dipping torque curve give better acceleration ?
Discussion
i was just doing a bit of research on torque curves and how they influence power delivery. i couldn't help wondering if a dipping torque curve would give better accelerations than a flat torque curve given the same hp..
i mean if you think about it, lets say one car engine produces 200hp at 6000rpm(also the redline) and a flat 175 ft/lbs from 2000-6000 (theres not such engine this is all theoretical)
another engine produces 200hp at 6000rpm too but produces 525lb/ft at 2000rpm but dips as the revs increase
if both cars were geared to go 40mph at 6000rpm .. surely the one with the dipping curve would be MUCH faster.. (given the tyres can put down 525ft/lbs with such short gears).
in this case, the dip is a bit extreme and unrealistic and would feel weird and limp at it revs but as it revs it be accelerating faster at every point till redline, than the flat torque curve..
why dont manufacture tune engines to with a slight dip from low revs rather than flat throughout ??
i mean if you think about it, lets say one car engine produces 200hp at 6000rpm(also the redline) and a flat 175 ft/lbs from 2000-6000 (theres not such engine this is all theoretical)
another engine produces 200hp at 6000rpm too but produces 525lb/ft at 2000rpm but dips as the revs increase
if both cars were geared to go 40mph at 6000rpm .. surely the one with the dipping curve would be MUCH faster.. (given the tyres can put down 525ft/lbs with such short gears).
in this case, the dip is a bit extreme and unrealistic and would feel weird and limp at it revs but as it revs it be accelerating faster at every point till redline, than the flat torque curve..
why dont manufacture tune engines to with a slight dip from low revs rather than flat throughout ??
Yes, the car with higher torque lower down the rev range will be faster.
It'll feel horrible though; I'll have the slower one please.
Manufacturers tend to limit peak torque because other components of the drive-train can't cope, or because it makes the engine feel odd to drive. Ultimate performance is one (very small) aspect of the way an engine behaves.
It'll feel horrible though; I'll have the slower one please.
Manufacturers tend to limit peak torque because other components of the drive-train can't cope, or because it makes the engine feel odd to drive. Ultimate performance is one (very small) aspect of the way an engine behaves.
blahblop123 said:
i was just doing a bit of research on torque curves and how they influence power delivery. i couldn't help wondering if a dipping torque curve would give better accelerations than a flat torque curve given the same hp..
i mean if you think about it, lets say one car engine produces 200hp at 6000rpm(also the redline) and a flat 175 ft/lbs from 2000-6000 (theres not such engine this is all theoretical)
another engine produces 200hp at 6000rpm too but produces 525lb/ft at 2000rpm but dips as the revs increase
if both cars were geared to go 40mph at 6000rpm .. surely the one with the dipping curve would be MUCH faster.. (given the tyres can put down 525ft/lbs with such short gears).
in this case, the dip is a bit extreme and unrealistic and would feel weird and limp at it revs but as it revs it be accelerating faster at every point till redline, than the flat torque curve..
why dont manufacture tune engines to with a slight dip from low revs rather than flat throughout ??
HP = torquw x rpms / 5252i mean if you think about it, lets say one car engine produces 200hp at 6000rpm(also the redline) and a flat 175 ft/lbs from 2000-6000 (theres not such engine this is all theoretical)
another engine produces 200hp at 6000rpm too but produces 525lb/ft at 2000rpm but dips as the revs increase
if both cars were geared to go 40mph at 6000rpm .. surely the one with the dipping curve would be MUCH faster.. (given the tyres can put down 525ft/lbs with such short gears).
in this case, the dip is a bit extreme and unrealistic and would feel weird and limp at it revs but as it revs it be accelerating faster at every point till redline, than the flat torque curve..
why dont manufacture tune engines to with a slight dip from low revs rather than flat throughout ??
In affect horse power is a representation of torque at speed or work done.
Therefore you cannot have HP without torque. The more torque you make at the same rpms will always equal more HP. The same HP at higher rpms will always equal more HP.
As for acceleration, that's a bit more complex. You need to consider 'under the curve' performance of the engine and not just PEAK numbers. You then also need to consider gearing and how big the engines powerband is. Changing gear takes time, and you don't want to have to rev past your powerband to keep the next gear in the power, or if you change earlier to drop off the power band.
This would be assuming vehicle weight, traction and aero are all stable and consistent.
StottyZr said:
Correct. Because with a flat curve 175nm will only produce 133hp@4000rpm wheres the car with a dipping torque curve will produce almost 200 throughout. Thus why peak HP isn't everything.
I think he is talking about a flat POWER curve.....ie. you start with a shed load of torque and taper it off as the revs rise.
eg. http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D602%...
Scuffers said:
I think he is talking about a flat POWER curve.....
ie. you start with a shed load of torque and taper it off as the revs rise.
eg. http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D602%...
woahh, that is what i had in mind.. ie. you start with a shed load of torque and taper it off as the revs rise.
eg. http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D602%...
that would be brilliant if it had few gears but through the gears acceleration is probably not that great i'm guessing..
Scuffers said:
StottyZr said:
Correct. Because with a flat curve 175nm will only produce 133hp@4000rpm wheres the car with a dipping torque curve will produce almost 200 throughout. Thus why peak HP isn't everything.
I think he is talking about a flat POWER curve.....ie. you start with a shed load of torque and taper it off as the revs rise.
eg. http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D602%...
I would like to add the following words and phrases for anyone to use, in any context, at any time, any where, within this thread:
Power and torque mean nothing without 'gearing'
A cyclist with strong legs pedalling slowly vs one with skinny legs pedalling quickly
Thermal efficiency losses
At the flywheel vs at the road wheels
How fast we are going when we hit the hedge vs how far we take the hedge into the field (feel free to deviate into whether the car hit the hedge using the bonnet or the boot)
What you perceive as acceleration in your tdi is actually 'jerk'
Zingy vs a thumper
Linear
Flexibility
But in the petrol I would have used the gearbox in order to select the appropriate ratio
Power and torque mean nothing without 'gearing'
A cyclist with strong legs pedalling slowly vs one with skinny legs pedalling quickly
Thermal efficiency losses
At the flywheel vs at the road wheels
How fast we are going when we hit the hedge vs how far we take the hedge into the field (feel free to deviate into whether the car hit the hedge using the bonnet or the boot)
What you perceive as acceleration in your tdi is actually 'jerk'
Zingy vs a thumper
Linear
Flexibility
But in the petrol I would have used the gearbox in order to select the appropriate ratio
blahblop123 said:
i think mercedes use this way of tuning their earlier AMG v12 twin turbo 65 engines.. they have 604hp @5000 but they weigh 2 tons, they still accelerate like the clappers !! 740ft/lbs from 2000-4000 and the dip starts from there..
that's done because that's the limit's (Merc's) for their turbo's, a given turbo can only flow so much air (for a given boost etc) so, it will naturally come to it's flow limit's the higher up the rev (and thus power) range you get, very easy to make monster torque at lower revs, very hard to maintain this as the revs (and thus power) rise.Power is dependent on speed and torque, so all else being equal you will never gain from having less torque (i.e introducing an artificial dip on the curve) at a given engine speed.
Yes, you can have too much torque for the tyres, but that's where the driver and/or traction control comes in to limit it. For that matter, there are things you can do to improve the traction like fitting sticky tyres.
So, in theory, you want as much torque as possible across the whole rev range - say maximum torque from 0 rpm to the redline. In reality, of course, with an IC engine you almost innevitably have some degree of curve. I guess in that case you could argue you want it at low revs for standing starts, because if you have an excess of grip then any gains you make early on the rev range will be multiplied as you go along the straight.
It's like the Toyotas versus the Audis last weekend. Running incredibly sticky tyres the TS030 had enough grip to make use of the extra power offered by its hybrid system out of the slow corners. Because the R18 couldn't deploy its hybrid boost until further on down the straight (due to the regulations regarding 4WD cars) it didn't get as much advantage.
Yes, you can have too much torque for the tyres, but that's where the driver and/or traction control comes in to limit it. For that matter, there are things you can do to improve the traction like fitting sticky tyres.
So, in theory, you want as much torque as possible across the whole rev range - say maximum torque from 0 rpm to the redline. In reality, of course, with an IC engine you almost innevitably have some degree of curve. I guess in that case you could argue you want it at low revs for standing starts, because if you have an excess of grip then any gains you make early on the rev range will be multiplied as you go along the straight.
It's like the Toyotas versus the Audis last weekend. Running incredibly sticky tyres the TS030 had enough grip to make use of the extra power offered by its hybrid system out of the slow corners. Because the R18 couldn't deploy its hybrid boost until further on down the straight (due to the regulations regarding 4WD cars) it didn't get as much advantage.
Matt UK said:
I would like to add the following words and phrases for anyone to use, in any context, at any time, any where, within this thread:
Power and torque mean nothing without 'gearing'
A cyclist with strong legs pedalling slowly vs one with skinny legs pedalling quickly
Thermal efficiency losses
At the flywheel vs at the road wheels
How fast we are going when we hit the hedge vs how far we take the hedge into the field (feel free to deviate into whether the car hit the hedge using the bonnet or the boot)
What you perceive as acceleration in your tdi is actually 'jerk'
Zingy vs a thumper
Linear
Flexibility
But in the petrol I would have used the gearbox in order to select the appropriate ratio
A 20 page thread in 11 lines. Superb.Power and torque mean nothing without 'gearing'
A cyclist with strong legs pedalling slowly vs one with skinny legs pedalling quickly
Thermal efficiency losses
At the flywheel vs at the road wheels
How fast we are going when we hit the hedge vs how far we take the hedge into the field (feel free to deviate into whether the car hit the hedge using the bonnet or the boot)
What you perceive as acceleration in your tdi is actually 'jerk'
Zingy vs a thumper
Linear
Flexibility
But in the petrol I would have used the gearbox in order to select the appropriate ratio
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