Is ballast really the equalizer it is suppose to be ?
05-17-2009, 11:33 AM
#32
Rennlist Member
Weight definitely makes a big difference - just watch F1 qualifying and see how the the fuel load (added weight) changes their lap times. It makes less of a difference in our race cars because our cars weigh so much more - but it does make a difference.
05-17-2009, 12:44 PM
#33
Rennlist Member
I think there is no question that weight effects lap time. How much, I think we are all in agreement. Where that weight is positioned in the car is important as well. Those effects can be calculated as well.
I layed out the relative effects of ballast weight in terms of HP/weight ratios and a couple folks (drduperman and VR) have disagreed and have gone silent.
Here is the post:
HP to drag ratio is much more of a factor at the higher speeds. also, a given amount of weigth will effect the Hp/weight ratios if a car starts out at a lighter weight. obviously, its always better to have a better aero car if HP to weight is even. On the same token, its better to have a lighter car, even though HP to weight is the same (all other things being equal like tire size, chassis width, etc). Since most of our cars have near 20sq-ft of frontal area and speeds are near 100mph on most tracks, for most of the time, the total aero drag is not that significant. (50hp range.) improvements of say 10%, which is a lot on aero would only have a 5hp advantage).
3000lbs/300hp 10:1
3100lbs/300hp 10.3:1
3000lbs/305hp 9.8:1
3050lbs/305hp 10:1 (at 100mph, 5hp aero advantage is worth 50lbs)
3100lbs/310hp 10:1 ( at 130mph, 10hp aero adatage is worth 100lbs because power required goes up with the CUBE of speed. speed went up by 30% and 30% cubed is 2.1X, so power goes up by 10hp vs 5hp at 100mph.)
What this shows is that if someone has a 10% aero advantage, its probably like having a 50lb advantage at near 100mph racing, but near 100lb advantage (near double) when the speeds get near 130mph as the power required goes up by the cube of speed. (and so does any differences) (strictly talking acceleration)
I layed out the relative effects of ballast weight in terms of HP/weight ratios and a couple folks (drduperman and VR) have disagreed and have gone silent.
Here is the post:
HP to drag ratio is much more of a factor at the higher speeds. also, a given amount of weigth will effect the Hp/weight ratios if a car starts out at a lighter weight. obviously, its always better to have a better aero car if HP to weight is even. On the same token, its better to have a lighter car, even though HP to weight is the same (all other things being equal like tire size, chassis width, etc). Since most of our cars have near 20sq-ft of frontal area and speeds are near 100mph on most tracks, for most of the time, the total aero drag is not that significant. (50hp range.) improvements of say 10%, which is a lot on aero would only have a 5hp advantage).
3000lbs/300hp 10:1
3100lbs/300hp 10.3:1
3000lbs/305hp 9.8:1
3050lbs/305hp 10:1 (at 100mph, 5hp aero advantage is worth 50lbs)
3100lbs/310hp 10:1 ( at 130mph, 10hp aero adatage is worth 100lbs because power required goes up with the CUBE of speed. speed went up by 30% and 30% cubed is 2.1X, so power goes up by 10hp vs 5hp at 100mph.)
What this shows is that if someone has a 10% aero advantage, its probably like having a 50lb advantage at near 100mph racing, but near 100lb advantage (near double) when the speeds get near 130mph as the power required goes up by the cube of speed. (and so does any differences) (strictly talking acceleration)
05-17-2009, 01:36 PM
#35
Rennlist Member
05-17-2009, 03:24 PM
#36
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..
05-17-2009, 10:08 PM
#38
Burning Brakes
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Comparing seconds/lap to weight or HP is "sort of" silly (but sometimes it works). You can compare power and weight easily in a straight line. Weight/power straight line if you're 280 whp and 2800 lbs then 1 hp = 10 lbs. In turns the weight/power affect is different and too dynamic to generalize, depends on the turn, weight, tires, etc...
Ok, so about Summit:
On my Integra race car, my new motor seems to be making about 10 hp more than the old (it dynod the same but it was a hot day, I know it's faster) and it's worth about 1 second a lap to me at Summit, so 150 whp (fwhp) and 2470 lbs. I ran a 1:27.5 in a race this year and 1:28.5 last year, nothing else changed.
That's weight/power ratio of 16.5 so I'd expect that each HP for me is worth 16.5 lbs, so that 10 hp is like (roughly) 165 lbs less weight for accel/decel.
Summit Point is not a HP track though. My Acura race car gets killed at PCA DE's at VIR or The Glen, but I can hang in there at Summit! Summit is about weight, VIR/Glen are about power.
And YES I believe your friend's approximation
Agreed it's more complicated than it seems, but the approximation also works in experience, for that track.
Ok, so about Summit:
On my Integra race car, my new motor seems to be making about 10 hp more than the old (it dynod the same but it was a hot day, I know it's faster) and it's worth about 1 second a lap to me at Summit, so 150 whp (fwhp) and 2470 lbs. I ran a 1:27.5 in a race this year and 1:28.5 last year, nothing else changed.
That's weight/power ratio of 16.5 so I'd expect that each HP for me is worth 16.5 lbs, so that 10 hp is like (roughly) 165 lbs less weight for accel/decel.
Summit Point is not a HP track though. My Acura race car gets killed at PCA DE's at VIR or The Glen, but I can hang in there at Summit! Summit is about weight, VIR/Glen are about power.
And YES I believe your friend's approximation
Agreed it's more complicated than it seems, but the approximation also works in experience, for that track.
05-18-2009, 01:06 AM
#39
Rennlist Member
and If I knew how to use Warf leaning on his forhead, I would use it for you.
DUDE, you just said someone was right. Did you think about it for even a microsecond?
HP required goes up with the cube of speed, not squard as JDuper said.
lets say you had 200lbs of drag at 100mph.
now what is the force at 200mph?? Based on JDuper's comment, aero drag goes up with the square, or for doubling speed, thats 4x. 800lbs.
what is the power now? Power = Force x Speed.
at 100mph 200 x 146 /550 = 53hp
at 200mph 800 x 292 /550 = 424hp
146 is 100mph x 1.46 for feet/second. and 550 is to bring the equations in terms of HP
Thats CUBED my friend and its 8x the power required when the speed doubles.
Any other questions? still think Duper is right? Think again.
mk
DUDE, you just said someone was right. Did you think about it for even a microsecond?
HP required goes up with the cube of speed, not squard as JDuper said.
lets say you had 200lbs of drag at 100mph.
now what is the force at 200mph?? Based on JDuper's comment, aero drag goes up with the square, or for doubling speed, thats 4x. 800lbs.
what is the power now? Power = Force x Speed.
at 100mph 200 x 146 /550 = 53hp
at 200mph 800 x 292 /550 = 424hp
146 is 100mph x 1.46 for feet/second. and 550 is to bring the equations in terms of HP
Thats CUBED my friend and its 8x the power required when the speed doubles.
Any other questions? still think Duper is right? Think again.
mk
05-18-2009, 01:08 AM
#40
Rennlist Member
Do you see where you made your error?
Dont let VR pump you up, just because he has the hots for you.
mk
Dont let VR pump you up, just because he has the hots for you.
mk
05-18-2009, 11:39 AM
#41
Rennlist Member
Well, care to recant your statement? You have a certain responsibility here as the resident head basher here, to step up and correct statements that are INCORRECT. Its one thing to argue "feelings" or "opinions", and quite another to contradict NEWTON!! Dont mess with the NEWTON!!
Duperman said:
I believe it is a squared equation, which means that to double your speed you need 4x the power. No cube:
Aerodynamic drag = 1/2 D x A x V^2
where D = air density, A = frontal area, V = velocity relative to the air
Duperman said:
I believe it is a squared equation, which means that to double your speed you need 4x the power. No cube:
Aerodynamic drag = 1/2 D x A x V^2
where D = air density, A = frontal area, V = velocity relative to the air
05-18-2009, 11:40 AM
#42
Race Director
Mark,
I really think you are digging in for no reason.
It is clear. less weight = faster and weight has less impact on top speed when aero drag is limiting factor. However how much so is a very difficult question to answer. It is based on many factors some of which are easy to calcuate and other which are not. In the end the basic question of weight being the equalizer is yes it is. However rarely in a series where you are trying to equalize performance is weight as simple as power/weight. Most series where weight is used to balance performance it starts with an equalized power/weight. Then uses on track performance or other estimated adds on to get to the right weight. Often times the first weight selected is not right and will be tweaked over time. In the end the constant tweaking serves to create as much performance balance as you can.
So weight can be used as a great equalizer, but to do so effectivly it must be administered trial and error style until the optimum is achieved. Even then two cars with optimized class weights still will have different strengths and weaknesses at certain tracks and a certain places on track.
I really think you are digging in for no reason.
It is clear. less weight = faster and weight has less impact on top speed when aero drag is limiting factor. However how much so is a very difficult question to answer. It is based on many factors some of which are easy to calcuate and other which are not. In the end the basic question of weight being the equalizer is yes it is. However rarely in a series where you are trying to equalize performance is weight as simple as power/weight. Most series where weight is used to balance performance it starts with an equalized power/weight. Then uses on track performance or other estimated adds on to get to the right weight. Often times the first weight selected is not right and will be tweaked over time. In the end the constant tweaking serves to create as much performance balance as you can.
So weight can be used as a great equalizer, but to do so effectivly it must be administered trial and error style until the optimum is achieved. Even then two cars with optimized class weights still will have different strengths and weaknesses at certain tracks and a certain places on track.
05-18-2009, 11:50 AM
#43
Rennlist Member
Well, care to recant your statement? You have a certain responsibility here as the resident head basher here, to step up and correct statements that are INCORRECT. Its one thing to argue "feelings" or "opinions", and quite another to contradict NEWTON!! Dont mess with the NEWTON!!
Duperman said:
I believe it is a squared equation, which means that to double your speed you need 4x the power. No cube:
Aerodynamic drag = 1/2 D x A x V^2
where D = air density, A = frontal area, V = velocity relative to the air
Duperman said:
I believe it is a squared equation, which means that to double your speed you need 4x the power. No cube:
Aerodynamic drag = 1/2 D x A x V^2
where D = air density, A = frontal area, V = velocity relative to the air
Mark, FYI, aerodynamic drag increases at the square of speed.
Professional Racing and Driving Coach
05-18-2009, 01:50 PM
#44
Rennlist Member
Dave, aerodynamic forces increase with the square of speed, yes. BUT , read the post please! It said that the power required to drive the force didnt go up with the cube of speed, and it does. Dupe said, " no cube". you said, " correct". Its CUBED! (For power required to go faster)
The statement was , (and read more than the first couple of words )
Dupe said: "I believe it is a squared equation, which means that to double your speed you need 4x the power. No cube:"
Let me assist you. aero is a squared equation and that is what he is talking about in the first part of the sentence. BUT, he defines it incorrectly on the second part, and re-emphasizes it with the "no cube". care to read it again and comment?
The statement was , (and read more than the first couple of words
)Dupe said: "I believe it is a squared equation, which means that to double your speed you need 4x the power. No cube:"
Let me assist you. aero is a squared equation and that is what he is talking about in the first part of the sentence. BUT, he defines it incorrectly on the second part, and re-emphasizes it with the "no cube". care to read it again and comment?
05-18-2009, 01:56 PM
#45
Rennlist Member
This has been agreed on. I only pointed out a way to compare acceleration with equal HP to weight vs aerodynamic consessions.
certainly we were also discussing how ballast in opimal positions help as well.
equal hp to weight and absolute weight are major factors, but there are a x-load of many others!!
Again, the point of the recent exchange was when Dupe, said that he "thought" that the power required went up with the square of speed, when refering to aero forces. I originally stated that aero forces will require a cube increase in power. double the aero, 8x the power required to drive it (cubed)
my example also then showed that a 10% better aero car , would have between 5 and 10hp advanges (or 50-100lbs) between 100 and 130mph, for only straight line acceleration. (all other things being equal on the 3000lb/300hp cars)
In otherwords, aero efffects for a 30% change in speed, can double the HP gain/loss effects. (the power of Cubed!)
mk
certainly we were also discussing how ballast in opimal positions help as well.
equal hp to weight and absolute weight are major factors, but there are a x-load of many others!!
Again, the point of the recent exchange was when Dupe, said that he "thought" that the power required went up with the square of speed, when refering to aero forces. I originally stated that aero forces will require a cube increase in power. double the aero, 8x the power required to drive it (cubed)
my example also then showed that a 10% better aero car , would have between 5 and 10hp advanges (or 50-100lbs) between 100 and 130mph, for only straight line acceleration. (all other things being equal on the 3000lb/300hp cars)
In otherwords, aero efffects for a 30% change in speed, can double the HP gain/loss effects. (the power of Cubed!)
mk
Mark,
I really think you are digging in for no reason.
It is clear. less weight = faster and weight has less impact on top speed when aero drag is limiting factor. However how much so is a very difficult question to answer. It is based on many factors some of which are easy to calcuate and other which are not. In the end the basic question of weight being the equalizer is yes it is. However rarely in a series where you are trying to equalize performance is weight as simple as power/weight. Most series where weight is used to balance performance it starts with an equalized power/weight. Then uses on track performance or other estimated adds on to get to the right weight. Often times the first weight selected is not right and will be tweaked over time. In the end the constant tweaking serves to create as much performance balance as you can.
So weight can be used as a great equalizer, but to do so effectivly it must be administered trial and error style until the optimum is achieved. Even then two cars with optimized class weights still will have different strengths and weaknesses at certain tracks and a certain places on track.
I really think you are digging in for no reason.
It is clear. less weight = faster and weight has less impact on top speed when aero drag is limiting factor. However how much so is a very difficult question to answer. It is based on many factors some of which are easy to calcuate and other which are not. In the end the basic question of weight being the equalizer is yes it is. However rarely in a series where you are trying to equalize performance is weight as simple as power/weight. Most series where weight is used to balance performance it starts with an equalized power/weight. Then uses on track performance or other estimated adds on to get to the right weight. Often times the first weight selected is not right and will be tweaked over time. In the end the constant tweaking serves to create as much performance balance as you can.
So weight can be used as a great equalizer, but to do so effectivly it must be administered trial and error style until the optimum is achieved. Even then two cars with optimized class weights still will have different strengths and weaknesses at certain tracks and a certain places on track.
Last edited by mark kibort; 05-18-2009 at 02:11 PM.