Torque vs Energy. Same units, not the same thing

[jz11]

The topic of conversation has changed a bit, but I don't think it's necessarily lock-worthy.

was the article called - "guide in abusing math and statistical analysis, or how to make nice looking charts that mean nothing"?

Off top trolling. Time to rethink it?

not really, that comparison by the author of those charts is what trolling is, I explained it above - you can sort of draw some extremely general conclusions like sosic2121 did earlier, but are they worth anything? without each samples data regarding engine power band and gear ratios those charts are way too general to get any useful information out of, in other words - waste of time by the author and reader, unless the aim was to show how how inaccurate talking about "torquey" engines in regards to acceleration really is, which would place those charts way earlier in this discussion that you just did

so tell me again - what those charts are good for?

p.s. I wasn't trying to be rude, least of all to gruntguru, I think he very well knows what sort of information you can pull out of those charts

[rjsa]

If you understand the physics behind the phenomena the worth is crystal clear.

But then again, this is not the torque x power thread so it's a moot point.

[jz11]

phenomena of gear reduction?

[Jersey Tom]

so tell me again - what those charts are good for?

I think they're a pretty great illustration that you don't need to know specifics of gearing to draw broad conclusions on power. Shows exactly what I mentioned before, that gross changes in power (or power to weight in this case) are indicative of gross changes in potential for performance... whereas gross changes in crank torque means nothing on its own.

[wuzak]

The topic of conversation has changed a bit, but I don't think it's necessarily lock-worthy.

was the article called - "guide in abusing math and statistical analysis, or how to make nice looking charts that mean nothing"?

Off top trolling. Time to rethink it?

Although he sounded kinda rude, I agree with him. These are just nice pictures with a whole lot of variations. I mean you can get the same acceleration with 125-180 bhp/t and if you squint a bit you can see a slight trend to higher accelerations with higher torque, although with also a lot of variations.
I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

In the power to weight chart you can draw a trend line through the data. It will be a curve, initially quite steep then flattening out to around 3-4s for the time taken from 30-70mph.

In the torque chart there is no discernible pattern or trend. I

[jz11]

so tell me again - what those charts are good for?

I think they're a pretty great illustration that you don't need to know specifics of gearing to draw broad conclusions on power. Shows exactly what I mentioned before, that gross changes in power (or power to weight in this case) are indicative of gross changes in potential for performance... whereas gross changes in crank torque means nothing on its own.

ok, so it was just another way of beating that already quite dead horse back to high school physics class

anyway, there will always be problems with these very broad generalizations, because one may not agree with that statement where you say gross changes in torque means nothing, because it can, it is simply missing more data, (dead horse is starting to show signs of life), but that data would instantly in a very magical way transform that torque into power, so a catch 22 situation right there

[sosic2121]

so tell me again - what those charts are good for?

I think they're a pretty great illustration that you don't need to know specifics of gearing to draw broad conclusions on power. Shows exactly what I mentioned before, that gross changes in power (or power to weight in this case) are indicative of gross changes in potential for performance... whereas gross changes in crank torque means nothing on its own.

ok, so it was just another way of beating that already quite dead horse back to high school physics class

anyway, there will always be problems with these very broad generalizations, because one may not agree with that statement where you say gross changes in torque means nothing, because it can, it is simply missing more data, (dead horse is starting to show signs of life), but that data would instantly in a very magical way transform that torque into power, so a catch 22 situation right there

I don't think that anyone was trying to say those charts are absolutely accurate or anything like that.
The point was while power to weight can give you some clue about car's performance, and torque can't.

Main issue is that today "they" sell us "tourqes"(often without rpm) as messure for performance and IMO that is just a worthless number.

[Just_a_fan]

When someone describes an engine as "torquey" or whatever, they are just using it as shorthand for "the engine produces good power low in the rev range". "Peaky" engines produce power high in the rev range and generally need to be kept at high revs in order to give good performance.

Sports cars (and racing cars, by extension) are best fitted with "peaky" engines. This is because revving the nuts off the thing is acceptable. Most road cars benefit from "torquey" engines because they are, generally, more relaxing to drive. They are also easier to drive smoothly. Both excellent attributes in a road car.

If someone said to me "both engines produce 200bhp at 6000rpm but engine A has more torque than B", I'd expect engine A to have better performance at low revs, even though both perform similarly at the top end. I would choose A over B ceteris paribus. A would give more gearing options too, which might be useful.

[strad]

I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

Well... That should start the whole mess all over again.

[ClarkBT11]

I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

Well... That should start the whole mess all over again.

Torque to the hand.. Coz the face ain't listening.

[Edis]

The topic of conversation has changed a bit, but I don't think it's necessarily lock-worthy.

was the article called - "guide in abusing math and statistical analysis, or how to make nice looking charts that mean nothing"?

Off top trolling. Time to rethink it?

Although he sounded kinda rude, I agree with him. These are just nice pictures with a whole lot of variations. I mean you can get the same acceleration with 125-180 bhp/t and if you squint a bit you can see a slight trend to higher accelerations with higher torque, although with also a lot of variations.
I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

There is no bad science here, the charts simply show, using real world data, that there is a relationship with higher power/mass and acceleration whereas there is no such relationship with torque/mass and acceleration. For instance, in the power chart the car with the highest power/mass accelerate twice as fast as the car with the lowest power/mass whereas in the torque chart the car with the highest and the lowest torque/mass accelerate just as fast.

This isn't surprising given basic physics:

power = force*velocity
force = mass*acceleration

so ignoring drag we get

acceleration = power/(mass*velocity)

[gruntguru]

The topic of conversation has changed a bit, but I don't think it's necessarily lock-worthy.

was the article called - "guide in abusing math and statistical analysis, or how to make nice looking charts that mean nothing"?

Off top trolling. Time to rethink it?

Although he sounded kinda rude, I agree with him. These are just nice pictures with a whole lot of variations. I mean you can get the same acceleration with 125-180 bhp/t and if you squint a bit you can see a slight trend to higher accelerations with higher torque, although with also a lot of variations.
I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

It is actually quite good data. If you were to fit a trendline with the equation P x t = C (Power, time (30-70mph) and a Constant) I wager you would get a correlation coefficient of 0.9 or better.

Anyone who doesn't understand the significance of that, is not qualified to judge "bad science".

[rscsr]

Off top trolling. Time to rethink it?

Although he sounded kinda rude, I agree with him. These are just nice pictures with a whole lot of variations. I mean you can get the same acceleration with 125-180 bhp/t and if you squint a bit you can see a slight trend to higher accelerations with higher torque, although with also a lot of variations.
I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

It is actually quite good data. If you were to fit a trendline with the equation P x t = C (Power, time (30-70mph) and a Constant) I wager you would get a correlation coefficient of 0.9 or better.

Anyone who doesn't understand the significance of that, is not qualified to judge "bad science".

How can you judge who can judge something. It is still garbage science. He tries to correlate average acceleration over a massive speed differential with peak power. The speed more than doubles and the drag can easily be a problem which is not accounted for and for some cars you need to shift while for others you won't.

But be glad that you haven't wagered anything. I checked the correlation and guess what. A Pxt=C trendline has a R² of 0.78. And it gets better. A linear correlation gets a R² of 0.84 and a P^(0.7)xt=C gets a R² of 0.89. So what conclusions do you draw from that? A linear corealtion is significantly better than a Pxt=C?

[sosic2121]

Off top trolling. Time to rethink it?

Although he sounded kinda rude, I agree with him. These are just nice pictures with a whole lot of variations. I mean you can get the same acceleration with 125-180 bhp/t and if you squint a bit you can see a slight trend to higher accelerations with higher torque, although with also a lot of variations.
I mean it pretty obvious to me that torque has not much to do with acceleration but this is still kinda bad science.

It is actually quite good data. If you were to fit a trendline with the equation P x t = C (Power, time (30-70mph) and a Constant) I wager you would get a correlation coefficient of 0.9 or better.

Anyone who doesn't understand the significance of that, is not qualified to judge "bad science".

I calculated theoretical minimum time to accelerate from 30 to 70 and compared with best engines from the picture.
Best engines took 50% more time, and IMO this is spot on when you consider couple of things:
-engines are not at peak power all the time, but on average probably some 10-15% down on power,
-10-15% transmission loss,
-inertia of crankshaft, flywheel, tires...
-drag,
-gearchange.

Any information on weights used in this comparison? Dry weight or were fuel and driver included?

[Brian Coat]

The endless back-and-forth about torque in this thread reminds me of my (almost) favourite engineering joke:

All couples have their moments ...