Gear Ratio 2.20 -> 2.64 ROCKS!!!!!!!!!!!!!!!!!!!!!!
08-27-2008, 05:02 PM
#1
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Gear Ratio 2.20 -> 2.64 ROCKS!!!!!!!!!!!!!!!!!!!!!!
I recently swapped my 2.2 LSD 5-speed gearbox for a 2.64 LSD box from a 1989 S4 5spd ... and I LOVE the end result! I had been concerned that with my car's comparatively high hp/tq (naturally aspirated) I'd lose any value in 1st gear, but that has turned out to be no problem ... I can take off in 2nd under rolling stops (that has always been the case) but the car flies through the gears wonderfully. I maintain traction in 1st gear except on slightly slippery roads.
I have driven GT's and found their 2.73 ratio to be so aggressive as to be bothersome for me (4,000RPM at freeways speeds seems odd) but my car now sits neatly in the sweet torque band while cruising in 5th. I love it ... gonna test 0-60 acceleration as soon as I can. On a recent PCA drive, others commented on how much quicker the 928 now is
I have driven GT's and found their 2.73 ratio to be so aggressive as to be bothersome for me (4,000RPM at freeways speeds seems odd) but my car now sits neatly in the sweet torque band while cruising in 5th. I love it ... gonna test 0-60 acceleration as soon as I can. On a recent PCA drive, others commented on how much quicker the 928 now is
08-27-2008, 05:06 PM
#2
Administrator - "Tyson"
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Kibort making a 9 page post showing the effects (or lack there of) changing gear ratios in 5....4....3...2...1
I have a 2.64 auto if anyone is interested in upgrading their slushbox
EDIT - it's a 2.54 auto.....
I have a 2.64 auto if anyone is interested in upgrading their slushbox
EDIT - it's a 2.54 auto.....
Last edited by hacker-pschorr; 08-28-2008 at 01:26 AM.
08-27-2008, 05:24 PM
#3
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I can no longer easily exceed 145mph ... i think the "easy top speed" of the car has dropped by 10mph. That's the point at which the car no longer continues accelerating at or near the same rate, but "hits the wall" and would take a long time and more road to get much faster.
08-27-2008, 06:00 PM
#5
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Brian I bought a car ... which had one ... but didn't have many other things ... I think it's a shame it is so rare, it should be an option open to anyone.
I think it's a shame it is so rare, it should be an option open to anyone.
08-27-2008, 06:10 PM
#6
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This is my experience at this point ... the car accelerates very well through 1st gear and gets off the line nice and quickly ..
Once and for all let's get this straight....first gear in a 2:20 rear geared 928 is for ZERO to about 50 MPH ! Up to about 30 MPH the engine is running below 4,000 RPM so it is much down on power. Unless you slip the clutch the engine boggs down when the wheels stop spinning after the launch and the wheels slow down to match the speed of the car at which time the LONG SLOW pull up to redline approx 50 MPH Put in a lower final drive and you get through 1 st gear much faster and spend much less time below 4,000 Rpm and maximize the time above 4,000 RPM. Quick cars are measured from zero-50 mph , fast cars from 50-100 mph , and most 928s from 100-150 mph To understand the effect of gearing on acceleration you need only try a drag racing start by starting out in second gear ! To feel quick you need lower gears ... 0-40 MPH it is ALL about gearing ! Road racing where you seldom go slower than 40 MPH it is a very different discussion.
Put in a lower final drive and you get through 1 st gear much faster and spend much less time below 4,000 Rpm and maximize the time above 4,000 RPM. Quick cars are measured from zero-50 mph , fast cars from 50-100 mph , and most 928s from 100-150 mph To understand the effect of gearing on acceleration you need only try a drag racing start by starting out in second gear ! To feel quick you need lower gears ... 0-40 MPH it is ALL about gearing ! Road racing where you seldom go slower than 40 MPH it is a very different discussion.
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08-27-2008, 06:30 PM
#8
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Ok Folks,
Heinrich, Im glad you are fired up about the 2.64. I does change the sweetspot of acceleration in any of the 4-5 gears (depending on whether its an auto or not)
BUT, its the sweetspot change. remember, the fastest rate of acceleration will be at the greatest HP available. dont forget my tag line: acceleration = power/(mass x velocity)
In a nut shell, there will be trade offs with acceleration rates (for everything after the end of 1st gear which inself is a discusssion due to grip ) But, forget about drag racing, tires, grip, surface and technique, and the trade offs will yield no change over all the possible speed ranges. (also with exception to the top speed potential that could go down with the higher numerical ratio rear end )
As I have mentioned before. All you need to do is plot out your max speed in each gear. glance at a HP curve and see where you end up. find the spots you would like to have the max acceleration vs RPM ranges and see what gear box works best . while racing, you will want to be near max hp as much of the time as possible to yeild the most amount of potential acceleration from the engine.
personally, i love the 2.2, because i can use the gear box to cruise to the track in 5th gear and 80mph is only 2400rpm . When i drive Scots 2.75:1 , its neat because there is a lower first, traffic is easy to keep it in and out of 1st, and the rpms are higher in 2nd when cruising around city streets at a slow pace.
But, when you jump on 1st in my 2.2, it breaks loose in a straight line at 4500rpm violently with race rubber on. 2nd, no problem, and it takes you to 80mph, and 3rd to 115mph, while 4th goes to 155mph.
As you all might know the full reduction is not shown by the rear end numbers, as the internal gears are different as well. 2.72 gear boxes are only about 10% off compared to a 2.2, gear for gear with the exception of 5th while the numerical rear end change comparison is much different (greater than 20%)
Now, lugging around the freeway, if you are in most cities, the 2.2 finds you driving 65 mph between gears. 5th is lugging and 4th is too reving (i.e. 3.2:1) so, a 2.64 might solve part of this. and for max speed, redline might give you a shot at 180mph easier than with a 2.2 if you are down on HP compared to the stroker boys.
enjoy.
as a side note, my vet competitor did, what is equivilant to the 2.75 conversion from a 2.2. He is not ripping off any faster lap time, but on some turns, he comes out of them better being in the sweetspot of his HP range. However, he hasnt seen me with flat HP curve stroker yet Ill have near 100 more hp to put down in those previously deficient turns!
mk
Heinrich, Im glad you are fired up about the 2.64. I does change the sweetspot of acceleration in any of the 4-5 gears (depending on whether its an auto or not)
BUT, its the sweetspot change. remember, the fastest rate of acceleration will be at the greatest HP available. dont forget my tag line: acceleration = power/(mass x velocity)
In a nut shell, there will be trade offs with acceleration rates (for everything after the end of 1st gear which inself is a discusssion due to grip ) But, forget about drag racing, tires, grip, surface and technique, and the trade offs will yield no change over all the possible speed ranges. (also with exception to the top speed potential that could go down with the higher numerical ratio rear end )
As I have mentioned before. All you need to do is plot out your max speed in each gear. glance at a HP curve and see where you end up. find the spots you would like to have the max acceleration vs RPM ranges and see what gear box works best . while racing, you will want to be near max hp as much of the time as possible to yeild the most amount of potential acceleration from the engine.
personally, i love the 2.2, because i can use the gear box to cruise to the track in 5th gear and 80mph is only 2400rpm . When i drive Scots 2.75:1 , its neat because there is a lower first, traffic is easy to keep it in and out of 1st, and the rpms are higher in 2nd when cruising around city streets at a slow pace.
But, when you jump on 1st in my 2.2, it breaks loose in a straight line at 4500rpm violently with race rubber on. 2nd, no problem, and it takes you to 80mph, and 3rd to 115mph, while 4th goes to 155mph.
As you all might know the full reduction is not shown by the rear end numbers, as the internal gears are different as well. 2.72 gear boxes are only about 10% off compared to a 2.2, gear for gear with the exception of 5th while the numerical rear end change comparison is much different (greater than 20%)
Now, lugging around the freeway, if you are in most cities, the 2.2 finds you driving 65 mph between gears. 5th is lugging and 4th is too reving (i.e. 3.2:1) so, a 2.64 might solve part of this. and for max speed, redline might give you a shot at 180mph easier than with a 2.2 if you are down on HP compared to the stroker boys.
enjoy.
as a side note, my vet competitor did, what is equivilant to the 2.75 conversion from a 2.2. He is not ripping off any faster lap time, but on some turns, he comes out of them better being in the sweetspot of his HP range. However, he hasnt seen me with flat HP curve stroker yet
Ill have near 100 more hp to put down in those previously deficient turns! mk
08-27-2008, 06:32 PM
#9
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LOL Jim ... I think that if one forgets the inertia of a car from a dead standstill, then other theories work ... but first gear does the heavy lifting and it does so better in my new gearbox ... not to mention that the gears are shorter, and at any speed I've got more torque to the ground across the entire rev range :icon105:
08-27-2008, 06:41 PM
#11
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Jim is correct, if grip is not an issue. for most skilled drag racers, it would be an advantage. On all my world challenge starts, i rev the engine to 4k, (while my competitors are at redline) and let out the clutch. It becomes kind of a high loss gear box in a way. (remember, gears dont give hp, they just determine the effectiveness of applying that hp at any speed)
now, i dont believe that anyone can run a 300rwhp engine WOT in 1st gear and be hooked up, unless you have race rubber, and even then, you have to feather the gas to stay hooked up near max torque of the engine. with the lower gear now comes the shift trade off. we have ploted all the theoretical times for the 0-60mph runs with different gear boxes. aside from the launch advantage, there is little difference, as when you shift in to 2nd, a taller gear box would be applying higher hp until it had to shift and then the trade offs begin on each consecutive gear shift.
You want to know what you go, go to the website with the calculator and plug in the numbers and speeds you like to frequent. Usually, in Heinrich's case, its just a personal preference thing around town or on the hyway.
mk
Quote:
Originally Posted by Jim bailey - 928 International
Once and for all let's get this straight....first gear in a 2:20 rear geared 928 is for ZERO to about 50 MPH ! Up to about 30 MPH the engine is running below 4,000 RPM so it is much down on power. Unless you slip the clutch the engine boggs down when the wheels stop spinning after the launch and the wheels slow down to match the speed of the car at which time the LONG SLOW pull up to redline approx 50 MPH Put in a lower final drive and you get through 1 st gear much faster and spend much less time below 4,000 Rpm and maximize the time above 4,000 RPM. Quick cars are measured from zero-50 mph , fast cars from 50-100 mph , and most 928s from 100-150 mph To understand the effect of gearing on acceleration you need only try a drag racing start by starting out in second gear ! To feel quick you need lower gears ... 0-40 MPH it is ALL about gearing ! Road racing where you seldom go slower than 40 MPH it is a very different discussion.
now, i dont believe that anyone can run a 300rwhp engine WOT in 1st gear and be hooked up, unless you have race rubber, and even then, you have to feather the gas to stay hooked up near max torque of the engine. with the lower gear now comes the shift trade off. we have ploted all the theoretical times for the 0-60mph runs with different gear boxes. aside from the launch advantage, there is little difference, as when you shift in to 2nd, a taller gear box would be applying higher hp until it had to shift and then the trade offs begin on each consecutive gear shift.
You want to know what you go, go to the website with the calculator and plug in the numbers and speeds you like to frequent. Usually, in Heinrich's case, its just a personal preference thing around town or on the hyway.
mk
Quote:
Originally Posted by Jim bailey - 928 International
Once and for all let's get this straight....first gear in a 2:20 rear geared 928 is for ZERO to about 50 MPH ! Up to about 30 MPH the engine is running below 4,000 RPM so it is much down on power. Unless you slip the clutch the engine boggs down when the wheels stop spinning after the launch and the wheels slow down to match the speed of the car at which time the LONG SLOW pull up to redline approx 50 MPH Put in a lower final drive and you get through 1 st gear much faster and spend much less time below 4,000 Rpm and maximize the time above 4,000 RPM. Quick cars are measured from zero-50 mph , fast cars from 50-100 mph , and most 928s from 100-150 mph To understand the effect of gearing on acceleration you need only try a drag racing start by starting out in second gear ! To feel quick you need lower gears ... 0-40 MPH it is ALL about gearing ! Road racing where you seldom go slower than 40 MPH it is a very different discussion.
08-27-2008, 06:42 PM
#12
Nordschleife Master
You definitely need the LSD.. mine is open diff at the moment.
I have an LSD sitting in a box in my garage, along with a full gearbox gasket set - I just need a second 928 to drive so I can take mine off the road for a bunch of work on torque tube, rear suspension, transaxle etc.
08-27-2008, 06:46 PM
#13
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Besides first, (and launch, hook up issues) that would only be true if the gears were closer together (close ratio gear box) since most all of our 928s are near a .73 multiplier RPM drop, gear spacing (besides 5th) is near the same.
a great example of this is my car at road america. I can only get to 155mph which is redline in 4th gear based on 320rwhp. now with more hp on a stroker, I will be a sitting duck for any car with a 2.72:1 rear end. Anderson did this for a few years and put down a 2:24, but now with his additional HP and his aero, his package running on a 2.72 gets him down to 2:18s. (some due to the power, and some due to the 2.72 giving him the ability to put down power from 155mph to 165mph)
a great example of this is my car at road america. I can only get to 155mph which is redline in 4th gear based on 320rwhp. now with more hp on a stroker, I will be a sitting duck for any car with a 2.72:1 rear end. Anderson did this for a few years and put down a 2:24, but now with his additional HP and his aero, his package running on a 2.72 gets him down to 2:18s. (some due to the power, and some due to the 2.72 giving him the ability to put down power from 155mph to 165mph)
LOL Jim ... I think that if one forgets the inertia of a car from a dead standstill, then other theories work ... but first gear does the heavy lifting and it does so better in my new gearbox ... not to mention that the gears are shorter, and at any speed I've got more torque to the ground across the entire rev range :icon105:
08-27-2008, 06:49 PM
#15
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