. should I jet up or down?) must be based on a variety
of good data (such as the air-fuel ratio is 14:1 at 5000
rpm). While weekend enthusiasts and amateur racers realize
the importance of having good data to tune with, the problem
has been in obtaining this data. We all have gauges in our
car to keep us apprised of vital stats, but they only give
us a single-point of data in real time. There is no easy
way to consolidate all the data, or go back and look at
what transpired. As a result most of us spend our time tuning
on a chassis dyno or at the track, where there is an end
result -a number, to work with. While this type of tuning
has merits, the information gained from it is limited and
many times circumstantial. For instance, if we come into
the dyno shop making 300 horsepower, and leave making 320,
we may erroneously conclude the engine is now properly tuned.
While many dynamometers have the ability to monitor air-fuel
ratio and rpm, you are still leaving out many other important
and vital engine tuning parameters, such as fuel pressure,
exhaust gas temperature, and boost pressure to name a few.
This is aside from the issue of not tuning under actual
road and load conditions.
Data Logging for Everyone
Take a glance in the pits of almost every professional auto
racing series and you'll witness just as many laptops as
tool boxes. The type of data logging system in use by professional
teams can record as many as 100 different parameters on
the race car and send it all back to the pit crew via telemetry.
Such systems cost tens of thousands of dollars and were
never intended for the recreational consumer. However, the
concepts and technology are certainly very applicable, and
it was just a matter of time until companies marketed streamlined,
and more affordable, data logging systems.
We recently tried out one such
system developed by Innovate Motorsports. The LM-1 digital
data logger incorporates a wide-band oxygen sensor plus
five additional channels in order to make for some very
powerful tuning capability. In its most basic form the LM-1
unit, which ships with
the Bosch LSU 4.2 wide-band O2 sensor and a 10 ft. cable,
can record and display air-fuel ratio from the exhaust stream.
The unit samples at a rate of 12 times per second and will
store up to 44 minutes of data. You do not need a laptop
in the car to record and you can record multiple sessions.
This means you can go out for a tuning session and separately
record each wide open throttle blast you make. You then
use the supplied cable to download the data to your PC and
analyze the results with the LogWorks software.
Wide-band O2 sensor eliminates
the need to visit a dyno just for A/F data.
While the wide-band O2 sensor is in itself a huge tuning tool,
the real power of the LM-1 is in its ability to log five other
channels. Think of a channel as a port though which data can
be captured. Data comes from sensors, and for the LM-1 the
sensors must generate an output signal between 0-5V. If this
sounds confusing don't worry, we'll get into that later in
this article. Using sensors enables you to view A/F ratio
in the context of other parameters, such as rpm, boost pressure,
throttle position, injector pulse, fuel pressure, or whatever
else you can think of.
In order to populate the five channels in the LM-1 unit you
need one of the two available auxiliary units (see side bar.)
With either of these devices
one can populate rpm using
a tach-lead and also the remaining channels using common automotive
0-5V sensors. For instance, if you wanted to view fuel pressure
you could use a pressure transducer, such as those in Autometer
fuel pressure gauges, which send a linear 0-5V signal corresponding
to rise in fuel pressure. Most sensors on late-model "computer
controlled" vehicles, such as throttle position and MAP
sensors, output a 0-5V signal. They can be easily adapted
onto early vehicles for purposes of data logging.
Capturing the Data
Over the past month we've been using the LM-1 to tune
and troubleshoot our supercharged Project '67 Mustang (see
on Carbs") as well as our '01 GT which recently received
a nitrous kit (see "Bottle
Feeding"). Project '67 is a great example of how
dyno tuning can paint an incomplete picture of where an engine
really stands. The supercharged 331-cid motor produced over
500 horsepower to the wheels on a dyno. While the numbers
were impressive we were experiencing different results on
the dyno than on the road. On the dyno we would see boost
hit 8 psi, while on the road we were only seeing 4-5psi. Rather
than continue to tune the car on the dyno we used the LM-1
to obtain actual road conditions for rpm, boost pressure,
fuel pressure, and air/fuel ratio. More
(Capturing and Analyzing Data)
We explore the power of data logging using Innovate
Motorsports LM-1 digital wide band oxygen sensor and
data logging device.
The LM-1 Digital Air/Fuel ratio meter. The base unit is
includes a Bosch LSU 4.2 wide-band oxygen sensor and software
for viewing/replaying the data. The unit has the ability
to capture five additional channels of data, using an auxiliary
input devices below. At about $350 the base unit pays for
itself in a few hours of dyno time.
The LMA-3 or "Aux Box" is
a necessary add-on device for the LM-1 if you want to take
advantage of the data logging capabilities. The unit comes
with built in sensors for MAP (manifold absolute pressure),
RPM converter, thermocouples (for exhaust gas or cylinder
head temperature), as well as an accelerometer and duty cycle
sensor. There are also five external inputs for connecting
your own 0-5V sensors. This unit is $250. A streamlined version,
is only $99 and has a built in RPM sensor.
|O2 Sensors - Wide vs. Narrow
Standard "narrow band" O2 sensors operate
between 0 and 1 volts, and are only capable of accurately
measuring a stoichiometric air/fuel ratio (e.g. 14.7:1).
A richer or leaner condition results in an abrupt voltage
change (see Fig 1.) and thus is only useful for qualitative
determination. Modern automobiles use this "switch"
like sensing at idle and part throttle to make small
compensations in fuel delivery to keep the air/fuel
ratio near 14.7:1.
|Wide band oxygen sensors, such as
the Bosch LSU 4.2, utilize a more sophisticated sensing
element which enable it to produce precise voltage output
in proportion to the air/fuel ratio (see Fig 2.) As
a result a wide band sensor can measure accurately from
as rich as 9.0:1 to as lean as free air. Wide band sensors
used to be cost prohibitive, however recently their
wide spread use has reduced prices to as low at $50.