[Calluhan]

Originally Posted by woggledog

Agee with most things above, but simply, HP is how fast you can get somewhere, Torque is how many knackered fridges you can get in the trailer

[Mattfox89]

It's still weird how a car with a lot of torque can make it feel like your going alot faster than u actually are and gives you the hit what pushes you back in the seat.

Also what would win a car with 1000 lb/ft of torque and 1bhp or a car with 1000bhp and 1lb/ft of torque

And yes sorry my car has 600nm not lb/ft

[ashmostro]

You feel the power, period.

People just use the torque-is-what-you-feel-down-low axiom because they don't really get that torque and power are intrinsically related by time (hp is torque, integrated over time). As Steve said, the only reason torquey cars feel faster is because, well they are, where it matters in the rpm band (down low, for the street).

[ashmostro]

Originally Posted by Mattfox89

Also what would win a car with 1000 lb/ft of torque and 1bhp or a car with 1000bhp and 1lb/ft of torque

Impossible to answer without much more context

[mob17]

Im sure a clever mathematician can make an torque equation for a given car's dyno graph/data. Or even use Excel to get a line of best fit.

Something like Torque = RPM then some fancy maths stuff.

Then integrating that equation will give the area under the curve.

Ah, memories of A Level Mathematics come flooding back.

[ashmostro]

Already shown on post 4 of this thread

[mob17]

Originally Posted by ashmostro

Already shown on post 4 of this thread

No it aint. I'm talking about integrating the dyno torque curve. Not the equation between bhp and torque.

Integrating ANY equation will give you the area under the line.

[ashmostro]

It's actually the same equation... It is in fact calculus it just doesn't look like it.

[mob17]

Originally Posted by ashmostro

It's actually the same equation... It is in fact calculus it just doesn't look like it.

I don't understand. Are you saying that the torque equation on post 4 gives you the area under the torque curve because it doesn't!

[MrPogle]

Originally Posted by ashmostro

You feel the power, period.

You "feel" the acceleration and acceleration is caused by force not power. You become aware of the power because the acceleration continues for a long time. The initial shove in the back is caused by torque.

[djgandy]

You often "feel" torque in diesels because they have a peaky power band and high torque low down. High torque low down gives a lot of acceleration. Peak torque is where you have peak acceleration. But acceleration is relative and once you are moving, the "feel" of torque starts to fade away.

[Rich_D]

Originally Posted by djgandy

You often "feel" torque in diesels because they have a peaky power band and high torque low down. High torque low down gives a lot of acceleration. Peak torque is where you have peak acceleration. But acceleration is relative and once you are moving, the "feel" of torque starts to fade away.

Not really, even at motorway speeds a car with lots of torque will pull happily without dropping a cog, you definitely feel that, doesn't matter if it's diesel or petrol, what you need is both power & torque.

Also, not all diesel engines have a peaky power band, my remapped 330d progressively makes power across the rev range and peaks at about 4100rpm, then gradually tails off. However I agree that some diesel engines (usually smaller 4 cylinder engines) have a big spike of power between 2-3000rpm then run out of steam, my sisters Golf GT TDi was like this, felt a lot quicker than it was.

[nicktyler]

Originally Posted by mob17

I don't understand. Are you saying that the torque equation on post 4 gives you the area under the torque curve because it doesn't!

Yes it does. All you need to know are the Horsepower or the Torque for 2 or more given RPM values (the more the better). then you can do the calculation, plot them on a graph and you will get and area.

[mob17]

Originally Posted by nicktyler

Yes it does. All you need to know are the Horsepower or the Torque for 2 or more given RPM values (the more the better). then you can do the calculation, plot them on a graph and you will get and area.

That gives you the torque value at a given RPM. You will always over estimate the true value slightly.

Using multiple points from 0-5000rpm will give you a rough idea of the area under the graph but it won't be accurate unless....

You use integration of either:

The equation of the line of best fit of the curve

Or...

the equation of the actual line, which i think is impossible as it's a really complicated line.

My initial point was using integration. Which basically uses maths to use an infinate amount of "points".

So you could plot as many points as you can on excel (using the torque values for each point/rpm from the graph), get a line of best fit, then excel will give you the equation, then u integrate that.

Wish i never even bothered trying to talk maths on here now.

[MrPogle]

Originally Posted by mob17

Wish i never even bothered trying to talk maths on here now.

Given the standard of some of the Physics, you were pushing it bringing up Calculus. What do they teach them in schools, nowadays? etc.

To be fair, even you messed up a bit with the units for torque. It is a product not a ratio. So it's lbft, not lb/ft. (lbfft if you are being picky).

[ashmostro]

Originally Posted by mob17

That gives you the torque value at a given RPM. You will always over estimate the true value slightly.

Using multiple points from 0-5000rpm will give you a rough idea of the area under the graph but it won't be accurate unless....

You use integration of either:

The equation of the line of best fit of the curve

Or...

the equation of the actual line, which i think is impossible as it's a really complicated line.

My initial point was using integration. Which basically uses maths to use an infinate amount of "points".

So you could plot as many points as you can on excel (using the torque values for each point/rpm from the graph), get a line of best fit, then excel will give you the equation, then u integrate that.

Wish i never even bothered trying to talk maths on here now.

Ignoring the silly remark at the end, I agree with you as you're absolutely right.

But you also concede that there isn't a formula for the curve here since the data is empirical. The best you can do is use the simplified tq-hp formula provided which was obtained from the same calculus you described. Just as you said, if you have the torque data plot by RPM in excel, you can use the TQ-HP formula to infer the HP curve by RPM (the time domain is consistent so the calculus can be simplified).

Physics is riddled with examples of special-case formulae that are simplifications of much more complex math. This is just one example (as are the common presentations of the pythagorean theorem, newton's laws, relativistic energy and mass, etc)

[windymissile]

To get an exact figure would require an infinite amount of data inputs along the X axis. Not practical.
For comparison of curves, we could agree on a standard "gap" between rpm along the X axis. Say 200 rpm. We could then overlay this in Excel to calculate the area under the curve.
Figures are only for comparison. So as long as we all use the same process we would all have a new figure to brag about down the pub.

http://www.statisticshowto.com/how-t...crosoft-excel/


WM

[ashmostro]

Originally Posted by windymissile

To get an exact figure would require an infinite amount of data inputs along the X axis. Not practical.
For comparison of curves, we could agree on a standard "gap" between rpm along the X axis. Say 200 rpm. We could then overlay this in Excel to calculate the area under the curve.
Figures are only for comparison. So as long as we all use the same process we would all have a new figure to brag about down the pub.

http://www.statisticshowto.com/how-t...crosoft-excel/


WM

Well put

[windymissile]

I have always been fascinated by the area under the curve *AUTC*. As I believe it shows the true power potential. A peak figure is is just that. And only good for comparing big numbers. Area under the curve *AUTC* explains why some "less powerful" cars are quicker than their more powerful competitors. Especially at slower tracks where out of corner acceleration is important.




In the above mock up of a standard 335i map. We could calculate a rough estimate of AUTC. Its not so accurate as, as you can see there is encroachment into the above curve area, especially on the upward X axis slope. But so long as we all use the same principle, it would be fine for comparison purposes.
We now have 36 simple (H x W) calculations. Add them all together and you would have AUTC.
As you will see, I have used no real units of measurement as it's an illustration for explanation purpose only. I separated each 1000rpm into 6 simple blocks as this is how it worked out in Paint to keep my life easier.
In reality I guess we would separate into 100 or 200 rpm blocks.

Don't shoot. It's just an idea. And in the decades of engine dynoing, I'm sure I'm not the first.

WM

[ashmostro]

Its not a terrible idea at all. Take a look at your X axis - it's RPM. Your result is not unitless!

[mob17]

Finally we all agree!

Windy explained it much better than me. I think for our purposes we could use points of 100-200rpm. I was just trying to explain something i learnt in school

[windymissile]

Originally Posted by ashmostro

Its not a terrible idea at all. Take a look at your X axis - it's RPM. Your result is not unitless!

Yeah, I see what you are saying. But you can't multiply Rpm by Hp to get a cm2 (Unit of area - AUTC*) measurement. And this is the unit of measurement we would be comparing.

E.g. Down the pub chatting shit about Rb v Vargas...

If we used the standard unit of measurement - cm2.
You - "I have 123 cm2 AUTC"
Me - " I have 150 cm2 AUTC"

Obviously my car is more powerful although yours, in theory, could have a higher peak figure..
We just need a standard of graph size for comparison.
Say -
20mm per 1000rpm X axis
20mm per 50 bhp Y axis

If we all stayed to this formula, we would have an international figure for comparison. It sounds so simple. I can't believe it isn't already done.
I guess more people are interested in the easy peak figure.

WM