Why can't diesel make more power than gasoline?
08-02-2007, 08:23 AM
#91
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Originally Posted by mark kibort
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.
wheel torque = crank torque x transmission gear ratio x differential gear ratio
08-02-2007, 11:51 AM
#92
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Thread Starter
Originally Posted by DrJupeman
If engine torque doesn't determine rear wheel torque, can you disprove this formula, posted earlier:
wheel torque = crank torque x transmission gear ratio x differential gear ratio
wheel torque = crank torque x transmission gear ratio x differential gear ratio
08-02-2007, 01:01 PM
#94
Rennlist Member
You are thinking about this a little out of context. I also should have clarified that we are talking about relative torque ratings, not determining rear wheel final torque values at different vehicle speeds. We are referring to wheel torque at a particular vehicle speed, so this is determined by HP. For max acceleration at any speed, it is created by engine torque, at the rpm required for the engine to be closest to its max hp.
The equation below is correct, because you have crank torque and gear ratios , and that will equal final rear wheel torque.
However, my example two 500hp vehicles, one with 500ft-lbs of peak torque and the other with 250ft-lbs of peak torque, shows that at any vehicle speed, because the RPMs are a factor of 2 off, the rear wheel torque will be the same. So, i can prove that two equal torque value engines can produce totally different rear wheel torque values. And i can prove that those two engines with the same torque at their redline rpm can produce totally different rear wheel torque as well.
It is part of the point of this discussion.
mk
The equation below is correct, because you have crank torque and gear ratios , and that will equal final rear wheel torque.
However, my example two 500hp vehicles, one with 500ft-lbs of peak torque and the other with 250ft-lbs of peak torque, shows that at any vehicle speed, because the RPMs are a factor of 2 off, the rear wheel torque will be the same. So, i can prove that two equal torque value engines can produce totally different rear wheel torque values. And i can prove that those two engines with the same torque at their redline rpm can produce totally different rear wheel torque as well.
It is part of the point of this discussion.
mk
Originally Posted by DrJupeman
If engine torque doesn't determine rear wheel torque, can you disprove this formula, posted earlier:
wheel torque = crank torque x transmission gear ratio x differential gear ratio
wheel torque = crank torque x transmission gear ratio x differential gear ratio
08-02-2007, 01:04 PM
#95
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Discussions of F at T=0. Hmmm, looks like this discussion could roll into some Quantum Physics! 
MK
MK
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.
08-02-2007, 01:33 PM
#96
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Originally Posted by mark kibort
Discussions of F at T=0. Hmmm, looks like this discussion could roll into some Quantum Physics!
MK
MK
08-02-2007, 06:32 PM
#97
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mark there is no relation between their rpms being a factor of 2 to what the wheel torques are ..
wheel torques are the same if the transmission x differential ratio are a factor of 2 e.g. 250x2=500x1
just use the referred to torque formula
just something to note
wheel torques are the same if the transmission x differential ratio are a factor of 2 e.g. 250x2=500x1
just use the referred to torque formula
just something to note
Originally Posted by mark kibort
However, my example two 500hp vehicles, one with 500ft-lbs of peak torque and the other with 250ft-lbs of peak torque, shows that at any vehicle speed, because the RPMs are a factor of 2 off, the rear wheel torque will be the same.
mk
mk
08-03-2007, 02:56 AM
#98
Rennlist Member
really? Hmmmmm
6000rpm redline for the big torque engine and 12000rpm for the little torque engine. this means gearing is a factor of 2 deeper for the higher rev engine.
now because we are matching equal HP engines, the 2x factor of RPM provides the lower torque engine to take advangae of deeper gearing for the same rear wheel torque. after all, you said it, its rear wheel torque that generates the Force in A=F/m
so, there is a relationship of a factor of 2 for RPMs and gearing to keep rear wheel torques (as a product of the engine torque through the gear ratios) equal at any speed.
MK
edit: PS , i now see your issue with your post. you are not talking about two cars at the same speed. see how that "speed" thing always gets in the way. stick to HP, it factors more into it. if you dont "factor in rpms" then you are talking the same torque at the rear wheels at two totally different speeds (vehicle speeds) This is a senseless anaylsis. to reach the same torque at the same vehicle speed at the rear wheels you need the same HP. its that simple . this uses the factor of 2 difference for the RPM and gearing ratios.
6000rpm redline for the big torque engine and 12000rpm for the little torque engine. this means gearing is a factor of 2 deeper for the higher rev engine.
now because we are matching equal HP engines, the 2x factor of RPM provides the lower torque engine to take advangae of deeper gearing for the same rear wheel torque. after all, you said it, its rear wheel torque that generates the Force in A=F/m
so, there is a relationship of a factor of 2 for RPMs and gearing to keep rear wheel torques (as a product of the engine torque through the gear ratios) equal at any speed.
MK
edit: PS , i now see your issue with your post. you are not talking about two cars at the same speed. see how that "speed" thing always gets in the way. stick to HP, it factors more into it. if you dont "factor in rpms" then you are talking the same torque at the rear wheels at two totally different speeds (vehicle speeds) This is a senseless anaylsis. to reach the same torque at the same vehicle speed at the rear wheels you need the same HP. its that simple . this uses the factor of 2 difference for the RPM and gearing ratios.
Originally Posted by krC2S
mark there is no relation between their rpms being a factor of 2 to what the wheel torques are ..
wheel torques are the same if the transmission x differential ratio are a factor of 2 e.g. 250x2=500x1
just use the referred to torque formula
just something to note
wheel torques are the same if the transmission x differential ratio are a factor of 2 e.g. 250x2=500x1
just use the referred to torque formula
just something to note
Last edited by mark kibort; 08-03-2007 at 04:18 AM.
08-03-2007, 06:44 AM
#99
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exactly, just talking about two engines 250x2=500x1 for 2:1 gear ratios regardless of redlines
edit: PS , i now see your issue with your post. you are not talking about two cars at the same speed...
Originally Posted by mark kibort
edit: PS , i now see your issue with your post. you are not talking about two cars at the same speed...
08-03-2007, 12:05 PM
#101
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Well then, thats just silly.
if Acceleration=power/(mass x velocity) then you can see that speed has to be kept constant to do a comparison. to have speed constant, and a factor of 2 different gear ratios, the RPMs HAVE to be a factor of 2 off as well. This is just common sense.
If you are going to an comparson, it should be a valid comparison. comparing a car with 250x2 = 500ft-lbs traveling at 100mph vs a second car with 1:1 with 500ft-lbs traveling at 200mph makes ABSOLUTELY no sense. (ignoring rpm as you say)
Now, if you pay attention to a critical factor, (i.e. speed, velocity, rpm), you see that at the same speed, the rpm will be as different as the gear ratios
This is the reason why power will dictate what the torque (or force) will be acting on the car at the rear tires.
MK
if Acceleration=power/(mass x velocity) then you can see that speed has to be kept constant to do a comparison. to have speed constant, and a factor of 2 different gear ratios, the RPMs HAVE to be a factor of 2 off as well. This is just common sense.
If you are going to an comparson, it should be a valid comparison. comparing a car with 250x2 = 500ft-lbs traveling at 100mph vs a second car with 1:1 with 500ft-lbs traveling at 200mph makes ABSOLUTELY no sense. (ignoring rpm as you say)
Now, if you pay attention to a critical factor, (i.e. speed, velocity, rpm), you see that at the same speed, the rpm will be as different as the gear ratios
This is the reason why power will dictate what the torque (or force) will be acting on the car at the rear tires.
MK
Originally Posted by krC2S
exactly, just talking about two engines 250x2=500x1 for 2:1 gear ratios regardless of redlines
08-03-2007, 12:06 PM
#102
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thats just idle speed for a F1! mk
Originally Posted by kurt M
After 10 min all your formulas become moot. The 12000 rpm motor will spin a bearing and throw a rod out the case.
08-03-2007, 03:59 PM
#103
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yes it's obvious algebra if you choose to fix speed...
Originally Posted by mark kibort
Well then, thats just silly.
if Acceleration=power/(mass x velocity) then you can see that speed has to be kept constant to do a comparison. to have speed constant, and a factor of 2 different gear ratios, the RPMs HAVE to be a factor of 2 off as well. This is just common sense.
If you are going to an comparson, it should be a valid comparison. comparing a car with 250x2 = 500ft-lbs traveling at 100mph vs a second car with 1:1 with 500ft-lbs traveling at 200mph makes ABSOLUTELY no sense. (ignoring rpm as you say)
Now, if you pay attention to a critical factor, (i.e. speed, velocity, rpm), you see that at the same speed, the rpm will be as different as the gear ratios
This is the reason why power will dictate what the torque (or force) will be acting on the car at the rear tires.
MK
if Acceleration=power/(mass x velocity) then you can see that speed has to be kept constant to do a comparison. to have speed constant, and a factor of 2 different gear ratios, the RPMs HAVE to be a factor of 2 off as well. This is just common sense.
If you are going to an comparson, it should be a valid comparison. comparing a car with 250x2 = 500ft-lbs traveling at 100mph vs a second car with 1:1 with 500ft-lbs traveling at 200mph makes ABSOLUTELY no sense. (ignoring rpm as you say)
Now, if you pay attention to a critical factor, (i.e. speed, velocity, rpm), you see that at the same speed, the rpm will be as different as the gear ratios
This is the reason why power will dictate what the torque (or force) will be acting on the car at the rear tires.
MK
08-03-2007, 06:01 PM
#105
Rennlist Member
If it had 400hp, you could count me in . especially with the price of gas these days!
MK
MK
Originally Posted by A.Wayne
OK, but how many of yah would drive a Diesel 911 .... 
Ok i thought so..
Ok i thought so..