LSD buster
Former Vendor
Joined: Oct 2009
Posts: 513
From: Boulder, CO
Rep Power: 0
Matt, may i ask you you a question (s). first , i do not fully understand the "anatomy " of the system. is the fluid in the lsd case the same that is in the transmission? is that the reason that the plates are made of softer material than the gears so that anything that is shed will not impact the gears . are the guard gears also this way ? finally, is the lsd in the 996 gt3 water cooled you have been very helpful to all that have read this thread thanks
As such, yes, anything going through the LSD and it's bath of oil also goes through all of the gearsets. It's all the same lubrication.
Also, the GT3 gearbox is sort of water cooled. It does have a small radiator style cooler on the side of the gearbox that's plumbed to the coolant system. It does use the coolant as a heat sink to transfer gear oil heat to the coolant and back out of the gearbox. However, pretty much any serious racer removes that and puts on an external air cooled remote radiator of a much larger volume that's mounted in the fender or rear bumper or any number of places under the chassis of the car. It's a very common track upgrade, even for guys who do still drive their cars on the street a bit.
Registered User
Joined: Nov 2008
Posts: 431
From: Reno NV
Rep Power: 59
1. Redirection of power output vs reduction of power output. PSM works (in large part) via the BRAKES.
2. Why would they still use a LSD?
Registered User
Joined: Apr 2009
Posts: 19
From: rochester ny
Rep Power: 0
well that was exactly my point . i believe there are cars with lsd and psm. it doesn't make sense to me for exactly the reason you say . i asked the question with the hope of understanding more the value and purpose of a functioning lsd
again i am sort of new at this and just trying to learn . it is amazing to me how little there is out there to study and there is a ton of misinformation . it is why this thread has been so valuable to me
thanks
again i am sort of new at this and just trying to learn . it is amazing to me how little there is out there to study and there is a ton of misinformation . it is why this thread has been so valuable to me
thanks
Former Vendor
Joined: Oct 2009
Posts: 513
From: Boulder, CO
Rep Power: 0
rkirshner,
I don't think sayboy was trying to patronize you with his response. His point is that an LSD lets you put more of the power to the ground without wasting the energy in something like wheelspin. When the psm kicks in, it's locking the brakes and reducing how much power you put to the ground. They are working at opposing ends. PSM is a safety feature, not a performance feature. It robs you of speed in return for making your car more stable.
I don't think sayboy was trying to patronize you with his response. His point is that an LSD lets you put more of the power to the ground without wasting the energy in something like wheelspin. When the psm kicks in, it's locking the brakes and reducing how much power you put to the ground. They are working at opposing ends. PSM is a safety feature, not a performance feature. It robs you of speed in return for making your car more stable.
Registered User
Joined: Jun 2005
Posts: 19
Rep Power: 0
The Oil pan under the Diff
This is what the LSD case look like inside
I tried to get to the oil pickup (?????) screen under the differential. I removed the screw, shown here and tried to pull rearward, but couldn't get it out (working blind and at a bad angle, on my back, under the car)
Any insight??? Is there anything preventing removal?? I think this is a screen and return oil tube that fits into a hole with an o-ring, but I can't see.
Thanks for any information.
I tried to get to the oil pickup (?????) screen under the differential. I removed the screw, shown here and tried to pull rearward, but couldn't get it out (working blind and at a bad angle, on my back, under the car)
Any insight??? Is there anything preventing removal?? I think this is a screen and return oil tube that fits into a hole with an o-ring, but I can't see.
Thanks for any information.
Registered User
Joined: Apr 2009
Posts: 19
From: rochester ny
Rep Power: 0
does psm really "lock the brakes" or does it preferentially add some brake to a wheel that is slipping to a greater degree than a preset amount? i am not an advocate for psm (it is one of the reasons i wont buy a 997 gt3) . i asked the question above to get a better understanding of what a lsd was made to do and how it works .another newbe question do cup cars have an lsd ?
Former Vendor
Joined: Oct 2009
Posts: 513
From: Boulder, CO
Rep Power: 0
Cup Cars have an LSD and NO PSM.
Any time the brakes are involved they have a slowing effect on the vehicle. This is true even if it's subtle and just for miliseconds. When someone is first learning to track a car they will be able to achieve gains in the realm of complete seconds at a time. Over the years those gains will come down to tenths.
For the pro guys at the top level of the game, they start to look to gain milliseconds. One example of that is the changes we've seen in dog box designs in recent years. For decades the standard for a dog box was to have 6 or 8 engagement teeth. What's the industry standard now? 5 teeth. Believe it or not that makes a difference on shifting speed and any time you stay on the accelerator versus off, the car is faster. That simple change in gearbox design has given guys gains of as much as .005 seconds per lap. Doesn't seem like much, but stretch that out over a 12 hour or 24 hour endurance event and it becomes seconds faster over the duration of the event. The PSM is no different. You may think it only brakes me just a little bit. But braking is braking and any time it happens when it's not needed it makes your times slower.
There are many who feel that we are at the end of a true driver's car from Porsche. The newest turbo is only offered with the PDK gearbox and what they are calling the ABD. ABD stands for automatic braking differential. For most of the population it won't matter in the least. The car performs so well, and has so much power, that for your average owner is just going to be so wow'ed by it. The magazines, which are generally populated by guys with some reasonable driving skills, but who aren't real racers, will rave about the car and their inability to find the limits on their usual road test or quick trip to the track, and we will see the cars raved about in print. The car will be stable and easy to handle, but it will not be racecar fast. It's been disabled while making it safe and predictable.
Hell, just look at the videos for the GT2-RS that have been going around. For nearly 2 minutes they take that car out and drift it around the airfield. We all know that drifting like that isn't the fastest way around the track. But how many times a day do we see a post from someone here talking about the "Weeeeee, that's fun" aspect of cutting it loose. Porsche is catering to that mentality. It's not the fastest. It's just fast while being fun. It's neat for people but it will never be racing. I hate to sound elitist, but it's Porsche going mainstream, hopping on the trackday bandwagon, and giving people what they want. They are letting people feel like they're the next Schumacher, and most of them won't even know that they don't have crap for skills because the car is so good and it covers their **** when in their ignorance and niavety they do something stupid. And in return for that, the car is not as fast as it could be. Technology and acronyns sell cars these days, not lap times.
Porsche sells more than 100,000 cars a year. Guess how many differentials we manufacture and sell worldwide per year? Probably around 500. That's for everything. That's from the 356, through the 901, 914,915 and 930, to the G50 family of gearboxes, which includes what the GT3 has become, and all of the modern line of 987 chassis. And while we're by no means the market volume leader, if you assume that Quiafe does 10 time that, it's still only 5% of one years sales for Porsche. And the fact that people buy so many TBDs over a true LSD speaks to who the owners are as well, since anyone who really understands what's going on in a gearbox knows that a TBD cannot compare to an LSD on the track. But that gives you an idea of what Porsche's market has really become. For better or for worse, our little handcrafted sports car manaufacturer has gone mainstream, and there's no turning back.
/rant
Any time the brakes are involved they have a slowing effect on the vehicle. This is true even if it's subtle and just for miliseconds. When someone is first learning to track a car they will be able to achieve gains in the realm of complete seconds at a time. Over the years those gains will come down to tenths.
For the pro guys at the top level of the game, they start to look to gain milliseconds. One example of that is the changes we've seen in dog box designs in recent years. For decades the standard for a dog box was to have 6 or 8 engagement teeth. What's the industry standard now? 5 teeth. Believe it or not that makes a difference on shifting speed and any time you stay on the accelerator versus off, the car is faster. That simple change in gearbox design has given guys gains of as much as .005 seconds per lap. Doesn't seem like much, but stretch that out over a 12 hour or 24 hour endurance event and it becomes seconds faster over the duration of the event. The PSM is no different. You may think it only brakes me just a little bit. But braking is braking and any time it happens when it's not needed it makes your times slower.
There are many who feel that we are at the end of a true driver's car from Porsche. The newest turbo is only offered with the PDK gearbox and what they are calling the ABD. ABD stands for automatic braking differential. For most of the population it won't matter in the least. The car performs so well, and has so much power, that for your average owner is just going to be so wow'ed by it. The magazines, which are generally populated by guys with some reasonable driving skills, but who aren't real racers, will rave about the car and their inability to find the limits on their usual road test or quick trip to the track, and we will see the cars raved about in print. The car will be stable and easy to handle, but it will not be racecar fast. It's been disabled while making it safe and predictable.
Hell, just look at the videos for the GT2-RS that have been going around. For nearly 2 minutes they take that car out and drift it around the airfield. We all know that drifting like that isn't the fastest way around the track. But how many times a day do we see a post from someone here talking about the "Weeeeee, that's fun" aspect of cutting it loose. Porsche is catering to that mentality. It's not the fastest. It's just fast while being fun. It's neat for people but it will never be racing. I hate to sound elitist, but it's Porsche going mainstream, hopping on the trackday bandwagon, and giving people what they want. They are letting people feel like they're the next Schumacher, and most of them won't even know that they don't have crap for skills because the car is so good and it covers their **** when in their ignorance and niavety they do something stupid. And in return for that, the car is not as fast as it could be. Technology and acronyns sell cars these days, not lap times.
Porsche sells more than 100,000 cars a year. Guess how many differentials we manufacture and sell worldwide per year? Probably around 500. That's for everything. That's from the 356, through the 901, 914,915 and 930, to the G50 family of gearboxes, which includes what the GT3 has become, and all of the modern line of 987 chassis. And while we're by no means the market volume leader, if you assume that Quiafe does 10 time that, it's still only 5% of one years sales for Porsche. And the fact that people buy so many TBDs over a true LSD speaks to who the owners are as well, since anyone who really understands what's going on in a gearbox knows that a TBD cannot compare to an LSD on the track. But that gives you an idea of what Porsche's market has really become. For better or for worse, our little handcrafted sports car manaufacturer has gone mainstream, and there's no turning back.
/rant
Registered User
Joined: Jan 2009
Posts: 314
From: Laguna Beach, CA
Rep Power: 50
Cup Cars have an LSD and NO PSM.
Any time the brakes are involved they have a slowing effect on the vehicle. This is true even if it's subtle and just for miliseconds. When someone is first learning to track a car they will be able to achieve gains in the realm of complete seconds at a time. Over the years those gains will come down to tenths.
For the pro guys at the top level of the game, they start to look to gain milliseconds. One example of that is the changes we've seen in dog box designs in recent years. For decades the standard for a dog box was to have 6 or 8 engagement teeth. What's the industry standard now? 5 teeth. Believe it or not that makes a difference on shifting speed and any time you stay on the accelerator versus off, the car is faster. That simple change in gearbox design has given guys gains of as much as .005 seconds per lap. Doesn't seem like much, but stretch that out over a 12 hour or 24 hour endurance event and it becomes seconds faster over the duration of the event. The PSM is no different. You may think it only brakes me just a little bit. But braking is braking and any time it happens when it's not needed it makes your times slower.
There are many who feel that we are at the end of a true driver's car from Porsche. The newest turbo is only offered with the PDK gearbox and what they are calling the ABD. ABD stands for automatic braking differential. For most of the population it won't matter in the least. The car performs so well, and has so much power, that for your average owner is just going to be so wow'ed by it. The magazines, which are generally populated by guys with some reasonable driving skills, but who aren't real racers, will rave about the car and their inability to find the limits on their usual road test or quick trip to the track, and we will see the cars raved about in print. The car will be stable and easy to handle, but it will not be racecar fast. It's been disabled while making it safe and predictable.
Hell, just look at the videos for the GT2-RS that have been going around. For nearly 2 minutes they take that car out and drift it around the airfield. We all know that drifting like that isn't the fastest way around the track. But how many times a day do we see a post from someone here talking about the "Weeeeee, that's fun" aspect of cutting it loose. Porsche is catering to that mentality. It's not the fastest. It's just fast while being fun. It's neat for people but it will never be racing. I hate to sound elitist, but it's Porsche going mainstream, hopping on the trackday bandwagon, and giving people what they want. They are letting people feel like they're the next Schumacher, and most of them won't even know that they don't have crap for skills because the car is so good and it covers their **** when in their ignorance and niavety they do something stupid. And in return for that, the car is not as fast as it could be. Technology and acronyns sell cars these days, not lap times.
Porsche sells more than 100,000 cars a year. Guess how many differentials we manufacture and sell worldwide per year? Probably around 500. That's for everything. That's from the 356, through the 901, 914,915 and 930, to the G50 family of gearboxes, which includes what the GT3 has become, and all of the modern line of 987 chassis. And while we're by no means the market volume leader, if you assume that Quiafe does 10 time that, it's still only 5% of one years sales for Porsche. And the fact that people buy so many TBDs over a true LSD speaks to who the owners are as well, since anyone who really understands what's going on in a gearbox knows that a TBD cannot compare to an LSD on the track. But that gives you an idea of what Porsche's market has really become. For better or for worse, our little handcrafted sports car manaufacturer has gone mainstream, and there's no turning back.
/rant
Any time the brakes are involved they have a slowing effect on the vehicle. This is true even if it's subtle and just for miliseconds. When someone is first learning to track a car they will be able to achieve gains in the realm of complete seconds at a time. Over the years those gains will come down to tenths.
For the pro guys at the top level of the game, they start to look to gain milliseconds. One example of that is the changes we've seen in dog box designs in recent years. For decades the standard for a dog box was to have 6 or 8 engagement teeth. What's the industry standard now? 5 teeth. Believe it or not that makes a difference on shifting speed and any time you stay on the accelerator versus off, the car is faster. That simple change in gearbox design has given guys gains of as much as .005 seconds per lap. Doesn't seem like much, but stretch that out over a 12 hour or 24 hour endurance event and it becomes seconds faster over the duration of the event. The PSM is no different. You may think it only brakes me just a little bit. But braking is braking and any time it happens when it's not needed it makes your times slower.
There are many who feel that we are at the end of a true driver's car from Porsche. The newest turbo is only offered with the PDK gearbox and what they are calling the ABD. ABD stands for automatic braking differential. For most of the population it won't matter in the least. The car performs so well, and has so much power, that for your average owner is just going to be so wow'ed by it. The magazines, which are generally populated by guys with some reasonable driving skills, but who aren't real racers, will rave about the car and their inability to find the limits on their usual road test or quick trip to the track, and we will see the cars raved about in print. The car will be stable and easy to handle, but it will not be racecar fast. It's been disabled while making it safe and predictable.
Hell, just look at the videos for the GT2-RS that have been going around. For nearly 2 minutes they take that car out and drift it around the airfield. We all know that drifting like that isn't the fastest way around the track. But how many times a day do we see a post from someone here talking about the "Weeeeee, that's fun" aspect of cutting it loose. Porsche is catering to that mentality. It's not the fastest. It's just fast while being fun. It's neat for people but it will never be racing. I hate to sound elitist, but it's Porsche going mainstream, hopping on the trackday bandwagon, and giving people what they want. They are letting people feel like they're the next Schumacher, and most of them won't even know that they don't have crap for skills because the car is so good and it covers their **** when in their ignorance and niavety they do something stupid. And in return for that, the car is not as fast as it could be. Technology and acronyns sell cars these days, not lap times.
Porsche sells more than 100,000 cars a year. Guess how many differentials we manufacture and sell worldwide per year? Probably around 500. That's for everything. That's from the 356, through the 901, 914,915 and 930, to the G50 family of gearboxes, which includes what the GT3 has become, and all of the modern line of 987 chassis. And while we're by no means the market volume leader, if you assume that Quiafe does 10 time that, it's still only 5% of one years sales for Porsche. And the fact that people buy so many TBDs over a true LSD speaks to who the owners are as well, since anyone who really understands what's going on in a gearbox knows that a TBD cannot compare to an LSD on the track. But that gives you an idea of what Porsche's market has really become. For better or for worse, our little handcrafted sports car manaufacturer has gone mainstream, and there's no turning back.
/rant
Registered User
Joined: Nov 2008
Posts: 1,115
From: Roseville, CA
Rep Power: 135
Matt,
A several questions if you don't mind?
1. Why isn't a geared differential offered like a Torsen or Quaife vs. the clutch-type by Porsche? What about changing to a geared type for the Porsche?
2. I heard years ago, and this could be totally wrong, if you put a car on a rack where the wheels hang freely, if you turn one wheel and the other turns in the SAME direction, it's an open diff. If it turns in the OPPOSITE direction, it's a/an (geared?) LSD. True?
The McLaren MP4-12C has an open differential. This prompted me to write an article about the disturbing trend of eliminating LSDs. http://www.examiner.com/sitemaps/x-5...McLaren-MP412C
Yet I also realize these are fundamental questions.
A several questions if you don't mind?
1. Why isn't a geared differential offered like a Torsen or Quaife vs. the clutch-type by Porsche? What about changing to a geared type for the Porsche?
2. I heard years ago, and this could be totally wrong, if you put a car on a rack where the wheels hang freely, if you turn one wheel and the other turns in the SAME direction, it's an open diff. If it turns in the OPPOSITE direction, it's a/an (geared?) LSD. True?
The McLaren MP4-12C has an open differential. This prompted me to write an article about the disturbing trend of eliminating LSDs. http://www.examiner.com/sitemaps/x-5...McLaren-MP412C
Yet I also realize these are fundamental questions.