Power to Weight versus Torque to Weight

[Paul Ranson]

Engines make power.

 

Paul

[Alias]

Apologies if I'm being a bit of a simpleton, but from what I understand...

 

Torque basically defines how quickly a car will accelerate.

Power basically defines how long it will accelerate for

 

In racing conditions, you want to be able to use as low a gear as you can for as long as you can. In this case, power is preferable.

 

If you simply like being pushed into the back of your seat then torque is preferable.

 

 

[AMMO]

A Ferrari 550 has more torque and horsepower than a GSXR 1000 Suzuki. The GSXR will out drag the Ferrari because it has better power to weight. As Peter C says power to weight tells you something about the vehicle in question.

 

The Bosch rolling road I have been using gives no torque figures, only power. Having tested a few Caterhams there it is interesting to overlay the power curves to see who has a better spread of useable power. My 1800 Zetec produces more power than Mike Bees' 1700 K series up to about 6000 rpm. At this point my power plummets and Mike's keeps going on for another 3000rpm. His car is a skimpy little thing mine has full weather gear etc. I would estimate that Mikes car has around 570 bhp/tonne and mine around 300 bhp /tonne. Which one is quickest?

 

Wake up and smell the coffee guys. Power to weight is what it's all about.

 

AMMO

[Highlander]

Your Bosch rolling road doesn't give torque because it's smart enough to do the basic P=CTw (w is omega representing rpm but I cant type it in here) calculation for you and giving you a nice power graph.

[AMMO]

Actually the reason it doesn't give torque figures is because when T&M in Colchester bought it they didn't want to fork out an extra £6,000.00. They reckoned that horsepower was good enough.

 

Being self-employed myself I can symapthise as it takes a lot of turnover to clear 6K.

 

As part of my job I have been dyno testing bikes and cars for over 17 years. I've used all sorts of rolling roads and engine brakes. Superflows, Dynojets, Heanan & Froude, Shenkes, Bosch , Sun etc. Since moving to Suffolk T&M are the closest rolling road with a good reputation. Can't say I miss the having the torque curve shown on a graph. Didn't pay much attention to it anyway.

 

AMMO

[Highlander]

AMMO

 

OK I bow to your experience working on Dyno's. didn't know what you did for a living.

 

In that case you can tell me. Do Dynos measure torque and do the necessary calculation to produce a power curve.

[Peter Carmichael]

Old adage use to be change gear so that the change up drop in revs hit max torque curve.

 

Adages are the partly to blame for problems in understanding this. If you change up a few hundred rpm after the power peak, you will be going faster than if you change up to drop you on the torque peak (presuming that the latter case is at lower revs than the former case).

 

I think DanB would concur that by "wide power spread" he also implied "wide torque spread"

 

I think DanB's example numbers are a little optimistic, but the model is a good one. Either percent of peak power developed at 50% and 75% of peak power revs or percentage of revs over which 70% (not 90) of peak power is developed.

 

RobF has brought us back to square one with:

Torque basically defines how quickly a car will accelerate.

Power basically defines how long it will accelerate for

---

 

I would refine it to:

Torque defines how quickly a car will accelerate in gear

Power defines how quickly a car will accelerate

---

 

Ammo's rolling road gives a power curve because it is the principle thing it has measured - however Highlander may sneer. Does it measure engine torque? Does it measure engine speed. No. It measures at the roller so it measures roller speed and it measures the load dumped into the roller, which it probably does from the electrical load developed in the load cell which is probably measured in volts and amps - If I remember correctly: 1 watt = 1 volt x 1 amp. So how exactly Mister Highlander did you suppose it was measuring engine torque and preferring not to tell you about it 🤔

 

Edited by - Peter Carmichael on 19 Sep 2002 10:29:43

[Highlander]

Not sneering, just asking a question, as AMMO works with these things. But her's the answer.

 

You can get an idea of how a dynamometer works in the following way: Imagine

that you turn on a car engine, put it in neutral and floor it. The engine

would run so fast it would explode. That's no good, so on a dynamometer you

apply a load to the floored engine and measure the load the engine can

handle at different engine speeds. You might hook an engine to a

dynamometer, floor it and use the dynamometer to apply enough of a load to

the engine to keep it at, say, 7,000 rpm. You record how much load the

engine can handle. Then you apply additional load to knock the engine speed

down to 6,500 rpm and record the load there. Then you apply additional load

to get it down to 6,000 rpm, and so on. You can do the same thing starting

down at 500 or 1,000 rpm and working your way up. WHAT DYNOMETERS ACTUALLY

MEASURE IS TORQUE (in pound-feet), and to convert torque to horsepower you

simply multiply torque by rpm/5,252.

 

Quote from the Froude literature on its eddy current dyno

 

"The dynamometer casing houses twin magnetising coils that produce a

retarding controllable magnetic field which absorbs the applied torque."

 

Their dynos are quoted as having a power range but detail the accuracy with

which they can measure torque!

 

Quote from the Superflow dyno brouchure

 

"The SF-901 can measure : engine speed, TORQUE, two fuel flows, [etc.]

... and can CALCULATE: POWER, air-fuel ratio, [etc.]"

 

Yes dynos use electrical brakes to absorb the energy some ultimately the

gauge needs to convert this back into a torque (or power) reading however to

calculate power you need to know torque and speed, all that is happening

here is people are forgetting that and burying it in the detail. Power is

not measured directly but calculated afterword whether by hand or

"magically" by a gauge.

 

[Peter Carmichael]

You mix up chassis dynamometers with engine dynamometers.

 

Of course the Froude dynamometer absorbs torque. It also absorbs power, which is sensible seeing as you can't have one without the other.

 

Do rolling roads measure engine torque 🤔 No.

 

Do they measure roller torque 🤔 Yes

 

Do they measure roller speed 🤔 Yes

 

Do they measure engine speed 🤔 Some do, some don't. Some get you to run the rollers at 60mph and check the rpm value to get a ratio.

 

So how do you get engine torque out of what you have measured. You take the roller torque, multiply it by the roller revs and divide by the engine revs. Oh what a strange thing it is that your intermediate result is power, yet you consider the engine torque to be more fundamental than the power; less calculated.

 

Why calibrate back to a roller torque at all if you can just measure power 🤔 If you measure volts and amps, you don't need to know roller speed to determine power, but you probably measure roller speed anyway so you can plot against speed and calculate the torque.

 

So. I have lost my patience again. You have missed the point again. If the rolling road did not measure speed it would be useless as a measuring device. That it measures torque and speed means that it has measured power. The torque it measures is roller torque not engine torque. That it measures power in two components is neither here nor there seeing as multiplication is not the most mysterious calculation in the world.

 

So the issue of "calculated or not-calculated" is a red herring. If you measure any two of the three quantities (torque,power and revs) you can derive the third by simple multiplication.

 

I take issue with your continuing description of power as some sort of poor relative to torque. This misleads people and if people like you who half understand the subject thought a bit harder before sowing confusion it would make it a lot easier for people like me to answer questions specifically and concisely. You should examine where you get your firmly held beliefs and examine how much received wisdom fuels your views seeing as you are uncomfortable if asked to trace them back to first principles.

 

Power is not measured directly but calculated afterword whether by hand or

"magically" by a gauge.

---

 

No. I have proved that this is tosh.

 

Rolling roads that inaccurately set the ratio between roller speed and engine speed give misleading torque outputs, but realistic power outputs. When you get curves from a rolling road the power curve is generally trustworthy (apart from its scaling against the rpm axis) and the torque curve needs to be taken with a pinch of salt.

 

Edited by - Peter Carmichael on 19 Sep 2002 12:45:57

[Highlander]

Does it measure engine torque? Does it measure engine speed. No. It measures at the roller so it measures roller speed and it measures the load dumped into the roller

---

And what is generating the load dumped to the rollers? Thrust at the contact point aka engine torque.

 

That it measures torque and speed means that it has measured power.

---

 

No, your calcualting power from the other two measurements. You need two measured variables to calculate the third. You cant stick a meter on something and measure the power directly as it is work done within a given time, (one second).

 

That it measures power in two components is neither here nor there

---

I disagree, it's exactly the point.

 

I'm not saying that Power is the poorer relation to Torque, not at all it cant be as they are directly proportional. What I am getting at is what you measure to CALCULATE the power at a given engine speed.

[AMMO]

Highlander

 

I do know that torque x rpm / 5250 gives bhp. The first engine brake I ever used in the mid eighties was a Shencke which only measured torque and rpm. The bhp had to be calculated.

 

One thing you will never be able to change my opinion on is the validity of the horsepower figure as a way of assessing engine performance. Especially if you then link it to the weight of the vehicle. This is what I personally find most useful. I can remember the power figures of dozens of engines I have tested but can't remember the torque figures at all. I am just not interested.

 

You cannot change my mind. Let's just agree to disagree.

 

 

AMMO

 

Edited by - Ammo on 19 Sep 2002 13:39:13

[Paul Ranson]

When you are tightening your de Dion hub nuts by standing on a breaker bar to produce a 200lbft torque, how much power are you developing?

 

Paul

[Highlander]

None as the force applied at the end of the bar is balanced by the force at the hub nut, cause the bar isn't moving.

 

And as we all know Power = Torque*speed

 

 

AMMO

Agree power is best way of assessing engine 'performance'

[Peter Carmichael]

You demonstrate that you are a dabbling amateur in metrology as well:

And what is generating the load dumped to the rollers? Thrust at the contact point aka engine torque.

No we have done this before. The thrust at the roller is a consequence of torque at the engine, just as it is a consequence of power produced by the engine. The engine and roller are rather remotely connected (by a gearbox amongst other things) making it easier to determine the power involved than the engine torque. Indeed the easiest way to calculate engine torque is to use power as an interim calculation.

 

You are setting out to measure engine output. You appreciate that the measurement process is imperfect because you are measuring at the wheels. It is important that you take some measurements at known accuracy as a starting point before applying the finger in the air approximations that will follow. The only things you have the ability to measure at known accuracy are roller speed and roller torque, AKA the roller power. The thing you have a reduced ability to measure accurately is the engine speed because of tyre slip and other effects. So therefore you cannot determine engine torque accurately.

 

£6000 allows you to be a bit more accurate.

[Highlander]

True you cannot easily measure the tyre slip on the rollers, so you're measuring torque transferred to the rollers and calculating power at the rollers.

So we agree that you're estimating the torque at the engine due to slip, but by the same token you're estimating the power at the engine.

[Highlander]

Going back to the Power v Torque debate

 

Try this . .

 

The Case For Torque

Now, what does all this mean in carland?

First of all, from a driver's perspective, torque, to use the vernacular,

RULES :-). Any given car, in any given gear, will accelerate at a rate that

*exactly* matches its torque curve (allowing for increased air and rolling

resistance as speeds climb). Another way of saying this is that a car will

accelerate hardest at its torque peak in any given gear, and will not

accelerate as hard below that peak, or above it. Torque is the only thing

that a driver feels, and horsepower is just sort of an esoteric measurement

in that context. 300 foot pounds of torque will accelerate you just as hard

at 2000 rpm as it would if you were making that torque at 4000 rpm in the

same gear, yet, per the formula, the horsepower would be *double* at 4000

rpm. Therefore, horsepower isn't particularly meaningful from a driver's

perspective, and the two numbers only get friendly at 5252 rpm, where

horsepower and torque always come out the same.

 

In contrast to a torque curve (and the matching pushback into your seat),

horsepower rises rapidly with rpm, especially when torque values are also

climbing. Horsepower will continue to climb, however, until well past the

torque peak, and will continue to rise as engine speed climbs, until the

torque curve really begins to plummet, faster than engine rpm is rising.

However, as I said, horsepower has nothing to do with what a driver *feels*.

 

 

You don't believe all this?

 

Fine. Take your non turbo car (turbo lag muddles the results) to its torque

peak in first gear, and punch it. Notice the belt in the back? Now take it

to the power peak, and punch it. Notice that the belt in the back is a bit

weaker? Fine. Can we go on, now? :-)

 

 

The Case For Horsepower

OK. If torque is so all-fired important, why do we care about horsepower?

Because (to quote a friend), "It is better to make torque at high rpm than

at low rpm, because you can take advantage of *gearing*.

 

For an extreme example of this, I'll leave carland for a moment, and

describe a waterwheel I got to watch awhile ago. This was a pretty massive

wheel (built a couple of hundred years ago), rotating lazily on a shaft

which was connected to the works inside a flour mill. Working some things

out from what the people in the mill said, I was able to determine that the

wheel typically generated about 2600(!) foot pounds of torque. I had clocked

its speed, and determined that it was rotating at about 12 rpm. If we hooked

that wheel to, say, the drivewheels of a car, that car would go from zero to

twelve rpm in a flash, and the waterwheel would hardly notice :-).

 

On the other hand, twelve rpm of the drivewheels is around one mph for the

average car, and, in order to go faster, we'd need to gear it up. To get to

60 mph would require gearing the wheel up enough so that it would be

effectively making a little over 43 foot pounds of torque at the output,

which is not only a relatively small amount, it's less than what the average

car would need in order to actually get to 60. Applying the conversion

formula gives us the facts on this. Twelve times twenty six hundred, over

five thousand two hundred fifty two gives us:

 

6 HP.

 

Repeat after me. "It is better to make torque at high rpm than at low rpm,

because you can take advantage of *gearing*."

 

Gearing is the key, which takes me back to my original point about thrust at

the wheel...

[Peter Carmichael]

None as the force applied at the end of the bar is balanced by the force at the hub nut, cause the bar isn't moving.

 

No Highlander. You keep embarrassing yourself with half-knowledge and inaccurate use of accurate physical terms.

 

There is no power involved when the bar is not moving - it is nothing to do with the balance of forces. If the bar was moving at constant rotational velocity, it would still have a balance of forces and work would be done at a determinable power. If there was an imbalance of forces the bar would accelerate.

[Highlander]

Peter, true to character you continue to miss quote/interpret me. I was speaking

specifically about the previous post on tightening a wheel nut which would

stop rotating at the point where the torque setting of the nut matched the

torque applied through the tool. At this point there is no movement and so

no power.

 

How did you then get to a turning wheel? The post was about tighten an wheel

nut!

 

[Peter Carmichael]

And you are true to character and wrong in detail yet again. I didn't misquote. I didn't mention wheels.

 

The nut does not stop moving when the forces equal one another. The nut stops accelerating when the forces are equal. In order for a nut that has been turning to stop turning, it needs to be decelerated; the restraining force needs to exceed the applied force momentarily.

 

My criticism was with what you wrote:

1. None [no power] as the force applied at the end of the bar is balanced by the force at the hub nut [No, this doesn't follow. I explained how the forces can be equal even when a system is in motion and therefore work and power are involved.]

2. Cause the bar isn't moving. [indeed if the bar isn't moving and isn't accelerating then the forces are equal, but the reverse is not true]

 

You can quibble all you like and accuse me of misquoting, but that was what you wrote.

 

You also missed entirely Paul's rhetorical point. If torque at the rear wheels is so important why don't you take the engine out and fit a torque wrench directly to the rear hubs and apply torque. If you did this, how fast would you go?

 

You know the answer, but you should take more care to be accurate in writing about it.

 

As for the remaining issue regarding rolling roads:

True you cannot easily measure the tyre slip on the rollers

Agreed.

so you're measuring torque transferred to the rollers and calculating power at the rollers

Agreed.

So we agree that you're estimating the torque at the engine due to slip

No. We haven't got that far yet. We need to measure engine speed somehow. You haven't even suggested how we do that. If we get it wrong (which generally we do because of factors like slip and tyre growth), we get a scaling factor wrong on the torque output. A scaling factor - it makes the numbers wrong:

 

For example:

An engine produces peak torque at 4000rpm. Because of tyre growth the rolling road sees peak torque at a roller speed that equates to 4200rpm. The engine is genuinely producing 120lbft @4000 rpm. The rolling road output makes it look like the engine is producing 114lbft @4200 rpm. The engine is genuinely making 91.4 horsepower @4000rpm. The rolling road output makes it look like the engine is producing 91.4 horsepower@4200rpm.

 

The torque figure is wrongly represented.

The power figure is correct, if at the wrong revs.

 

I haven't got into the matter of losses yet because you keep undermining the foundation knowledge required to move on, but it will be very much easier to deal with once you roll over and accept that power is measured and is easy to measure and indeed is more easily measured on a rolling road than engine torque.

 

Thank you for your web search. The torque vs. horsepower article is a good one that many sites replicate. It humours the widely misunderstood torque myth and then takes it apart ruthlessly. It is worth reading in full:

Torque vs. Horsepower article in full

 

Edited by - Peter Carmichael on 19 Sep 2002 16:34:48

[Gary G]

Peter,

 

I follow your technical postings with interest, although for much of the time I have trouble understanding them and I am always left with one question: How do you know all about this stuff? Is it part of your job/profession or are you just interested and have learnt about it over the years?

 

 

 

C7 GAR

Oh Yes Yes Yes Yes

 

[Highlander]

1. None [no power] as the force applied at the end of the bar is balanced by the force at the hub nut [No, this doesn't follow. I explained how the forces can be equal even when a system is in motion and therefore work and power are involved.]

---

 

Fundamentally it is possible to have a torque applied to a system without doing any work on that system, if it is opposed by an equivalent and opposite torque. i.e a fully tightened bolt. For the avoidance of doubt a non-moving system.

What you are talking about is a torque applied to system rotating at a constant velocity which is not what was being described. I’m not disputing that an unbalanced force will cause acceleration in this system, whereas a balanced force will maintain a constant velocity.

 

But I digress

 

To get this discussion back to where I came in, Torque create thrust, and something about F1 cars and Traction Control ...

 

Torque and power are (almost) flip sides of the same coin. Increasing the

torque of an engine at a particular RPM is the same as increasing the power

output at the same RPM.

 

Power is just as useful and relevant in determining vehicle performance as

is torque. In some situations it's more useful, because you may not have to

play with gear ratios and a calculator to understand what's going on.

 

A car accelerates hardest with gearing selected to stay as close as possible

to the engine power peak, subject to the traction capability of the tires.

And the big assumtion is that it is geared correctly.

 

Not all cars should be shifted at the redline for maximum performance. But

it's true for many cars. You can determine optimal shift points for best

performance by graphing horsepower vs. velocity or transmission torque vs.

RPM.

 

Engine torque or engine power alone is not enough to determine or compare a

vehicles performance.

[Peter Carmichael]

Highlander,

 

I have been ripping you to bits on inaccurate use of terms. You haven't got it yet. Deliberately misunderstanding you? No. Being very pedantic. Yes.

 

Fundamentally it is possible to have a torque applied to a system without doing any work on that system

Yes.

if it is opposed by an equivalent and opposite torque.

No. Only if it is not moving.

For the avoidance of doubt a non-moving system.

This is your continuing confusion. It is not for the avoidance of doubt, it is an absolute necessity. If this is not the case then work is done. Always.

 

I am being very tenacious on this point because it undermines your credibility in all other areas.

 

To answer gary's question: MA Hons (Oxon) Engineering Science but this is O-level stuff.

 

I really do believe you understand a lot of this stuff, but you let yourself down with loose use of terminology.

 

Torque and power are (almost) flip sides of the same coin. Increasing the

torque of an engine at a particular RPM is the same as increasing the power

output at the same RPM.

---

 

Agreed.

 

Power is just as useful and relevant in determining vehicle performance as

is torque. In some situations it's more useful, because you may not have to

play with gear ratios and a calculator to understand what's going on.

---

 

Agreed.

 

A car accelerates hardest with gearing selected to stay as close as possible

to the engine power peak, subject to the traction capability of the tires.

---

 

Agreed.

 

And the big assumtion is that it is geared correctly.

Disagree and it doesn't follow from your previous point. If you have any gears at all (correct or otherwise), the one that provides the best acceleration is the one that gets the engine spinning higher up the power curve.

 

Not all cars should be shifted at the redline for maximum performance.

Not necessarily the redline, but certainly beyond the power peak.

 

But

it's true for many cars. You can determine optimal shift points for best

performance by graphing horsepower vs. velocity or transmission torque vs.

RPM.

---

 

Transmission torque? You had better have a definition up your sleeve, but I think I know what you mean and therefore agree but it doesn't change the answer which is: Just beyond the power peak.

 

Engine torque or engine power alone is not enough to determine or compare a

vehicles performance.

---

 

Agree that you need to know weight as well but that was where this discussion came in. I otherwise disagree because low speed acceleration (ie. before aerodynamic losses become large) can be determined from engine power (meaning the entire power curve). You plot the power to weight against a normalised engine speed axis.

 

The normalised engine speed axis that I use runs from zero to 1, where 1 is the change up rpm to within a couple of hundred rpm. This gives a very insightful comparison of vehicles.

[Gary G]

MA Hons (Oxon) Engineering Science but this is O-level stuff

 

Jeez, if this is O-level then I don't stand a chance! Think I'll stick to Finance and let Caterham service my car!

 

C7 GAR

Oh Yes Yes Yes Yes

 

[Bilbo]

Hi all

 

Peter in particular, think you by now you have properly guessed I am just playing devils advocate

 

Just out of interest a few nice manufactures articles on dyno's

 

here

 

Think it nicely sums up what a dyno actually measures and the fact BHP is calculated.

 

As to pretty pictures here

 

How about this for a big one here

 

Plus one about how to use a torque wrench or your input on its effect here

 

Hi Paul Ranson "Engines make power".

 

Well they do produce power but I did say they only produce torque as an OUTPUT again power= rev x TORQUE.

 

Hi AMMO "Can't say I miss the having the torque curve shown on a graph" that's what everyone asks "me want more BHP more more more". Then again how many really know what an engines OUTPUT really is if you said the rotational force has increased by XX ft lbs they would look at you with a VERY blank expression. .

In the end ... me at a RR just wants better than I had when arrived that day. If I ask someone to design or modify an engine I tend to look at the BHP and the torque as a composite unit and where they occur. This for me, is often not related to a car engine.

 

Oh Peter I remembered where the old adage came from, it was from rallying friends years back. In fact all they ever talked about was torque and always keeping it just on or on the cam when change down.

 

Very off topic.

 

Nice degree Peter, its also nice to see you can apply what you learnt practically it was getting to be a very rare trait a few years back well it was in what I do. Lots of symptoms of I have a degree now I can be instantly be a line manager (shudder). After 35 years in design I am now constantly pleased to see its swung the other way to what can I personally design. That's the fun bit... well it is for me. [:}]

 

 

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BD? with Brooklands and Clamshell wings, Freestyle Motorsport suspension. Q 979 CGY

 

[Highlander]

Peter,

I think we have got to the point where were looking for inaccuracies rather than what we're actually saying.

 

Fundamentally it is possible to have a torque applied to a system without doing any work on that system, if it is opposed by an equivalent and opposite torque. i.e a fully tightened bolt. For the avoidance of doubt a non-moving system.

---

 

i.e. in the bolt scenario the machine in question, is static, non-moving, stationary, bereft of life it rests in peace. Oops bit of Monty Python there.

Is there something about the above sentence that states that the system is anything other than stationary?

 

No? Good.

 

Hence if we both agree that the bolt system is NOT moving, (other than as the earth spins around its axis or rotates around the sun that it), then no work done. and no power. Agreed.

 

Your exapmle involved motion and hence there was work done and power. No arguments ther from me.

 

For the avoidance of doubt a non-moving system.

--------------------------------------------------------------------------------

 

 

This is your continuing confusion. It is not for the avoidance of doubt, it is an absolute necessity. If this is not the case then work is done. Always.

---

 

Nope, not confused, no movement = no work done, movement implies work done implies power

 

I think perhaps you're assume my 'avoidance of doubt statement' related to something else other than the tight bolt with a torque wrench scenario, but just to say it again, the system I was discussing is STATIC.

 

 

 

And yes I do understand this very well, as I also have a B.Eng. (hons) in Engineering. but perhaps I'm not quite as eloquent as I might be. To busy taking things apart when I should have been listening in English class at school. 😬

 

Disagree and it doesn't follow from your previous point. If you have any gears at all (correct or otherwise), the one that provides the best acceleration is the one that gets the engine spinning higher up the power curve.

---

 

And the big assumtion is that it is geared correctly.

---

This isn't a follow on point, but merely reiterating the fact the to perform at its best an engine MUST be geared correctly.

 

To my mind regardless of the torque or power of an engine, be it a 500hp Ferrari or the 6hp waterwheel, it wont do jack unless it's geared properly.

 

Take the Honda v BMW comparison I talked about earlier. Both have 186hp one peaks at 7900, the other at 4200. Now in top gear (this is just an example) the Honda pulls 18.2 mph/1000rpm the BMW 33mph/1000rpm. Now if you put the BMW 'box in the Honda, it's going nowhere, but the BMW deals with this gearing easily due to it's power/torque characteristics. Put the Honda 'box in the BMW and it'll take of like a rocket ship (ish), but run out of useable engine speed at about 80mph.

 

So gearing is everything to an engines performance given it's available power. Gearing effectively provides the 'leverage' necessary, and as the man said 'Give me somewhere to stand an I'll move the earth'.

 

transmission torque vs. RPM

 

You had better have a definition up your sleeve

---

 

Assume that this is torque at the wheels, but agree it's not a very intuitive statement.

 

I otherwise disagree because low speed acceleration (ie. before aerodynamic losses become large) can be determined from engine power (meaning the entire power curve).

---

You also need to know the gearing to determine the non-drag limiting acceleration, not just the power and the weight.

 

Do we get to do losses now?

 

BTW Peter, I'm not having a go, trying to prove I'm better than you or anything else like that. I just dont accept facts blindly rather like to err 'discuss' things to get a better understanding, and get it clear in my mind that what they're saying is indeed fact and not rollocks.

 

Are we having fun yet?

 

P.S. Some of my posts may not be expertly written as I have to do it covertly without the project manager seeing!