Draft Test / Performance Test 2000-4000 rpm (Articles)

First of all, my heartfelt thanks to Ernst S. for his work in developing the ventilation calculator from its initial stages to its current scope!

The basic principle of the dynamometer (DZR) involves measuring the pulling power of a vehicle at full throttle on a flat surface using a stopwatch, in order to derive information about the engine power within the tested RPM range.
In this case, the vehicle's mass (including luggage, passengers, etc.) essentially replaces the inertia masses of a dynamometer.
For measuring the engine speed on a TDI, a range between 2000 and 4000 rpm is suitable, as the engines operate with full boost pressure in this range, thus always providing the maximum possible torque.
Measurements taken in 3rd gear show a speed range of approximately 50 to 100 km/h, which poses no problems in terms of track selection (a few hundred meters of country road is sufficient), and typically occur within timeframes of 6-8 seconds. With some practice, these times can be determined with an accuracy of approximately 3% (or better) using a stopwatch.


How is it measured?

When measuring the time at 2000-4000 rpm, to avoid the turbo lag, you must apply full throttle no later than 1500 rpm and then measure the time between 2000 and 4000 rpm according to the tachometer.
Air conditioning systems must be completely turned off, otherwise, some horsepower will be lost during the dynamometer test!

Because measurement errors tend to average out statistically, the average value obtained from multiple measurements increases the accuracy.
To eliminate distortions caused by inclines or declines, as well as headwinds and tailwinds, the measurement runs should be conducted equally in both directions. Generally, a reliable average time can be obtained from a total of 4 or 6 measurements.

Those who have access to VCDS (formerly VAG-COM) can replace the stopwatch with data logging during the test. VCDS-RKS includes the KPower tool, which automates the entire evaluation process.

To achieve the highest possible sampling rate and thus a more accurate result, it is recommended to log only one measurement block that contains the motor speed.
The time and speed of the last measurement before 2000 rpm and 4000 rpm, as well as the first measurement after 2000 rpm and 4000 rpm, are then transferred from the log to the "Time Interpolation" sheet.
The exact time range from 2000 to 4000 rpm is interpolated and transferred to the "Durchzugsrechner" (flow rate calculator) sheet, where it is displayed next to the calculated time.


Comparison of measured time and calculation

Using an Excel calculation (the actual DZR, see download), which specifically includes the overall gear ratio (rpm -> km/h) and the vehicle weight, a vehicle-specific target value for the time at 2000 to 4000 rpm can be calculated and compared to the actual or logged time.
Comparing the measured/logged time with the target value allows us to determine whether the engine power between 2000 and 4000 rpm, on average, corresponds to the factory specifications, or by what percentage it deviates upwards or downwards (more details will follow below).


What is needed for the calculation?

The accuracy of the calculated target time depends entirely on the precision of the vehicle data, particularly the weight and the overall gear ratio (rpm to km/h), which must be determined as accurately as possible.
As a reward for this effort, the comparison between actual and target times yields an accuracy in performance calculation that, in principle, is not inferior to that of correctly executed dynamometer tests.

Note: Even when performing a power measurement on a trainer, there is only one value that is guaranteed to be accurate – the price you paid!
And because customers prefer to read about high performance for their money, process tolerances are often adjusted in that direction as well.
see, for example,


In order for the DZR (presumably a device or software) to calculate the values, the normal torque values of the respective engine (without any tuning) must be entered in the fields B45 to B55 beforehand.
The data for common motors can be found in the bottom right corner of the spreadsheet: simply copy the data for the desired motor from cells B45 to B55.
Alternatively, users can enter their own values or modified values.

The DZR (Dynamic Response System) takes into account the dependence of acceleration (in addition to engine power) on the gear ratio and combat weight through fields E8 and E9.

When calculating the transit time, it is crucial to include the weight of passengers, any special equipment (like air conditioning!), luggage, and any other cargo as accurately as possible. Otherwise, the calculated transit time will be significantly different from the actual time under the relevant conditions. Vehicle, and the calculation is already half-done for the scrap heap!
Ideally, a careful assessment is needed here.
Otherwise, it is best to refer to the vehicle's registration documents, the owner's manual, or the catalog data.

"In German vehicle registration documents, the (generally) stated unladen weight refers to the base model, including..." Rider (75 kg), 90% fuel tank, and onboard tools.

However, your own vehicle is usually a bit heavier.
For optional equipment, you can roughly expect the following weights (provided they are not standard equipment in the base model!):
Air conditioner = 25 kg.
4 doors = 30 kg.
Tow hitch = 20 kg.
elFH and ZV = 20 kg.
electrical. Sunroof = 20 kg.
Full-size spare tire = 10 kg.
Wider tires instead of standard tires = 10 kg (for 4 wheels).
Radio (standard version, not a high-end system) = 10 kg.
Additional subwoofer = 10 kg.
Split-folding rear bench = 10 kg.
Comfort seats / Easy Entry, etc. (manual operation) = 3 kg per seat.
Electric seat adjustments = 5 kg per seat.
Leather equipment = 5 kg.
ESP = 5 kg
Headbags = 4 kg
Xenon headlight = 4 kg.
Seat heaters = 3 kg.
Electric mirror = 3 kg.
Floor mats = 2 kg.


The field E9 accounts for the gear ratio and the rolling circumference of the tires. The "Geschw.Rechner" sheet enables a precise calculation and simultaneously provides the range of speed variation due to the permissible manufacturing tolerances in the rolling circumference of the tires entered.
When you input these parameters into the design calculation software, many people will be surprised to see how much the transit time can change simply due to tolerances within the same tire size.
Comparable influence is also exerted by other tire sizes: For example, someone who uses smaller tires but compares their measured 2000-4000 time to the calculation for the factory tires is essentially cheating themselves!

The actual rolling circumference of the tires is correspondingly important for an accurate calculation of the airflow.
It can be determined with sufficient accuracy in the following way:
On a level surface (parking lot, garage, etc.), with normal tire pressure and the steering wheel straight, precisely mark the position of the car to the nearest centimeter, for example, by establishing a vertical reference line from the bumper to the road surface (using a level or plumb bob if possible - no joke!).
Attach a piece of crepe tape tightly across the tire sidewall and fender on the front wheel, ensuring it's taut. Then, push the vehicle forward until the ends of the crepe tape are aligned again. Mark the new position of the vehicle using the same sighting method, and measure the distance to the first marked position. This is the actual rolling circumference of the tires, which should fall within the calculated tolerances, and can be converted into the actual starting speed at 2000 rpm.
People who are not good at math can use the Batt Geschw. Rechner (speed calculator) to, for example, adjust the tire width until the calculated rolling circumference (field D11) matches the measured value.

You can find gear ratios, for example, in the relevant technical article if you know the model letter of your gearbox.
The potentially inaccurate speedometer reading should only be used for providing the rpm-to-km/h conversion due to its central importance in the calculation, and only "in emergency situations."

The remaining variables in the DZR (German tire data sheet) should remain at their default values, unless an extra rolling resistance measurement is performed to determine the rolling resistance accurately (using the "Rolling Resistance Calculator" sheet), or if you have specific knowledge about the individual case.
Note: Moisture can extend the measured time by a fraction of a second compared to a dry road surface.

The optional input of a headwind or tailwind component, as well as inclines or declines, should generally only be provided when measurements are only possible in one direction. Otherwise, this should be zero.


The evaluationhttps://www.tuneline.at/go/ZjAzYTE0MD

If the measured time of your car differs significantly from the calculated time, you can enter the values in fields E12 and/or... Enter the percentage deviations from the paper value until the calculated time largely matches the actual time.
The corresponding corrected torque values for the engine will then appear in fields D40 to D50, as an estimate (!) based on the assumption that any increase or decrease in power is distributed proportionally and evenly across the entire range of 2000 - 4000 rpm.

It's simpler to use the DZR (Dynamic Rollout) method when you only need a comparison on the same vehicle, rather than the actual engine power, for example, before and after a tuning modification. In such cases, approximate values for weight and initial speed are sufficient. The actual time measurements should, of course, be carried out under as identical conditions as possible (track, weather, weight, tires).
Subsequently, simply compare the torque values in fields D40 to D50 of the "before" and "after" measurements: the difference represents the average improvement achieved by the tuning within the 2000 - 4000 rpm range.
And it does so with an accuracy that is practically only dependent on the precision of the stopwatch: With a little practice, errors of 0.1 seconds can be achieved, which, with a measurement time of 6 seconds, results in an error of approximately 0.017% in the 3rd decimal place. A margin of error of less than 2% is achieved.

For comparison: Good dynamometers have tolerances of 5%, but this value can practically increase arbitrarily if they are not operated 100% correctly.