Total losses during the penetration test!!????

Hello everyone,

While calculating using the flow rate calculator, I noticed that when I enter a higher value for 'Total Losses,' the time at 2000-4000 U/min becomes shorter! Am I making a mistake in my thinking, or is this a programming error???

Does the vehicle not need to slow down if I have higher losses (tires, transmission)? Or do I need to add a plus or minus sign before the value?

Sorry for the question, I've already searched the forum for similar questions but couldn't find anything.

Hello!

Total losses at Vmax: These are only there to estimate air resistance. Increasing this value will therefore reduce air resistance, which in turn will shorten the time it takes.

The actual losses in the powertrain are listed under 'losses due to flank friction.' And if you increase this value, the time will also increase.
Best regards,
Ernst.

'When we're talking about 'losses due to flank friction' in gears. What does that even mean? Gear flanks don't rub against each other; they roll over each other, practically without friction (at least with involute tooth profiles, which are commonly used).' Therefore, these types of transmissions have a high efficiency.

I read somewhere that the frictional losses in the transmission (front-wheel drive) are approximately 0.02% and the friction is approximately 0.03% of the engine's power output. Don't kill me, but I can't remember where it was.

Okay, so, if I can believe the values from the dynamometer, then my TDI has a parasitic power loss of 25.5 kW (34.6 hp), which is essentially wasted power. The power loss consists of the transmission, friction in all rotating parts (wheel bearings, etc.), and that's why I was surprised that the table in the traction calculator is labeled as 'Total Power Loss' (wheels, transmission).

The engine, after the roller test (approximately 108 horsepower), produced 80 kW, with 254 Nm of torque. Of this, 25.5 kW (34.6 horsepower) was parasitic loss, and the final output at the wheels was 54.5 kW (74.1 horsepower).

Okay, so what's actually correct, approximately?

Since we're already talking about 'losses due to tooth flank friction.' What is this supposed to be?

At the very least, they are responsible for a portion (4%) of the overall energy loss. I would rather call it 'drivetrain efficiency.' It is caused by the transmission, axle gears, and half-shaft joints, and is approximately 0.96-0.98 (meaning a total loss of 2-4%, although individual gear stages themselves do not lose much).


The power loss consists of the transmission, friction in all rotating parts (wheel bearings, etc.), and that's why I was also surprised that the table in the traction calculator is labeled as 'total power loss' (wheels, transmission).


Okay, so let me reiterate: The total loss in the DZR (drag coefficient ratio) is only used for the preliminary calculation of air resistance; it has no other relevance in the calculation. It mainly consists of rolling resistance and losses in the powertrain. A precise entry in the DZR (German registration document) is not that important, as it has little impact on the outcome.

Currently, in the DZR (presumably a specific organization or standard), losses in the powertrain are still referred to as 'losses due to flank friction.' Composition: see above.

The friction losses are included in the rolling resistance, which you determine through the rolling test.

If you took the power output at the correct RPM during the test run, then you have 108 horsepower. You shouldn't take the maximum power output as the limit, because the power loss increases with the speed, even beyond the engine's maximum power output.
Accurate performance data can only be obtained on a dynamometer; a rolling road is just an estimate.
Best regards, Ernst.

Hi,
acha, thank you for the explanation, I understand now, thank you.