2.73 Ring and Pinion in G28/11
08-17-2015, 01:55 PM
#31
Rennlist Member
If you dont understand the concepts... think about this:
two cars one 2.75 and the other 2.2:1
topspeed in 1st 50mph vs 55mph.....
topspeed in 2nd 75 mph vs 80mph.
just racing to 80mph, the 2.2:1 has a HUGE advantage. it loses from 0-50mph with a 10% loss in torque to the rear wheels.... BUT, from 50-55mph it has a 30% advantage!!!!!!! then its down 10% to 75mph, but then 30% advantage to 80mph.... in the end, the 2.2 is faster , PERIOD. Now, find a speed somewhere in the middle of both, and they even out, OR, you can find a speed where the 2.75 wins too.. Like to 105mph where the 2.75 redlines in 3rd.
see how that works? its a series of trade offs!!
gearing DOESNT make HP it only optimizes the power available for the speed ranged used.
the smart racers get this... the ones that believe all the misconception about gearing, dont. someone that gets this at the race track, always seems to finish ahead of a equal competitor. the differences are slight, but just enough to make a pass at the end of a straight, going into the braking zone!
and dont forget about that little punch that the 2.2 can make at the race track in 1st gear ,where the 2.75 would never be able to use 1st. turn 11 at laguna seca, on occasion i will use 1st in traffic to get a jump on cars exiting the turn. others with lower gearing cant do this and every little bit helps... COSMO, this is where the 2.2 actually gives MORE gears to be used than a 2.75.... get it????
two cars one 2.75 and the other 2.2:1
topspeed in 1st 50mph vs 55mph.....
topspeed in 2nd 75 mph vs 80mph.
just racing to 80mph, the 2.2:1 has a HUGE advantage. it loses from 0-50mph with a 10% loss in torque to the rear wheels.... BUT, from 50-55mph it has a 30% advantage!!!!!!! then its down 10% to 75mph, but then 30% advantage to 80mph.... in the end, the 2.2 is faster , PERIOD. Now, find a speed somewhere in the middle of both, and they even out, OR, you can find a speed where the 2.75 wins too.. Like to 105mph where the 2.75 redlines in 3rd.
see how that works? its a series of trade offs!!
gearing DOESNT make HP it only optimizes the power available for the speed ranged used.
the smart racers get this... the ones that believe all the misconception about gearing, dont. someone that gets this at the race track, always seems to finish ahead of a equal competitor. the differences are slight, but just enough to make a pass at the end of a straight, going into the braking zone!
and dont forget about that little punch that the 2.2 can make at the race track in 1st gear ,where the 2.75 would never be able to use 1st. turn 11 at laguna seca, on occasion i will use 1st in traffic to get a jump on cars exiting the turn. others with lower gearing cant do this and every little bit helps... COSMO, this is where the 2.2 actually gives MORE gears to be used than a 2.75.... get it????
08-17-2015, 02:28 PM
#32
Rennlist Member
I get it Mark on that track and that situation. But I understand Laguna is a pretty fast track that lends itself to taller gearing. A track where you top out at say 120 mph and more technical would be better with a lower final ratio. I am not confused with individual gear ratios and final ratios I know the difference.
Your drag race argument to 80 mph, convenient you pick a speed where the 2.2 redlines and doesn't need to shift again. Again series of tradeoffs. But if your overall theory is true all cars set up for drag racing would have taller final gears. I would like to see you argue this point to the Mustang drag racing crowd that pull out their 3.08 rear end gears and throw in 4.11's and some even do 4.56's. Convince them that their 3.08's will give them a better 1/4 mile et, they will laugh at you hysterically! And they put lower rear and gears in the 928GT to make it slower than an S4? C'mon man...
Repeat after me: lower gearing allows a vehicle to accelerate more quickly from a standing start.
Your drag race argument to 80 mph, convenient you pick a speed where the 2.2 redlines and doesn't need to shift again. Again series of tradeoffs. But if your overall theory is true all cars set up for drag racing would have taller final gears. I would like to see you argue this point to the Mustang drag racing crowd that pull out their 3.08 rear end gears and throw in 4.11's and some even do 4.56's. Convince them that their 3.08's will give them a better 1/4 mile et, they will laugh at you hysterically! And they put lower rear and gears in the 928GT to make it slower than an S4? C'mon man...
Repeat after me: lower gearing allows a vehicle to accelerate more quickly from a standing start.
08-17-2015, 04:04 PM
#33
Nordschleife Master
No. You did. Infinity.
I'm not talking about that. I'm responding to your comments about what I posted.
That's what I did and with explicit gearboxes since you can't reasonably put a 2.73 into a later box.
It all depends on what the goals are and where the yardsticks are placed. It always depends.
Oh, for christ's sake. Not this again. Your understanding isn't "unique" it's skewed and myopic. The only thing that accelerates a car is force on the pavement. (Or going downhill.) "Power at speed" is force and that's it. The gears multiply torque. That's what gears do.
I'm not talking about that. I'm responding to your comments about what I posted.
That's what I did and with explicit gearboxes since you can't reasonably put a 2.73 into a later box.
It all depends on what the goals are and where the yardsticks are placed. It always depends.
Oh, for christ's sake. Not this again. Your understanding isn't "unique" it's skewed and myopic. The only thing that accelerates a car is force on the pavement. (Or going downhill.) "Power at speed" is force and that's it. The gears multiply torque. That's what gears do.
08-17-2015, 04:10 PM
#34
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First fuel economy with your gas prices! At the time being it is about half of what we are used to. During the days when the 928 was produced I recall it was about a quarter of what we had. I really cannot see a measurable difference in fuel economy if you are running a 2.20 or 2.73 rear end. It is the way you drive which is crucial. The same goes for emissions, you have always had catalysts - right? All my cars -85, -87 and -91 do not have catalysts.
Noise at highway speed, if you want to drive a silent car you should not drive a 928. OK my newest car is a little better insulated and therefore having a slightly lower noise level than the other cars. First time I was over there I was shocked of how slow traffic moved on your highways, usually around 55 mph, it was upstate New York in 1994. Understand your limits have changed to 65 or 70 mph which is much slower than 120 to 150 mph which people usually drive on the Autobahn when allowed by the traffic. Early Sunday morning is the best time for high speed driving. We all know the noise level at 120 mph is much, much higher that at 60 mph.
I have never been driving a 928 having a 2.20 rear end but I imagine the car will never go to 6000+ rpm in 5th gear, there is simply not enough power. A good supercharger kit will do the difference.
Regarding the special US-version of the M3 I have been told BMW considered the US-market was not ready for a high revving sporty limousine in those days.
Åke
Last edited by Strosek Ultra; 08-18-2015 at 04:50 AM.
08-17-2015, 05:00 PM
#35
Rennlist Member
Ken, I fully agree with your priority.
First fuel economy with your gas prices! At the time being it is about half of what we are used to. During the days when the 928 was produced I recall it was about a quarter of what we had. I really cannot see a measurable difference in fuel economy if you are running a 2.20 or 2.73 rear end.
First fuel economy with your gas prices! At the time being it is about half of what we are used to. During the days when the 928 was produced I recall it was about a quarter of what we had. I really cannot see a measurable difference in fuel economy if you are running a 2.20 or 2.73 rear end.
08-17-2015, 06:10 PM
#36
Rennlist Member
I get it Mark on that track and that situation. But I understand Laguna is a pretty fast track that lends itself to taller gearing. A track where you top out at say 120 mph and more technical would be better with a lower final ratio. I am not confused with individual gear ratios and final ratios I know the difference.
Your drag race argument to 80 mph, convenient you pick a speed where the 2.2 redlines and doesn't need to shift again. Again series of tradeoffs. But if your overall theory is true all cars set up for drag racing would have taller final gears. I would like to see you argue this point to the Mustang drag racing crowd that pull out their 3.08 rear end gears and throw in 4.11's and some even do 4.56's. Convince them that their 3.08's will give them a better 1/4 mile et, they will laugh at you hysterically! And they put lower rear and gears in the 928GT to make it slower than an S4? C'mon man...
Repeat after me: lower gearing allows a vehicle to accelerate more quickly from a standing start.
Your drag race argument to 80 mph, convenient you pick a speed where the 2.2 redlines and doesn't need to shift again. Again series of tradeoffs. But if your overall theory is true all cars set up for drag racing would have taller final gears. I would like to see you argue this point to the Mustang drag racing crowd that pull out their 3.08 rear end gears and throw in 4.11's and some even do 4.56's. Convince them that their 3.08's will give them a better 1/4 mile et, they will laugh at you hysterically! And they put lower rear and gears in the 928GT to make it slower than an S4? C'mon man...
Repeat after me: lower gearing allows a vehicle to accelerate more quickly from a standing start.
now, gearing with drag racers..... same reigns true!! this is simple stuff ted. just plug the gear ratos and hp into the simulartors and you will get the same answers..... lots of confusion and blame of this on gearing in the race world... go talk to the top pros.... they willl agree.... power, grip and mechanical factors , as well as transmission ratios, determine the final drive. you think the mustang that has 400hp uses the same gear ratios as the one that puts out 800hp with a blower? think again
the 928 GT is only slightly faster, and its not due to the gear box change.....its due to 330hp vs the stock S4 at 312hp.
again, the target speed range is what you need to look at..... you miss the point if you can argue mine about racing to a convenient speed. I did that for a reason. 80mph will favor the 2.2..... 100mph will favor the 2.75... add a shift and the same things happens. where ever you redline, if that speed is where you want to be, then thats the best gear box for that drag race or straight on a road course..(generally... and certainly a great place to start). caveats might be lots of slower straights that require a differnet gear that doesnt get to redline...... So you have to weigh out what gear box gives the best HP-seconds!
Also, lower gearing doesnt always give you the best standing start... trust me on this plenty of care is made to find that gear and it always IS NOT the lowest gear posssible. you have to look at power, clutch capabilities, and grip coefficient. remember, you have to look at slip percentages and figure out launch forces, shift time, etc.... again, its a series of trade offs and you need to analyse.... do yourself a favor, get any drag simulator and plug in some numbers .. they are very good and will be very good at making my points here a reality for you.
anderson saw it at willow springs . (no time change going from 2.2 to 2.72) and i did this with scots car with the same HP as my old 290rwhp racer, at laguna. 2.2 vs 2.75... no time increase or decrease... the only thing i notices was more shifting in in opportune spots on the track. (mark anderson said this too. )
Last edited by mark kibort; 08-17-2015 at 06:29 PM.
08-17-2015, 06:26 PM
#37
Rennlist Member
No. You did. Infinity.
I'm not talking about that. I'm responding to your comments about what I posted.
That's what I did and with explicit gearboxes since you can't reasonably put a 2.73 into a later box.
It all depends on what the goals are and where the yardsticks are placed. It always depends.
Oh, for christ's sake. Not this again. Your understanding isn't "unique" it's skewed and myopic. The only thing that accelerates a car is force on the pavement. (Or going downhill.) "Power at speed" is force and that's it. The gears multiply torque. That's what gears do.
I'm not talking about that. I'm responding to your comments about what I posted.
That's what I did and with explicit gearboxes since you can't reasonably put a 2.73 into a later box.
It all depends on what the goals are and where the yardsticks are placed. It always depends.
Oh, for christ's sake. Not this again. Your understanding isn't "unique" it's skewed and myopic. The only thing that accelerates a car is force on the pavement. (Or going downhill.) "Power at speed" is force and that's it. The gears multiply torque. That's what gears do.
yes, force accelerates the car and that force is determined by how much power you can utilze from the engine. power is the rate of change of KE, its that simple. and yes, power at a speed will be a force. gears multipy the engine torque, but at any speed, because there is a torque/HP curve, it wont be optimal at any speed. SO....... you need a gear box to optimize it. Lets face it Glen, if we could, we would have INIFINITE gear ratios (aka IVT) and the car would instantly run to max power and have gear ratio for each speed interval to keep the engine at max power. gear boxes try to get as close to this as possible. close ratios are the next best thing and choosing the best set of ratios with fixed spacing (the discussion here) is the next best after that.
a 2.75 vs a 2.2 is a choice made for a track and a 2.75 not good for all conditions purposes. driver ability, hp of car, target speeds, tires, all determine what gear ratio will work best.
my understanding its not "skewed" it's true to the LAW!
acceleration = power/(mass x velocity) this is a Newtonian identity! it says that acceleration is proportional to power!!
Its short sighted to think that a lower gear box is better for all conditions. even keeping things in the "force" realm.... the trust curves are clear as well and are analogous and proportional.
If you "love" your 2.75, its because you "love" the speed range you are now attached to. its not true for all speed ranges, tracks, or uses.
again, gear boxes are just HP utilizers for any application.
08-17-2015, 08:46 PM
#38
Rennlist Member
Actually laguna seca has top speeds of near 120mph for most of the race groups, so the 2.2 gearing is pretty optimal . there is also a though that goes into this on how much HP you want to extract...... in otherwords, if you really want to use all of the HP available, the 2.2 is the most optimal.. ONLY at 330 to 375rwhp.... then any more hp and its starts to shift to the 2.75..... this is the point i was trying to make... it depends!! more clearly, it depends on the target speed ranges your driving and power are able to achieve.
now, gearing with drag racers..... same reigns true!! this is simple stuff ted. just plug the gear ratos and hp into the simulartors and you will get the same answers..... lots of confusion and blame of this on gearing in the race world... go talk to the top pros.... they willl agree.... power, grip and mechanical factors , as well as transmission ratios, determine the final drive. you think the mustang that has 400hp uses the same gear ratios as the one that puts out 800hp with a blower? think again
the 928 GT is only slightly faster, and its not due to the gear box change.....its due to 330hp vs the stock S4 at 312hp.
again, the target speed range is what you need to look at..... you miss the point if you can argue mine about racing to a convenient speed. I did that for a reason. 80mph will favor the 2.2..... 100mph will favor the 2.75... add a shift and the same things happens. where ever you redline, if that speed is where you want to be, then thats the best gear box for that drag race or straight on a road course..(generally... and certainly a great place to start). caveats might be lots of slower straights that require a differnet gear that doesnt get to redline...... So you have to weigh out what gear box gives the best HP-seconds!
Also, lower gearing doesnt always give you the best standing start... trust me on this plenty of care is made to find that gear and it always IS NOT the lowest gear posssible. you have to look at power, clutch capabilities, and grip coefficient. remember, you have to look at slip percentages and figure out launch forces, shift time, etc.... again, its a series of trade offs and you need to analyse.... do yourself a favor, get any drag simulator and plug in some numbers .. they are very good and will be very good at making my points here a reality for you.
anderson saw it at willow springs . (no time change going from 2.2 to 2.72) and i did this with scots car with the same HP as my old 290rwhp racer, at laguna. 2.2 vs 2.75... no time increase or decrease... the only thing i notices was more shifting in in opportune spots on the track. (mark anderson said this too. )
now, gearing with drag racers..... same reigns true!! this is simple stuff ted. just plug the gear ratos and hp into the simulartors and you will get the same answers..... lots of confusion and blame of this on gearing in the race world... go talk to the top pros.... they willl agree.... power, grip and mechanical factors , as well as transmission ratios, determine the final drive. you think the mustang that has 400hp uses the same gear ratios as the one that puts out 800hp with a blower? think again
the 928 GT is only slightly faster, and its not due to the gear box change.....its due to 330hp vs the stock S4 at 312hp.
again, the target speed range is what you need to look at..... you miss the point if you can argue mine about racing to a convenient speed. I did that for a reason. 80mph will favor the 2.2..... 100mph will favor the 2.75... add a shift and the same things happens. where ever you redline, if that speed is where you want to be, then thats the best gear box for that drag race or straight on a road course..(generally... and certainly a great place to start). caveats might be lots of slower straights that require a differnet gear that doesnt get to redline...... So you have to weigh out what gear box gives the best HP-seconds!
Also, lower gearing doesnt always give you the best standing start... trust me on this plenty of care is made to find that gear and it always IS NOT the lowest gear posssible. you have to look at power, clutch capabilities, and grip coefficient. remember, you have to look at slip percentages and figure out launch forces, shift time, etc.... again, its a series of trade offs and you need to analyse.... do yourself a favor, get any drag simulator and plug in some numbers .. they are very good and will be very good at making my points here a reality for you.
anderson saw it at willow springs . (no time change going from 2.2 to 2.72) and i did this with scots car with the same HP as my old 290rwhp racer, at laguna. 2.2 vs 2.75... no time increase or decrease... the only thing i notices was more shifting in in opportune spots on the track. (mark anderson said this too. )
08-17-2015, 09:02 PM
#39
Nordschleife Master
220 gearbox is a let down for the s3. I`d sooner put a g05 in, then race a luggy stock box. Please figure it out Ken!
08-17-2015, 09:17 PM
#40
Nordschleife Master
Now back to your regular programming.
08-17-2015, 10:03 PM
#42
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What Kibort is trying to make into a "Law" only applies to closed course racing, where one is already moving....and there is ample torque to be able to only use a couple/three gears (like with a V8 engine.) I completely understand what he is saying regarding his scenario. However, his argument is just that....arguing for the sake of arguing, for this thread's topic.
Once a "broad" torque range starts to go away and an engine makes higher rpm horsepower, instead of midrange torque, shorter/closer ratio gears become mandatory. If you own a 906, with a very limited torque range...Kibort's "my ideas fit every scenario" are completely wrong. You better have short enough gears to keep the engine in the power range, or you are going to be terribly slow around a closed course! Simply stated, you need the short gears/closer ratios to keep the engine in the effective power range. You leave the "highest" gear completely unused and the next one down only effective through half of the rpm range....and you are going to be very slow around a closed course.
Take this idea "one step further" and think about a Formula One engine or an Indy car engine....which make even less torque and more high rpm horsepower. They figure out their top speed possible on a given course and then gear their tallest gear to be at the peak horsepower (which is very close to redline.) All of the other ratios are calculated backwards, from that gear! There's no way they would gear their cars to not even use the top gear, like Kibort does at Laguna....that would be very slow "way" around any race course.
And, of course, as soon as one leaves the "closed course" racing situation, everything changes. If you are doing a "standing start slalom" course (where speeds very rarely get above 75mph)...a very "tall" ratio gearbox (like the G28/11), is most likely going to be a disadvantage to a "shorter" gear ratio gearbox (like the G28/05 or the G28/10.)
Street driving is almost always more fun, with "shorter" gear ratios. Almost all cars will accelerate quicker, from a standing stop, with shorter gear ratios.
Porsche didn't built the G28/10, for Europe, because they ordered the incorrect ring and pinions and had to use them up....it was intentional! Most Europeans would have never purchased the "slug" of a gear ratio that the US cars had!
Once a "broad" torque range starts to go away and an engine makes higher rpm horsepower, instead of midrange torque, shorter/closer ratio gears become mandatory. If you own a 906, with a very limited torque range...Kibort's "my ideas fit every scenario" are completely wrong. You better have short enough gears to keep the engine in the power range, or you are going to be terribly slow around a closed course! Simply stated, you need the short gears/closer ratios to keep the engine in the effective power range. You leave the "highest" gear completely unused and the next one down only effective through half of the rpm range....and you are going to be very slow around a closed course.
Take this idea "one step further" and think about a Formula One engine or an Indy car engine....which make even less torque and more high rpm horsepower. They figure out their top speed possible on a given course and then gear their tallest gear to be at the peak horsepower (which is very close to redline.) All of the other ratios are calculated backwards, from that gear! There's no way they would gear their cars to not even use the top gear, like Kibort does at Laguna....that would be very slow "way" around any race course.
And, of course, as soon as one leaves the "closed course" racing situation, everything changes. If you are doing a "standing start slalom" course (where speeds very rarely get above 75mph)...a very "tall" ratio gearbox (like the G28/11), is most likely going to be a disadvantage to a "shorter" gear ratio gearbox (like the G28/05 or the G28/10.)
Street driving is almost always more fun, with "shorter" gear ratios. Almost all cars will accelerate quicker, from a standing stop, with shorter gear ratios.
Porsche didn't built the G28/10, for Europe, because they ordered the incorrect ring and pinions and had to use them up....it was intentional! Most Europeans would have never purchased the "slug" of a gear ratio that the US cars had!
__________________
greg brown
714 879 9072
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Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
08-17-2015, 10:17 PM
#43
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Of course, I'm in the minority of people which really love the pre-Borg Warner transmissions. I love the way they feel. One gets feedback from every shift. You miss a shift and stick the transmission into the wrong gear....you know it way before you let the clutch out....way before you even get the shifter all the way into gear.
The Borg Warner transmissions were made for doctor's wives to be able to drive.....transmissions for girls to be able to drive Porsches. They are like moving a joystick around on a computer game....zero feeling.
08-18-2015, 04:41 AM
#44
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It likely had more to do with avoiding the US Gas Guzzler tax, which had a significant bump starting in '85 (then a minimum of $1800). The EPA standard fuel economy test, which was the sole basis of calculating the tax, would have been significantly assisted by a 2.20 rear end, especially in a 55mph steady-state highway cruise.
Åke
08-18-2015, 05:16 AM
#45
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For example my blue car a 1987 S4 manual (G28/12, 2.64) is hard to get up to 6000 rpm in 5th gear. It really take some time and the car must be driven hard being warmed up a while before any top speed test is performed. If it should have a 2.20 rear end I strongly believe it would only manage to reach a much lower rpm in 5th gear and the top speed would be lower as well as acceleration especially in top gear. I also feel the step between 4th and 5th gear is too wide, the rpm drops too much when going from 4th to 5th.
The blue car is a Strosek wide body car having really wide tires and a large rear wing resulting in increased air drag which will slow down the car at high speed. The 335/35x17 rear tires have a larger circumference (+ 6,4%) which is the same as having a 2.48 rear end.
Åke
The blue car is a Strosek wide body car having really wide tires and a large rear wing resulting in increased air drag which will slow down the car at high speed. The 335/35x17 rear tires have a larger circumference (+ 6,4%) which is the same as having a 2.48 rear end.
Åke
Last edited by hacker-pschorr; 08-18-2015 at 03:26 PM. Reason: Re-sized photo