Power vs Torque Questionnaire -RESULTS

[machin]

Torque is to get moving, power is to keep moving.
Torque is what you want, power is additional.

This!! You need Torque to get moving and in everyday driving you need better driveability.

Can one or both of you guys agree that;

At a given road speed, More torque at the driven wheels equals more acceleration (assuming there is sufficient grip)?

And;

More torque at the driven wheels is achieved either with more flywheel torque, or by using a bigger gear ratio between the flywheel and the driven wheels (E.g. using 3rd gear instead of 5th)?

I think it is important everyone grasps these aspects, and I'd like one of you two to confirm this before I go on... Cheers.

[Manoah2u]

Can one or both of you guys agree that;

At a given road speed, More torque at the driven wheels equals more acceleration (assuming there is sufficient grip)?

agreed partially.

torque creates accelaration with grip,
horsepower creates acceleration with less 'grip'. that's why horsepower creates spinning wheels and torque causes 'catch'.

as like torque is the muscle of the legs to cause movement and heartrate [horsepower] defines how fast the movement can be maintained. strong legs can give powerfull movement, and carry lots of weight. A strong heart can make legs move faster and longer. But a strong heart with weak legs will make the carrier have problems pulling weight, whilst strong legs with a 'weaker' heart will make carrying load/weight easy at the 'cost' of not doing that at a high rate of speed.

And;

More torque at the driven wheels is achieved either with more flywheel torque, or by using a bigger gear ratio between the flywheel and the driven wheels (E.g. using 3rd gear instead of 5th)?

can't agree here.

flywheel torque? bigger gear ratio to flywheel?

the gearbox is connected through the clutch to the crankshaft, not to the flywheel. the flywheel works to keep the engine's intertia alive / balanced.

I think it is important everyone grasps these aspects, and I'd like one of you two to confirm this before I go on... Cheers.

well, there's no confirming in flywheel to gearbox connections since there simply aren't any......

[langwadt]

Can one or both of you guys agree that;

At a given road speed, More torque at the driven wheels equals more acceleration (assuming there is sufficient grip)?

agreed partially.

torque creates accelaration with grip,
horsepower creates acceleration with less 'grip'. that's why horsepower creates spinning wheels and torque causes 'catch'.

as like torque is the muscle of the legs to cause movement and heartrate [horsepower] defines how fast the movement can be maintained. strong legs can give powerfull movement, and carry lots of weight. A strong heart can make legs move faster and longer. But a strong heart with weak legs will make the carrier have problems pulling weight, whilst strong legs with a 'weaker' heart will make carrying load/weight easy at the 'cost' of not doing that at a high rate of speed.

And;

More torque at the driven wheels is achieved either with more flywheel torque, or by using a bigger gear ratio between the flywheel and the driven wheels (E.g. using 3rd gear instead of 5th)?

can't agree here.

flywheel torque? bigger gear ratio to flywheel?

the gearbox is connected through the clutch to the crankshaft, not to the flywheel. the flywheel works to keep the engine's intertia alive / balanced.

I think it is important everyone grasps these aspects, and I'd like one of you two to confirm this before I go on... Cheers.

well, there's no confirming in flywheel to gearbox connections since there simply aren't any......

anyways, the torque at the crankshaft end up at the wheels multiplied by the ratio of the gear box

power is torque times speed, the only difference between two engines making the same power is the gear ratios needed
and the numbers on the rev counter

[machin]

agreed partially.

torque creates accelaration with grip,

.....

the gearbox is connected through the clutch to the crankshaft, not to the flywheel.

Excellent, you clearly have a lot of experience in this field and I think we can together convince a lot of people how this whole power and torque thing works!

Ok, so, assuming sufficient grip, and if I change the word from "flywheel" to "crankshaft" would you agree with this:

"The acceleration of a given vehicle is proportional to the torque at the crankshaft multiplied by the gear ratio in use" ???

Or as an equation:

(Crankshaft torque) x (gear ratio) ∝ Acceleration

(Where ∝ simply means "proportional to", I.e increase one, and the other increases too).



And do you agree that

"the overall gear ratio, including final drive, can be defined as the relative difference between the crankshaft rotational speed and the rotational speed of the driven wheels" ?

Or as an equation:

(Crank RPM) / (wheel RPM) = overall Gear ratio

...????

[Tim.Wright]

The key to understanding this stuff is to forget all the cute one-liners and BS analogies and instead use physics and numeric examples...

[machin]

Don't worry Tim, we'll get there.

[langwadt]

The key to understanding this stuff is to forget all the cute one-liners and BS analogies and instead use physics and numeric examples...

it is quite strange that just because an engine is involved things get all about feelings and some people forget simple math
and physics

[mrluke]

At a given road speed, More torque at the driven wheels equals more acceleration (assuming there is sufficient grip)?

Torque doesn't have a time property. Once you give torque a time property it becomes a measure of power.

Therefore a single revolution of a very high torque engine is unlikely to give a better acceleration than a lower torque engine for a longer time period.

[Tim.Wright]

Take the NEW Power vs Torque quiz! -instant feedback!

Actually, the (real world) example in your survey is a damn near perfect explanation of powertrain mechanics.

[machin]

At a given road speed, More torque at the driven wheels equals more acceleration (assuming there is sufficient grip)?

Torque doesn't have a time property. Once you give torque a time property it becomes a measure of power.

Therefore a single revolution of a very high torque engine is unlikely to give a better acceleration than a lower torque engine for a longer time period.

Step by step I will derive the calculation for the instantaneous acceleration of a vehicle based on crankshaft torque. This is perfectly possible and is essentially an application of Sir Isaac Newton's well proven formula, F=m.A

But all in good time, let's not rush until we're all onboard...

From there we could determine the time taken to accelerate from one speed to another if we wanted to.

[strad]

Just how many times must we wade thru this?
lock it up quick!

[Manoah2u]

your analogy is nice, but flawed, or let's just call it contradictory.

let's take this for example:

Peak Power: 204 bhp (Diesel), 211 bhp (Petrol)
Peak Torque: 368 lbft (Diesel), 258 lbft (Petrol)

selected statement:

" 1. The car with the Diesel engine has a very similar power: weight ratio as the petrol engined car, however it has 40% higher torque:weight ratio therefore it will accelerate faster. As both cars have a similar power:drag ratio and optimised final drive ratios they will have a very similar top speed. "

reply:

"INCORRECT ANSWER"

given explenation:

The performance results as independently tested by Autocar magazine were actually very similar in all aspects, as follows:

blablabla numbers

As you can see, both cars have very similar performance results in all tests; acceleration and top speed.

ok, so according to this claim, more torque does not equal more acceleration.

right? after all, despite the diesel engine having loads more torque, the results between diesel and petrol are 'similar'.
in other words; the 110lbft of torque the diesel engine has extra over the petrol engine, 40% more, results, performance-wise, in 'nothing'.

so, according to the given figures, more torque does not equal more acceleration.

HOWEVER, in your explenation,

the following 'analogy' is given:

http://www.competition-car-engineering. ... Torque.htm

if we want to increase acceleration, and we can't change the mass, we need to increase the force

yes.

and this is added to the analogy:

with Torque and Engine RPM; if you can increase one or both of these parameters you will be able to accelerate your car quicker.

wait, what?

so, you claim the answer that the car with 40% more torque should accelerate faster is an INCORRECT ANSWER,
and then you try to explain why it's wrong by stating MORE TORQUE equals HIGHER ACCELERATION.



please, explain this contradictory statement. because clearly either something then must be wrong with this analogy, or there must be something wrong with the given numbers.

according to the analogy "increase one or both of these parameters you will be able to accelerate your car quicker",
and "if we want to increase acceleration....we need to increase the force"

then according to these figures

Peak Power: 204 bhp (Diesel), 211 bhp (Petrol)
Peak Torque: 368 lbft (Diesel), 258 lbft (Petrol)

the diesel car has a higher torque 'parameter' thus should accelerate faster.

yet, you claim that this is not true.

so go ahead, explain this, because you can't have both.

you can't say more torque should bring more acceleration,
and then state that a car with 40% more torque does not accelerate more. then a car with 40% less torque.

if given a correct explenation, i could agree to the claim that "flywheel power would detirmine vehicle performance, and not flywheel torque"

however you explain flywheel torque does not determine vehicle perforamance, by explaining higher torque equals more acceleration.

the only 'proof' you give that more torque does not equal higher acceleration are the performance figures given by autocar, supposedly showing similar performance figures.

so according to the analogy, the autocar performance figures MUST be wrong.
but if the autocar performance figures are correct, then the analogy must be wrong.

if two cars are 100% equal in everything, except that one has an engine with 40% more torque,
then clearly, the one with 40% more torque, should be faster or more powerfull. that is a absolute fact.

so if both merc's indeed are just as fast,
then either the analogy must be wrong,
or the power figures are incorrect and the diesel car does not have 40% more torque but is similar.

so, explain.

[langwadt]

your analogy is nice, but flawed, or let's just call it contradictory.

let's take this for example:

Peak Power: 204 bhp (Diesel), 211 bhp (Petrol)
Peak Torque: 368 lbft (Diesel), 258 lbft (Petrol)

http://www.competition-car-engineering. ... e_comp.jpg

selected statement:

" 1. The car with the Diesel engine has a very similar power: weight ratio as the petrol engined car, however it has 40% higher torque:weight ratio therefore it will accelerate faster. As both cars have a similar power:drag ratio and optimised final drive ratios they will have a very similar top speed. "

reply:

"INCORRECT ANSWER"

given explenation:

The performance results as independently tested by Autocar magazine were actually very similar in all aspects, as follows:

blablabla numbers

As you can see, both cars have very similar performance results in all tests; acceleration and top speed.

ok, so according to this claim, more torque does not equal more acceleration.

right? after all, despite the diesel engine having loads more torque, the results between diesel and petrol are 'similar'.
in other words; the 110lbft of torque the diesel engine has extra over the petrol engine, 40% more, results, performance-wise, in 'nothing'.

so, according to the given figures, more torque does not equal more acceleration.

HOWEVER, in your explenation,

the following 'analogy' is given:

http://www.competition-car-engineering. ... Torque.htm

if we want to increase acceleration, and we can't change the mass, we need to increase the force

yes.

and this is added to the analogy:

with Torque and Engine RPM; if you can increase one or both of these parameters you will be able to accelerate your car quicker.

wait, what?

so, you claim the answer that the car with 40% more torque should accelerate faster is an INCORRECT ANSWER,
and then you try to explain why it's wrong by stating MORE TORQUE equals HIGHER ACCELERATION.



please, explain this contradictory statement. because clearly either something then must be wrong with this analogy, or there must be something wrong with the given numbers.

according to the analogy "increase one or both of these parameters you will be able to accelerate your car quicker",
and "if we want to increase acceleration....we need to increase the force"

then according to these figures

Peak Power: 204 bhp (Diesel), 211 bhp (Petrol)
Peak Torque: 368 lbft (Diesel), 258 lbft (Petrol)

the diesel car has a higher torque 'parameter' thus should accelerate faster.

so go ahead, explain this.

sigh, .. Because the engines runs at different RPM they need different gear ratios to go the same speed, that ratio also multiplies the torque at the wheels. With the prober gear 200Nm@6000rpm, is exactly the same as 400Nm@3000rpm

it's like beating dead horse, this is really simple physics

[hollus]

No contradiction, more torque, at the same rpm, will bring more acceleration. However, these two cars will never run at the same rpm at any given moment, at least not while they are at similar speeds.
While you'll keep your diesel car in the 3000rpm range, you'll keep your petrol car in the 5000rpm range as much as you can. Your torque there will be lower than that of the diesel by about the same amount as your revs are higher. "If you can increase torque or rpm..."
It's all in the gear box!

[Manoah2u]

sigh, .. Because the engines runs at different RPM they need different gear ratios to go the same speed, that ratio also multiplies the torque at the wheels. With the prober gear 200Nm@6000rpm, is exactly the same as 400Nm@3000rpm

it's like beating dead horse, this is really simple physics

yes, but you claim the only difference to both cars is FINAL gear, not the rest of the gears.

Gearbox: 7 Speed "7G-Tronic" automatic gearbox (Both cars)
Final Drive: Optimised to suit each engine

thus, we should assume 1-6 gear are the same, and only 7th gear [final drive] is different.

if that is the case, then the higher torque vehicle should accelerate faster.

but if ALL the gears (ratios) are different, then yes, then they could accelerate the same.