Question about BHP + Torque

[xRIEx]

wormus said:

GroundEffect said:

I can make a graph. It will take me about 30 seconds in Excel. Doesn't mean it actually represents anything that the rollers are feeling as a torque.

What they are calculating is power at the wheels through the torque at the wheels (the 'tractive effort' you keep mentioning) then multiplying this by a predefined factor - typically 85% efficiency - to calculate the power at the flywheel/crank.

To get the 'torque at the wheels' you want, they would just take the power they calculate at the wheels and do standard linear manipulation to turn it to a 'torque'...but it actually doesn't mean anything. No part of your drivetrain will ever see it.

What you should care about:

1) Engine torque curve
2) Driveline efficiency
3) Trans/DL ratios

With the above you can basically work out all your performance metrics...assuming wheel slip etc is known.

Torque is the entire game. That's the closest to base unit there is.

Thanks for taking the time to explain. I'm not sure how this thread escalated. I was referring to a number on a graph, I have had many numbers on similar graphs to compare to to know 770lbs "at the wheels" is too much while 600lbs is about right to avoid constant loss of traction. As many of you don't own a Monaro, with my combination of engine, power, diff or gearbox the whole discusiion seems a little ridiculous.

That's a valid point, Monaros do use different Physics compared to other cars.

[deeen]

wormus said:

Thanks for taking the time to explain. I'm not sure how this thread escalated. I was referring to a number on a graph, I have had many numbers on similar graphs to compare to to know 770lbs "at the wheels" is too much while 600lbs is about right to avoid constant loss of traction. As many of you don't own a Monaro, with my combination of engine, power, diff or gearbox the whole discusiion seems a little ridiculous.

If that's the baseline you're looking for, bear in mind the torque at the wheels for a given revs is different in every gear, while the figures usually quoted are torque output from the engine.

[anonymous-user]

xRIEx said:

That's a valid point, Monaros do use different Physics compared to other cars.

Guess you'd never know given your catastrophically slow fleet?

Edited by anonymous-user on Tuesday 29th July 18:25

[anonymous-user]

deeen said:

If that's the baseline you're looking for, bear in mind the torque at the wheels for a given revs is different in every gear, while the figures usually quoted are torque output from the engine.

Yep that's while all shootout_8F runs are carried out in 4th gear

[GoTea]

wormus said:

xRIEx said:

That's a valid point, Monaros do use different Physics compared to other cars.

Guess you'd never know given your catastrophically slow fleet?

Ooof, and a new PH rivalry was born

[bigkeeko]

T0MMY said:

Compulsory viewing for diesel fans who like to explain how they have more torque than a [insert supercar name] or quote some specific superior in gear acceleration time that relies on said supercar being in completely the wrong gear.

Hahahahahhahahaaa. Class. I love a good pissonheads brawl.

[anonymous-user]

GoTea said:

wormus said:

xRIEx said:

That's a valid point, Monaros do use different Physics compared to other cars.

Guess you'd never know given your catastrophically slow fleet?

Ooof, and a new PH rivalry was born

Pow pow, You better know yourself little girl

[mackie1]

I do love power and torque threads.

[T0MMY]

wormus said:

Irrespective of the fact the man you are arguing with about the TT is a TT racer who had put in a 127mph lap? I'm surprised he was as patient as he was TBH.

Actually as I recall he accepted that a 4 wheeler could quite easily beat the TT record...merely questioning whether a production car could (which is perfectly reasonable). So in a way, you were arguing with him yourself as you were about the only person on the thread that decided no car could beat the bikes (which is perfectly ridiculous).

There were definitely some errors in the torque/power part of the discussion though...being an excellent rider/driver doesn't make you correct on all matters automotive!

Edited by T0MMY on Tuesday 29th July 18:53

[GroundEffect]

wormus said:

GroundEffect said:

I can make a graph. It will take me about 30 seconds in Excel. Doesn't mean it actually represents anything that the rollers are feeling as a torque.

What they are calculating is power at the wheels through the torque at the wheels (the 'tractive effort' you keep mentioning) then multiplying this by a predefined factor - typically 85% efficiency - to calculate the power at the flywheel/crank.

To get the 'torque at the wheels' you want, they would just take the power they calculate at the wheels and do standard linear manipulation to turn it to a 'torque'...but it actually doesn't mean anything. No part of your drivetrain will ever see it.

What you should care about:

1) Engine torque curve
2) Driveline efficiency
3) Trans/DL ratios

With the above you can basically work out all your performance metrics...assuming wheel slip etc is known.

Torque is the entire game. That's the closest to base unit there is.

Thanks for taking the time to explain. I'm not sure how this thread escalated. I was referring to a number on a graph, I have had many numbers on similar graphs to compare to to know 770lbs "at the wheels" is too much while 600lbs is about right to avoid constant loss of traction. As many of you don't own a Monaro, with my combination of engine, power, diff or gearbox the whole discusiion seems a little ridiculous.

What they really mean is 'X amount of power at the fly * 0.85 * (X/(rpm*5252)' is too much for traction. Which isn't really the torque as I explained above.

But given Monaros will share the common gearing etc then it is a fairly valid comparison for lay-people. It's just physically wrong...but that's my engineer head getting in the way.

[xRIEx]

GoTea said:

wormus said:

xRIEx said:

That's a valid point, Monaros do use different Physics compared to other cars.

Guess you'd never know given your catastrophically slow fleet?

Ooof, and a new PH rivalry was born

Haha, I'm not going to remember this in a couple of days.

[sleeky]

T0MMY said:

There's a chap on You Tube who does some decent videos on car engineering. He has one just on power vs torque but I rather like this F1 vs Nascar one as recommended viewing for anyone that thinks torque is about acceleration and power is about top speed

https://www.youtube.com/watch?v=CxK0x7AE3s8&li...

Compulsory viewing for diesel fans who like to explain how they have more torque than a [insert supercar name] or quote some specific superior in gear acceleration time that relies on said supercar being in completely the wrong gear.

Thank you for posting this. I always understood this some what, but seeing it all in a spreadsheet really cleared things up in my mind. Funny how seeing it in excel allowed me to relate and understand things! (I spend most of my time staring at spreadsheets)