LSD or not?
11-19-2013, 12:37 PM
#51
MBWorld Fanatic!
I'll try and explain my experience better, but hey we don't have to agree, just need to enjoy the discussion and try to learn from each other. I am talking about RWD applications here.
For a clutch LSD to be effective for a heavy, high torque vehicle with sticky tires it has to be very tight. When they are set up that way they act a lot like a spool until torque bias overcomes clutch friction/resistance to different wheel speeds. That resistance is greatest to different speeds before there is a difference in wheel speed (when going in a straight line). That means on turn in there is some resistance to directional change. This is a lot more obvious when driving on ice, which I understand many don't do. Trust me on this though, a tight clutch type LSD will cause under steer on ice exactly like a spool does. Both clutch and spool diffs also do it on pavement, it's just not as obvious as on ice, and the spool is obviously a lot worse on high traction situations than the clutch diff.
When accelerating out of a turn at the limit of traction you again get the clutch type diff acting like a spool and increasing the likely hood of oversteer/ getting sideways. This happens because it is attempting to keep the tires at exactly the same speed, just like a spool does. A gear type diff like the quaife and wave track allow slightly different speeds with minimal resistance.
If we agree that a spool acts exactly as I have described (turn in under steer & hard acceleration oversteer when exiting a corner). If that is the case then maybe a clutch type LSD also has some of these tendencies?
You have probably driven the same vehicle with different types of differentials in it and maybe your experience was different than mine when switching between them, just trying to share my own experience.
For a clutch LSD to be effective for a heavy, high torque vehicle with sticky tires it has to be very tight. When they are set up that way they act a lot like a spool until torque bias overcomes clutch friction/resistance to different wheel speeds. That resistance is greatest to different speeds before there is a difference in wheel speed (when going in a straight line). That means on turn in there is some resistance to directional change. This is a lot more obvious when driving on ice, which I understand many don't do. Trust me on this though, a tight clutch type LSD will cause under steer on ice exactly like a spool does. Both clutch and spool diffs also do it on pavement, it's just not as obvious as on ice, and the spool is obviously a lot worse on high traction situations than the clutch diff.
When accelerating out of a turn at the limit of traction you again get the clutch type diff acting like a spool and increasing the likely hood of oversteer/ getting sideways. This happens because it is attempting to keep the tires at exactly the same speed, just like a spool does. A gear type diff like the quaife and wave track allow slightly different speeds with minimal resistance.
If we agree that a spool acts exactly as I have described (turn in under steer & hard acceleration oversteer when exiting a corner). If that is the case then maybe a clutch type LSD also has some of these tendencies?
You have probably driven the same vehicle with different types of differentials in it and maybe your experience was different than mine when switching between them, just trying to share my own experience.
Last edited by Dr Matt; 11-19-2013 at 12:42 PM.
11-19-2013, 03:13 PM
#52
I woke up way too early this morning and decided to google LSD's in the American car forums. I don't know which forums are the good ones because it was my first time on any of them but the LSD-related discussions seemed to be exactly the same, one after another, where half preferred the gear type, the other half the clutch type. It was amazing how one discussion mirrored the next but just seemed to boil down to experience, application and setup. Personally, after three clutch-type LSD's in other cars and then my experience with the P30 C63, I'm somewhat surprised by how readily discernible some of the differences are between the two types in this car. I wasn't looking for, or expecting that. That makes me happy though. Sometime in the upcoming weeks before my car goes to Weistec I'll be trading off with a friend's P31 (w/ OE LSD) and doing our 20 mile late night "test loop," so in the process we'll have a direct comparison of the two. So far, I'm extremely satisfied with the Wavetrac….there are absolutely no downsides to it that I've yet discovered nor now do I expect to. I can't speak to the Quaife but the Wavetrac rocks!
11-19-2013, 03:16 PM
#53
MBWorld Fanatic!
Join Date: Jan 2013
Location: Toronto, Canada
Posts: 3,720
Received 794 Likes
on
545 Posts
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
I'll try and explain my experience better, but hey we don't have to agree, just need to enjoy the discussion and try to learn from each other. I am talking about RWD applications here.
For a clutch LSD to be effective for a heavy, high torque vehicle with sticky tires it has to be very tight. When they are set up that way they act a lot like a spool until torque bias overcomes clutch friction/resistance to different wheel speeds. That resistance is greatest to different speeds before there is a difference in wheel speed (when going in a straight line). That means on turn in there is some resistance to directional change. This is a lot more obvious when driving on ice, which I understand many don't do. Trust me on this though, a tight clutch type LSD will cause under steer on ice exactly like a spool does. Both clutch and spool diffs also do it on pavement, it's just not as obvious as on ice, and the spool is obviously a lot worse on high traction situations than the clutch diff.
When accelerating out of a turn at the limit of traction you again get the clutch type diff acting like a spool and increasing the likely hood of oversteer/ getting sideways. This happens because it is attempting to keep the tires at exactly the same speed, just like a spool does. A gear type diff like the quaife and wave track allow slightly different speeds with minimal resistance.
If we agree that a spool acts exactly as I have described (turn in under steer & hard acceleration oversteer when exiting a corner). If that is the case then maybe a clutch type LSD also has some of these tendencies?
You have probably driven the same vehicle with different types of differentials in it and maybe your experience was different than mine when switching between them, just trying to share my own experience.
For a clutch LSD to be effective for a heavy, high torque vehicle with sticky tires it has to be very tight. When they are set up that way they act a lot like a spool until torque bias overcomes clutch friction/resistance to different wheel speeds. That resistance is greatest to different speeds before there is a difference in wheel speed (when going in a straight line). That means on turn in there is some resistance to directional change. This is a lot more obvious when driving on ice, which I understand many don't do. Trust me on this though, a tight clutch type LSD will cause under steer on ice exactly like a spool does. Both clutch and spool diffs also do it on pavement, it's just not as obvious as on ice, and the spool is obviously a lot worse on high traction situations than the clutch diff.
When accelerating out of a turn at the limit of traction you again get the clutch type diff acting like a spool and increasing the likely hood of oversteer/ getting sideways. This happens because it is attempting to keep the tires at exactly the same speed, just like a spool does. A gear type diff like the quaife and wave track allow slightly different speeds with minimal resistance.
If we agree that a spool acts exactly as I have described (turn in under steer & hard acceleration oversteer when exiting a corner). If that is the case then maybe a clutch type LSD also has some of these tendencies?
You have probably driven the same vehicle with different types of differentials in it and maybe your experience was different than mine when switching between them, just trying to share my own experience.
Absolutely - our experiences and opinions may be different, but I always welcome a good argument or hearing a differing opinion. It's how we all learn.
To the topic at hand, I follow your argument (with the spool being a 100% locking diff or the live axle in my example) but IMHO there are two issues with it. The first one is your assertion that a clutch-based LSD acts as a spool. In the steady-state scenario (no acceleration or deceleration), a clutch type LSD acts like an open diff, not a locked one (spool). The pinion shaft is not transmitting any pressure to the friction rings and the clutches are not compressed (they are freely spinning) even if you are in the middle of a turn. Moreover, most OEM clutch LSDs are ramped on the loose side (about 40% lock or thereabouts) which is far from a 100% locked spool.
The second issue is the more debatable one if you will, in that the spool (live rear axle) is IMHO more likely to induce oversteer both during deceleration and acceleration. If the rear wheels of the car are locked, they always want to continue rotating at the same speed and thus continue to travel in a straight line. When the car is turning (regardless of whether you are increasing or decreasing the lock) but the rear wants to continue to travel straight is the definition of oversteer. I am not suggesting that it wasn't happening to you during your racing experience, only that it is likely due to other factors (like suspension geometry or damping) rather than the LSD itself. Every time I've repacked the clutch packs on the various cars and LSDs I've had, it has resulted in less understeer at turn-in, not more, but again, that is just my experience. The effect was similar to adding a stiffer sway bar at the rear to eliminate understeer at the front.
I managed to find a good little presentation on YouTube about clutch-type LSDs (and there is a Torsen one later on in the series) at
Cheers,
Doug
Last edited by Diabolis; 11-19-2013 at 03:26 PM. Reason: stupid double space again...
11-19-2013, 06:15 PM
#54
MBWorld Fanatic!
Thread Starter
^ That serie of videos is definitely worth watching if you are not familiar with LSDs (which I was 
).
Thanks for sharing.
).Thanks for sharing.
11-27-2013, 03:00 PM
#56
I won't get into the pissing match of LSD vs non LSD, etc., but they are an advantage if traction is less than optimal, be it torque> coef friction, wet/snow, debris, etc.
A gear type is far superior in every way to a friction type of LSD...every way, track, off road, street:
-it lasts longer
-has more of a turn down ratio or throttling range, far more precise control
-is more proportioal, less 'grabby' in application/distribution of torque
-won't over heat and lose efficiency
-lb for lb can handle more torque
Having said that, if my car had an oem friction type I would not spend the money to change to a gear type. But if I were adding LSD to a no- LSD car, I'd go gear type. Either will suffice in 90% of street applications. The reason friction types are used more often is that they are cheaper and were developed long before the gear type, not because they are technically 'better'. Because anyone with a rudimentary understanding of physics/engineering/mechanics would conclude otherwise.
My car does not have a LSD, but I am contemplating one...I'd like a Gleason TorSen but I don't think one is made for my car so I'm contemplating a Quaife.
The gear type came about in the early 80's because prior to that the machining was so complex that is was cost prohibitive to do it manually. CCM (used to be NCM) changed all that. There is a reason the military, Audi, etc., use the gear type.
A gear type is far superior in every way to a friction type of LSD...every way, track, off road, street:
-it lasts longer
-has more of a turn down ratio or throttling range, far more precise control
-is more proportioal, less 'grabby' in application/distribution of torque
-won't over heat and lose efficiency
-lb for lb can handle more torque
Having said that, if my car had an oem friction type I would not spend the money to change to a gear type. But if I were adding LSD to a no- LSD car, I'd go gear type. Either will suffice in 90% of street applications. The reason friction types are used more often is that they are cheaper and were developed long before the gear type, not because they are technically 'better'. Because anyone with a rudimentary understanding of physics/engineering/mechanics would conclude otherwise.
My car does not have a LSD, but I am contemplating one...I'd like a Gleason TorSen but I don't think one is made for my car so I'm contemplating a Quaife.
The gear type came about in the early 80's because prior to that the machining was so complex that is was cost prohibitive to do it manually. CCM (used to be NCM) changed all that. There is a reason the military, Audi, etc., use the gear type.
Last edited by Ingenieur; 11-27-2013 at 03:38 PM.
11-27-2013, 04:36 PM
#57
Senior Member
Join Date: Sep 2008
Location: SoCal
Posts: 317
Likes: 0
Received 0 Likes
on
0 Posts
997.2 GT3
I can think of one situation that disadvantages a gear type LSD - if one wheel becomes airborne, the gear type LSD would act like an open differential. The scenario where this would come into play is putting wheels onto curbs at the track.
11-27-2013, 08:23 PM
#58
MBWorld Fanatic!
Join Date: Jan 2013
Location: Toronto, Canada
Posts: 3,720
Received 794 Likes
on
545 Posts
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
I won't get into the pissing match of LSD vs non LSD, etc., but they are an advantage if traction is less than optimal, be it torque> coef friction, wet/snow, debris, etc.
A gear type is far superior in every way to a friction type of LSD...every way, track, off road, street:
-it lasts longer
-has more of a turn down ratio or throttling range, far more precise control
-is more proportioal, less 'grabby' in application/distribution of torque
-won't over heat and lose efficiency
-lb for lb can handle more torque
Having said that, if my car had an oem friction type I would not spend the money to change to a gear type. But if I were adding LSD to a no- LSD car, I'd go gear type. Either will suffice in 90% of street applications. The reason friction types are used more often is that they are cheaper and were developed long before the gear type, not because they are technically 'better'. Because anyone with a rudimentary understanding of physics/engineering/mechanics would conclude otherwise.
My car does not have a LSD, but I am contemplating one...I'd like a Gleason TorSen but I don't think one is made for my car so I'm contemplating a Quaife.
The gear type came about in the early 80's because prior to that the machining was so complex that is was cost prohibitive to do it manually. CCM (used to be NCM) changed all that. There is a reason the military, Audi, etc., use the gear type.
A gear type is far superior in every way to a friction type of LSD...every way, track, off road, street:
-it lasts longer
-has more of a turn down ratio or throttling range, far more precise control
-is more proportioal, less 'grabby' in application/distribution of torque
-won't over heat and lose efficiency
-lb for lb can handle more torque
Having said that, if my car had an oem friction type I would not spend the money to change to a gear type. But if I were adding LSD to a no- LSD car, I'd go gear type. Either will suffice in 90% of street applications. The reason friction types are used more often is that they are cheaper and were developed long before the gear type, not because they are technically 'better'. Because anyone with a rudimentary understanding of physics/engineering/mechanics would conclude otherwise.
My car does not have a LSD, but I am contemplating one...I'd like a Gleason TorSen but I don't think one is made for my car so I'm contemplating a Quaife.
The gear type came about in the early 80's because prior to that the machining was so complex that is was cost prohibitive to do it manually. CCM (used to be NCM) changed all that. There is a reason the military, Audi, etc., use the gear type.
Please enlighten us how you would achieve a different amount of lock-up on acceleration and deceleration (i.e. a 1.5-way LSD) with a gear-based limited-slip diff. Most high-grip driving requires less lock up on deceleration than on acceleration.
And, for what it's worth, all of the military and Audi diffs that you're talking about are CENTER differentials, not left-to-right between the driven wheels. If a gear type LSD is so much superior to a clutch-type LSD for all intents and purposes, the clutch based diffs would have all but disappeared by now.
11-28-2013, 08:09 PM
#60
That's a pretty ignorant statement.
Please enlighten us how you would achieve a different amount of lock-up on acceleration and deceleration (i.e. a 1.5-way LSD) with a gear-based limited-slip diff. Most high-grip driving requires less lock up on deceleration than on acceleration.
And, for what it's worth, all of the military and Audi diffs that you're talking about are CENTER differentials, not left-to-right between the driven wheels. If a gear type LSD is so much superior to a clutch-type LSD for all intents and purposes, the clutch based diffs would have all but disappeared by now.
Please enlighten us how you would achieve a different amount of lock-up on acceleration and deceleration (i.e. a 1.5-way LSD) with a gear-based limited-slip diff. Most high-grip driving requires less lock up on deceleration than on acceleration.
And, for what it's worth, all of the military and Audi diffs that you're talking about are CENTER differentials, not left-to-right between the driven wheels. If a gear type LSD is so much superior to a clutch-type LSD for all intents and purposes, the clutch based diffs would have all but disappeared by now.
It is obviously beyond your grasp. And lighten up on the 'ignorant' comments skippy, you are in way over your head. If you don't understand what supplies the driving/retarding torque in the case of +a and -a I don't have time to explain it, but the gears are cut directionally.
A gear based diff transfers torque as a vector, with both direction and magnitude components, side to side and load.
The clutch based are cheaper and provide 60 to 70% of the benefits, that is why they are still in use.
You can find the mathematics here: Section 3.2 pg. 77 forward, section 2.5 might help you also
http://www.torsen.com/files/Traction...ol_Article.pdf
you are wrong about the hummer
The HMMWV, or Hummer, uses Torsen® differentials on the front and rear axles. The owner's manual for the Hummer proposes a novel solution to the problem of one wheel coming off the ground: Apply the brakes. By applying the brakes, torque is applied to the wheel that is in the air, and then five times that torque can go to the wheel with good traction.
Audi uses in the center with open diffs at the axles.
The best may be an electronically controlled metal clutch pack.
btw: the 1.5 BS is directly out of a wiki article
why not a 2:1?
The gear type will proportion and apportion torque regardless of direction of its flow, either due to braking, engine braking or selecting reverse gear
and will do so seamlessly, unlike a pre-loaded friction clutch.
Last edited by Ingenieur; 11-28-2013 at 09:12 PM.
11-29-2013, 04:45 PM
#61
MBWorld Fanatic!
Join Date: Jan 2013
Location: Toronto, Canada
Posts: 3,720
Received 794 Likes
on
545 Posts
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
Just because you don't understand it doesn't render it invalid.
It is obviously beyond your grasp. And lighten up on the 'ignorant' comments skippy, you are in way over your head. If you don't understand what supplies the driving/retarding torque in the case of +a and -a I don't have time to explain it, but the gears are cut directionally.
A gear based diff transfers torque as a vector, with both direction and magnitude components, side to side and load.
The clutch based are cheaper and provide 60 to 70% of the benefits, that is why they are still in use.
You can find the mathematics here: Section 3.2 pg. 77 forward, section 2.5 might help you also
http://www.torsen.com/files/Traction...ol_Article.pdf
you are wrong about the hummer
The HMMWV, or Hummer, uses Torsen® differentials on the front and rear axles. The owner's manual for the Hummer proposes a novel solution to the problem of one wheel coming off the ground: Apply the brakes. By applying the brakes, torque is applied to the wheel that is in the air, and then five times that torque can go to the wheel with good traction.
Audi uses in the center with open diffs at the axles.
The best may be an electronically controlled metal clutch pack.
btw: the 1.5 BS is directly out of a wiki article
why not a 2:1?
The gear type will proportion and apportion torque regardless of direction of its flow, either due to braking, engine braking or selecting reverse gear
and will do so seamlessly, unlike a pre-loaded friction clutch.
It is obviously beyond your grasp. And lighten up on the 'ignorant' comments skippy, you are in way over your head. If you don't understand what supplies the driving/retarding torque in the case of +a and -a I don't have time to explain it, but the gears are cut directionally.
A gear based diff transfers torque as a vector, with both direction and magnitude components, side to side and load.
The clutch based are cheaper and provide 60 to 70% of the benefits, that is why they are still in use.
You can find the mathematics here: Section 3.2 pg. 77 forward, section 2.5 might help you also
http://www.torsen.com/files/Traction...ol_Article.pdf
you are wrong about the hummer
The HMMWV, or Hummer, uses Torsen® differentials on the front and rear axles. The owner's manual for the Hummer proposes a novel solution to the problem of one wheel coming off the ground: Apply the brakes. By applying the brakes, torque is applied to the wheel that is in the air, and then five times that torque can go to the wheel with good traction.
Audi uses in the center with open diffs at the axles.
The best may be an electronically controlled metal clutch pack.
btw: the 1.5 BS is directly out of a wiki article
why not a 2:1?
The gear type will proportion and apportion torque regardless of direction of its flow, either due to braking, engine braking or selecting reverse gear
and will do so seamlessly, unlike a pre-loaded friction clutch.
I very much like your explanation how the gear-based diff transfers torque as a vector especially in proportion and apportion and how the gears are cut directionally. I always thought it was teleportation, voodoo lemon recoil and pixie dust but your explanation sounds so much better. You have no doubt also heard the bong sound recently. Did the laughing pink armadillo flying in and out of the air vents look at you? Did it look at you?
We're talking about a different type of LSD here. LSD as in Limited Slip Differential, not Lysergic acid diethylamide.
Last edited by Diabolis; 11-29-2013 at 06:05 PM.
11-29-2013, 05:07 PM
#62
This guy man
Don't waste your breath diabolis
Don't waste your breath diabolis
11-29-2013, 06:07 PM
#63
Senior Member
Join Date: Dec 2012
Location: Wyoming
Posts: 301
Likes: 0
Received 4 Likes
on
4 Posts
ford svt's, and C63!!!
I still run an open diff with a "tune" and now "headers" and have yet to just spin one tire, I'm a straight line performance kinda guy and have tracked the car a few times, and until there's a problem, I'm not bothering with a solution?
11-29-2013, 06:46 PM
#65
Senior Member
Join Date: Oct 2013
Location: Montreal, QC
Posts: 352
Likes: 0
Received 2 Likes
on
2 Posts
2013 C63 coupe P31
I still run an open diff with a "tune" and now "headers" and have yet to just spin one tire, I'm a straight line performance kinda guy and have tracked the car a few times, and until there's a problem, I'm not bothering with a solution?
If I ever went to accelerate and fried one tire, I'd have a posi diff of some sort ordered in a matter of minutes though!
If I ever went to accelerate and fried one tire, I'd have a posi diff of some sort ordered in a matter of minutes though!
12-01-2013, 11:52 AM
#67
Obviously beyond *my* grasp... yeah, whatever makes you feel happy.
I very much like your explanation how the gear-based diff transfers torque as a vector especially in proportion and apportion and how the gears are cut directionally. I always thought it was teleportation, voodoo lemon recoil and pixie dust but your explanation sounds so much better. You have no doubt also heard the bong sound recently. Did the laughing pink armadillo flying in and out of the air vents look at you? Did it look at you?
We're talking about a different type of LSD here. LSD as in Limited Slip Differential, not Lysergic acid diethylamide.
I very much like your explanation how the gear-based diff transfers torque as a vector especially in proportion and apportion and how the gears are cut directionally. I always thought it was teleportation, voodoo lemon recoil and pixie dust but your explanation sounds so much better. You have no doubt also heard the bong sound recently. Did the laughing pink armadillo flying in and out of the air vents look at you? Did it look at you?
We're talking about a different type of LSD here. LSD as in Limited Slip Differential, not Lysergic acid diethylamide.
My original comment was not directed at you or in response to a post you made, it was a general comment, but for some reason you took it personally and attacked it as 'ignorant'.
I don't use drugs, never have. I bet those around you wish you could say the same. How you make the leap from a mechanical system discussion to your personal druge abuse issues is beyond me. 'pink armadillos'? Freudian perhaps? Maybe you speak to Herr Dr. Hofmann in your dreams? Maybe Dr. Leary?
Put the pipe down and pick up a book, preferably a text book or non-fiction, **** doesn't count.
I know your ilk: you are smarter and wittier than everyone, you 'see the light', others are blind. Insecure like a child.
As I said, over your head, instead of actually responding to the technical merit (or not) of my post, you redirect and make a lame attempt at ridicule. With that attitude your life is already over and you don't even know it, lol. A waste of oxygen.
12-01-2013, 03:13 PM
#68
MBWorld Fanatic!
Join Date: Jan 2013
Location: Toronto, Canada
Posts: 3,720
Received 794 Likes
on
545 Posts
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
Are you serious? The only way to possibly interpret the pile of garbage you wrote is to discount it as either drug abuse or the ramblings of a lunatic. Yet you have the audacity to actually want to talk about the "technical merit" of your statements? Dr. Seuss books have more technical merit than the pile of random important sounding words that you managed to throw together and pretend that you actually know something. If it's not drugs, I would seriously suggest you stop listening to the voices in your head and the Marshall Applewhite recordings and seek professional help. You make L. Ron Hubbard sound like a reasonable man.
12-01-2013, 03:23 PM
#69
Are you serious? The only way to possibly interpret the pile of garbage you wrote is to discount it as either drug abuse or the ramblings of a lunatic. Yet you have the audacity to actually want to talk about the "technical merit" of your statements? Dr. Seuss books have more technical merit than the pile of random important sounding words that you managed to throw together and pretend that you actually know something. If it's not drugs, I would seriously suggest you stop listening to the voices in your head and the Marshall Applewhite recordings and seek professional help. You make L. Ron Hubbard sound like a reasonable man.
It is you who brought up drug use, not I.
And again, no substantial input or response, just a bunch of insecure personal attacks. Read the paper them we can discuss this, until then it is obvious you are full of $%#^.
You make Charles Manson seem rational. You actually hear voices in your head?! not good
You have serious issues, professionals can manage that with drug therapy, but you attempt to do by self-medicating. I see you did not deny your drug abuse problem, at least that is a first step to recovery. Good luck with your journey.
