1 Car Length = 37rwkw (50rwhp)

[Blonk]

Of course the curve will be parabolic but I could add another equation (or 2) to justify this...........

[PozzE]

you may have time slips but BOSE has mathmatics on his side.  25M in .5 of a second is not 1 car length for your 30kws :wacko:

<{POST_SNAPBACK}>

Bose and Shock, your maths are correct but your frame of reference is wrong. To the other car you are not travelling 51m/s faster, because it is travelling at a similar speed. You would be travelling 51m/s compared to a fixed point.

Blonk, I nearly went insane today trying to figure it out basically what you've done, did it many times many ways and still wasn't happy

We both know you've used formulae for linear acceleration, but that's more than fair enough, otherwise you would have to take readings as the car went down the 1/4 and intergrate and NO ONE can be stuffed doing that. (ok maybe the guy from numb3rs)

Assuming linear acceleration, the force applied to the car doesn't change, as the acceleration doesn't change

BUT IT DOES. Traction, drivers, fuel, magic pixies all aside. The main thing that would matter is where in the rev range and how long for the car gets to max power.

my question would be, Where in the rev range is the extra 37RWKW?  if I have a car that produces 200RWKW at 2000rpm and holds it through to 6000rpm, are you saying that it would loose to a car that has 140RWKW at 2000rpm but 237RWKW at 5000rpm??

there are soo many variables that your expert has not specified, there for you can only say IT IS POSSABLE that your expert is correct but far more likely that he is not.

<{POST_SNAPBACK}>

spoton Shock

If a car only develops 300KW for 500RPM and 140kw for the rest, a car that develops 260kw for most of the range will flog it. A more accurate way would to be to caculate the area under the power graphs for the two cars to get an avg power then apply the linear acceleration formulae... but once again WHO CAN BE STUFFED.

T's with more power will in general go faster, but to make a statement as specific as 37KW = 1 car length is just wrong and ill imformed it might work for one example but I'd never use as a general rule...

Now where is that 747 on the treadmill....

[Blonk]

Before I start, you guys must realise it is all about a question of torque not power.???

Should I continue??

Blonk, I nearly went insane today trying to figure it out basically what you've done, did it many times many ways and still wasn't happy

We both know you've used formulae for linear acceleration, but that's more than fair enough, otherwise you would have to take readings as the car went down the 1/4 and intergrate and NO ONE can be stuffed doing that. (ok maybe the guy from numb3rs)

Assuming linear acceleration, the force applied to the car doesn't change, as the acceleration doesn't change

BUT IT DOES. Traction, drivers, fuel, magic pixies all aside. The main thing that would matter is where in the rev range and how long for the car gets to max power.

Power is the rate at which a device can consume energy being 1 J/s or 1W..

Creating linear power requires torque.... Simple really........... that's why we need to consider weight.

Its not the power equation we are looking for, its the Torque Einstein....

that's why we need to include force into the equation...

A 1000kw motor will not beat an F6 if it only generates

200nm of torque... Unless the strip is 10kms long.....

Just because it can consume 1,000 kilojoules of energy a second, doesnt mean it is going to get a chance to..... Think about it... We are generating torque, not measuring it.

We are measuring power not generating it.

All relative remember Newtons first 3 laws...

[Lawsy]

Before I start, you guys must realise it is all about a question of torque not power.???

Should I continue??

Oh, you're infact wrong, and yet right all at the same time there. I've been bending my mind around this very problem for over a year now, trying to consider all of the different aspects of each (to tell you all of what I've tried to figure out, it would take pages and pages of explanation).

In a nutshell, its all about the area under the POWER curve for between the relevant RPM points for each shift, then averaged, multiplied by the gear ratios....

You will find that this average is almost the same for every gear other than 1st, as you use a wider RPM band.

You then multiply this average for each RPM point with the total gear ratio (including diff) then factor in a few constants with weight and you can work out accelerative force almost exactly, as long as you have an accurate traction equation (which is actually possible).

This sounds lame but its actually easy to understand if you think about it. Power is work over time. Torque is a Force.

Power is also (torque*RPM)/9550.

It should be noted that 9550 is the RPM at which the power and torque curves will cross on a single scale graph where kW and Nm are the units.

So I'll tell you what its all about.

Its about how much area there is under the power curve, within a relevant RPM range, factoring in the gear ratios...

Thast how you're wrong.

This is how you're right!

Within each gear, disregarding wind resistance, your linear accelerative force curve will exactly follow your engine torque curve... And the added engine RPM is infact converted to added torque through the gearbox for any given speed.

I was going to go on and explain this in a bit of detail, but there is just so much too it, I really can't be bothered now....

[Blonk]

Go to bed lawsy, your brain has run out.....

A 1000kw motor will not beat an F6 if it only generates

200nm of torque... Unless the strip is 10kms long.....

Just because it can consume 1,000 kilojoules of energy a second, doesnt mean it is going to get a chance to..... Think about it... We are generating torque, not measuring it.

We are measuring power not generating it.

power without torque = nothing........

Every single argument you add has torque or force involved.. Make the torque value zero and see how your maths go... It will all equal zero......

Power is nothing more than a thermometer on the wall telling you how hot it is.

Torque = potential

Power is also (torque*RPM)/9550

Power = (0*rpm)/9550 = farkin zero

[Lawsy]

Ok I'm gonna have to explain this... Sigh.

At the engine, you want power. that's it. Power.

At the wheels you want torque, nothing but torque.

What is in between? A gearbox.

So in reality what do we actually want? A good combination of both.

The rest is yours to figure out.

Hint: Do a torque/power vs gear ratio graph for each gear and you'll get the idea.

[Blonk]

Why have 1000kw at the engine when it has 200nm of torque??????

Why have 1000000kw at the engine if it only has 50nm of torque..

Why does an F6 beat a 297 clubby - Farkin Torque

Edited 22/03/06 06:37 PM by ducatijb

[Lawsy]

Go to bed lawsy, your brain has run out.....

A 1000kw motor will not beat an F6 if it only generates

200nm of torque... Unless the strip is 10kms long.....

Just because it can consume 1,000 kilojoules of energy a second, doesnt mean it is going to get a chance to..... Think about it... We are generating torque, not measuring it.

We are measuring power not generating it.

power without torque = nothing........

Every single argument you add has torque or force involved.. Make the torque value zero and see how your maths go... It will all equal zero......

Power is nothing more than a thermometer on the wall telling you how hot it is.

Torque = potential

Power is also (torque*RPM)/9550

Power = (0*rpm)/9550 = farkin zero

You are indeed correct, every power figure has some sort of torque or force involved.

But, heres the trick.

Without the right gear ratios, all the torque in the world will get you no where. But with the right gear ratio's, power will dominate as because power is work, and when you start getting into higher RPM bands, the work done starts to converge with the accelerative force curve vs gear ratio's (which is a bloody good grahp if you can make a nice one, might I add).

We rate everything today in terms of power, not torque. This is because power is usefull, torque on its own, is not. You can have power/work/energy in many different forms in complete isolation to any torque or force, and it is still usefull. But we are talking about kenetics and rotational motion.

This can be mathematically shown as

Torque = work*9549/RPM

If either power goes down, RPM must also go down to give the same torque. Eventually, if you converge both to 0, you have an infinitely large torque value, but the work done is 0. So what have you achieved? If we were talking about vector forces, then yes, you can have massive torque, zero applied distance and still have massive energy consumption. This can be shown through the manipulation of varies statics equations, which is what I think you were getting at in the back of your mind somewhere... Which is fair enough.

The problem is, firstly, most F6's with the same gearbox and diff ratio wont beat a clubsport, sadly, and secondly, 1000kw with 200nm of torque will dominate any F6 currently on the road. It would have a diff ratio somewhere around the 8:1 mark (pretty stupid, but meh) and it would have more torque at the wheels....

I think you're getting confused. Power at the wheels will be roughly the same regardless of the gear you pick to run it in, only speed varies. Torque, or more importantly, tracive effort, changes from gear to gear. Wheel torque is what you want. Meaning you can have increadible amounts of power at the ENGINE and gear it down to give increadible amounts of torque at the WHEELS. This is why almost every single race engine on the planet is pushed to its RPM limit wherever possible, but the car they are put in have shorter diff ratio's... What I'm explaining to you is basically what race teams have been physically showing you for the last century.

So, my personal preference would be to have an engine that made a perfectly flat torque curve untill its theoretical maximum RPM. Power is therefore ever increasing until this point, meaning you can achieve more work, with linear acceleration throughout the entire rev range, geared down to give increadible amounts of torque at the wheels. That would rock!

Since I can't have that, then I wan't max power at 7500rpm, max torque at 5000rpm and 70% of that torque available from 2500rpm onwards with 4.10 diff gears.

It would have greater wheel torque as opposed to having max power at 5000 rpm, with max torque at 2500 tapering off until 70% at max power, dropping further till redline...

This would give insanely larger amounts of wheel torque. This can also be proven via graphing torque vs rpm vs gear ratio's on a 3d graph. The resultant is wheel torque, or simply work it out mathematically, using (total ratio) * torque * RPM,if you can be bothered.

But right now, I can't.

Enjoy :D

I'm now going to sleep for 6 hours and then goto uni to do a test which I was meant to be studying for over the last 2 hours that I've spent getting my brain back into horsepower theory mode...

Doh.

[gogo]

Power at the wheels will be roughly the same regardless of the gear you pick to run it in, only speed varies. Torque, or more importantly, tracive effort, changes from gear to gear. Wheel torque is what you want. Meaning you can have increadible amounts of power at the ENGINE and gear it down to give increadible amounts of torque at the WHEELS.

<{POST_SNAPBACK}>

Great explanation Lawsy, and 100% correct.

I think the other thing is dynamically many of the other losses such as aerodynamic etc can be worked basically as a power drain (conservation of energy). If you are not producing the power to overcome these, then no acceleration either...

Cheers,

Ben.