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Instruction manual for Dynomet road dyno.
If you have any questions please email: firstname.lastname@example.org or
call +48 603 678 785
1. Software installation
2. In which gear should the power
3. How to measure power.
4. Other software functions.
5. Acceleration tests.
Power testing on cars with automatic gearboxes.
1. SOFTWARE INSTALLATION
Run the .exe
file and follow the steps on the screen.
Before plugging the dyno to USB run the CDM20824_Setup.exe program (in
the Dynomet folder), these are the drivers required to run the dyno.
You were given a registration file called 'reg.fil', overwrite the
file in the Dynomet folder with your file. This will enable you to
use your program and will display your name on top of the window.
Now you can connect the dyno and run the software.
When the software is launched for the first time it asks for the
language and type of dyno - choose Road car (for cars) or Road Truck
(for heavy trucks).
If you want to measure both cars and trucks, this
setting can later be altered by going into Options and on the bottom
of the window, under Dealer code type: setup and press OK. This will
show other options where you will find dyno type selection (under
Software basic settings).
The difference in the car and truck versions is the RPM range for
gear ratios (lower for trucks).
This is how the main menu should look like:
for the buttons in the main menu
1. Speed vs
2. Power graph
4. Power testing etc.
a. This shows
how much the power will be altered accordingly to the DIN70020 norm
for power tests. This changes with pressure and air temp you input
into 'b' and 'c'
b. air pressure (only for NA - naturally aspirated cars, all
turbocharged cars should have 1013 put in, as this means 0%
correction for pressure)
c. air temperature - put in the ambient temperature, not intake
d. Total ratio - this is the gear ratio for the gear in which power
will be tested. This is measured while driving in the selected gear
at 3000 rpm (1000rpm for trucks in truck mode). If you know the gear
ratios for the car from a manual etc. you need to multiply the gear
ratio by the differential ratio. For example, you test in 3rd gear,
3rd gear ratio is 1.333 and differential in the gearbox is 4.1,
multiply 1.333 by 4.1 and the result of 5.46 should be put in
e. weight - put in the total weight of the car, with driver,
passanger, anything there is in the car's trunk etc. If the weight
is incorrect by 5% the power will be shown incorretly by about 5%
too. But remember, if you are using this dyno to compare a car
before and after modifications (like chiptuning etc.) you don't need
exact weight in order to show the difference in power. If you have a
1.9 TDI 130 HP VW Passat, which weighs about 1500kg and you put in
1450kg, the power will be about 126HP, if you put in 1550kg, the
power will be about 134HP. After you tune it and add about 30HP, the
power for 1450kg will be about 155HP and for 1550kg about 165HP, so
the difference will be clearly visible.
f. Differential - this is the ratio for the differential in the
gearbox. Also measured while driving. In a 5 speed gearbox, usually
the 4th gear will be the direct 1:1 gear. This value should be
measured in 4th gear. For 6 speed gearboxes it is usually the 5th
gear (4th in diesel cars usuallu, but you should check). 7 speed
dual clutch gearboxes have 2 final drives, but usually using 5th
gear will be OK. 8 speed automatics usually have the 6th gear as a
direct gear. This value has little effect on the power value, so
it's not a problem if you don't know if the direct gear is the 4th
or 5th, measure both parameters and put in an average number.
g. Wheel circumference - the software has the ability to measure the
circumference by measuring rotations of the wheel on a given
distance (like 1000meters), it divides the rotation by the distance
and the circumference is the result. If you have a stretch of road
where you know the exact lenght, you can put in that length into the
software and it will measure the circumference. I was using the 100
meter markers on the roads but have personally stopped doing this -
it turned out to be inaccurate. I use a tire size calculator,
something like this:
other people use measuring tape. A difference of 1cm will be less
than 0.5% in power, so don't worry.
h. This is the number of impulses from the sensor per 1000 meters,
this is just for information purposes.
i. Here you put in the same value as under 'g'. This is for cars
with different wheel circumferences for front and rear wheels. But
since all cars with ABS/ESP have to have the same circumference for
front and rear in order for the ABS and ESP to work properly, you
just put in the same value. If you do find a car with very different
wheels in front and rear, the software will tell you where to put
which value - hover your mouse over the box and the description will
appear in the bottom.
2. MEASURING POWER: IN WHICH GEAR?
The power should
be measured in a gear where the time it takes to accelerate from
around 1000-1200 rpm to maximum rpm is between 10 and 20 seconds
(optimum is around 15-20 seconds). This means that in 90% of cars,
the power should be measured in 3rd gear.
If the acceleration takes less than around 10 seconds we have 2
Risk 1 - the software has not enough data points to accurately
measure the power with sufficient resolution, but more importantly
Risk 2 - the engine might not make 100% power because the load was
if a car accelerates in 3rd gear from 1000rpm to max rpm in less
than 10 seconds, this means it's a fast car, with big engine or
turbocharged engine (probably with power above 300HP or a big diesel
with short gears). Cars with high power will not make 100% power in
1st and 2nd gears, and probably not in 3rd also.
What can you do if the car is too fast in 3rd gear? You can use 4th
gear if the road you are on allows higher speed (maximum rpm in 4th
gear will mean about 130-150km/h for a diesel car or more for petrol
cars, maybe 160-180!). Or stay in 3rd gear and put 2-3 friends in
the back seat :) this will add 250-300kg to the cars' weight and
will slow it down so it will accelerate slower and you will have
more accurate measurement. Of course you need to add the weight of
the people in the file. I have personally tested 500-600HP cars in
4th gear (Porsche 911 turbo, Toyota Supra, etc) and 4th gear was OK.
Both cars could be measured in 3rd gear, but full power and more
accurate graph was achieved in 4th gear.
If the car is really slow, has 50-60HP, the 3rd gear might be too
long, use 2nd gear or use the slider shown below to make the graph
In both of these situations you can also increase or decrease the
amount of data points and smoothness of the power and torque curves,
you can do it here (this only applies if you are sure the car made
By default the software is setup in Auto mode (left of the Detect
automatic gearbox button), but if you depress it, a slider will
become visible. This slider will let you 'play' with your file.
Going up and down will make your curves more accurate or more even.
The default setting is 6.
Below is the same file with 3 different filter setting, 9, 6 and 3.
Here is the file at level 6:
The curve is smooth.
Here is the same file but at level 9:
Notice how the same line became much smoother - too smooth for this
file. Also notice how the maximum values changed, the follow the
curves which are now shaped a bit different.
Here is the same file at level 3:
This is to rough, level 3 for this car is too much. Now we can see
all bumps in the road we used.
As you can see, level 6 - the default level - is the best filter for
most cars. But now you know how the filter alters the curves.
1. Create a new file by clicking the wide bar by number 1 (for
example: powertest). The software will add a number at the end of
the file's name and will automatically create new files with numbers
with every new test (so after you named the file: powertest, the
software will automatically name it powertest01, for the first test,
and powertest02 for the second, etc).
2. before performing the power test, you need to put in 4 values:
- air temp
- air pressure (for turbocharged cars put in 1013 so the pressure
correction is 0%)
- total weight of the car (with driver, passanger etc.)
- wheel circumference (the circumference has to be put in Wheel circ.
and Road wheel).
(all these values can be changed after you measure the power, if you
are not sure of the weight of the car, put in an estimate and
correct later. Same applies to pressure and temperature. But make
sure you put in the correct value for the wheel as this affects how
the gear ratios are measured)
After you put in these 4 values, you can drive the car.
click on the icon number 4, this is what you will see:
The buttons are
listen in the order you should be using them.
Button 1, Calibrate wheel, this is only used if you want to
calculate the wheel circumference with the software, if you used the
tyre calculator like I use or measuring tape, you don't use this
Button 2, Find Total Ratio - this is where you calculate the ratio
for the gear you will be measuring power in (usually 3rd, like I
explained earlier). Drive in selected gear (usually 3rd) at 3000rpm
(or 1000rpm for truck mode) and press Space bar, you will
notice the values change after hitting space bar. If they stay at
0.00 press space bar again.
Press Enter to save the value and exit this menu.
Button 3, Find Differential - do as you did with the last operation,
but while driving in direct gear (as I explained earlier, usually
4th gear or higher for 7-8speed gearboxes). While driving at 3000rpm
(or 1000 for trucks) press Space bar, you will notice the
values change after hitting space bar. If they stay at 0.00 press
space bar again. Press Enter to save the value and exit this menu.
- If you knew the gear ratios from a manual or the internet and put
them in manually, you don't need to do these last 2 steps, go
straight to 'Collect'! These 2 steps will overwrite whatever you put
Button 4 - Speedo
Control - this is for checking the speedometer values against the
actual speed from the sensor mounted on the wheel. You don't need to
do this, I never do.
Button 5 - Collect - this is where you measure power:
The rev counter is now calibrated for the gear you will be measuring
power in, and the speedometer shows the speed you are travelling at.
If either of these is off by more than 5-10%, you did something
wrong. Check the previous steps. The speedometer will usually show
3-5% higher than actual speed, this is normal on all cars. But rpms
To measure the power select the 3rd gear (or other, as explained
earlier), slow down to around 1000-1200 rpm, press the space bar,
wait 1-2seconds for the software to start counting seconds in the
box below the speedometer and accelerate at 100% to the maximum revs
(rev limiter for petrol, or about 4500 rpm for diesel cars). After
reaching the maximum revs release the accelerator pedal and press
the clutch pedal. Coast for 15 seconds (still with the gear lever in
selected gear) with pressed clutch - this is when the power loss
from friction, wind resistance etc is measured. After 15 seconds the
software will stop the test. You can press the space bar before the
15 seconds have passed but there is a risk that the test will not be
accurate. Allow at least 10 seconds of deceleration.
The table on the right is a preview of the power - this is not the
final power! The red curve will be the power at the wheels. The blue
curve will be the power loss. This is just to show you if everything
is working OK.
After deceleration, a window will show the power estimate.
In order to see the exact power measurement, exit this window, open
your file from the main menu and press the button 2 on the main
if you want to perform a second test, you don't need to exit the 'Collect'
window, just press space bar again to start a new test. On top of
the window you will see your file name with an incremented number (like:
In the right preview window power and rpm scale can be changed by
clicking the numbers with left mouse button and right mouse button.
OTHER SOFTWARE FUNCTIONS
Comparing files - open file number 1, and then open file number 2 by
clickig the icon by the number 2. After you opened the second file,
number 3 will appear. You can open up to 4 files at a time.
Here, under Options - Colour you can set the color for the files. If
you want to compare 2 tests, you want them to be in different colors.
You want to change HP Engine and Nm, these are the colors in the
you can set few things:
Line thickness changes the lines on the power curves
Loose curve will show an extra window after opening a power file, it
shows what you saw during the power test in the preview window.
Mainly for checking the loose curve.
Use fixed scales is to set your own scales in the power graph. I
always put in the same value for HP and Nm, this way the graph is
more clear for the customer.
Logo and printer setup - Logo is to switch your logo on the printout
(file: comp.jpg in the program folder) and the width height is the
size of the printout.
Pressing button number 1 on the main screen will show the
acceleration graph - speed vs time
Here's an example of a power file. Window no 1 shows power, window
no 2 shows the acceleration graph and window no 3 shows the loose
curve (if you selected the Loose Curve option in Options - View/Print).
Here is a maximised power graph window. If you right click on it, a
pop-up menu will appear where you can set the position of power and
If you want to measure acceleration (like 0-100km/h, 80-120 km/h,
1/4 mile time and speed, braking distance etc) make a new file (called
accelerationtest for example) and all you really need to put in is
the wheel circumference. Weight, air temp, gear ratios are not
relevant now. We are only iterested in speed.
Go straight to collect and if you are testing 0-100 times, stop the
car, press space, wait for the software to start counting time and
AFTER that, you can start driving. Don't start the car with space
bar, you will loose the first 1-2 seconds of the run. Start whenever
you want, don't worry if you start later. Now, the software is
logging all that you are doing.
After you finished the test, load your file from the main menu and
click on the Table text (by Exit) in the top left of the screen.
This is what you will see:
We are interested in the 3 first columns, Time, Speed and Distance.
From that, we can calculate anything. If you started in the 5th
second and reached 100km/h in 12th second, 12-5 = 7s. This is you
0-100 time. From this table you can extract acceleration times,
braking distance, 1/4 mile time and speed etc.
To measure the power of a truck, your software needs to be in the
truck mode (here is how to change
In order to measure the power of a truck correctly on the road, the
truck needs to have a trailer with a load. Only then it will have
full power. You need to put in the correct weight of the whole set.
The rest of the test is done like with a
normal car - testing should be done
in a gear where it takes between 10 to 20 seconds to accelerate from
lowest rpm to maximum rpm. The optimum is 15-20 seconds.
7. HOW TO MEASURE CARS WITH AUTOMATICS
Many current cars have automatic gearboxes - here is a guide on how
to measure different types of automatic gearboxes.
(4 gear, no gear selector, only P R N D 3 2 1 or P R N D 2 L with an
overdrive button on the lever).
This is the most difficult gearbox to test. Having only 4 gears
means these gears are long, usually 3rd gear will be the direct 1:1
gear and also quite long (on petrol cars up to 160-190km/h or more),
so the power test should be performed in 2nd gear. This might be too
short. But there is no other way, because using 3rd gear will mean
2nd gear will probably reach around 100-130km/h depending on car.
This might be enough, if not, put your 3 friends in the car to slow
In order to measure gear ratios you need to select 2nd gear, so slow
down, put the lever in position 2, accelerate, observe the
speedometer and rev counter, these cars usually have torque
converters with no lockup, so it's possible that the car will be
still accelerating even at steady 3000 rpm, wait for the car to stop
accelerating and press space bar to measure the gear ratio.
Do the same for Differential, but use 3rd gear, put in the gear
lever in position '3' or, if the car does not have one, put it in
'D' and switch off overdrive (usually a small button on the gear
lever). Accelerate to 3000 rpm, wait for the car to stop
accelerating (torque converter) and hit space bar then. After we
measured the ratios, we can continue to power tests.
These gearboxes will downshift a gear (kick-down) if the accelerator
pedal is pressed too much in lower revs, so accelerating at 100%
throttle from 1200rpm is impossible. If we are measuring power in
2nd gear we need to make sure we are IN the 2nd gear. This can be
done by accelerating to 50-60km/h, you can feel the car switching
from 1st to 2nd, now slow the car down, trying to feel it not
shifting back into 1st. There is no point going lower than 2000 rpm,
as the gearbox will downshift anyway. At around 2000rpm hit the
space bar to start the test, now press the accelerator around
50-60%, the revs will rise a lot, the car starts accelerating, press
the accelerator more and more, but don't overdo it, you should reach
around 3500 in a petrol car before pressing the accelerator 100% (or
around 2500-2800 in a diesel). After reaching maximum revs, shift
the gearbox into Neutral (position N), and coast for 15 seconds.
This of course only measures 100% power from around 3500 rpm, where
you have pressed the accelerator 100%, but it's OK, since this type
of gearbox will not allow 100% throttle at rpms lower than around
3500 rpms, so we don't really need to know what happens below these
rpms. It's a limitation of the gearbox, not the dyno.
Tiptronic. Automatics with gear selection.
Please read the above description for old automatics, the
information there might come useful with tiptronics too.
Some types of tiptronic gearboxes, like the ones on BMW, will allow
lockup in lower rpms, so accelerating at 100% in 3rd gear from about
1500-2000rpm will be possible. This is easy and power tests look
almost like on a car with a manual gearbox. Unfortunately some
Tiptronics like on some Audis or Mercedes even though allow gear
selection, will still downshift at 100% throttle in low rpms. The
acceleration technique described above for old automatics should be
used, so acceleratig gradually from about 50% throttle to 100% after
mid rpms, where downshift is not possible anymore.
type tiptronic (8 speed ZF, 6 Speed)
Almost all new automatics will lock up gears and allow 100% throttle
from 1200-1500rpm in manual mode. So no problem here.
These behave like manuals, so treat them like manuals.
Neutral while driving:
Any car's manual will tell you that you should not switch to
neutral while driving. While towing a car with the engine off might
damage the gearbox I have not found any information on the internet
what could happen to a gearbox when the engine is running and you
put it in neutral while still moving. The pump for hydraulic is
still running, so no risk there. I know a person who did 250
000 km in his automatic car and switched to Neutral every time he
was slowing down for a crossroad or red light and nothing happened
to the gearbox, so I don't think there is any risk.
Some cars might not allow to switch back do Drive while moving, you
just need to stop then.
But if the owner of the car will not allow to switch to neutral
while driving, what you can do is perform a normal power test,
accelerate like usual but instead of decelerating in neutral to
measure power loss, decelerate in Drive. This will of course change
the result of the test by 20-30HP or more (engine breaking), but in
such case, open that file, go to Options - Calculation and click
Fixed Loose - this enables you to set the power loss level. Look at
a similar car you tested before and see the level of power loss
there - put that number into your file and you have an estimate
power you can use (depending on a car and gear you measured the
power in, this could be 20-30HP for small cars, to even 80-100HP if
it was a big SUV measured in 4th gear). The power loss value is
displayed in the bottom right box (77.7HP in the example below or
25.7 - 3 pictures above).
There is a special button in Options - Calculation, called
This is for cars, where shifting into Neutral after reaching maximum
revs does not instantly disengage the gear and a few seconds of
engine braking accurs.
Notice the blue line (in the bottom right window), which is the
actual power loss line - there is a bump in the highest part of the
line at around 4200 rpm, this is where engine braking accured. This
could potentially add more power to the wheel power resulting in
wrong power at the engine. Pressing the Detect Automatic Gearbox
button ignores this bump and the green line is taken into the
calculation. Press this button when you notice engine braking for a
few seconds after switching into neutral.
Last update: 1.2014