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Instruction manual for Dynomet road dyno.
If you have any questions please email: or call +48 603 678 785

1. Software installation
2. In which gear should the power be measured?
3. How to measure power.
4. Other software functions.
5. Acceleration tests.

6. Truck testing.
7. Power testing on cars with automatic gearboxes.


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:


Description for the buttons in the main menu

1. Speed vs time graph
2. Power graph
3. Options
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 temp!

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.


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 risks.
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 not sufficient.
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 smoother.

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 100% power):

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.

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.

REMEMBER - 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 in!

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 should match.

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 screen.
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: powertest02.acc).

In the right preview window power and rpm scale can be changed by clicking the numbers with left mouse button and right mouse button.



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 power curve.

Under View/Print 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 torque values:




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 it).
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.



Many current cars have automatic gearboxes - here is a guide on how to measure different types of automatic gearboxes.

Old type automatic (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 high speeds.
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 it :)
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.

2. 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.

3. New 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.

4. DSG, PDK, DKG etc.
These behave like manuals, so treat them like manuals.

Shifting into 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
Detect Automatic Gearbox. 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