Torque Myths: Debunking Common Misconceptions

Hello,

I've been watching historical car tests recently, and I've noticed that diesel engines need to have a significantly higher torque than similarly (horsepower) powerful gasoline engines in order to be faster during acceleration tests (60-100 km/h, 80-120 km/h). Is there an explanation for this? I think I understand what 'power' and 'torque' are. If anyone feels like seeing some formulas:
http://www.kfztech.de/kfztechnik/motor/steuerung/leistung.htm

Now, let's get to the actual problem. I have compared 5 Volkswagen Passats:

1) 115 hp TDI PD Sedan, 1390 kg, 285 Nm at 1900 rpm.
60-100 km/h im 4. Time: 8.1 seconds.
80-120 km/h im 5. Time: 11.4 seconds.

2) 100 hp TDI PD station wagon, 1503 kg, 250 Nm at 1900 rpm.
60-100 km/h: 9.9 seconds.
80-120 km/h: 14.5 seconds.

3) 110 hp TDI sedan, 1427 kg, 235 Nm of torque at 1900 rpm.
60-100 km/h: 10.6 seconds.
80-120 km/h: 14.7 seconds.

4) 125 horsepower gasoline engine, sedan, 1.8 liter displacement, 1362 kg weight, 168 Nm of torque at 3500 RPM.
60-100: 11.2 seconds.
80-120: 16.1 seconds.

5) 115 horsepower gasoline engine, sedan, 2.0 liter displacement, 1413 kg weight, 172 Nm of torque at 3500 rpm.
60-100: 11.2 seconds.
80-120: 15.9 seconds.


Why are the differences so small? The 110 hp TDI weighs approximately the same as the 2.0L gasoline engine, has 38% more torque, but isn't faster in acceleration. The 8% time advantage (14.7 seconds vs. 15.9 seconds in 5th gear from 80-120 km/h) could also be due to measurement inaccuracies.
You need an engine with 115 horsepower and 285 Nm of torque, which is almost 66% more torque than a comparable 2.0-liter gasoline engine, to be about 39% faster. These values would also have a positive impact in everyday driving. But what else? Where is the torque that diesel engines are known for?

I obtained all the values from 'Auto Motor Sport' to ensure the most consistent conditions. All the cars have 5 gears.

Best regards,

Adrian.

Hello Adrian,

The most important factor is the performance curve (torque curve) in each gear within the relevant speed range.
While the statement isn't entirely accurate, it's approximately correct if we disregard factors like air resistance: The higher the integral of power over the measured speed range, the shorter the transit time.
Therefore, the gear design must also be appropriate.
Peak performance and maximum torque are completely irrelevant here.
Just try experimenting with different torque curves in the Ulfs torque calculator and create a table showing the power output at each speed; you'll quickly understand the relationship.

P = M * 2 * π * f(s) = M * 2 * π * (f(min) / 60) = M * 0.10472 * f(min)

Best regards, Rainer.

Hi Adrian,

Maybe you should think about the transmission.

Sure, here are a few different translations of the German text:

**Option 1 (More literal):**

'Different translations!!'

**Option 2 (Slightly more natural):**

'Various translations!!'

**Option 3 (Emphasizing the variety):**

'A range of translations!!'

**Option 4 (Focusing on the differences):**

'Different versions of the translation!!'

I hope this helps! Let me know if you have any other questions.

Best regards, Holger.

Adrian wrote:

... Why are the differences so small? The 110 hp TDI weighs approximately the same as the 2.0L gasoline engine, has 38% more torque, but isn't faster in acceleration. The 8% time advantage (14.7 seconds versus 15.9 seconds in 5th gear from 80-120 km/h) could also be due to measurement inaccuracies. ...

This is likely due to the significantly different gear ratios.

Quote:

... You need an engine with 115 horsepower and 285 Nm of torque, which is almost 66% more torque than a comparable 2.0-liter gasoline engine, to be about 39% faster. These values would also have a positive impact in everyday driving. But what else? Where is the torque that diesel engines are known for? ...

"... Attach a 1500 kg trailer to the gasoline engine (I think the Passat is allowed to tow that much), and then do the same with the diesel engine."
If you then find a suitable incline (hill), the gasoline car won't be able to keep up with the diesel. At that point, you will finally understand what torque means for a diesel engine!

Hello,

Thank you for the (initial) responses.

@ Rainer K.
I have already experimented with the Ulf test. I obtained the torque curves from http://www.hs-elektronik.com/auswahl-d.html. That's why this 'phenomenon' also caught my attention.
What's even more frustrating for diesel enthusiasts is the fact that diesel engines produce their maximum torque over a relatively wide range of RPMs. However, both gasoline engines only achieve their maximum torque at a single point. After that, power drops off significantly. Therefore, my initial thought was that the advantage of diesel engines with their high torque would have been even greater.
Thanks for the tip about the integral! I'll take a closer look at that.

@ Holger
Yes, there's no other way to do it with the transmission. The diesel engine runs at about 1500 RPM less than the gasoline engine.

@Bertil
Unfortunately, I don't have a trailer. Therefore, what matters to me is only the driving pleasure. For me, it's essentially just a means of transportation.
f(large car, good acceleration, low fuel consumption, low running costs). Based on my driving habits, the gasoline engine seems to have an advantage. I honestly didn't expect that.



Best regards,

Adrian.

Adrian wrote:

... What's even more frustrating for diesel enthusiasts is the fact that diesel engines produce their maximum torque over a relatively wide range of engine speeds. ...

Why would that be annoying? Isn't it nice not to always have to worry about the speed?

Quote:

... However, both gasoline engines only reach their maximum torque at a single point. After that, the power drops off significantly. ...

Exactly - it's really annoying to have to keep the engine in the correct RPM range all the time...

Quote:

... Therefore, my first thought was that the advantage of diesel engines with their high torque would have had to be even greater. Thanks for the tip about the integral! I'll take a closer look at that. ...

This is initially a fallacy (as you have already noticed).

Quote:

... @Bertil Unfortunately, I don't have a trailer. Therefore, what matters to me is only the driving pleasure. ...

Then the gasoline-powered version is the right choice for you.

Quote:

... "Mathematically speaking," for me, it's the function. f(large car, good acceleration, low fuel consumption, low running costs). Given my driving habits, the gasoline engine seems to have an edge. I honestly didn't expect that. ...

Your "formula" isn't actually that wrong:

Large car --- Doesn't matter (diesel or gasoline).
Good ventilation --- Diesel (especially when loading!)
Low fuel consumption --- Diesel.
low maintenance --- depends on the annual mileage.

I think the last point is the most important for you. The less you drive, the more "fuel-efficient" the gasoline engine will be.
However, since I also need to tow a caravan, diesel is probably essential!

The comparative tests conducted by specialist magazines should be viewed with caution, as the various engine designs may operate in unfavorable speed ranges, which can significantly distort the results. Try it yourself and form your own opinion. The driving pleasure is certainly not diminished with a (TDI) diesel engine.

Why are the differences so small? The 110 hp TDI weighs approximately the same as the 2.0L gasoline engine, has 38% more torque, but isn't faster in acceleration. The 8% time advantage (14.7 seconds versus 15.9 seconds in 5th gear from 80-120 km/h) could also be due to measurement inaccuracies.
You need an engine with 115 horsepower and 285 Nm of torque, which is almost 66% more torque than a comparable 2.0-liter gasoline engine, to be about 39% faster. These values would also have a positive impact in everyday driving. But what else? Where is the torque that diesel engines are known for?


I think the torque you're missing is very noticeable at the gas station. The gasoline engine might have similar performance, but it requires at least 50% more fuel (6 to 9 liters). And we haven't even talked about the overall cost.

Hi Varianti,

Even though it's not directly related to the main topic: The insurance company (in Germany) will eventually recover those 50%. And if there's even a single cent left in the account, the higher tax rate will take care of the rest.
I once created an Excel spreadsheet and calculated the ongoing costs for diesel and gasoline vehicles. If I don't factor in the higher purchase price for the diesel and the increased maintenance costs, the costs are the same for me (insurance, fuel, taxes). Unfortunately, the diesel doesn't offer any advantages for me in this case.

Best regards,

Adrian.

Hello!

As a rule of thumb, you can say that approximately 285 diesel Nm corresponds to about 200 gasoline Nm, assuming the diesel engine operates up to 4500 RPM and the gasoline engine up to 6500 RPM, while each gear reaches the same maximum speed.
When you find vehicles for comparison, the diesel engine offers advantages in terms of elasticity (torque range), while the gasoline engine provides better acceleration in sporty driving conditions, both due to the torque curve.

Today, a diesel engine (150 hp / 300 Nm) can travel at speeds up to around 115 km/h in third gear, while a gasoline engine (150 hp / 200 Nm) only needs second gear to achieve the same speed. Because people often compare the third gear of a diesel with that of a gasoline engine, and because VW TDIs often have 10% more power than stated in their specifications, some believe that driving a diesel is more fun.

Anyone who makes a fair comparison can only say: Diesel engines offer efficiency (and good pulling power in economical driving conditions).
Gasoline = Fun.
Best regards,
Ernst

The diesel engine is more fun to drive, even with the same peak power output (in horsepower). If you were to look at the total power output (e.g., the area that the power curve occupies on a standardized graph), the diesel would be superior.
Compared to a gasoline engine versus a TDI (2.0B vs 1.9TDi, both 85kW), the gasoline engine can't keep up until around 140 km/h, but then it gradually catches up and has a higher top speed.

Hi!

In a previous thread, this exact topic was discussed. A 110 and a 115 PD engine were compared to a naturally aspirated VR5 with 150 horsepower. In fact, the VR5 had overall better performance figures on paper. However, to take advantage of this, you need to operate above approximately 3,500 RPM. In real-world driving, this means being in 2nd or 3rd gear at typical country road speeds. The TDI engine makes its power available even in 5th gear due to its more robust torque curve. Instead of downshifting, you only need to adjust your right foot. In reality, a 115 horsepower PD engine offers better performance on its own compared to the 150 horsepower gasoline engine; it feels significantly faster.
The new price advantage does not apply because the diesel vehicle depreciates significantly less than a comparable gasoline-powered vehicle.


Here's another excerpt from the discussion:

"I have an A3 with a 110 horsepower engine that has been chipped to produce 140 horsepower. My wife has an A4 with an 115 horsepower engine. Due to troubleshooting on the engine, I had temporarily disabled the chip for some time, so I was used to having only 110 horsepower, or even slightly less due to a defect. The workshop lent me a V5 Bora with a 150 horsepower engine. My initial impression was that it felt like driving a car with maybe only 90 horsepower (I didn't know the actual engine power). It felt rather sluggish. After downshifting a few times, I realized there was still more power to be found."
Overall, the performance is comparable to a car with around 115 horsepower. The extra power of the V5 engine can mostly be utilized on the highway at speeds above 180 km/h. The high torque you noticed is normal; this is what sets modern diesel engines apart from gasoline engines. Typically, you drive a TDI in the lower RPM range. There's plenty of power available, the fuel consumption is sensational, and you don't even need to shift gears."


"I have to disagree with you! While the torque is indeed dependent on the rotating turbocharger, it comes into play in pump-injection systems at just 1,200 rpm. At 1,600 rpm, there's already a lot of power, and at 1,900 rpm, the 115 hp pump-injection system produces 310 Nm! TDIs are also known for their torque curve, which extends far beyond the legal tolerance limits. For example, my distributor injector in standard configuration has 235 Nm, but just a few weeks ago, it was measured at 281 Nm on a Bosch test bench in its stock condition!! Now, with a chip installed, I haven't measured it yet, but it runs very well )."

The V5 or VR5 engine reaches its peak power output near its maximum torque. With the TDI engine, it's quite the opposite: it achieves its top performance in a less than ideal RPM range, specifically around 4,000 RPM, where the torque already drops significantly. At lower RPMs, the torque is higher, which means that after shifting gears, you have optimal power delivery. Even if you skip a gear, this has little impact. Therefore, the overall driving performance surpasses that of a naturally aspirated engine with a higher maximum power output, as mentioned earlier.



Take a look at the torque curves...

www.mehr-drehmoment.de/chiptuning/datasheet_show.php?id=28
www.hs-elektronik.com/diagramme/kfvw-23v5.gif
The black curve represents a 115 hp engine with 285 Nm of torque, while the lower link (hs-electronics) refers to a VR5 engine with 150 hp.

I recommend you take a test drive with the PD.



Best regards,
Uwe

Sure, here is the translation of the text from German to English:

"Addendum:"

Old Forum: forumalt/messages/4518.html

Best regards,
Uwe

Thank you for the two examples. That's exactly the kind of comparison I was looking for. I also wanted to emphasize that neither principle is inherently better than the other; they are simply good at different things.

The purpose of this thread was to discuss the significance of torque figures. And as has already been pointed out, just like horsepower or any other values, graphs, or time measurements, torque figures cannot be used to assess a vehicle.

Driving isn't just about accelerating from 60 to 100 in fourth gear.

It's not just about how individual components are matched, but above all, how the vehicle is tailored to the *driver's* specific driving style.

Then it happens that, in practice, one person might get more out of a diesel engine than a gasoline engine, while for another person, it's the opposite. Ultimately, everyone has to figure that out for themselves.

Best regards,
Certainly! Please provide the text you would like me to translate from German to English. I will only provide the translation.

Whether you're a gasoline or diesel driver... please all pay attention to the motorcycle riders. Thank you.

Hi there,

I initially had reservations about getting the Octavia Combi with only 90 horsepower TDI engine, as the automatic version is unfortunately only available with this particular engine.

Before that, I had an Ascona C 2.0i with an automatic transmission.

And even though the Octavia weighs about 300 kg more, its performance is slightly better. Even the (same) top speed is reached more easily.
The Opel engine (C20NE) actually doesn't have a bad torque curve (170 Nm at 2600 rpm, very flat).
Note that, on paper, the Octavia is slower, but according to my stopwatch when driving up my measuring hill, it's actually faster.

When comparing the operating speed range of both engines, the TDI always has more torque than the gasoline engine. Only when the TDI exceeds 3600 RPM does its torque drop below that of the gasoline engine. However, by then, I'm already exceeding the legal speed limit.
'Even the colleagues with manual transmissions and 115 hp gasoline engines are struggling, and a comparison between a 'tuned' 90 hp engine (presumably referring to modifications costing around 10 cents) and a 1.8T Passat resulted in a tie. The automatic transmission in 3rd gear (with the WK closed) starts at 60 km/h / 1800 RPM, producing no smoke.'

I can only say that the electric version offers a higher fun factor compared to the gasoline-powered models.
Leaving the parking tickets at the location is no problem for the automatic transmission version with 90 horsepower... of course, without paying the fine.

CU Gremlin.


edit:
Here's a rough torque comparison of the two engines. Of course, the gear ratios are not taken into account here, but if I compare the engine speeds against each other, it almost works out. Let's see, I might calculate it more precisely later. Be careful, the gasoline engine diagram is stretched so much that the usable range appears to be the same. The RPM values are NOT valid for the gasoline engine, nor is the power scale. The torque scale is 1:1. Oh, and... the blue curve is the one that matters, right ?
What fascinates me is the torque curve of this ancient gasoline engine. It's a 2-valve fuel injection engine with Bosch Motronic, and that's it. No variable valve timing or any of that stuff. Back then, they could still build engines without computers .

http://www.ralfhandel.de/drehmomentvergleich.jpg

Hello,

Do you remember the early road tests of the Volkswagen Golf 3 TDI with its 90 horsepower engine? I dug up one of those old tests:

Volkswagen Golf 3 TDI, 90 horsepower, 202 Nm of torque at 1900 rpm, 1164 kg.
60-100 km/h im 4. Time: 10.8 seconds.
80-120 km/h im 5. Run time: 16.2 seconds.

For comparison's sake:

Volkswagen Golf 3, 1.8L engine, 90 horsepower, 145 Nm of torque at 2500 RPM, weight: 1099 kg.
60-100: 11.0 seconds.
80-120: 15.9 seconds.

Volkswagen Golf 3, 1.6L engine, 100 horsepower, 140 Nm of torque at 3500 rpm, weighing 1117 kg.
60-100: 10.7 seconds.
80-120: 15.1 seconds.
The 1.6L gasoline engine has a transmission with approximately 7% shorter gear ratios compared to the 1.8L gasoline engine.


I wanted to add this here for the golfers.
'Personally, I tend to 'push' every car within its normal operating range, around 2000 RPM. Of course, it's a bit more on the highway. That's why I prefer gasoline engines with relatively large displacement, like the 2.0L 115 HP engine from VW, or turbocharged engines, whether diesel or gasoline. I don't have any other particular preferences. Small 16V gasoline engines just aren't really my thing.'

The next time I buy a new car and the salesperson 'explains' to me that I need a diesel engine because of its high torque and the resulting power, I will bombard them with approximation formulas and integrals. Let's see if I can use that to lower the purchase price.

Best regards,

Adrian.

Volkswagen Golf 3, 1.6L engine, 100 horsepower, 140 Nm of torque at 3500 rpm, weighing 1117 kg.
60-100: 10.7 seconds.
80-120: 15.1 seconds.
The 1.6L gasoline engine has a transmission with approximately 7% shorter gear ratios compared to the 1.8L gasoline engine.


Are you sure that's a Golf GT? A 1.6-liter engine with 100 horsepower seems unusual. I wonder about the extra weight compared to the 1.8-liter version.

But haggling is always good when buying a car. I think the people at the dealership can probably adjust the price quite a bit...