Viscous Limited-Slip Differential
03-17-2006 | 12:34 AM
#1
Viscous Limited-Slip Differential
As the title says, what is the greatness of this? I ask this because this seems to be the biggest difference (that i care about) between the base and enthusiast. The following is from howstuffworks.com
Viscous Coupling
The viscous coupling is often found in all-wheel-drive vehicles. It is commonly used to link the back wheels to the front wheels so that when one set of wheels starts to slip, torque will be transferred to the other set.
The viscous coupling has two sets of plates inside a sealed housing that is filled with a thick fluid, as shown in below. One set of plates is connected to each output shaft. Under normal conditions, both sets of plates and the viscous fluid spin at the same speed. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping.
When a car is turning, the difference in speed between the wheels is not as large as when one wheel is slipping. The faster the plates are spinning relative to each other, the more torque the viscous coupling transfers. The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
A simple experiment with an egg will help explain the behavior of the viscous coupling. If you set an egg on the kitchen table, the shell and the yolk are both stationary. If you suddenly spin the egg, the shell will be moving at a faster speed than the yolk for a second, but the yolk will quickly catch up. To prove that the yolk is spinning, once you have the egg spinning quickly stop it and then let go -- the egg will start to spin again (unless it is hard boiled). In this experiment, we used the friction between the shell and the yolk to apply force to the yolk, speeding it up. When we stopped the shell, that friction -- between the still-moving yolk and the shell -- applied force to the shell, causing it to speed up. In a viscous coupling, the force is applied between the fluid and the sets of plates in the same way as between the yolk and the shell.
So I assume the base has limited slip differential but not "Viscous"?? This is what stuck out to me: The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
Really my whole point of posting this is, I can afford either a new 06 base, or find a used enth. I am trying to make a decision, this is my sticking point. Thanks!
Viscous Coupling
The viscous coupling is often found in all-wheel-drive vehicles. It is commonly used to link the back wheels to the front wheels so that when one set of wheels starts to slip, torque will be transferred to the other set.
The viscous coupling has two sets of plates inside a sealed housing that is filled with a thick fluid, as shown in below. One set of plates is connected to each output shaft. Under normal conditions, both sets of plates and the viscous fluid spin at the same speed. When one set of wheels tries to spin faster, perhaps because it is slipping, the set of plates corresponding to those wheels spins faster than the other. The viscous fluid, stuck between the plates, tries to catch up with the faster disks, dragging the slower disks along. This transfers more torque to the slower moving wheels -- the wheels that are not slipping.
When a car is turning, the difference in speed between the wheels is not as large as when one wheel is slipping. The faster the plates are spinning relative to each other, the more torque the viscous coupling transfers. The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
A simple experiment with an egg will help explain the behavior of the viscous coupling. If you set an egg on the kitchen table, the shell and the yolk are both stationary. If you suddenly spin the egg, the shell will be moving at a faster speed than the yolk for a second, but the yolk will quickly catch up. To prove that the yolk is spinning, once you have the egg spinning quickly stop it and then let go -- the egg will start to spin again (unless it is hard boiled). In this experiment, we used the friction between the shell and the yolk to apply force to the yolk, speeding it up. When we stopped the shell, that friction -- between the still-moving yolk and the shell -- applied force to the shell, causing it to speed up. In a viscous coupling, the force is applied between the fluid and the sets of plates in the same way as between the yolk and the shell.
So I assume the base has limited slip differential but not "Viscous"?? This is what stuck out to me: The coupling does not interfere with turns because the amount of torque transferred during a turn is so small. However, this also highlights a disadvantage of the viscous coupling: No torque transfer will occur until a wheel actually starts slipping.
Really my whole point of posting this is, I can afford either a new 06 base, or find a used enth. I am trying to make a decision, this is my sticking point. Thanks!
Last edited by NissanZfan; 03-17-2006 at 12:39 AM.
03-17-2006 | 06:04 AM
#2
Your right, the Viscous limited slip (in non base models) differentiates itself buy not slipping under torque (i.e. when you slam on the gas).
Think of it this way. If your back wheels are on snow/ice and you give it gas, the base will spin one tire and the other will be stationary. With viscous limited slip, both tires will spin giving more traction. This analogy of course applies to pavement as well and can be noticed particularly under hard turning when there is less weight on the inside wheel and it has a tendency to spin under throttle (in the absence of limited slip).
IMO, a 300hp car without limited slip is a contradiction. Why get the power if you can't put it to the pavement.
Think of it this way. If your back wheels are on snow/ice and you give it gas, the base will spin one tire and the other will be stationary. With viscous limited slip, both tires will spin giving more traction. This analogy of course applies to pavement as well and can be noticed particularly under hard turning when there is less weight on the inside wheel and it has a tendency to spin under throttle (in the absence of limited slip).
IMO, a 300hp car without limited slip is a contradiction. Why get the power if you can't put it to the pavement.
Last edited by maxpowers; 03-17-2006 at 06:06 AM.
03-17-2006 | 07:18 AM
#3
First, the Base does not come with a LSD. It has an open diff. However the LSD in the other models is not that great, Viscous LSD just dont work that well, you want a mechanical LSD.
My suggestion is get the base model and then purchase an aftermarket Torsen LSD, everyone from Nismo to Kazz make really good differentials for these cars. Figure on paying roughly $850 for the diff and about $400 for the install.
My suggestion is get the base model and then purchase an aftermarket Torsen LSD, everyone from Nismo to Kazz make really good differentials for these cars. Figure on paying roughly $850 for the diff and about $400 for the install.
03-17-2006 | 08:29 AM
#4
^+1 with added stress that VLSD is NOT that great
Though I would edit the last sentance to read. "Figure on paying roughly $850 for a clutch type LSD and $1400 for a Torsen, then about $400 to install either.
Though I would edit the last sentance to read. "Figure on paying roughly $850 for a clutch type LSD and $1400 for a Torsen, then about $400 to install either.
03-17-2006 | 10:03 AM
#5
Registered User
Joined: Mar 2006
Posts: 72
Likes: 0
From: So, Ca.
Anyone here ever added an aftermarket LSD on a base model.
I've been wanting on getting one, but haven't gotten and information on the cost and process.
Quick question! So there is no other parts to purchase other than the LSD right!.
I want a daily driver LSD, would it be better to get a Viscous or mechanical.
I'm looking for quit and daily driving use, not ***** out performance.
Ive heard that some of the mechanical ones get kinda clanky and loud. Is this true?
I've been wanting on getting one, but haven't gotten and information on the cost and process.
Quick question! So there is no other parts to purchase other than the LSD right!.
I want a daily driver LSD, would it be better to get a Viscous or mechanical.
I'm looking for quit and daily driving use, not ***** out performance.
Ive heard that some of the mechanical ones get kinda clanky and loud. Is this true?
03-17-2006 | 02:48 PM
#6
Registered User
Joined: Sep 2005
Posts: 173
Likes: 0
From: Appleton, WI
Any LSD will be fine on the road. The disadvantage of clutch pack based LSD's is that they wear out over time, where as LSD's that use helical gears, etc, never wear out. You shouldn't really get any noise out of a LSD... A locker for offroading, yes, LSD, no. The only situation I can think of noise coming from a LSD would be if you have one with clutch packs and you put in a gear lube withouth friction modifier. Then you could get some clutch chatter from it.
Trending Topics
03-17-2006 | 05:26 PM
#8
I would add that for street driving everyday use, VLSD is what you want given the cost of mechanical LSD. I bought a Quaiffe (sp?) for my old VW. Great diff for the track, pretty much mandatory, but on the street you will rarely realize its benefits (unless your a crazy driver).
03-18-2006 | 09:58 AM
#10
This article compaires VLSD to mechanical LSD
http://www.sportcompactcarweb.com/pr...8scc_proj350z/
there is to much info in this page to cut and paste the whole thing.
This article talks about how it is to drive on the street with the settings to tight.
http://sportcompactcarweb.com/roadtests/0405scc_nismo/
Chris
http://www.sportcompactcarweb.com/pr...8scc_proj350z/
there is to much info in this page to cut and paste the whole thing.
This article talks about how it is to drive on the street with the settings to tight.
http://sportcompactcarweb.com/roadtests/0405scc_nismo/
That's all S-Tune. R-Tune adds a clever, adjustable clutch-type limited slip. The NISMO limited slip can be set up as a two-way (works under acceleration and engine braking) or 1.5-way (same thing, but it's not as strong under engine braking). We recommend 1.5-way. The pre-load on the clutch packs is also adjustable by removing the right-hand stub axle and stuffing a 19mm socket in the hole. The three settings give a breakaway torque of 50, 69, or 101 lb-ft.
If you disassemble the differential, of course, you could also lower the breakaway torque even more by re-arranging the 10 clutch plates on each side of the diff so that some of them are inactive. NISMO doesn't officially state this, but it doesn't have to, that's just how clutch-type diffs work. The NISMO diff is also stronger than the stock one, since it transmits torque through four pinion gears instead of the stock diff's two.
We don't know how the diff in our car was set up, but whatever it was, it was too tight for the street. On the track, where you brake, turn, and accelerate through every corner in the same smooth, predictable fashion, a tight limited slip can be good. Drive a narrow, twisty mountain road at night, though, and you won't be laying into the gas at the apex and holding it down all the way to the next corner. Not with 249 hp at the wheels. Instead, you tend to feed in and out of the gas as you try to stay between the yellow line and the white one and figure out when this damn corner is going to end.
Rolling on and off the throttle like this makes the rear wheels lock together and release every time, which makes the front tires push and then grab with every move of your right foot. That makes you look like a swervy monkey. Don't believe us? Look at the skidpad results. The S-Tune car, which uses the loose factory limited slip, pulled an impressive 0.98g. The R-Tune Z, with exactly the same suspension, but the NISMO diff, pulled "only" 0.95.
Based on our experience with Project 350Z, we'd still recommend the NISMO diff, but set it at the loosest setting and if it still does the swervy thing described above, take it apart and start swapping discs. Remember, it took us three tries to get the KAAZ diff right in our project car.
If you disassemble the differential, of course, you could also lower the breakaway torque even more by re-arranging the 10 clutch plates on each side of the diff so that some of them are inactive. NISMO doesn't officially state this, but it doesn't have to, that's just how clutch-type diffs work. The NISMO diff is also stronger than the stock one, since it transmits torque through four pinion gears instead of the stock diff's two.
We don't know how the diff in our car was set up, but whatever it was, it was too tight for the street. On the track, where you brake, turn, and accelerate through every corner in the same smooth, predictable fashion, a tight limited slip can be good. Drive a narrow, twisty mountain road at night, though, and you won't be laying into the gas at the apex and holding it down all the way to the next corner. Not with 249 hp at the wheels. Instead, you tend to feed in and out of the gas as you try to stay between the yellow line and the white one and figure out when this damn corner is going to end.
Rolling on and off the throttle like this makes the rear wheels lock together and release every time, which makes the front tires push and then grab with every move of your right foot. That makes you look like a swervy monkey. Don't believe us? Look at the skidpad results. The S-Tune car, which uses the loose factory limited slip, pulled an impressive 0.98g. The R-Tune Z, with exactly the same suspension, but the NISMO diff, pulled "only" 0.95.
Based on our experience with Project 350Z, we'd still recommend the NISMO diff, but set it at the loosest setting and if it still does the swervy thing described above, take it apart and start swapping discs. Remember, it took us three tries to get the KAAZ diff right in our project car.
Chris
03-18-2006 | 07:13 PM
#14
Registered User
Joined: Feb 2005
Posts: 62
Likes: 0
From: Utah
The only LSD that I know of where you can get everything for 900$ is the Nismo. I have heard if you don't use the correct gear oil you will have a noisy experience. The install is going to be around 400 for any LSD you get. If you get the Kaaz or Cusco you will have to buy other axle stubs and other stuff.
I got the Quaife LSD in my base about 3 months ago, it is so cold out here in Utah still that I can't really tell how much of a difference it is going to be when I really get on it. It seems to go around turns a little better now and the rear end doesn't go out when I shift from 1st to 2nd at redline. It has no noise at all though. The bad thing is it costs around 1400$ just for the diff so I am into it around ~1800 now. It seems like a few people on here don't really care for the Quaife and prefer a clutch type LSD. You can do a search and get some good info and make your choice from there.
Hope this helps.
Jeremy
I got the Quaife LSD in my base about 3 months ago, it is so cold out here in Utah still that I can't really tell how much of a difference it is going to be when I really get on it. It seems to go around turns a little better now and the rear end doesn't go out when I shift from 1st to 2nd at redline. It has no noise at all though. The bad thing is it costs around 1400$ just for the diff so I am into it around ~1800 now. It seems like a few people on here don't really care for the Quaife and prefer a clutch type LSD. You can do a search and get some good info and make your choice from there.
Hope this helps.
Jeremy
08-01-2012 | 06:47 PM
#18
i have a base model and i added a vlsd pumpkin. best mod i did. not being able to spin the car sideways is pretty depressing
Does this mean with the new vlsd ur able to out er sideways or still no. Cause I have a base too and im stressing cause every car ive owned had a LSD, kinda sucks not having one.
Does this mean with the new vlsd ur able to out er sideways or still no. Cause I have a base too and im stressing cause every car ive owned had a LSD, kinda sucks not having one.
08-01-2012 | 06:56 PM
#19
i have a base model and i added a vlsd pumpkin. best mod i did. not being able to spin the car sideways is pretty depressing
Does this mean with the new vlsd ur able to out er sideways or still no. Cause I have a base too and im stressing cause every car ive owned had a LSD, kinda sucks not having one.
Does this mean with the new vlsd ur able to out er sideways or still no. Cause I have a base too and im stressing cause every car ive owned had a LSD, kinda sucks not having one.
08-01-2012 | 10:13 PM
#20
Does anyone know if there are quality helical limited slip differentials available for the 350z? I had an s15 hlsd in my old s14 with a 4.36 FD ring and pinion. I'd like to do a 4.08 hlsd in the Z but I have only seen ones made by OBX...