Why can't diesel make more power than gasoline?
08-01-2007, 05:42 PM
#76
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Originally Posted by mark kibort
NET force. at any point in time where there is a net force appliced their will be acceleration. as the force applied from 0 to something, acceleration will start from 0 to something. they are tied together. sitting on a chair, there is a force and no movement, because the chair is acting against the force to an equal level. no NET force, no movment, no acceleration. pull the chair out, you start to fall based on gravity's force. as you fall the kinetic energy goes up with velocity unitl impact where the power at that moment would equal the potential energy stored in your body before the chair was pulled.
Its not that complicated, you are thinking too hard!
mk
Its not that complicated, you are thinking too hard!
mk
i know it's pretty simple that is why it's so amusing to discuss.
i ask this question and mean no disrespect. are you familiar with ordinary differential equations and methods for solving them? if so i could make my point in a different way in a later post.
the moment you pull the chair the body is subjected to a sudden force of gravity alone since the reaction force from the chair is gone. this causes a sudden "initial acceleration that the body is subjected to and that acceleration stay constant. over time that acceleration causes the velovity to change from zero and continue to increase until the point of impact.
i have no problem with your energy arguments but it does not explain the initial response the body experiences.
08-01-2007, 05:43 PM
#77
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see my comment above..the dyno didn't show anything it's obvious without the need for any power analysis..i only misread your statement of being for the same gear ratios vs same spacing
read my brakdown of the whole thing a few pages earlier i think it will help you see things more directly without wondering around too much just to use that formula
read my brakdown of the whole thing a few pages earlier i think it will help you see things more directly without wondering around too much just to use that formula
Originally Posted by mark kibort
im glad you brought up dynos. And i hope at the end of this you finally admit that you do know about how to calcualte HP with torque and RPMs, but didnt fully understand the relatioship of power to the accelerative forces.
Do you now see how the 6000rpm, 500max torque 500hp engine can make the same torque at the driven wheels at ANY vehicle speed compared to the same 500hp 12,000rpm engine with 250ft-lbs of engine torque?
all you needed to do was calcualte the torque using the equation you seem to be so versed in. it would have yeilded the same torque at the rear tires at any speed, in my question to you, it was 40mph.
Now, for the dyno. do you know what a dyno actually is measureing. ever do a dyno run on a rolling dyno that didnt have a spark signal? whats the output? you get HP and MPH. what about enging torque????? well, how does a dyno know? all it sees is that the drums are accelerated over a speed range. since, POWER is the change of kinetic energy, it can easily produce power curves. It could also have a torque curve, but it would be something we wouldnt understand as it would be torque values that have been multiplied through the gear box and rear end ratios. Its not until the dyno gets the rpm signal from the spark is it able to give you engine torque values.
this dyno wouldnt know if the 450rwhp if from a 911 RSR or a Viper. all it would be able to tell us is HP over a speed range. Now, plug in the spark signal and watch the 9000rpm porsche give only 270ft-lbs of torque, while the viper produces 550ft-lbs, however the dyno just showed you that both have the same accelerative forces at the rear tires!
mk
Do you now see how the 6000rpm, 500max torque 500hp engine can make the same torque at the driven wheels at ANY vehicle speed compared to the same 500hp 12,000rpm engine with 250ft-lbs of engine torque?
all you needed to do was calcualte the torque using the equation you seem to be so versed in. it would have yeilded the same torque at the rear tires at any speed, in my question to you, it was 40mph.
Now, for the dyno. do you know what a dyno actually is measureing. ever do a dyno run on a rolling dyno that didnt have a spark signal? whats the output? you get HP and MPH. what about enging torque????? well, how does a dyno know? all it sees is that the drums are accelerated over a speed range. since, POWER is the change of kinetic energy, it can easily produce power curves. It could also have a torque curve, but it would be something we wouldnt understand as it would be torque values that have been multiplied through the gear box and rear end ratios. Its not until the dyno gets the rpm signal from the spark is it able to give you engine torque values.
this dyno wouldnt know if the 450rwhp if from a 911 RSR or a Viper. all it would be able to tell us is HP over a speed range. Now, plug in the spark signal and watch the 9000rpm porsche give only 270ft-lbs of torque, while the viper produces 550ft-lbs, however the dyno just showed you that both have the same accelerative forces at the rear tires!
mk
08-01-2007, 05:52 PM
#78
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Again, you are taking snips and making objections.
Acceleration = power/(mass x velocity)
Let me be clear. This above newtonian identiy tells us that acceleration is proportional to power, and inversely proportioal to speed. this is true for a given power. maybe thats the point you are missing.
Its basic algebra at this point, yet you still fight it?
tell you what, tell me where this isnt true? (good luck)
now, #2
If i tell you that one car has 1/2 the engine torque as another yet revs twice as high, and you understand that at any speed the actual torque at the rear wheels is the same, then yes, you dont need to know HP. this tells us that we are dealing with equivilant HP, but you dont need to know this. However, the entire exercise here was to talk about how engine torque doesnt determine rear wheel torque. You need to know RPMs and as sooon as you tie RPM to the discussion, you are talking about relative HPs. and yes, you need to know about HP to do the comparisons. if the HP is different, then the torque values as multiplied through the gear box at any speed would be different. The entire point of this is to show that power dictates what the torque at the rear wheels will be at any vehicle speed.
The next level of this discussion would go to the areas of the shapes of the HP curves, where then the great equalizer, close ratio gear boxes would give the peaky HP curve cars a level playing field compared to the flat HP cars like the audi R10, or big block high torque V10s and V8s.
mk
Acceleration = power/(mass x velocity)
Let me be clear. This above newtonian identiy tells us that acceleration is proportional to power, and inversely proportioal to speed. this is true for a given power. maybe thats the point you are missing.
Its basic algebra at this point, yet you still fight it?
tell you what, tell me where this isnt true? (good luck)
now, #2
If i tell you that one car has 1/2 the engine torque as another yet revs twice as high, and you understand that at any speed the actual torque at the rear wheels is the same, then yes, you dont need to know HP. this tells us that we are dealing with equivilant HP, but you dont need to know this. However, the entire exercise here was to talk about how engine torque doesnt determine rear wheel torque. You need to know RPMs and as sooon as you tie RPM to the discussion, you are talking about relative HPs. and yes, you need to know about HP to do the comparisons. if the HP is different, then the torque values as multiplied through the gear box at any speed would be different. The entire point of this is to show that power dictates what the torque at the rear wheels will be at any vehicle speed.
The next level of this discussion would go to the areas of the shapes of the HP curves, where then the great equalizer, close ratio gear boxes would give the peaky HP curve cars a level playing field compared to the flat HP cars like the audi R10, or big block high torque V10s and V8s.
mk
Originally Posted by krC2S
1."you make a comment below about pushing a block with constant force.
if you could do this, power would go up proportional to velocity. See how simple that is?"
sure but that has nothing to do with your statament which you repeated many times as a general newtonian thing (forget cars) is that " acceleration is inversly proporional to speed." which is still wrong!
2. sorry i misread your statemnt so different ratios but same spacing..so what's the argument then?
it's obvious without even looking at power and rpm!
torque at wheel=crank torque X transmission ratio
so torque at wheels =250X 10= 500X5
this is true regardless of how much power we will make ( different redlines etc)
if you could do this, power would go up proportional to velocity. See how simple that is?"
sure but that has nothing to do with your statament which you repeated many times as a general newtonian thing (forget cars) is that " acceleration is inversly proporional to speed." which is still wrong!
2. sorry i misread your statemnt so different ratios but same spacing..so what's the argument then?
it's obvious without even looking at power and rpm!
torque at wheel=crank torque X transmission ratio
so torque at wheels =250X 10= 500X5
this is true regardless of how much power we will make ( different redlines etc)
08-01-2007, 06:00 PM
#79
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yes, if you want to talk DFE's, thats fine. I was trying to keep this simple as it is some of the most misunderstood concepts in racing and when understood, helps racers go faster!
what part of the intial forces are you talking about? As you apply a force on a body, it will accelerate proportional to that force. as fast as you can apply it, it will start accelerating. But remember, its a NET force.
Thanks for the comment.
mk
what part of the intial forces are you talking about? As you apply a force on a body, it will accelerate proportional to that force. as fast as you can apply it, it will start accelerating. But remember, its a NET force.
Thanks for the comment.
mk
Originally Posted by doc2s
i know it's pretty simple that is why it's so amusing to discuss.
i ask this question and mean no disrespect. are you familiar with ordinary differential equations and methods for solving them? if so i could make my point in a different way in a later post.
the moment you pull the chair the body is subjected to a sudden force of gravity alone since the reaction force from the chair is gone. this causes a sudden "initial acceleration that the body is subjected to and that acceleration stay constant. over time that acceleration causes the velovity to change from zero and continue to increase until the point of impact.
i have no problem with your energy arguments but it does not explain the initial response the body experiences.
i ask this question and mean no disrespect. are you familiar with ordinary differential equations and methods for solving them? if so i could make my point in a different way in a later post.
the moment you pull the chair the body is subjected to a sudden force of gravity alone since the reaction force from the chair is gone. this causes a sudden "initial acceleration that the body is subjected to and that acceleration stay constant. over time that acceleration causes the velovity to change from zero and continue to increase until the point of impact.
i have no problem with your energy arguments but it does not explain the initial response the body experiences.
08-01-2007, 06:06 PM
#80
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please read my post i will say this for the last time
the argument about acceleration and speed is NOW obviously correct by adding " for a fixed power"
I was just trying to explain that your original statement without the extra condition was clerly wrong
"However, the entire exercise here was to talk about how engine torque doesnt determine rear wheel torque. "
how so?
wheel torque=engine torque x effective transmission factor
i have been repeating the same answers for quite sometime..if you don't agree then there's nothing else i can do
the argument about acceleration and speed is NOW obviously correct by adding " for a fixed power"
I was just trying to explain that your original statement without the extra condition was clerly wrong
"However, the entire exercise here was to talk about how engine torque doesnt determine rear wheel torque. "
how so?
wheel torque=engine torque x effective transmission factor
i have been repeating the same answers for quite sometime..if you don't agree then there's nothing else i can do
Originally Posted by mark kibort
Again, you are taking snips and making objections.
Acceleration = power/(mass x velocity)
Let me be clear. This above newtonian identiy tells us that acceleration is proportional to power, and inversely proportioal to speed. this is true for a given power. maybe thats the point you are missing.
Its basic algebra at this point, yet you still fight it?
tell you what, tell me where this isnt true? (good luck)
now, #2
If i tell you that one car has 1/2 the engine torque as another yet revs twice as high, and you understand that at any speed the actual torque at the rear wheels is the same, then yes, you dont need to know HP. this tells us that we are dealing with equivilant HP, but you dont need to know this. However, the entire exercise here was to talk about how engine torque doesnt determine rear wheel torque. You need to know RPMs and as sooon as you tie RPM to the discussion, you are talking about relative HPs. and yes, you need to know about HP to do the comparisons. if the HP is different, then the torque values as multiplied through the gear box at any speed would be different. The entire point of this is to show that power dictates what the torque at the rear wheels will be at any vehicle speed.
The next level of this discussion would go to the areas of the shapes of the HP curves, where then the great equalizer, close ratio gear boxes would give the peaky HP curve cars a level playing field compared to the flat HP cars like the audi R10, or big block high torque V10s and V8s.
mk
Acceleration = power/(mass x velocity)
Let me be clear. This above newtonian identiy tells us that acceleration is proportional to power, and inversely proportioal to speed. this is true for a given power. maybe thats the point you are missing.
Its basic algebra at this point, yet you still fight it?
tell you what, tell me where this isnt true? (good luck)
now, #2
If i tell you that one car has 1/2 the engine torque as another yet revs twice as high, and you understand that at any speed the actual torque at the rear wheels is the same, then yes, you dont need to know HP. this tells us that we are dealing with equivilant HP, but you dont need to know this. However, the entire exercise here was to talk about how engine torque doesnt determine rear wheel torque. You need to know RPMs and as sooon as you tie RPM to the discussion, you are talking about relative HPs. and yes, you need to know about HP to do the comparisons. if the HP is different, then the torque values as multiplied through the gear box at any speed would be different. The entire point of this is to show that power dictates what the torque at the rear wheels will be at any vehicle speed.
The next level of this discussion would go to the areas of the shapes of the HP curves, where then the great equalizer, close ratio gear boxes would give the peaky HP curve cars a level playing field compared to the flat HP cars like the audi R10, or big block high torque V10s and V8s.
mk
08-01-2007, 06:11 PM
#81
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Originally Posted by mark kibort
yes, if you want to talk DFE's, thats fine. I was trying to keep this simple as it is some of the most misunderstood concepts in racing and when understood, helps racers go faster!
what part of the intial forces are you talking about? As you apply a force on a body, it will accelerate proportional to that force. as fast as you can apply it, it will start accelerating. But remember, its a NET force.
Thanks for the comment.
mk
what part of the intial forces are you talking about? As you apply a force on a body, it will accelerate proportional to that force. as fast as you can apply it, it will start accelerating. But remember, its a NET force.
Thanks for the comment.
mk
a=F/m (1)
dV/dt =a =F/m (2)
where V is velocity, F is force, A is acceleration, t is time, and m is mass.
at t=0 the instant you poull the chair the inital condition is V=0. the Force at t>=0 is F=m g.
the point is at t=0 F is non zero, hence a is non zero and power is zero. so your argument of power is what dictates force is not valid as seen at t=0. force is what dictates power the reason is force accelerates an object of given mass (we both agree). the velocity is governed by that acceleration (equation (2) ) and the product of force and V is power. it's simple as you said.
08-01-2007, 06:24 PM
#82
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that's exactly what i have been saying all along force generates motion and then mechncial power is generated
Originally Posted by doc2s
a=F/m (1)
dV/dt =a =F/m (2)
where V is velocity, F is force, A is acceleration, t is time, and m is mass.
at t=0 the instant you poull the chair the inital condition is V=0. the Force at t>=0 is F=m g.
the point is at t=0 F is non zero, hence a is non zero and power is zero. so your argument of power is what dictates force is not valid as seen at t=0. force is what dictates power the reason is force accelerates an object of given mass (we both agree). the velocity is governed by that acceleration (equation (2) ) and the product of force and V is power. it's simple as you said.
dV/dt =a =F/m (2)
where V is velocity, F is force, A is acceleration, t is time, and m is mass.
at t=0 the instant you poull the chair the inital condition is V=0. the Force at t>=0 is F=m g.
the point is at t=0 F is non zero, hence a is non zero and power is zero. so your argument of power is what dictates force is not valid as seen at t=0. force is what dictates power the reason is force accelerates an object of given mass (we both agree). the velocity is governed by that acceleration (equation (2) ) and the product of force and V is power. it's simple as you said.
08-01-2007, 06:26 PM
#83
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Originally Posted by doc2s
the point is at t=0 F is non zero, hence a is non zero and power is zero. so your argument of power is what dictates force is not valid as seen at t=0. force is what dictates power the reason is force accelerates an object of given mass (we both agree). the velocity is governed by that acceleration (equation (2) ) and the product of force and V is power. it's simple as you said.
you say that force dictates power. it only partially describes the situation. the instant a force causes motion, work is done. we're interested in the rate of work. simply looking at force won't tell us this. power will. it doesn't matter if the power is made up more of velocity or of force, it will accomplish work at the same rate as long as the power is equal.
08-01-2007, 06:37 PM
#84
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Originally Posted by insite
the INSTANT there is a net force, there is motion. there is no point in time where there is a net force and zero motion.
you say that force dictates power. it only partially describes the situation. the instant a force causes motion, work is done. we're interested in the rate of work. simply looking at force won't tell us this. power will. it doesn't matter if the power is made up more of velocity or of force, it will accomplish work at the same rate as long as the power is equal.
you say that force dictates power. it only partially describes the situation. the instant a force causes motion, work is done. we're interested in the rate of work. simply looking at force won't tell us this. power will. it doesn't matter if the power is made up more of velocity or of force, it will accomplish work at the same rate as long as the power is equal.
you just said it power is a rate of work so it needs time to be generated even if it is very little time..work done is also the change of kinetic energy and in this system( free fall) there is 0 kinetic energy at first t1=0 then we need kinetic energy at another time t2 to define work and power
you can also say work is force x distance but we need time to move some distance and do work
this is way torque/force generates power
08-01-2007, 06:37 PM
#85
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Originally Posted by insite
the INSTANT there is a net force, there is motion. there is no point in time where there is a net force and zero motion.
velocity is not a discontinuous function. so velocity will not change instantaneously as evident by the diff. eq. (2). the initial condition at t=0 is zero velocity and a=g.
the model is valid for all t>=0 until the point of impact. the solution is
V(t)= g x t +V(0); V(0)=0. no jump in velocity at t=0. so there is an INSTANT with a non zero NET force and no motion at t=0.
08-01-2007, 06:53 PM
#86
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Originally Posted by doc2s
velocity is not a discontinuous function. so velocity will not change instantaneously as evident by the diff. eq. (2). the initial condition at t=0 is zero velocity and a=g.
the model is valid for all t>=0 until the point of impact. the solution is
V(t)= g x t +V(0); V(0)=0. no jump in velocity at t=0. so there is an INSTANT with a non zero NET force and no motion at t=0.
the model is valid for all t>=0 until the point of impact. the solution is
V(t)= g x t +V(0); V(0)=0. no jump in velocity at t=0. so there is an INSTANT with a non zero NET force and no motion at t=0.
08-01-2007, 07:00 PM
#87
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So we really are in the quest for which came first, the chicken or egg
i think you have to go back to the source .
potential energy of a gallon of gas creates all of it!
MK
i think you have to go back to the source .
potential energy of a gallon of gas creates all of it!
MK
Originally Posted by krC2S
you just said it power is a rate of work so it needs time to be generated even if it is very little time..work done is also the change of kinetic energy and in this system( free fall) there is 0 kinetic energy at first t1=0 then we need kinetic energy at another time t2 to define work and power
you can also say work is force x distance but we need time to move some distance and do work
this is way torque/force generates power
you can also say work is force x distance but we need time to move some distance and do work
this is way torque/force generates power
Last edited by mark kibort; 08-01-2007 at 08:36 PM.
08-01-2007, 07:10 PM
#88
Rennlist Member
one minor explanation.
Initial conditions are defined at T=0 Not T= 1, or 1/10, or 1 microsecond.
it is 0. take any force equation and make sure there is a T in it!
MK
Initial conditions are defined at T=0 Not T= 1, or 1/10, or 1 microsecond.
it is 0. take any force equation and make sure there is a T in it!
MK
Originally Posted by doc2s
a=F/m (1)
dV/dt =a =F/m (2)
where V is velocity, F is force, A is acceleration, t is time, and m is mass.
at t=0 the instant you poull the chair the inital condition is V=0. the Force at t>=0 is F=m g.
the point is at t=0 F is non zero, hence a is non zero and power is zero. so your argument of power is what dictates force is not valid as seen at t=0. force is what dictates power the reason is force accelerates an object of given mass (we both agree). the velocity is governed by that acceleration (equation (2) ) and the product of force and V is power. it's simple as you said.
dV/dt =a =F/m (2)
where V is velocity, F is force, A is acceleration, t is time, and m is mass.
at t=0 the instant you poull the chair the inital condition is V=0. the Force at t>=0 is F=m g.
the point is at t=0 F is non zero, hence a is non zero and power is zero. so your argument of power is what dictates force is not valid as seen at t=0. force is what dictates power the reason is force accelerates an object of given mass (we both agree). the velocity is governed by that acceleration (equation (2) ) and the product of force and V is power. it's simple as you said.
08-01-2007, 09:48 PM
#89
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Originally Posted by mark kibort
one minor explanation.
Initial conditions are defined at T=0 Not T= 1, or 1/10, or 1 microsecond.
it is 0. take any force equation and make sure there is a T in it!
MK
Initial conditions are defined at T=0 Not T= 1, or 1/10, or 1 microsecond.
it is 0. take any force equation and make sure there is a T in it!
MK
F(t)=mg for all t>=0 (until impact ) and that is why i left out the dependence of F on t. so nothing changes and i don't the point you were trying to make.
08-01-2007, 10:51 PM
#90
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Originally Posted by mark kibort
one minor explanation.
Initial conditions are defined at T=0 Not T= 1, or 1/10, or 1 microsecond.
it is 0.
MK
Initial conditions are defined at T=0 Not T= 1, or 1/10, or 1 microsecond.
it is 0.
MK