Torque and driving fun in everyday life (Articles)

"Gasoline engines have no chance against the torque of similarly powerful TDIs!" - "Nonsense! Acceleration isn't achieved with engine torque, but with the tractive force at the wheel. And that's where the gasoline engine, with its shorter gear ratios, compensates for the TDI's higher torque!" "In addition, it has a wider operating speed range than a diesel engine, which means it needs to be shifted into a higher gear later."

If one wants to test the effects of such arguments in everyday driving situations, it is not the person with the loudest voice or the most impressive demeanor who is right, but rather it comes down to relatively simple physical processes.
The interplay of factors such as vehicle weight, torque curve, transmission, tire size, etc., can be incorporated into relatively simple calculations that provide realistic results regarding the acceleration capabilities of different vehicles in each gear.

The download compares data for various diesel/gasoline combinations, representing many models of the first generation VW Polo 9N. It shows, through acceleration curves for each gear, for two selectable vehicles, that the "fun factor" of TDI engines – the ability to accelerate without downshifting – is not just a topic of conversation, but a reality, despite the weight disadvantage of TDIs compared to gasoline engines with similar horsepower.
Because while torque isn't what accelerates the vehicle, it's power – but TDIs already operate significantly closer to their maximum power output in the mid-rpm range compared to gasoline engines, as the power curves available for download show.
The high performance of TDIs in the mid-range is, of course, due to their high torque, which means that the arguments often made about raw Nm values actually have a certain truth to them.

The advantage of the TDIs in terms of acceleration from 0 to 100 km/h is hardly noticeable, because this acceleration is typically achieved with high engine speeds. In addition, gasoline-powered vehicles benefit from the increased range of their lower gears in this scenario.
As a result, the 0-100 km/h (0-62 mph) times of comparable TDIs and gasoline engines are significantly closer to each other than their acceleration figures.

In everyday driving, where the engine is mostly operated in the mid-range of its RPMs, the following general rules apply:
To keep up with a TDI engine when accelerating, the driver of a similarly powered and weighted car with a naturally aspirated gasoline engine typically needs to downshift one gear.
-> To overtake a TDI, he often has to downshift two gears, but then the gasoline engine immediately hits the rev limiter, and you have to upshift again, etc. From this perspective, there's definitely some truth to the common argument about constantly having to change gears with a gasoline engine.


More recently, modern gasoline engines seem to be outperforming even TDIs in terms of acceleration, as demonstrated by the comparison test of the Golf 5, specifically the 150 hp FSI versus the 140 hp TDI, featured in the "Gute Fahrt" magazine.
Therefore, these two vehicles and their data are also included in the download. Those who compare it to vehicles with similar power outputs can also see the familiar superiority of the TDI engine in terms of torque and pulling power.

The reason why the conditions in the test were exactly the opposite of what was expected has not yet been fully clarified.
Based on this calculation, for example, it seems plausible that the test TDI weighed approximately 350 kg more than the FSI (as a sum of basic weight, additional equipment, fuel tank fill, occupants, measuring equipment, etc.). Notably, the weights of the test cars were not documented during the measurements, but only the minimum unladen weights as stated in the catalog were provided.


To calculate the data for other vehicles, the corresponding information must be researched.

The calculation parameters for rolling resistance and air resistance are approximately designed for vehicles in the Golf class with 2-wheel drive and can be modified in the "Calculation" sheet if necessary.


Thank you again to Ernst S., who provided the initial idea with the driving diagram!