3.09 ring & pinion
11-06-2005, 01:30 PM
#76
Rennlist Member
Interestingly, remember the moster RS6 audi, in speedGT??? with 550+hp and 4x4 it had some interesting ratios. in fact, it had the 3.09 bolted on a stock S4 equivilant, but with one extra gear(it was a 6 speed) it would have a deeper
15.4:1 1st
8.4 2nd
5.8 3rd
4.35 4th
3.53 5th
3.0 6th.
all of these gears are close to what you are talking about. remember the gap on the S4 box between 4th to 5th that still is a big jump with a 3.09? well, the Audi puts in gear to make it a 6 speed to fix the problem. AND, the max speed issue is solved with an engine that can go to 7000rpm (making the top speed more like the 2.64 box) AND the 1st gear useablilty issue is solved with a 550hp engine driving 4 305x35x18s (by the way, there is a 3% taller difference vs a 275x35x18)
so, it can drive all 4 wheels out of the hole with race rubber! Thats why those cars would just lurch to the front, no matter where they were in the grid.
All of these things of the audi, using an equivilant gear set (sans the 4-5th gear stuck in there to make the 6speed) are different compared to the 928. (ie 2 wheel drive, 200 less hp , and 800less rpms to play with)
this is a top pro team that could have used any set of ratios.
If you look at the GT3 porsche cup car, their gear sets are close to the s4, except they put 2 more gears in the usable range, so it is a very close ratio set, putting max hp to the wheels almost 8% more of the time!
Just a little more real life perspective put on the subject.
MK
15.4:1 1st
8.4 2nd
5.8 3rd
4.35 4th
3.53 5th
3.0 6th.
all of these gears are close to what you are talking about. remember the gap on the S4 box between 4th to 5th that still is a big jump with a 3.09? well, the Audi puts in gear to make it a 6 speed to fix the problem. AND, the max speed issue is solved with an engine that can go to 7000rpm (making the top speed more like the 2.64 box) AND the 1st gear useablilty issue is solved with a 550hp engine driving 4 305x35x18s (by the way, there is a 3% taller difference vs a 275x35x18)
so, it can drive all 4 wheels out of the hole with race rubber! Thats why those cars would just lurch to the front, no matter where they were in the grid.
All of these things of the audi, using an equivilant gear set (sans the 4-5th gear stuck in there to make the 6speed) are different compared to the 928. (ie 2 wheel drive, 200 less hp , and 800less rpms to play with)
this is a top pro team that could have used any set of ratios.
If you look at the GT3 porsche cup car, their gear sets are close to the s4, except they put 2 more gears in the usable range, so it is a very close ratio set, putting max hp to the wheels almost 8% more of the time!
Just a little more real life perspective put on the subject.
MK
11-06-2005, 02:48 PM
#77
Nordschleife Master
Mark,
I think the relationship that you overlook in this is how the final drive ratio changes the relationship between engine rotational speed and ground speed.
Whatever the final drive, the gear ratios do have the same proportionate relationship. It's the relationship to ground speed that has changed. All 5 power peaks are at low velocities and are at closer velocities. This means the street-driven car is more likely to be near one when that fun-time urge hits. With more force to the pavement, the car accelerates more. There's no imagining it.
I wish I had a decent version of Excel at home. Then I could create an automated tool to illustrate all of this.
I think the relationship that you overlook in this is how the final drive ratio changes the relationship between engine rotational speed and ground speed.
Whatever the final drive, the gear ratios do have the same proportionate relationship. It's the relationship to ground speed that has changed. All 5 power peaks are at low velocities and are at closer velocities. This means the street-driven car is more likely to be near one when that fun-time urge hits. With more force to the pavement, the car accelerates more. There's no imagining it.
I wish I had a decent version of Excel at home. Then I could create an automated tool to illustrate all of this.
11-06-2005, 06:56 PM
#79
Drifting
This stuff makes my head hurt. All I can say is, doesn't a person on a bicycle pedaling up hill make a good analogy for this discussion. Using 1st gear on a 21 speed bike will get you moving better than starting in 5th, using the same powerplant (the bike rider)
Adding gears to a gearbox and starting lower would make the car accelrate much faster because the engine (bike rider) can pedal fastest when geared properly. The top end might be the same but the lower geared bike/car will get to it much faster.
Adding gears to a gearbox and starting lower would make the car accelrate much faster because the engine (bike rider) can pedal fastest when geared properly. The top end might be the same but the lower geared bike/car will get to it much faster.
11-06-2005, 06:56 PM
#80
Sounds like the Audi has the box that lots of us would like. The recent comparison of the Ferrari 308 to the 928 in Hemmings Exotics shows the 308 topping out at the 140 MPH range with a close gearset. The Audi, with an astounding 15.4 to 1 first gear has an equally astounding 500 HP, and yet they don't consider it needs a steeper first. Most drivers on the street would probably shift into second almost immediately. Most of the time that is.
Attending the NY, NJ fun run today, I got to witness a Noble M400 in action. Even with the engine right over the rear wheels, the driver was able to put the car sideways in first at will. One of the new Caddilacs was also present. Tire squeal and rapid acceleration from a standstill. An 83 Porsche 911 with a built engine had to hit about 20 MPH before anything happened in first, but the new Porsches hook up hard from a standstill. Clearly a modern trend.
From what I am gathering, closer gearing gives closer incremental increases in leverage. Wider spaces between the gears can be partially offset by a broader torque curve. I will assume however, that if a 15 to 1 first will work for a 500 hp car, it will work for a 928. From everything I am gathering, the only loss to a street 928 with a 3.06 final drive is the loss of a sixth gear with high overdrive.
However, after talking to Carl F at frenzy, it sounds like a twin screw supercharger will broaden the torque curve while signifigantly increasing it over the whole range. Balance is the key. A big fat torque curve would overcome the lack of useful increase one would get from a 3.06 in a rolling start, as well as mate the engine to the current gearing off the line. But the 3.06 would reduce overall stress on the driveline and the SC signifigantly increase it. All for fun of course.
Attending the NY, NJ fun run today, I got to witness a Noble M400 in action. Even with the engine right over the rear wheels, the driver was able to put the car sideways in first at will. One of the new Caddilacs was also present. Tire squeal and rapid acceleration from a standstill. An 83 Porsche 911 with a built engine had to hit about 20 MPH before anything happened in first, but the new Porsches hook up hard from a standstill. Clearly a modern trend.
From what I am gathering, closer gearing gives closer incremental increases in leverage. Wider spaces between the gears can be partially offset by a broader torque curve. I will assume however, that if a 15 to 1 first will work for a 500 hp car, it will work for a 928. From everything I am gathering, the only loss to a street 928 with a 3.06 final drive is the loss of a sixth gear with high overdrive.
However, after talking to Carl F at frenzy, it sounds like a twin screw supercharger will broaden the torque curve while signifigantly increasing it over the whole range. Balance is the key. A big fat torque curve would overcome the lack of useful increase one would get from a 3.06 in a rolling start, as well as mate the engine to the current gearing off the line. But the 3.06 would reduce overall stress on the driveline and the SC signifigantly increase it. All for fun of course.
11-06-2005, 11:01 PM
#81
Burning Brakes
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i think the bicycle comparison is a little flawed because you don't spin the tires much. the problem with the really low 1st is you just light them up on the start and to 25mhp or so, then you let off the gas, shift, then light them up again shifting to second. with the normal 1st, you light them up a little at the start, then your good to 50 mhp or so. wouldn't it appear then, that the stockl geared car would be faster to 50? this is assuming street tires.
11-06-2005, 11:07 PM
#82
Rennlist Member
Glen, im frustrated that maybe even you are not getting the message. I am not over looking anything . ive made it as clear as possible that the gear ratio set that make up the gear box, are a system. think of each gear as an independent ratio, rather than its numerical name. (ie 1st, 2nd , 3rd ) if you do do this you may break the code here. its pretty darn simple and i know you are a smart guy. the final drive does nothing more than shift the entire set of ratios up or down by a proprotionate %. read heinrich's post, it couldnt be more simple than that. all im TALKING about is the engines rotational speed and the vehichle speed relationship. you are fighing my fight here!
why do you think i talk about the 2.2 having a 118mph 3rd gear max rpm, while the 3.09 would have the same 118mph 4th gear, and 3rd would be 2nd, 2nd would be 1st and the new lowest and only difference would be the ".5" sub 1st gear as i call it, maxing out the rpms at near 25mph. if you notice, ALL i do is compare the rpms to the vehicle speed.
By NO means do the power peaks get closer together. since all the gear changes of our 928 gear boxes have a 73% rpm drop, (WHICH IS THE SPACING) this will not change by getting a 3.09 vs anything stock in the ring and pinion. THE ONLY thing that changes, is that you do get an additional "power peak" as you say, in the new 3.09 first gear, at 25mph. the rest of the power peaks are identical why, the 3.09 vs the 2.75 or 2.2 just creates enough of a shift that almost matches the 928 transmission spacing.
trust me. do the ratio vs speed vs rpms match it is painfully clear.
what are you really trying to say here? (below)
let me private email you the excel spreadsheet. its totally automated and gives all the speeds and rpms for any gear ratio combination.
if anyone wants the spreadsheet, it will help tremendously!!!!!!!!!
email me at mkibort@compuserve.com
Mk
why do you think i talk about the 2.2 having a 118mph 3rd gear max rpm, while the 3.09 would have the same 118mph 4th gear, and 3rd would be 2nd, 2nd would be 1st and the new lowest and only difference would be the ".5" sub 1st gear as i call it, maxing out the rpms at near 25mph. if you notice, ALL i do is compare the rpms to the vehicle speed.
By NO means do the power peaks get closer together. since all the gear changes of our 928 gear boxes have a 73% rpm drop, (WHICH IS THE SPACING) this will not change by getting a 3.09 vs anything stock in the ring and pinion. THE ONLY thing that changes, is that you do get an additional "power peak" as you say, in the new 3.09 first gear, at 25mph. the rest of the power peaks are identical why, the 3.09 vs the 2.75 or 2.2 just creates enough of a shift that almost matches the 928 transmission spacing.
trust me. do the ratio vs speed vs rpms match it is painfully clear.
what are you really trying to say here? (below)
let me private email you the excel spreadsheet. its totally automated and gives all the speeds and rpms for any gear ratio combination.
if anyone wants the spreadsheet, it will help tremendously!!!!!!!!!
email me at mkibort@compuserve.com
Mk
Originally Posted by GlenL
Mark,
I think the relationship that you overlook in this is how the final drive ratio changes the relationship between engine rotational speed and ground speed.
Whatever the final drive, the gear ratios do have the same proportionate relationship. It's the relationship to ground speed that has changed. All 5 power peaks are at low velocities and are at closer velocities. This means the street-driven car is more likely to be near one when that fun-time urge hits. With more force to the pavement, the car accelerates more. There's no imagining it.
I wish I had a decent version of Excel at home. Then I could create an automated tool to illustrate all of this.
I think the relationship that you overlook in this is how the final drive ratio changes the relationship between engine rotational speed and ground speed.
Whatever the final drive, the gear ratios do have the same proportionate relationship. It's the relationship to ground speed that has changed. All 5 power peaks are at low velocities and are at closer velocities. This means the street-driven car is more likely to be near one when that fun-time urge hits. With more force to the pavement, the car accelerates more. There's no imagining it.
I wish I had a decent version of Excel at home. Then I could create an automated tool to illustrate all of this.
11-06-2005, 11:15 PM
#83
Rennlist Member
exactly. the bike comparison is flawed for that reason. remember, we are only talking about stuffing an extra low super 1st gear (if you will) then the rest of the gears are the same. the problem that most are having here,is they are too darn caught up in the gear designators. folks, if two boxes have the same ratios from 1st to 5th and one has the same rations from 2nd to 6th. they are same and will accelerate the same in every gear EXCEPT the one box with the extra low first gear. Now,i did some testing with the Holbert car today, I got to tell you, i have a hard time putting down 320 rear wheel hp with 335x30x18 tires sticky tires in a stock 2.2 S4 rear end. it launches hard and burns rubber very easily. this means , you are above the coefficient of friction of the tires. having even more torque, would just make the problem worse, plus, you have .2 seconds lost to an extra mechanical shift, unless you speed shift.
i also ran the car up to about 20mph and then floored it straight, it just lit up the tires and i looked in the rear view mirror and saw two beautiful 13" wide big black streaks for about 20feet.
Mk
i also ran the car up to about 20mph and then floored it straight, it just lit up the tires and i looked in the rear view mirror and saw two beautiful 13" wide big black streaks for about 20feet.
Mk
Originally Posted by jyoon
i think the bicycle comparison is a little flawed because you don't spin the tires much. the problem with the really low 1st is you just light them up on the start and to 25mhp or so, then you let off the gas, shift, then light them up again shifting to second. with the normal 1st, you light them up a little at the start, then your good to 50 mhp or so. wouldn't it appear then, that the stockl geared car would be faster to 50? this is assuming street tires.
11-06-2005, 11:27 PM
#84
Rennlist Member
the reason the 550hp audi can use the 15:1 1st, is due to 305s on all 4 corners. do you get that this strategy is for a launch, and nothing more they get to jump out of the start, and within 10mph are in to the "normal" 1st gear type ratio . without 4x4, it would just be an exersize in wheel spin. this is the main reason that the 997 porsche GT3 cup cars dont even have this kind of ratio in 1st. ( 10:1 range) this racer does MORE standing starts than ANY other model in the world. its all about effective gearing for the start. the rest is optimizing the gear ratios for most tracks. as i have said , that is to allow for the most amount of HP to the wheels over the operational range of speeds.
dont get me started about "broader " torque curves.. this is near to meaningless. its all about the shape of the HP curve up top, over a range of 4500 to 6400rpm.(the gear spacing of a 928 regardless of the ring and pinion)
since max torque happens at 4000rpm and falls from there, you can see that since you are operating from 4500 to redline, that torque will fall off slowely and this is how HP continues to rise. when torque is flat, HP is rising at a 45 degree angle. when torque falls at a 45 degree angle, HP is flat . you want the most hp to the wheels over the range of rpms . this is why you shift at over max HP to get the average hp to be as high as possible.
Mk
dont get me started about "broader " torque curves.. this is near to meaningless. its all about the shape of the HP curve up top, over a range of 4500 to 6400rpm.(the gear spacing of a 928 regardless of the ring and pinion)
since max torque happens at 4000rpm and falls from there, you can see that since you are operating from 4500 to redline, that torque will fall off slowely and this is how HP continues to rise. when torque is flat, HP is rising at a 45 degree angle. when torque falls at a 45 degree angle, HP is flat . you want the most hp to the wheels over the range of rpms . this is why you shift at over max HP to get the average hp to be as high as possible.
Mk
Originally Posted by Daniel Dudley
Sounds like the Audi has the box that lots of us would like. The recent comparison of the Ferrari 308 to the 928 in Hemmings Exotics shows the 308 topping out at the 140 MPH range with a close gearset. The Audi, with an astounding 15.4 to 1 first gear has an equally astounding 500 HP, and yet they don't consider it needs a steeper first. Most drivers on the street would probably shift into second almost immediately. Most of the time that is.
Attending the NY, NJ fun run today, I got to witness a Noble M400 in action. Even with the engine right over the rear wheels, the driver was able to put the car sideways in first at will. One of the new Caddilacs was also present. Tire squeal and rapid acceleration from a standstill. An 83 Porsche 911 with a built engine had to hit about 20 MPH before anything happened in first, but the new Porsches hook up hard from a standstill. Clearly a modern trend.
From what I am gathering, closer gearing gives closer incremental increases in leverage. Wider spaces between the gears can be partially offset by a broader torque curve. I will assume however, that if a 15 to 1 first will work for a 500 hp car, it will work for a 928. From everything I am gathering, the only loss to a street 928 with a 3.06 final drive is the loss of a sixth gear with high overdrive.
However, after talking to Carl F at frenzy, it sounds like a twin screw supercharger will broaden the torque curve while signifigantly increasing it over the whole range. Balance is the key. A big fat torque curve would overcome the lack of useful increase one would get from a 3.06 in a rolling start, as well as mate the engine to the current gearing off the line. But the 3.06 would reduce overall stress on the driveline and the SC signifigantly increase it. All for fun of course.
Attending the NY, NJ fun run today, I got to witness a Noble M400 in action. Even with the engine right over the rear wheels, the driver was able to put the car sideways in first at will. One of the new Caddilacs was also present. Tire squeal and rapid acceleration from a standstill. An 83 Porsche 911 with a built engine had to hit about 20 MPH before anything happened in first, but the new Porsches hook up hard from a standstill. Clearly a modern trend.
From what I am gathering, closer gearing gives closer incremental increases in leverage. Wider spaces between the gears can be partially offset by a broader torque curve. I will assume however, that if a 15 to 1 first will work for a 500 hp car, it will work for a 928. From everything I am gathering, the only loss to a street 928 with a 3.06 final drive is the loss of a sixth gear with high overdrive.
However, after talking to Carl F at frenzy, it sounds like a twin screw supercharger will broaden the torque curve while signifigantly increasing it over the whole range. Balance is the key. A big fat torque curve would overcome the lack of useful increase one would get from a 3.06 in a rolling start, as well as mate the engine to the current gearing off the line. But the 3.06 would reduce overall stress on the driveline and the SC signifigantly increase it. All for fun of course.
11-07-2005, 07:19 AM
#85
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one of the questions you should ask yourself on this topic, is why porsche didnt ALWAYS change the transmission ratio as well as the rear end ring and pinion! they always did, because they knew that some of these radical changes in rear end, would do nothing but remove a 5th gear and give a very low 1st gear that would not be of any use for 99% of most drivers, especially on how most folks dont spend much time in 1st gear anyway.
Change the rear and all the gears to get the same result, think not.
They produced the 2:20 for fuel economy in the US.
11-07-2005, 10:12 AM
#86
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Since most street driven 928's are automatics, and automatics (with a seperate ring and pinion), are the most likely candidate for a FDR change, why is the discussion limited to manual transmissions? Wouldn't there be some differences ? Any worth considering?
11-07-2005, 10:39 AM
#87
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Lex,
Not to get dragged into the gearing issues, but the steeper 3.09's will allow quicker acceleration from a dead stop at launch (0-60 or drag racing 1/4 mile). For that purpose there is a benefit IF you have the traction available to make use of that gearing with a hard launch. The advantage off the line will translate to a ET advantage for short distances (1/4 mile or less), but for longer distances you would eventually get "run down" and caught/passed. There will be a loss of top end speed, but here in LI, NY not really an issue.
Now, if you were into roadracing, then the advantages/disadvantages would be dependant on the track you are on.
Hope that helps.
Jim
Not to get dragged into the gearing issues, but the steeper 3.09's will allow quicker acceleration from a dead stop at launch (0-60 or drag racing 1/4 mile). For that purpose there is a benefit IF you have the traction available to make use of that gearing with a hard launch. The advantage off the line will translate to a ET advantage for short distances (1/4 mile or less), but for longer distances you would eventually get "run down" and caught/passed. There will be a loss of top end speed, but here in LI, NY not really an issue.
Now, if you were into roadracing, then the advantages/disadvantages would be dependant on the track you are on.
Hope that helps.
Jim
11-07-2005, 10:53 AM
#88
Rennlist Member
Thread Starter
"why is the discussion limited to manual transmissions?"
EXACTLY. It wasn't in the beginning. The idea of the gear change was originally intended for street driven cars, manual or auto, for the purpose of some extra kick for fun driving. Then Kibort decided to save us from ourselves & changed the thread to manual trans track driving. I don't give a **** what it does coming out of turn nine at Riverside! Personally, what I want the gears for is TOTALLY irrelevant to what he keeps rambling on about. He complains about it taking "30 to 300 pages" on this list. Look at the posts. More than half of the lines are his! Nobody asked you to change your gears Mark. Members on the list that have these gears all said there is no doubt about experiencing more snap during acceleration. You keep trying to convince them that it's their imagination. Try the decaf!
Hammer
EXACTLY. It wasn't in the beginning. The idea of the gear change was originally intended for street driven cars, manual or auto, for the purpose of some extra kick for fun driving. Then Kibort decided to save us from ourselves & changed the thread to manual trans track driving. I don't give a **** what it does coming out of turn nine at Riverside! Personally, what I want the gears for is TOTALLY irrelevant to what he keeps rambling on about. He complains about it taking "30 to 300 pages" on this list. Look at the posts. More than half of the lines are his! Nobody asked you to change your gears Mark. Members on the list that have these gears all said there is no doubt about experiencing more snap during acceleration. You keep trying to convince them that it's their imagination. Try the decaf!
Hammer
11-07-2005, 11:12 AM
#89
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i would agree the 3.09 would probably be alot of fun on the street as you could lay rubber pretty easily. but i don't think it's gonna get you anywhere faster. so whatever one prefers i guess. one other thing to consider, it's quite an expensive mod for no real performance gain.
