2.20 vs 2.54 ratio?
01-09-2005, 01:23 PM
#121
Rennlist Member
Ok, is your example a car that just has the rear end changed. If so, we can plug in the values just as i did above (all the actual torques are listed for each gear vs time spent in those gears) what evidence is clear?
So, if we are talking about acceleration, and you use algebra to get an accleration based on Force, that is fine. However the force you use HAS to be an integration of the force curve. also the correct resultant term will be:
a= NET force / mass. (there is only accleration if you have a two unequal forces acting on a mass) Meaning area under the total force/torque curve. the area under the force curve for the entire acceleration range of speed or distance will give you an averae acceleration rate. So, the average acceleration will be made up of an aggrigate of all the gears accelerative force and also the engines torque over the speed range in each gear (also, ive clearly given these values in a chart above) THIS IS KEY to the discussion. it doesnt disprove anything, in fact, it clearly re-enforces my points. what part of this are you having an issue with.
AGAIN, acceleration is change in velocity over change in speed. the greater the force at any particular speed, the greater the acceleration. this why you get greater acceleration in 1st gear vs 2nd gear, and in each gear the greatest rate of acceleration is at peak torque.
Just shifting the entire set of curves up or down with a rear end ratio change doesnt change the average acceleration rate over an infinite speed range. (notice i didnt mention anything about top speed)
If you dont agree, or dont understand, and feel comfort that others are in the same boat. Fine. ignorance can be taught. stupidity is forever! Clearly, i know you are a smart individual. all im asking is for you to open your mind (or a book!!!)
mk
A BIG PS:
KEY example : remember there was talk of a 3.09 :1 gear box that was used on a GTS?? this is a great example, because on a GTS gear box, all the gears end up with close to the same spacing. What i proved with simple reporting of the resultant gear ratios for each gear, was that 1-2nd had an average increase of 8% (so yes, at the end of redline, in 2nd gear, comparatively, the 3.09 would have this advantage of 8%. HOWEVER, every gear after that was perfectly matched to a stock S4 through its 4th gear, where it then would have no more gears left to shift into. or in otherwords, 155mph speed limited)
What this shows is that a simple change of rer end of 12% just shifted the gears down perfectly to create another already used gear box that actually has a 40% difference over all ( 2.2 vs 3.09) Now, does the 3.09 have a 40% advantage over all speeds??? will it accelerate faster in all gears? dont get hung up on the numerical ratios. again, the actual ratios through 4th gear , even though the GTS 3.09 uses all 5 over the same speed range . certainly the advantage would be 0-60 by the average gain of 8%, but after that, the gear ratios are identical!!!!! If you can understand this, you broke the code!!
MK
So, if we are talking about acceleration, and you use algebra to get an accleration based on Force, that is fine. However the force you use HAS to be an integration of the force curve. also the correct resultant term will be:
a= NET force / mass. (there is only accleration if you have a two unequal forces acting on a mass) Meaning area under the total force/torque curve. the area under the force curve for the entire acceleration range of speed or distance will give you an averae acceleration rate. So, the average acceleration will be made up of an aggrigate of all the gears accelerative force and also the engines torque over the speed range in each gear (also, ive clearly given these values in a chart above) THIS IS KEY to the discussion. it doesnt disprove anything, in fact, it clearly re-enforces my points. what part of this are you having an issue with.
AGAIN, acceleration is change in velocity over change in speed. the greater the force at any particular speed, the greater the acceleration. this why you get greater acceleration in 1st gear vs 2nd gear, and in each gear the greatest rate of acceleration is at peak torque.
Just shifting the entire set of curves up or down with a rear end ratio change doesnt change the average acceleration rate over an infinite speed range. (notice i didnt mention anything about top speed)
If you dont agree, or dont understand, and feel comfort that others are in the same boat. Fine. ignorance can be taught. stupidity is forever! Clearly, i know you are a smart individual. all im asking is for you to open your mind (or a book!!!)
mk
A BIG PS:
KEY example : remember there was talk of a 3.09 :1 gear box that was used on a GTS?? this is a great example, because on a GTS gear box, all the gears end up with close to the same spacing. What i proved with simple reporting of the resultant gear ratios for each gear, was that 1-2nd had an average increase of 8% (so yes, at the end of redline, in 2nd gear, comparatively, the 3.09 would have this advantage of 8%. HOWEVER, every gear after that was perfectly matched to a stock S4 through its 4th gear, where it then would have no more gears left to shift into. or in otherwords, 155mph speed limited)
What this shows is that a simple change of rer end of 12% just shifted the gears down perfectly to create another already used gear box that actually has a 40% difference over all ( 2.2 vs 3.09) Now, does the 3.09 have a 40% advantage over all speeds??? will it accelerate faster in all gears? dont get hung up on the numerical ratios. again, the actual ratios through 4th gear , even though the GTS 3.09 uses all 5 over the same speed range . certainly the advantage would be 0-60 by the average gain of 8%, but after that, the gear ratios are identical!!!!! If you can understand this, you broke the code!!
MK
Originally Posted by GlenL
Mark,
In my example one car was used with different final drive ratios. That's good science. At the end where the evedence is clear, you can't follow the logic because it disproves your point.
What you miss is that we're talking acceleration and I'm working it through F = ma re-arranged to a = F/m. As m is constant, examining F gives acceleration directly. But this abstraction doesn't follow your model so, apparently, you can't grasp it. Your "BZZZT wrong answer" is itself wrong.
That said, I've done enough. I'll bet all the people who "agree" with you are hoping to get to another topic, too.
In my example one car was used with different final drive ratios. That's good science. At the end where the evedence is clear, you can't follow the logic because it disproves your point.
What you miss is that we're talking acceleration and I'm working it through F = ma re-arranged to a = F/m. As m is constant, examining F gives acceleration directly. But this abstraction doesn't follow your model so, apparently, you can't grasp it. Your "BZZZT wrong answer" is itself wrong.
That said, I've done enough. I'll bet all the people who "agree" with you are hoping to get to another topic, too.
Last edited by mark kibort; 01-09-2005 at 02:33 PM.
01-09-2005, 01:36 PM
#122
Addict
Rennlist Member
Rennlist Member
Here's some 'real' world numbers. I have advertised this software once or twice before but have no connection to it what so ever. It's just so good in pointing what effects gearing has.
http://www.cartestsoftware.com
Numbers are from old software version 4.5. These cars are copies of '88 S4 5sp that comes in db. Everyting else is same except rear gearing. 2.00:1 for car 1. and 4.00:1 for 2.
Numbers are of course not absolutely correct but pattern is there. Some results like may seem odd like 30-50 time being longer for smaller start gear but it just comes from fact that there is one extra gear change that costs time. Time it takes to change is adjustable.
Now lets pretend there is tight corner in race track where exit speed is 30 mph and 1/4 mile long straight after it. Which car is at end of straight first?
Now lets pretend there is little faster corner where exit speed is 50 mph and 500 feet long straight after it. Which car is at end of straight first?
Now cut the crap. 
On traffic lights 4.00:1 is clearly faster up to a point but on race track gearing doesn't matter other than minor differencees that come from different shifting points as long 5th is long enough for fastest straight. 
http://www.cartestsoftware.com
Numbers are from old software version 4.5. These cars are copies of '88 S4 5sp that comes in db. Everyting else is same except rear gearing. 2.00:1 for car 1. and 4.00:1 for 2.
Code:
PERFORMANCE COMPARISON ANALYSIS
-------------------------------
Selected Cars: 1. PORSCHE 928 S4 2.00:1 gearing 1987
2. PORSCHE 928 S4 4.00:1 gearing 1987
Car Number 1 2
--------- ---------
Time to Speed
0-30 mph.... 2.5 2.1
0-40 mph.... 3.3 2.9
0-50 mph.... 4.3 4.5
0-60 mph.... 6.1 6.3
0-70 mph.... 7.5 7.6
0-80 mph.... 9.1 10.0
0-90 mph.... 11.9 12.1
0-100 mph.... 14.2 14.4
Time to Distance
0-100 ft..... 3.3 2.9
0-500 ft..... 8.0 7.9
0-1320ft..... 14.4 14.4
@ mph .... 100.9 99.9
Top Speed.... 156 109
5-60 mph, 1st
Gear Start... 6.1 6.0
30-50 mph
1st Gear..... 1.8
2nd Gear..... 2.5 2.2
3rd Gear..... 3.8 1.8
4th Gear..... 5.5 2.3
5th Gear..... 10.0 3.8
50-70 mph
1st Gear..... 3.2
2nd Gear..... 2.7
3rd Gear..... 3.7 3.1
4th Gear..... 5.2 2.6
5th Gear..... 9.2 3.6
30 mph start 1st 3rd
0-100 ft.... 1.7 1.7
0-500 ft.... 6.1 6.2
0-1320 ft.... 12.4 12.6
@ mph .... 102.2 101.5
50 mph start 1st 3rd
0-100 ft.... 1.3 1.2
0-500 ft.... 5.2 5.2
0-1320 ft.... 11.2 11.2
@ mph .... 105.0 105.0
Now lets pretend there is tight corner in race track where exit speed is 30 mph and 1/4 mile long straight after it. Which car is at end of straight first?
Code:
Car 1. out of corner 30 mph in 1st gear: 12.4 seconds 102.2 mph Car 2. out of corner 30 mph in 3rd gear: 12.6 seconds 101.5 mph
Code:
Car 1. out of corner 50 mph in 1st gear: 5.2 seconds Car 2. out of corner 50 mph in 3rd gear: 5.2 seconds
On traffic lights 4.00:1 is clearly faster up to a point but on race track gearing doesn't matter other than minor differencees that come from different shifting points as long 5th is long enough for fastest straight.
01-09-2005, 01:37 PM
#123
Rennlist Member
I think we are getting closer here.
agree with your first paragraph.
However, second paragraph I can only comment that keeping the car in areas of the torque band is a function of gear closeness, not of total rear end ratio.
a drag racer knows this even better as he has to factor in the car's HP to the estimated final speed to select the right ratio rear end to give him redline at the end of drag run. as the car gets more and more hp with a given gear box, he will have to make the final gear drive actually taller to allow for the higher speed achieved. conversely, if he uses that taller gear box before he has an engine that can make the greater hp, he will be leaving speed/ time on the table as he will be crossing the finish line at a lower rpm with a lower rate of acceleration.
in my road racing, i select total ratios that give me the most amount of time at max HP. we are stuck with our over all ratio closeness in a 928, so i have to pick a rear end that gives me close to redline at all straights of a given track. Since it is impossible to do this for every straight of every track, i select a rear end that gives me the most duratoin at max hp over the straights i spend the most time at . right now, its the 2.2 for tracks like Road america (especially) and laguna. but, tracks like Sears and thunderhill would be better to have a 2.72
mk
agree with your first paragraph.
However, second paragraph I can only comment that keeping the car in areas of the torque band is a function of gear closeness, not of total rear end ratio.
a drag racer knows this even better as he has to factor in the car's HP to the estimated final speed to select the right ratio rear end to give him redline at the end of drag run. as the car gets more and more hp with a given gear box, he will have to make the final gear drive actually taller to allow for the higher speed achieved. conversely, if he uses that taller gear box before he has an engine that can make the greater hp, he will be leaving speed/ time on the table as he will be crossing the finish line at a lower rpm with a lower rate of acceleration.
in my road racing, i select total ratios that give me the most amount of time at max HP. we are stuck with our over all ratio closeness in a 928, so i have to pick a rear end that gives me close to redline at all straights of a given track. Since it is impossible to do this for every straight of every track, i select a rear end that gives me the most duratoin at max hp over the straights i spend the most time at . right now, its the 2.2 for tracks like Road america (especially) and laguna. but, tracks like Sears and thunderhill would be better to have a 2.72
mk
Originally Posted by heinrich
Let's remember who Mark Kibort is. He is no drag racer. He is a racing driver.
What does this mean ....
It means that he understands that he can select the right gear at any given time and make enough "GO" (I like to call it torque and he likes to call it horsepower but whatever) to beat any car of equal rating, whether that car has taller or shorter gears.
I think I understand very clearly the major misunderstanding on Mark's part here. He thinks that by saying that taller gearing accelerates more slowly, we're saying he cannot select gears well enough in his 2.2 to stay in its torque band. Of course, we're not saying that. We're stating the obvious ... ad nauseam .....
What does this mean ....
It means that he understands that he can select the right gear at any given time and make enough "GO" (I like to call it torque and he likes to call it horsepower but whatever) to beat any car of equal rating, whether that car has taller or shorter gears.
I think I understand very clearly the major misunderstanding on Mark's part here. He thinks that by saying that taller gearing accelerates more slowly, we're saying he cannot select gears well enough in his 2.2 to stay in its torque band. Of course, we're not saying that. We're stating the obvious ... ad nauseam .....
01-09-2005, 02:03 PM
#124
Rennlist Member
and the problem or issue is?
force = mass x acceleration, AND dv/dt, work is force x displacement, and HP is work over a time. (of course displacement can be replaced with speed x time)
The problem that most are having, especially Glen, is that accleration is an average, just as the torque over an operation range is an average for a given time and speed. (or distance.) more accurately, area under the curve.
if you try to calculate accleration with no movement, you integrate from a range of from 0 to 0. the answer will be 0. no acceleration even if you have a force!! in order for you to have acceleration, you have to have UNEQUAL forces acting on a body. the real definition of newtons 2nd law, is :
a = NET force/mass. a force without movement has no acceleration by definition.
Get it????
MK
PS, PHD certified!
QUOTE=heinrich]Agreed. Here is the very worst one. Run it by your PhD friends Mark.[/QUOTE]
force = mass x acceleration, AND dv/dt, work is force x displacement, and HP is work over a time. (of course displacement can be replaced with speed x time)
The problem that most are having, especially Glen, is that accleration is an average, just as the torque over an operation range is an average for a given time and speed. (or distance.) more accurately, area under the curve.
if you try to calculate accleration with no movement, you integrate from a range of from 0 to 0. the answer will be 0. no acceleration even if you have a force!! in order for you to have acceleration, you have to have UNEQUAL forces acting on a body. the real definition of newtons 2nd law, is :
a = NET force/mass. a force without movement has no acceleration by definition.
Get it????
MK
PS, PHD certified!
QUOTE=heinrich]Agreed. Here is the very worst one. Run it by your PhD friends Mark.[/QUOTE]
01-09-2005, 02:06 PM
#125
Rennlist Member
30 guys on a boat are yelling, "the ship is sinking!!!"
great chart and post.
sorry mine were not clear enough.
guys, what do you think?????? get the point now???
Mk
great chart and post.
sorry mine were not clear enough.
guys, what do you think?????? get the point now???
Mk
Originally Posted by Vilhuer
Here's some 'real' world numbers. I have advertised this software once or twice before but have no connection to it what so ever. It's just so good in pointing what effects gearing has.
http://www.cartestsoftware.com
Numbers are from old software version 4.5. These cars are copies of '88 S4 5sp that comes in db. Everyting else is same except rear gearing. 2.00:1 for car 1. and 4.00:1 for 2.
Numbers are of course not absolutely correct but pattern is there. Some results like may seem odd like 30-50 time being longer for smaller start gear but it just comes from fact that there is one extra gear change that costs time. Time it takes to change is adjustable.
Now lets pretend there is tight corner in race track where exit speed is 30 mph and 1/4 mile long straight after it. Which car is at end of straight first?
Now lets pretend there is little faster corner where exit speed is 50 mph and 500 feet long straight after it. Which car is at end of straight first?
Now cut the crap. On traffic lights 4.00:1 is clearly faster up to a point but on race track gearing doesn't matter other than minor differencees that come from different shifting points as long 5th is long enough for fastest straight.
http://www.cartestsoftware.com
Numbers are from old software version 4.5. These cars are copies of '88 S4 5sp that comes in db. Everyting else is same except rear gearing. 2.00:1 for car 1. and 4.00:1 for 2.
Code:
PERFORMANCE COMPARISON ANALYSIS
-------------------------------
Selected Cars: 1. PORSCHE 928 S4 2.00:1 gearing 1987
2. PORSCHE 928 S4 4.00:1 gearing 1987
Car Number 1 2
--------- ---------
Time to Speed
0-30 mph.... 2.5 2.1
0-40 mph.... 3.3 2.9
0-50 mph.... 4.3 4.5
0-60 mph.... 6.1 6.3
0-70 mph.... 7.5 7.6
0-80 mph.... 9.1 10.0
0-90 mph.... 11.9 12.1
0-100 mph.... 14.2 14.4
Time to Distance
0-100 ft..... 3.3 2.9
0-500 ft..... 8.0 7.9
0-1320ft..... 14.4 14.4
@ mph .... 100.9 99.9
Top Speed.... 156 109
5-60 mph, 1st
Gear Start... 6.1 6.0
30-50 mph
1st Gear..... 1.8
2nd Gear..... 2.5 2.2
3rd Gear..... 3.8 1.8
4th Gear..... 5.5 2.3
5th Gear..... 10.0 3.8
50-70 mph
1st Gear..... 3.2
2nd Gear..... 2.7
3rd Gear..... 3.7 3.1
4th Gear..... 5.2 2.6
5th Gear..... 9.2 3.6
30 mph start 1st 3rd
0-100 ft.... 1.7 1.7
0-500 ft.... 6.1 6.2
0-1320 ft.... 12.4 12.6
@ mph .... 102.2 101.5
50 mph start 1st 3rd
0-100 ft.... 1.3 1.2
0-500 ft.... 5.2 5.2
0-1320 ft.... 11.2 11.2
@ mph .... 105.0 105.0
Now lets pretend there is tight corner in race track where exit speed is 30 mph and 1/4 mile long straight after it. Which car is at end of straight first?
Code:
Car 1. out of corner 30 mph in 1st gear: 12.4 seconds 102.2 mph Car 2. out of corner 30 mph in 3rd gear: 12.6 seconds 101.5 mph
Code:
Car 1. out of corner 50 mph in 1st gear: 5.2 seconds Car 2. out of corner 50 mph in 3rd gear: 5.2 seconds
On traffic lights 4.00:1 is clearly faster up to a point but on race track gearing doesn't matter other than minor differencees that come from different shifting points as long 5th is long enough for fastest straight.
01-09-2005, 06:39 PM
#126
Nordschleife Master
Mark, (mark,mark)
Read the last sentence of Vilheur's post. That's what we have been trying to tell you!
But you don't listen. You've PM'd me twice on this. Please stop. Especially when you write to ask if I undestand that I'm "WRONT" (sic). (Don't you ever proofread?) You just don't have the background to understand the points people, including myself, have made. And yes, I understand what you are saying, even when you are unclear and off from correct terminology and logic.
Read the last sentence of Vilheur's post. That's what we have been trying to tell you!
But you don't listen. You've PM'd me twice on this. Please stop. Especially when you write to ask if I undestand that I'm "WRONT" (sic). (Don't you ever proofread?) You just don't have the background to understand the points people, including myself, have made. And yes, I understand what you are saying, even when you are unclear and off from correct terminology and logic.
01-09-2005, 06:49 PM
#127
Nordschleife Master
And then I see this one!
In the REAL WORLD acceleration is an instantaneous value.
And if you go back to my post on having acceleration without displacement, you, or someone who can understand it, will note that it's clearly described as occuring at the limit of time approaching zero.
Get it????????
In the REAL WORLD acceleration is an instantaneous value.
And if you go back to my post on having acceleration without displacement, you, or someone who can understand it, will note that it's clearly described as occuring at the limit of time approaching zero.
Get it????????
Originally Posted by mark kibort
and the problem or issue is?
force = mass x acceleration, AND dv/dt, work is force x displacement, and HP is work over a time. (of course displacement can be replaced with speed x time)
The problem that most are having, especially Glen, is that accleration is an average, just as the torque over an operation range is an average for a given time and speed. (or distance.) more accurately, area under the curve.
if you try to calculate accleration with no movement, you integrate from a range of from 0 to 0. the answer will be 0. no acceleration even if you have a force!! in order for you to have acceleration, you have to have UNEQUAL forces acting on a body. the real definition of newtons 2nd law, is :
a = NET force/mass. a force without movement has no acceleration by definition.
Get it????
force = mass x acceleration, AND dv/dt, work is force x displacement, and HP is work over a time. (of course displacement can be replaced with speed x time)
The problem that most are having, especially Glen, is that accleration is an average, just as the torque over an operation range is an average for a given time and speed. (or distance.) more accurately, area under the curve.
if you try to calculate accleration with no movement, you integrate from a range of from 0 to 0. the answer will be 0. no acceleration even if you have a force!! in order for you to have acceleration, you have to have UNEQUAL forces acting on a body. the real definition of newtons 2nd law, is :
a = NET force/mass. a force without movement has no acceleration by definition.
Get it????
01-09-2005, 07:01 PM
#128
Drifting
mark, you did a poor job of qualifying your statement. to me "0, none, nothing." means exactly that, and that is not correct.
are you now saying that there is a difference in the acceleration of the two automatics with the different final drives?
are you now saying that there is a difference in the acceleration of the two automatics with the different final drives?
01-09-2005, 08:33 PM
#129
Burning Brakes
Join Date: Jan 2002
Location: Springfield, MO
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Originally Posted by drnick
mark, you did a poor job of qualifying your statement. to me "0, none, nothing." means exactly that, and that is not correct.
are you now saying that there is a difference in the acceleration of the two automatics with the different final drives?
are you now saying that there is a difference in the acceleration of the two automatics with the different final drives?
There would be a difference in acceleration between the two final drives within each separate gear, but depending upon distance travelled, which would affect the amount of time available to reach the peak torque of each gear used, the overall acceleration rate could be slower, faster, or none at all by the time the distance was travelled.
Depending on how you were looking at the original question:
"0, none, nothing" is one possible answer.
"Yes, there is a difference in acceleration" is another possible answer.
The distance travelled becomes the deciding factor of whether there is an overall difference of acceleration between the final drive ratios. Most of the time I would think there would be a difference; either faster or slower, but there could be those distances where there is no difference...where either final drive will get you to the same place in the same time. Both answers have the potential to be correct and both answers have the potential to be wrong. That is why this thread has gone on for so long without any finality. Actually, I think it's pretty cool.
01-09-2005, 11:31 PM
#130
Racer
Join Date: Dec 2002
Location: Gilbert, AZ. U.S.A.
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I had some fun for a change today. I was out in my "other" car, a Toyota Tundra 4x4, when it I relized it has 4 wheel High and Low ranges. Quick get the GTEC and let do a couple of runs. The black line in the Tundra in 4 wheel Hi, the green line is the Tundra in four wheel Lo. The blue line in the 928 for referance. Being a truck with a 5400 redline it runs out of breath fast. But it is interesting to note the differences the gearing makes.
Sure its only good for about 45mph, but it will take your head off getting there!!
Sure its only good for about 45mph, but it will take your head off getting there!!
01-10-2005, 12:51 AM
#131
Rennlist Member
Glen, still wrong . the rust is starting to show on your remembering your high school physics. now your are talking about limits of 0 to 0, the net acceleration is 0 PERIOD. if you want instantaneous velocity, you still have a period of time and there for a distance. you can get as small of a sample that you want, but make no mistake, no movement, distance ,no acceleration.
by definition, instantaneous velocity is a limiting process in which smaller and smaller time intervals are used, each interval containing the INSTANT in which the VELOCITY (not acceleration)is found. v=lim delta t-0 ( ds/ dt) where "s" is distance in case you forgot.
THEREFORE , INSTANTANEOUS velocity is the time derivative of displacement!!!!
Its not time aproaching 0 its the time and distance approaching 0
I think i have slice that one up as best i can. anyone care to help. bottom line, we are in agreement that the force (or average force) over a time or distance will yeild an acceleration.
In the "real world" acceleration is a rate of speed change.
But, again, you are divergine. the acceleration we really want and better said, average acceleration over an operational speed range. WITH all the gear ratio torque outputs integrated and added together. with this, you get an average acceleration and average torque. (which then can be conferted to force as well, by taking torque and converting to force and mass converted to slugs or poundels if you really want to be technically correct)
MK
by definition, instantaneous velocity is a limiting process in which smaller and smaller time intervals are used, each interval containing the INSTANT in which the VELOCITY (not acceleration)is found. v=lim delta t-0 ( ds/ dt) where "s" is distance in case you forgot.
THEREFORE , INSTANTANEOUS velocity is the time derivative of displacement!!!!
Its not time aproaching 0 its the time and distance approaching 0
I think i have slice that one up as best i can. anyone care to help. bottom line, we are in agreement that the force (or average force) over a time or distance will yeild an acceleration.
In the "real world" acceleration is a rate of speed change.
But, again, you are divergine. the acceleration we really want and better said, average acceleration over an operational speed range. WITH all the gear ratio torque outputs integrated and added together. with this, you get an average acceleration and average torque. (which then can be conferted to force as well, by taking torque and converting to force and mass converted to slugs or poundels if you really want to be technically correct)
MK
Originally Posted by GlenL
And then I see this one!
In the REAL WORLD acceleration is an instantaneous value.
And if you go back to my post on having acceleration without displacement, you, or someone who can understand it, will note that it's clearly described as occuring at the limit of time approaching zero.
Get it????????
In the REAL WORLD acceleration is an instantaneous value.
And if you go back to my post on having acceleration without displacement, you, or someone who can understand it, will note that it's clearly described as occuring at the limit of time approaching zero.
Get it????????
01-10-2005, 01:05 AM
#132
Rennlist Member
give me a break glen. I have a baby in one arm and a home computer with 4 keys that need a hammer to make a letter post!
Im feverishy trying to help you and others understand the concepts. clearly, by your statements, you are a little off the mark. please tell me where i am off in terminology. last i heard, it was you that was promoting acceleration without movement.
I think the discussion is narrowing down. sure, i was WRONG to post the original statement regarding "0 change in acceleration" even though i qualified it by "our uses on the street , etc" there are still differences speed to speed range. so, yes, ill admit that was silly. However, i think everyone got my point, as the information feeding back did not incorporate trade offs of gear speeds and times to give average torque over an operational range.
Vilheur's post closing, was just a polite way to say, it really doesnt make a differnce, based on the .1 to .2 second segments in 1st gear where the lower ratios would have an advantage. Ive already mentioned that there was a give an take up to 105mph. the net result is no difference in average acceleration over the entire range. and, depending on the speed segments, a taller rear end gear box, may have advantages in 3 spots over the speed range, in fact, your S4 with a taller rear end , willl spend time in these 3 spots for over 45% of the total time spent accelerating from 0-105mph. the net result is shown on Vilheur's graph.
Mk
Im feverishy trying to help you and others understand the concepts. clearly, by your statements, you are a little off the mark. please tell me where i am off in terminology. last i heard, it was you that was promoting acceleration without movement.
I think the discussion is narrowing down. sure, i was WRONG to post the original statement regarding "0 change in acceleration" even though i qualified it by "our uses on the street , etc" there are still differences speed to speed range. so, yes, ill admit that was silly. However, i think everyone got my point, as the information feeding back did not incorporate trade offs of gear speeds and times to give average torque over an operational range.
Vilheur's post closing, was just a polite way to say, it really doesnt make a differnce, based on the .1 to .2 second segments in 1st gear where the lower ratios would have an advantage. Ive already mentioned that there was a give an take up to 105mph. the net result is no difference in average acceleration over the entire range. and, depending on the speed segments, a taller rear end gear box, may have advantages in 3 spots over the speed range, in fact, your S4 with a taller rear end , willl spend time in these 3 spots for over 45% of the total time spent accelerating from 0-105mph. the net result is shown on Vilheur's graph.
Mk
Originally Posted by GlenL
Mark, (mark,mark)
Read the last sentence of Vilheur's post. That's what we have been trying to tell you!
But you don't listen. You've PM'd me twice on this. Please stop. Especially when you write to ask if I undestand that I'm "WRONT" (sic). (Don't you ever proofread?) You just don't have the background to understand the points people, including myself, have made. And yes, I understand what you are saying, even when you are unclear and off from correct terminology and logic.
Read the last sentence of Vilheur's post. That's what we have been trying to tell you!
But you don't listen. You've PM'd me twice on this. Please stop. Especially when you write to ask if I undestand that I'm "WRONT" (sic). (Don't you ever proofread?) You just don't have the background to understand the points people, including myself, have made. And yes, I understand what you are saying, even when you are unclear and off from correct terminology and logic.
01-10-2005, 02:26 AM
#133
Rennlist Member
Gearing DOES Affect Acceleration: PROVEN
That's funny, Chuck... I went and did the same thing! Here is the test "mule"... It has all the qualifications.... ugly, ornery, good for pulling stumps. Full-time 4 wheel drive, 2:1 reduction at the transfer case. Effectively this amounts to changing the "mule" from 3.54:1 gears to 7.08:1. The engine has 415,000 original miles and has never been opened up past slapping in an RV cam at about 175,000. There is no danger whatsoever of wheelspin affecting the outcome of this experiment. 
I ended up with a similar result(All main runs at 2:1 reduction):
I might have matched shiftpoints better, but I didn't have a ton of time to spend on this so I didn't bother setting the G-Tech shiftlights. I don't have a tach in the truck, BTW. I still have the wheezy 2-barrel on there from smogging it; believe me, there is no real advantage going another 1000 RPM. At that point it's making more noise, not more power. I think this is borne out by the clear trend of higher acceleration with the lower gearing. Consider that the weight being accelerated was 4930 pounds, so a couple of extra HP(if any) from the higher revs wouldn't count for much. Anyway, on the RPM graph you can see the "area under the curves" more clearly, and no I don't care to calculate the exact area.
Also from the above two charts alone you can see a clear trend of higher acceleration with lower gears.
Mark Kibort said:
How many angels can dance on the head of a pin? Here we have a real-world example of increased acceleration due to a simple change of rear-end gears. Here is the G-chart:
Except for a brief period between 5 and 6 seconds when the main run is engaging 3rd just as the comparison run is topping out in first gear, the numerically higher (7.08:1) gearing is providing higher acceleration. Mark, let your PhD(Piled Higher & Deeper) friends come up with a theory as to why lower gearing should not result in greater acceleration. They all need to sharpen their pencils it seems, because whatever it is they are blathering about doesn't square with real world results from what I'm seeing. Not if they think a reduction in gearing won't affect acceleration.
I weighed the truck on 3 adjacent scales in Sunnyvale; weights were 4920, 4920, 4940 so I went with 4930.
Here's what changed between runs:
final drive(downstream of transmission) changed from 3.54:1 to 7.08:1
Weight difference:
Maybe a half pound of fuel
Maybe a tablespoon of oil
Oh, and I farted. Hopefully this weight difference is of no consequence as I have no way to calculate how much blew out the window by the time I started the second run.
Here's the rest of the charts.
This one really shows off the "Area under the curve". This is the explanation for the increased acceleration; lowering the gears put the "sweet spot" into the 0-50 range:
I ended up with a similar result(All main runs at 2:1 reduction):
I might have matched shiftpoints better, but I didn't have a ton of time to spend on this so I didn't bother setting the G-Tech shiftlights. I don't have a tach in the truck, BTW. I still have the wheezy 2-barrel on there from smogging it; believe me, there is no real advantage going another 1000 RPM. At that point it's making more noise, not more power. I think this is borne out by the clear trend of higher acceleration with the lower gearing. Consider that the weight being accelerated was 4930 pounds, so a couple of extra HP(if any) from the higher revs wouldn't count for much. Anyway, on the RPM graph you can see the "area under the curves" more clearly, and no I don't care to calculate the exact area.
Also from the above two charts alone you can see a clear trend of higher acceleration with lower gears.
Mark Kibort said:
torque increase by increasing the rear end doesnt produce increased acceleration, HP does this, and better said, by maximizing HP over the operational range, you gain the greatest acceleration.
Except for a brief period between 5 and 6 seconds when the main run is engaging 3rd just as the comparison run is topping out in first gear, the numerically higher (7.08:1) gearing is providing higher acceleration. Mark, let your PhD(Piled Higher & Deeper) friends come up with a theory as to why lower gearing should not result in greater acceleration. They all need to sharpen their pencils it seems, because whatever it is they are blathering about doesn't square with real world results from what I'm seeing. Not if they think a reduction in gearing won't affect acceleration.
I weighed the truck on 3 adjacent scales in Sunnyvale; weights were 4920, 4920, 4940 so I went with 4930.
Here's what changed between runs:
final drive(downstream of transmission) changed from 3.54:1 to 7.08:1
Weight difference:
Maybe a half pound of fuel
Maybe a tablespoon of oil
Oh, and I farted. Hopefully this weight difference is of no consequence as I have no way to calculate how much blew out the window by the time I started the second run.
Here's the rest of the charts.
This one really shows off the "Area under the curve". This is the explanation for the increased acceleration; lowering the gears put the "sweet spot" into the 0-50 range:
01-10-2005, 03:12 AM
#135
Racer
Join Date: Dec 2002
Location: Gilbert, AZ. U.S.A.
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Interesting program Vilhuer came up with. I got different results, see 2.2 vs 2.54 below. The 2.54 does better as expected. Top speed is higher too. See below. I think this program interesting but it does some funny things depending on how you tweak the variables. It also has no clue to some of the finer points of how our cars run, but its fun to play with anyway. It is also neat that it can be made to prove my point, YMMV. The only difference between the two runs is the rear ratio.
Last edited by 928Quest; 01-10-2005 at 03:57 AM.