3.09 ring & pinion
11-15-2005, 04:42 PM
#316
Rennlist Member
MS sniper, let me blow your mind for one more second.
Now that we understand that the gains of the 3.09 are only in the "sub" 1st gear and the gains would be to only 39mph. (based on the sub 1st gear having a mechanical advantage of 40% vs the 26% actual gains calculated based on normal 928 hp curves, guess what? I was leaving the best for last to show why the 3.09 mod is a waste in a 1/4 mile distance range.
remember the last discussion , 2.2 vs 2.54, well you now know about the trade offs and application of HP over ranges, and even the HP -seconds (units of work, not of power) I introduced to show the accelerative forces applied over time over a distance.
well, as soon as the 3.09 shifts into its next gear, both the 2.2 vs the 3.09 are in the same ratio (as we said, BUT WAIT) they are not identical, the 2.2 is in a 8.9 vs the 3.09 being in a 8.3. there is some trade off to 55mph with the advantage being with the 2.2 until 55mph. THEN, they both shift into a exactly the same 5.9 til 80mph, to the demise of the 3.9, even though it is still ahead by the launch, the next 2 shifts are 5-6% more advantageous to the 2.2. being 4.24 vs 4.5 and 3.2 vs 3.09. (if the target speeds are 115mph or 155mph) BECAUSE This advantage happens for over 6 seconds vs the 2 seconds in the "sub" 1st gear with 26% more hp to the wheels, those gains are almost completely negated. at any other target speed , say 120mph or 165mph, the 3.09 could get that initial advantage back.
this is just looking at the applied hp to the wheels over the operational range through the gear box.
now, the above is for a race to 115mph or close to the quartermile top speed. if the race was to 155mph , the total advantage of the gear package would be with the 2.2. now, if you put a 2.75 rear end in the 2.2 box, there is an argument for some gains at certain speed ranges. (just as there is for the 2.2) but, we are talking 3.09.
chew on that for a while. do some research on what causes acceleration over a distance.. remember, its F=ma, but work is force X distance. and HPs the rate of doing work (even instantaneously) and over a 1/4mile, you will be applying hp all the way to the end.
when the clutch goes in, there is no acceleration, because there is no force. yes, you can go from 1G of acceleration to , not only 0 G (of accelertion) but slighly negative (actually slowing down.) basic basic physics here! you keep the pedal floored and some energy is stored as kinetic engergy in the flywheel, only to be released in the drivetrain upon putting the car in the next gear, but you never make up the shifting loss.
MK
Now that we understand that the gains of the 3.09 are only in the "sub" 1st gear and the gains would be to only 39mph. (based on the sub 1st gear having a mechanical advantage of 40% vs the 26% actual gains calculated based on normal 928 hp curves, guess what? I was leaving the best for last to show why the 3.09 mod is a waste in a 1/4 mile distance range.
remember the last discussion , 2.2 vs 2.54, well you now know about the trade offs and application of HP over ranges, and even the HP -seconds (units of work, not of power) I introduced to show the accelerative forces applied over time over a distance.
well, as soon as the 3.09 shifts into its next gear, both the 2.2 vs the 3.09 are in the same ratio (as we said, BUT WAIT) they are not identical, the 2.2 is in a 8.9 vs the 3.09 being in a 8.3. there is some trade off to 55mph with the advantage being with the 2.2 until 55mph. THEN, they both shift into a exactly the same 5.9 til 80mph, to the demise of the 3.9, even though it is still ahead by the launch, the next 2 shifts are 5-6% more advantageous to the 2.2. being 4.24 vs 4.5 and 3.2 vs 3.09. (if the target speeds are 115mph or 155mph) BECAUSE This advantage happens for over 6 seconds vs the 2 seconds in the "sub" 1st gear with 26% more hp to the wheels, those gains are almost completely negated. at any other target speed , say 120mph or 165mph, the 3.09 could get that initial advantage back.
this is just looking at the applied hp to the wheels over the operational range through the gear box.
now, the above is for a race to 115mph or close to the quartermile top speed. if the race was to 155mph , the total advantage of the gear package would be with the 2.2. now, if you put a 2.75 rear end in the 2.2 box, there is an argument for some gains at certain speed ranges. (just as there is for the 2.2) but, we are talking 3.09.
chew on that for a while. do some research on what causes acceleration over a distance.. remember, its F=ma, but work is force X distance. and HPs the rate of doing work (even instantaneously) and over a 1/4mile, you will be applying hp all the way to the end.
when the clutch goes in, there is no acceleration, because there is no force. yes, you can go from 1G of acceleration to , not only 0 G (of accelertion) but slighly negative (actually slowing down.) basic basic physics here! you keep the pedal floored and some energy is stored as kinetic engergy in the flywheel, only to be released in the drivetrain upon putting the car in the next gear, but you never make up the shifting loss.
MK
Last edited by mark kibort; 11-15-2005 at 08:49 PM.
11-15-2005, 04:48 PM
#317
Rennlist Member
you are right with the bullet, as the force is dispersed gradually , as after the mussel the mass behind the bullet disperses out into the air. after the force is no longer pushing on the bullet, and overcoming aerodynamic drag, it imeadiately starts to decelerate.
with the clutch, its instantaneous. (well, as soon as its put in an the engine is not connected)
MK
with the clutch, its instantaneous. (well, as soon as its put in an the engine is not connected)
MK
Originally Posted by m21sniper
I agree with that definition.
The only thing i take exception to is your statement that it is instantaneous. It is not.
It takes time(albeit normally very little) to overcome momentum and accelerative forces.
For a typical rifle bullet it takes several feet from the muzzle(ever wondered why chronographs are set up six feet from the muzzle when measuring muzzle velocity?) before air resistance overcomes the rapidly dissipating expanding gas column and imparts decelleration on the projectile. Further, the BC(or CD to use a car term) of the projectile determines at what rate it decelerates, as does atmospheric density.
So in the end, decelleration is decidedly not instantaneous, even if you hit a pole.
It is incremental and gradual.
A car with big fat tires driving into a 5kt headwind will decelerate much more quickly than one with skinnies(hence serious drag cars running skinnies) and no wind at all.
The only thing i take exception to is your statement that it is instantaneous. It is not.
It takes time(albeit normally very little) to overcome momentum and accelerative forces.
For a typical rifle bullet it takes several feet from the muzzle(ever wondered why chronographs are set up six feet from the muzzle when measuring muzzle velocity?) before air resistance overcomes the rapidly dissipating expanding gas column and imparts decelleration on the projectile. Further, the BC(or CD to use a car term) of the projectile determines at what rate it decelerates, as does atmospheric density.
So in the end, decelleration is decidedly not instantaneous, even if you hit a pole.
It is incremental and gradual.
A car with big fat tires driving into a 5kt headwind will decelerate much more quickly than one with skinnies(hence serious drag cars running skinnies) and no wind at all.
11-15-2005, 04:51 PM
#318
Rennlist Member
excellent as well. (i hope Ms21 is reading this!)
also, how many times do i have to write down that the gears are not closer together. look at the ratios. you get a "sub "1st of 12.5:1 and then all the other gears match up almost identically and have the same spacing. after 39mph, all the gears and mechanical advantages are close to the same.
MK
[QUOTE=Louie928]
also, how many times do i have to write down that the gears are not closer together. look at the ratios. you get a "sub "1st of 12.5:1 and then all the other gears match up almost identically and have the same spacing. after 39mph, all the gears and mechanical advantages are close to the same.
MK
[QUOTE=Louie928]
Originally Posted by m21sniper
M21,
You gotta get a grip here. With a 3.09 vs a 2.2 you'd use more of the gears in a 0.25 mile run just as you say. But they aren't more closely spaced. It's a simple math thing. Count the teeth on the tranny gears. Changing the diff teeth doesn't change the tranny gear teeth to make each gear change closer. Now, if you are re-difining tranny gear spacing as in shifting more times in a given distance, well, sure. Use a 12:1 final drive and you'd be through all 5 gears in a few feet, but the transmission gear ratio change is still the same.
Acceleration of a car does cease immediately as soon as the clutch is depressed. You've removed the force that causes acceleration. It's just a fact and not even open for discussion. Your analogy of being slammed against the windshield assumes that in addition to no more acceleration, you also have instant 1 G deceleration. No one said that happens with clutch disengagement. The car is only not accelerating for a tenth second, that's all. The velocity doesn't change much, but it does slow slightly during that tenth second. A car isn't a bullet that continues to be propelled a short distance from the barrel end by the continuing gas flow from the barrel.
You gotta get a grip here. With a 3.09 vs a 2.2 you'd use more of the gears in a 0.25 mile run just as you say. But they aren't more closely spaced. It's a simple math thing. Count the teeth on the tranny gears. Changing the diff teeth doesn't change the tranny gear teeth to make each gear change closer. Now, if you are re-difining tranny gear spacing as in shifting more times in a given distance, well, sure. Use a 12:1 final drive and you'd be through all 5 gears in a few feet, but the transmission gear ratio change is still the same.
Acceleration of a car does cease immediately as soon as the clutch is depressed. You've removed the force that causes acceleration. It's just a fact and not even open for discussion. Your analogy of being slammed against the windshield assumes that in addition to no more acceleration, you also have instant 1 G deceleration. No one said that happens with clutch disengagement. The car is only not accelerating for a tenth second, that's all. The velocity doesn't change much, but it does slow slightly during that tenth second. A car isn't a bullet that continues to be propelled a short distance from the barrel end by the continuing gas flow from the barrel.
11-15-2005, 05:35 PM
#319
Range Master
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Mark and Louie, you guys have a lot of patience....compliments to you.....BTW, Louie, fedex picks up the sneakers tomorrow morning......Hope you like 'em.
11-16-2005, 01:33 PM
#320
Originally Posted by Imo000
Snipe, others are correct in this case. Let me explain:
Stopping of acceleration doesn’t mean you come to a stop. It means that your stop increasing your velocity. Think about it for a sec. If your throw a stone, it will start to decelerate as soon as it leaves your hand. It’s the same thing that happens when you push in the clutch. Deceleration is the same as negative acceleration. When you are accelerating, you are experiencing positive Gs and when you are deceleration you are experiencing negative Gs, right? Therefore, as soon as the clutch goes in your are starting gradually to pull negative Gs.
Stopping of acceleration doesn’t mean you come to a stop. It means that your stop increasing your velocity. Think about it for a sec. If your throw a stone, it will start to decelerate as soon as it leaves your hand. It’s the same thing that happens when you push in the clutch. Deceleration is the same as negative acceleration. When you are accelerating, you are experiencing positive Gs and when you are deceleration you are experiencing negative Gs, right? Therefore, as soon as the clutch goes in your are starting gradually to pull negative Gs.
Anyway, that's my understanding of it. If i'm wrong, it certainly won't be the first time....nor the last.
Of course none of this has anything to do with the actual purpose of this thread.
11-16-2005, 01:38 PM
#321
Originally Posted by mark kibort
yes, as long as the mass behind the projectile is moving at a faster rate, then it can accelerate passed the mussel. however, this point doesnt equate to what happens in autos . clutch put in, accleration stops.
Period
no force, no acceleration.
why dont you tell us the different speeds through and out of a bullet out of a gun. that would be interesting
Mk
Period
no force, no acceleration.
why dont you tell us the different speeds through and out of a bullet out of a gun. that would be interesting
Mk
Last edited by m21sniper; 11-16-2005 at 01:59 PM.
11-16-2005, 01:46 PM
#322
[QUOTE=Louie928]
I understand fully that mathematically neither is more closely spaced, but effectively(a word i've used many times in this discussion), one becomes a 4 speed, and the other a three.
You can assign whatever term you like for that advantadge, i'm not that particular, and 'effectively closer spaced' got across the point i was trying to communicate pretty well(i thought).
As i've said several times in this thread, i don't know all the proper terminology.
What i do know is that 2 cars drag racing where one has 4 gears and the other has only the last three of the 1st car, the 4 speed car is going to have a huge advantadge(all other things being equal).
Originally Posted by m21sniper
M21,
You gotta get a grip here. With a 3.09 vs a 2.2 you'd use more of the gears in a 0.25 mile run just as you say. But they aren't more closely spaced. It's a simple math thing. Count the teeth on the tranny gears. Changing the diff teeth doesn't change the tranny gear teeth to make each gear change closer. Now, if you are re-difining tranny gear spacing as in shifting more times in a given distance, well, sure. Use a 12:1 final drive and you'd be through all 5 gears in a few feet, but the transmission gear ratio change is still the same.
You gotta get a grip here. With a 3.09 vs a 2.2 you'd use more of the gears in a 0.25 mile run just as you say. But they aren't more closely spaced. It's a simple math thing. Count the teeth on the tranny gears. Changing the diff teeth doesn't change the tranny gear teeth to make each gear change closer. Now, if you are re-difining tranny gear spacing as in shifting more times in a given distance, well, sure. Use a 12:1 final drive and you'd be through all 5 gears in a few feet, but the transmission gear ratio change is still the same.
You can assign whatever term you like for that advantadge, i'm not that particular, and 'effectively closer spaced' got across the point i was trying to communicate pretty well(i thought).
As i've said several times in this thread, i don't know all the proper terminology.
What i do know is that 2 cars drag racing where one has 4 gears and the other has only the last three of the 1st car, the 4 speed car is going to have a huge advantadge(all other things being equal).
Last edited by m21sniper; 11-16-2005 at 02:34 PM.
11-16-2005, 01:58 PM
#323
Originally Posted by mark kibort
excellent as well. (i hope Ms21 is reading this!)
also, how many times do i have to write down that the gears are not closer together. look at the ratios. you get a "sub "1st of 12.5:1 and then all the other gears match up almost identically and have the same spacing. after 39mph, all the gears and mechanical advantages are close to the same.
MK
also, how many times do i have to write down that the gears are not closer together. look at the ratios. you get a "sub "1st of 12.5:1 and then all the other gears match up almost identically and have the same spacing. after 39mph, all the gears and mechanical advantages are close to the same.
MK
Would a big, fat, "No kidding?" finally get that broken record to stop???
PS: By 39mph for most cars in a drag race, the race is already more than 1/3 over.
Therefore in your 3.09 you have held a significant advantadge for fully 1/3 of the race vs the 2.2 car. The whole rest of the race the 2.2 car is going to be playing catchup, but because as you've said again and again, the gearing for both cars the rest of the way to the finish line is the same, the 2.2 car will never catch up, and like almost all drag races, the race will have been won off the line.
Last edited by m21sniper; 11-16-2005 at 02:16 PM.
11-16-2005, 02:14 PM
#324
Race Car
A car that starts in 2nd against a car that starts in 1st. In most cases yes. But if there was a car that could start and spin tires in second gear and the driver could actually launch the thing, then maybe no?
I know nothing about drag racing but would suspect that the choice of 1st gear ratio would have much to do with optimizing the control of the hook-up in conjuction with ensuring a good 2nd gear transition. Running through the remainder of the gears requires less precision as it is all about HP.
To put into perspective the real world compromise between having an extra shift, we need to understand how much there is to gain by optimizing launches. Isn't the 60 foot (60 feet 100 feet, I don't remember) thing a good measure of launch? How much variability might we see here due to set up, and how much variability due to driver inconsistency?
Physics aside, there may be something to what M21 is saying in the context of drag racing, but I suspect that much depends on the car and set up.
I know nothing about drag racing but would suspect that the choice of 1st gear ratio would have much to do with optimizing the control of the hook-up in conjuction with ensuring a good 2nd gear transition. Running through the remainder of the gears requires less precision as it is all about HP.
To put into perspective the real world compromise between having an extra shift, we need to understand how much there is to gain by optimizing launches. Isn't the 60 foot (60 feet 100 feet, I don't remember) thing a good measure of launch? How much variability might we see here due to set up, and how much variability due to driver inconsistency?
Physics aside, there may be something to what M21 is saying in the context of drag racing, but I suspect that much depends on the car and set up.
11-16-2005, 02:21 PM
#325
Traction certainly becomes the key when you do gearing changes(or increase HP for that matter).
There are a lot of things that are far less than ideal in the 928 suspension wrt drag racing, and making some suspension changes(like very soft rear coils that allowed a maximum weight transfer to the rear of the car, just for instance) and tire changes would likely yield excellent results.
Also, for drag racing with lower gears, the A/T 4 speeds would by far be the best way to go. The shift time in my A/T is lightning fast, much faster than any human being can shift, even legendary manual trans drag racer Ronnie Sox. manuals are far less than ideal for drag racing too(from a consistency standpoint), which is why so few purpose built drag cars are manuals.
There are a lot of things that are far less than ideal in the 928 suspension wrt drag racing, and making some suspension changes(like very soft rear coils that allowed a maximum weight transfer to the rear of the car, just for instance) and tire changes would likely yield excellent results.
Also, for drag racing with lower gears, the A/T 4 speeds would by far be the best way to go. The shift time in my A/T is lightning fast, much faster than any human being can shift, even legendary manual trans drag racer Ronnie Sox. manuals are far less than ideal for drag racing too(from a consistency standpoint), which is why so few purpose built drag cars are manuals.
Last edited by m21sniper; 11-16-2005 at 02:36 PM.
11-16-2005, 02:36 PM
#326
Race Car
Originally Posted by mark kibort
when the clutch goes in, there is no acceleration, because there is no force. yes, you can go from 1G of acceleration to , not only 0 G (of accelertion) but slighly negative (actually slowing down.) MK
Acceleration and deceleration have to slope. Enough to matter, probably not. A clutch 1/2 depressed may still be accelerating the car for an instant.
11-16-2005, 02:38 PM
#327
Thank you James, that is exactly what i was trying to say(In my own ham-fisted way, lol).
It is not an instantaneous transition from 1g to 0g(or whatever), but incremental. Even if you run dead square into a wall, or shoot a steel plate with a bullet, it's still not instantaneous, but incremental.
The times involved are extremely small, but it's still an incremental change.
It is not an instantaneous transition from 1g to 0g(or whatever), but incremental. Even if you run dead square into a wall, or shoot a steel plate with a bullet, it's still not instantaneous, but incremental.
The times involved are extremely small, but it's still an incremental change.
11-16-2005, 02:38 PM
#328
Captain Obvious
Super User
Super User
Originally Posted by m21sniper
Oh i do agree with that, all i'm saying is that it takes some time(probably measured in milliseconds) to transition from(for example) 1g positive acceleration to a nuetral or negative g state. Say you had a very accurate and fast acting G meter...As you pushed in the clutch it would not go instantly to zero, it would tick down(very quickly) from 1, .9, .8, .7, etc as the drag overcame the momentum of the vehicle.
Anyway, that's my understanding of it. If i'm wrong, it certainly won't be the first time....nor the last.
Of course none of this has anything to do with the actual purpose of this thread.
Anyway, that's my understanding of it. If i'm wrong, it certainly won't be the first time....nor the last.
Of course none of this has anything to do with the actual purpose of this thread.
11-16-2005, 02:49 PM
#330
Captain Obvious
Super User
Super User
Originally Posted by James-man
Well sort of. If you break up time into an infinite number of points, wouldn't you find it is impossible to instantly go positive acceleration to negative acceleration? It is a continuum isn't it? There is acceleration at an increasing rate, acceleration at a decreasing rate, no acceleration, deceleration at an increasing rate and decelerating at a decreasing rate.
Acceleration and deceleration have to slope. Enough to matter, probably not. A clutch 1/2 depressed may still be accelerating the car for an instant.
Acceleration and deceleration have to slope. Enough to matter, probably not. A clutch 1/2 depressed may still be accelerating the car for an instant.