Interpreting your dyno graph
to understand a dyno graph for the first time can some
times be confusing. Let’s try to clarify some things. A
typical dyno graph from Axcelerated Motorsports will show
you horsepower, torque, and the Air to fuel ratio that
was recorded during the run. The graph has an X axis and
a Y axis. The Y axis runs vertical and X runs horizontal.
You will always find the horsepower and torque on the Y
axis. The X axis is at the bottom of the graph and almost
always represents RPM, sometimes speed if a good RPM signal
was not available. An easy way to tell the horsepower and
torque curves apart are to look closely at the two. Horsepower
always starts on the low side of the graph and peaks toward
the end. The torque curve will start out higher up earlier
in the RPM range and gradually drop off. A really nice
torque curve will actually be flat and hold steady through
out the RPM range.
Q. Why should I get a baseline
a baseline dyno test done before any modifications will give
an accurate starting point to measure the horsepower and
torque gains of the new modifications.
Why Did I make the same/less power after I did all this work?
is a common question, with many answers. I will assume
that both dyno tests were done on Dynojets. Comparing a
Dynojet run to another manufacturer’s dyno will not give
you an accurate comparison. The first thing to do is compare
the conditions and the correction factors. All of Axcelerated
Motorsports Dyno runs include the conditions of the day
on the “numbers” format page. The first thing to do is
to compare the conditions of the 2 days. Obviously, if
you have one test conducted on a 60* day and one on a 90*
day, it isn’t going to be an honest comparison.
reading the last paragraph, you maybe thinking, isn’t that
what the correction factor is for? To correct for differences
between run conditions? Yes, but it is primarily used to
correct for differences between runs during that same dyno
session, on the same day, on the same dyno. It corrects
for the ever changing barometric pressure, water in the
air and of course temperature.
the graph, or “numbers” page you will see the correction
factor. It may be abbreviated “CF”. There are 3 commonly
used corrections factors. Axcelerated Motorsports uses
the SAE correction factor. It is the correction factor
developed by the Society of Automotive Engineers, and most
commonly used throughout the industry. The SAE CF will
apply it’s own conditions to the run. Another commonly
used CF is the standard or “STD”. The standard correction
factor is an optimistic version of SAE, meaning it corrects
to better weather conditions. The third CF is “uncorrected”.
As it states there is 0 correction applied and is the actual
horsepower and torque figures.
again if you look at the data on the “numbers” page or
in the run notes you will see the correction factor. An
example would be CF=1.01 SAE. This is the correction factor
for what I would call a bad day. Let’s say this car made
300hp at the wheels uncorrected. To obtain the SAE correction
for this day it multiplied 300 X 1.01 to get 303 rwhp.
On a good day the CF might be .99 and the Rear wheel horsepower
would be corrected to 297 rwhp. Keep in mind that was only
an example. In a perfect world that same car that made
300 hp on a bad day should make slightly more on a good
compared my runs and I still don’t know why I am making
less power. Could the dyno be off?
One of the best attributes of a Dynojet dyno is the accuracy
and repeatability of their inertia dynos. Dynojets are
individually calibrated by their drum mass at the factory.
This calibration is not user adjustable, so no “fudging” of
numbers can occur. This type of design leaves virtually
no other variables to skew horsepower figures. Due to regular
maintenance on our part those variables are non existant.
We take our accuracy seriously!
no car is as repeatable as a Dynojet Dyno. There are
too many variables. Here is a list I will elaborate on
pressure. Low tire pressure will cause drag
Wheel change. Bigger wheels and tires have shown as much
as a 10 hp loss on the dyno
Brake Caliper or parking brake. Creates drag and less horsepower
weight. Heavier weight oil will cause more drag. Also oil
not up to temperature, including trans and gear oil.
to fuel ratio has changed.This is a big deal when comparing
runs so check it out!
above apply to all cars, below is for late model EFI cars.
timing has changed slightly. Late model EFI cars have
many different spark tables that dictate spark based
on feedback from other sensors, vehicle load, engine
conditions, environment, etc. These tables are add up
to come up with final spark. This can be a major variable
since a 2 degree change in spark advance can mean a major
further complicate matters, a new modification lets say heads
for example may change the vehicles calculated load. Since
now it can breathe better it’s efficiency has increased. So
let’s say before the headers, at 5500 RPM the calculated
load was .75. The spark table at this point was commanding
spark advance. Now with the new headers, calculated load
is now .80 at 5500 RPM. The spark table at .80 is commanding
of total spark advance. So basically you just lost 2 degrees
of timing at 5500 RPM. The spark table has to be changed
to optimize the new combination. Time to have it tuned!
I had my car dynoed at another shop, and now at yours after
making some changes. I have 2 dyno results that are significantly
different than what I expected. What is going on?
first step here is to determine if both dyno tests were conducted
on the same machine. Our Dyno is a Dynojet 248H high inertia
dyno. All Dynojet Dynos are supposed to be accurate to +
or - 1%. If both tests were run on a Dynojet, one factor
is ruled out. There is no way to correlate a Mustang Dyno
a Dynocom, or any other dyno's result to a Dynojet. Some
say to add or subtract a percentage but it is totally untrue.
A2. Check if
both sheets use the same correction factor. there are 3 commonly
used, SAE, standard, and uncorrected. The correction factor
adds a correction to the dyno results based on the temperature
and barometric pressure. SAE is the correction factor that
Society of Automotive Engineers uses. Standard is a more "optimistic" version
of SAE using a lower temperature and pressure. Uncorrected
is with no correction factor applied.
correction factor is mainly used to correct between runs.
Since temperature and barometric pressure change through
the course of the day, the correction factor eliminates this
variable. The correction factor is not able to make up the
difference from a dyno run on a 95 degree day compared to
a 60 degree day.
Motorsports uses the SAE correction factor. The information
recorded contains the correction factor, temperature, and
barometric pressure.It can be found on the dyno run "numbers" format
As an example, a car with 300
rear wheel horsepower uncorrected on a really bad weather
day, would correct to 306 rear wheel horsepower, with a correction
factor of 1.02.
do I find my PCM catch code?
can find the catch code for your PCM in a few places. You
are looking for a combination of letters and numbers in bold.
Older vehicles will have a 3 digit code while later vehicles
have a 4 digit code. In most 2000 and newer vehicles it will
be on small white sticker located in the driver's door jam
even with the dash. Older vehicles you will have to locate
the PCM and read it off of either the connector at the front
or the J3 cover at the back of the computer. Once you have
the PCM code, this code can be entered directly into our
Advantage 3.0 software to create a custom tuning file. The
PCM code can also be retrieved using an SCT flash device
such as the XCalibrator 3.
2005 to current Mustangs can find it
on the PCM next to the battery.
My car is running really bad, it needs to be tuned?
too often the customer believes the tune is the problem.
More often the problem is a defective sensor, part installed
incorrectly, mechanical issues, or a combination that was
not designed to work together. Fouled plugs, bad wires,
bad gas, grounds all cause driveability issues that may
mimic a tuning issue. Very rarely tuning will solve major