Cusco central diff 35/65 power split
23 December 2003, 10:33 PM
#31
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Once an open diff has lost traction at one side, all torque goes to that side
I still think you guys are wrong. If an open diff loses traction on one side then the total torque transmitted drops..period. That's why the engine rpm increases, there is no load due to the lack of torque reaction. Once you get a 4wd car in a spin, you don't need much power to keep it going, thats because there is low torque reaction from the slipping wheels.
An open axle diff will transmit torque equally (dccd in its 2:1 geared ratio) regardless, even if one wheel is in the air, when of course total torque = zero
Torque biasing diff, as Paul states, does the opposite. It biases torque to the wheel with the grip.
[Edited by Andy.F - 12/23/2003 10:45:42 PM]
23 December 2003, 10:43 PM
#32
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Watching the video (didn't really cos I've seen it before) I know exactly what happens but it is for the opposite reason you state !
As the eng rpm is allowed to drop, the rears gain some grip, it follows that the fronts then get more torque (via the fixed ratio in the differential) and the front starts to tug. Temporarily apply more power (blip) to break traction again at the rear and the total torque output is reduced, this is as a result of reduced traction. The front then stops tugging as it's (fixed) percentage of torque has also dropped.
Andy
(Adam - Tell him he's going to lose this one )
I know, lets bet a case of beer on it That sharpens the focus somewhat 
thats bolloks too
[Edited by Andy.F - 12/23/2003 11:40:51 PM]
As the eng rpm is allowed to drop, the rears gain some grip, it follows that the fronts then get more torque (via the fixed ratio in the differential) and the front starts to tug. Temporarily apply more power (blip) to break traction again at the rear and the total torque output is reduced, this is as a result of reduced traction. The front then stops tugging as it's (fixed) percentage of torque has also dropped.
Andy
(Adam - Tell him he's going to lose this one
)I know, lets bet a case of beer on it
That sharpens the focus somewhat
Torque always follows the path of least resitance
thats bolloks too [Edited by Andy.F - 12/23/2003 11:40:51 PM]
24 December 2003, 09:08 AM
#35
haha i knew this was coming.
I agree with this, as traction drops you do see a loss in transmited torque, however the reason rpm rises is due to increased wheel speed as it spins, not because of the drop in torque.
I dont agree with that, there is substantial load, you dont get 2 tyres smoking without a significant load being applied, likewise there is a significant load there to provide the rotational forces and the forces propelling the car forward as it exits the donut. I understand what you are saying andy, but i dont agree with you on the fact the torque ratio stays to the same once wheel slip occurs.
I have been looking at the design of the DCCD centre diff a bit more, and if i am understanding it properly, it does indeed look like the torque split is being altered. This is entirely due to the design of how the plates are clamping the two sides together and isnt a function of the fact you have a locking LSD in the system.
If you look closely, in open diff setting you are relying 100% on the sun/planet gear ratios at 2:1. What the clutch plates do is bypass the sun/planet gears by locking together the carriers, which are running at physically diferent geared ratios of 1:1 rather than 2:1. So it does look like you get 50/50 torque split when the clutch plates are clamp hard enough to prevent any slip.
So the DCCD is in fact an LSD and a variable torque biasing system, it isnt a variable torque biasing system because it is an LSD though, you could have had it keep the torque split 2:1 if the way the plates transfer the load had been diferent and followed the same physical leverage ratio as the sun/planet gears. Very clever.
I still think you guys are wrong. If an open diff loses traction on one side then the total torque transmitted drops..period. That's why the engine rpm increases
there is no load due to the lack of torque reaction.
I have been looking at the design of the DCCD centre diff a bit more, and if i am understanding it properly, it does indeed look like the torque split is being altered. This is entirely due to the design of how the plates are clamping the two sides together and isnt a function of the fact you have a locking LSD in the system.
If you look closely, in open diff setting you are relying 100% on the sun/planet gear ratios at 2:1. What the clutch plates do is bypass the sun/planet gears by locking together the carriers, which are running at physically diferent geared ratios of 1:1 rather than 2:1. So it does look like you get 50/50 torque split when the clutch plates are clamp hard enough to prevent any slip.
So the DCCD is in fact an LSD and a variable torque biasing system, it isnt a variable torque biasing system because it is an LSD though, you could have had it keep the torque split 2:1 if the way the plates transfer the load had been diferent and followed the same physical leverage ratio as the sun/planet gears. Very clever.
24 December 2003, 10:33 AM
#36
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With a open 35/65 centre diff like on Theo´s car, you will ALWAYS have a 35/65 torque distribution between front and rear! This is also the "weak" point when using it with a standard LSD (which doesn´t do much locking in my opinion...) at the rear.
If we assume the rear diff to be an open diff, it´s a bit easier to explane:
If you are accelerating and a total amount of 1000 Nm is split into 350 Nm to the front wheels and 650 Nm to the rears. 325 Nm is fed to the LH rear wheel and 325 Nm to the RH rear wheel. If one rear wheel loses traction because of sand on the road or because it´s unloaded during cornering, it can (example!) only transfer about 100 Nm of torque. With an open diff, this means "automaticly" the other wheel also transfers "only" 100 Nm. The total amount of torque that will be transfered will be 200 / 0.65 = 307.7 Nm. This means not much power is left to accelerate the car!
This "story" is only true if both the front wheels are able to distribute 307.7 * 0.35 = 107.7 Nm to the road.
With a "stiffer" LSD at the rear, there will be more torque distributed to the wheel with more traction and the total amount of torque (also at the front) available for accelerating the car will increase.
Because of the 35/65 torque split, a front LSD is less important than a rear LSD.
Mark.
If we assume the rear diff to be an open diff, it´s a bit easier to explane:
If you are accelerating and a total amount of 1000 Nm is split into 350 Nm to the front wheels and 650 Nm to the rears. 325 Nm is fed to the LH rear wheel and 325 Nm to the RH rear wheel. If one rear wheel loses traction because of sand on the road or because it´s unloaded during cornering, it can (example!) only transfer about 100 Nm of torque. With an open diff, this means "automaticly" the other wheel also transfers "only" 100 Nm. The total amount of torque that will be transfered will be 200 / 0.65 = 307.7 Nm. This means not much power is left to accelerate the car!
This "story" is only true if both the front wheels are able to distribute 307.7 * 0.35 = 107.7 Nm to the road.
With a "stiffer" LSD at the rear, there will be more torque distributed to the wheel with more traction and the total amount of torque (also at the front) available for accelerating the car will increase.
Because of the 35/65 torque split, a front LSD is less important than a rear LSD.
Mark.
24 December 2003, 11:36 AM
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Mark
Thank you
You are bang on correct. JF still does not get it, I think he is still confusing power with torque.
We need to go back to basics, for every action there has to be an equal and opposite reaction. (no doubt about that)
So you can only transmit more torque if there is more grip available. If grip available drops (ie wheelspin) then the torque to turn that wheel must reduce.
Where JF states "Torque always follows the path of least resitance" he is clearly wrong.
Torque will only exist to the level of the opposing reaction force (traction in this case)
Andy
Thank you
You are bang on correct. JF still does not get it, I think he is still confusing power with torque.We need to go back to basics, for every action there has to be an equal and opposite reaction. (no doubt about that
)So you can only transmit more torque if there is more grip available. If grip available drops (ie wheelspin) then the torque to turn that wheel must reduce.
Where JF states "Torque always follows the path of least resitance" he is clearly wrong.
Torque will only exist to the level of the opposing reaction force (traction in this case)
Andy
24 December 2003, 11:44 AM
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Because of the 35/65 torque split, a front LSD is less important than a rear LSD.
In the rain, I can light up a rear tyre in 3rd gear with only about 300 BHP, not good at all
(can you kick Quaifes butt for me again so they finally deliver the rear diff ?
)
24 December 2003, 02:38 PM
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Interestingly, this also means moray is worse off with his standard non plated r160 rear viscous lsd.
Andy, in the light of the above explanation (mark's), what would fitting a rear atb do as opposed to the plated r180 I have at the mo. How agressive is an auto torque biasing diff?
[Edited by Adam M - 12/24/2003 2:56:39 PM]
Andy, in the light of the above explanation (mark's), what would fitting a rear atb do as opposed to the plated r180 I have at the mo. How agressive is an auto torque biasing diff?
[Edited by Adam M - 12/24/2003 2:56:39 PM]
24 December 2003, 04:57 PM
#41
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An ATB is totally non aggressive in operation. There may be a slight issue when one wheel is in the air though with an ATB unless it has some form of preload on it. I believe the Quaife has this preload built in.
I'm surprised Murray can drive his car with a std viscous rear and the dccd open ? My car was spinning an inner rear if I wound it on a bit (maybe he just drives slow and doesn't notice)
Andy
I'm surprised Murray can drive his car with a std viscous rear and the dccd open ? My car was spinning an inner rear if I wound it on a bit (maybe he just drives slow and doesn't notice
)Andy
24 December 2003, 05:06 PM
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Just to add - sometimes the quick locking action of a plated rear diff is desireable in order to allow the tail to be kicked out easier. I don't however believe this is the quickest way to drive on the road
Andy
Andy
24 December 2003, 05:29 PM
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There may be a slight issue when one wheel is in the air though with an ATB
My goal since 1999 has been to have a car that would power oversteer on, say, an airfield. I had tried everything (DMS suspension, more power, rollbars, geometry, bump steer mod, front ATB diff, etc...) and it all helped to reduce understeer, but never got anywhere near power oversteer except at MIRA. The Cusco finally changed that, and I can't wait to loon about on an airfield again once the ATB rear is fitted
[Edited by EvilBevel - 12/25/2003 3:38:07 PM]
25 December 2003, 12:58 PM
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Quaife told me they are going to send out the parts needed ASAP.........
We will see how it will behave in your car! In my opinion a setup like in the RS version of the EVO is the best thing to have: Torsen (or similar) diff in front combined with plated rear diff. I like the "trick" with the 35/65 Cusco!
Mark.
We will see how it will behave in your car! In my opinion a setup like in the RS version of the EVO is the best thing to have: Torsen (or similar) diff in front combined with plated rear diff. I like the "trick" with the 35/65 Cusco!
Mark.
25 December 2003, 01:34 PM
#45
That is basically the config my car has. Plated rear, DCCD centre, conventional mechanical front LSD. It seems to work extremely well.
You may find benefits with running softer ARB's with ATB type diffs, allowing the car to roll a little more but picking up a lot of traction in the process.
You may find benefits with running softer ARB's with ATB type diffs, allowing the car to roll a little more but picking up a lot of traction in the process.
25 December 2003, 02:13 PM
#47
ah, sorry. STi installed 2 diferent types of torsen front LSD in the TypeRA's prior to them using the AP Suretrack. My LSD is the 2nd version they used. I dont know that much about its spec though and unfortunately didnt take a good look at it when the box was apart. Maybe Andy can help, he seems to have boxes apart every 2 minutes.
The TypeR's and other STi's, Turbo's etc always used an open front diff as standard, although a front LSD was a factory option i believe. There are often wierd little diferences on these cars, for example my RA has a 22B steering rack rather than an RA steering rack.
The TypeR's and other STi's, Turbo's etc always used an open front diff as standard, although a front LSD was a factory option i believe. There are often wierd little diferences on these cars, for example my RA has a 22B steering rack rather than an RA steering rack.
25 December 2003, 04:49 PM
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I thought that Sti differentials are viscous or plated type. Dont know if STi support any viscous coupling type on the front. I think all the STi diffs suited to front position are mechanical type = plated.
For the new age STi made Suretrack but I dont know what is the princip: if they are torsen gearing type or plated or some mechanical uses pins for locking the diff. Can somebody clarify infos about suretracks?
For the new age STi made Suretrack but I dont know what is the princip: if they are torsen gearing type or plated or some mechanical uses pins for locking the diff. Can somebody clarify infos about suretracks?
25 December 2003, 11:21 PM
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Front LSD Options
Front LSD's minimize wheel slip under hard acceleration and allow you to get on the power sooner out of a corner. Clutch type front LSD's can have a negative effect on handling so care should be taken in choosing the proper one for your application. 1.5-way front LSD's should be used for rally on low traction surfaces. 1.5-way front LSD's can be used for tarmac use if set up with low lock-up ratio. 1-way LSD's are better options for tarmac use. Helical front LSD (similar to Quaife & Torsen) is best option for road use (also good for autocross and track).
5 Speed Gearbox:
RST-1901 STi Group N 1.5way LSD for 5MT (all models) -- $1417
KZ-2015 Kaaz 1.5way LSD for 5MT (all models) -- $880
CU-180F Cusco 1way RS-type LSD for 5MT (all models) -- $1150
RST-1903 STi Helical LSD for 5MT (all models) -- $910
(STi) 6 Speed Gearbox:
RST-1902 STi Group N 1.5way LSD for STi 6MT -- $1437
CU-180F Cusco 1way RS-type LSD for STi 6MT -- $1150
Rear Limited Slip Differential
Clutch type mechanical rear LSDs provide for additional traction on loose surfaces. The 2-way differential action of the STi unit provides limited slip action in both acceleration and braking for optimal cornering control and brake action (by limiting rear wheel slip in braking more effective use of the rear brake system occurs). For tarmac use a 1.5way type is preferrable. The Suretrack unit is a torque sensing cam-type LSD with low lock-up ratio for seamless operation and is the best option for road use. No axle changes are necessary for these LSD's. Please contact us for pricing on older Ver.1-4 applications.
R160 Rear Differential (MY99-04):
RST-1950 STi Group N 2way LSD for R160 -- $1493
CU-183L2 Cusco 2way RS-type LSD for R160 -- $1045
CU-183L Cusco 1.5way RS-type LSD for R160 -- $1150
CU-183K Cusco 1.5way MZ-type LSD for R160 -- $920
CU-183F Cusco 1way RS-type LSD for R160 (autocross spec.) -- $1045
RST-1959 STi Suretrack LSD for R160 -- $890
R180 (STi) Rear Differential:
CU-182L2 Cusco 2way RS-type LSD for R180 -- $1150
KZ-2040 Kaaz 1.5way LSD for R180 -- $880
CU-182L Cusco 1.5way RS-type LSD for R180 -- $1150
CU-182K Cusco 1.5way MZ-type LSD for R180 -- $962
CU-182FG Cusco 1way RS-type LSD for R180 (autocross spec.) -- $1150
Center Limited Slip Differential
Upgraded center differential options for Subaru 5 & 6 speed gearboxes. 20kgf/100rpm heavy duty viscous units provide considerably more responsive torque transfer action then the stock 4kgf/100rpm center diff. Increased clutch plate quantity and oil viscosity withstands greater abuse. Kaaz and Cusco units provide torque sensitive LSD action as opposed to the speed sensitive action of the viscous units therefore maximizing wheel slip control. The upgraded center diff. is the best place to start when seeking to optimize the AWD traction of the Subaru as this allows more instantaneous torque transfer to the axle with more grip when wheelspin is encountered.
RST-1215 STi 20kgf Center LSD for MY99-02 5MT -- $878
RST-1212 STi 20kgf Center LSD for MY90-98 5MT -- $711
RST-1219 STi 20kgf Center LSD for STi 6MT -- $946
KZ-2020 Kaaz Center 1.5way LSD for MY90-98 5MT -- $1360
CU-187F Cusco Center 2way RS-type LSD for 6MT -- $1383
CU-1200 Cusco Tarmac Gear (rear biased center differential) -- $1464
Front LSD's minimize wheel slip under hard acceleration and allow you to get on the power sooner out of a corner. Clutch type front LSD's can have a negative effect on handling so care should be taken in choosing the proper one for your application. 1.5-way front LSD's should be used for rally on low traction surfaces. 1.5-way front LSD's can be used for tarmac use if set up with low lock-up ratio. 1-way LSD's are better options for tarmac use. Helical front LSD (similar to Quaife & Torsen) is best option for road use (also good for autocross and track).
5 Speed Gearbox:
RST-1901 STi Group N 1.5way LSD for 5MT (all models) -- $1417
KZ-2015 Kaaz 1.5way LSD for 5MT (all models) -- $880
CU-180F Cusco 1way RS-type LSD for 5MT (all models) -- $1150
RST-1903 STi Helical LSD for 5MT (all models) -- $910
(STi) 6 Speed Gearbox:
RST-1902 STi Group N 1.5way LSD for STi 6MT -- $1437
CU-180F Cusco 1way RS-type LSD for STi 6MT -- $1150
Rear Limited Slip Differential
Clutch type mechanical rear LSDs provide for additional traction on loose surfaces. The 2-way differential action of the STi unit provides limited slip action in both acceleration and braking for optimal cornering control and brake action (by limiting rear wheel slip in braking more effective use of the rear brake system occurs). For tarmac use a 1.5way type is preferrable. The Suretrack unit is a torque sensing cam-type LSD with low lock-up ratio for seamless operation and is the best option for road use. No axle changes are necessary for these LSD's. Please contact us for pricing on older Ver.1-4 applications.
R160 Rear Differential (MY99-04):
RST-1950 STi Group N 2way LSD for R160 -- $1493
CU-183L2 Cusco 2way RS-type LSD for R160 -- $1045
CU-183L Cusco 1.5way RS-type LSD for R160 -- $1150
CU-183K Cusco 1.5way MZ-type LSD for R160 -- $920
CU-183F Cusco 1way RS-type LSD for R160 (autocross spec.) -- $1045
RST-1959 STi Suretrack LSD for R160 -- $890
R180 (STi) Rear Differential:
CU-182L2 Cusco 2way RS-type LSD for R180 -- $1150
KZ-2040 Kaaz 1.5way LSD for R180 -- $880
CU-182L Cusco 1.5way RS-type LSD for R180 -- $1150
CU-182K Cusco 1.5way MZ-type LSD for R180 -- $962
CU-182FG Cusco 1way RS-type LSD for R180 (autocross spec.) -- $1150
Center Limited Slip Differential
Upgraded center differential options for Subaru 5 & 6 speed gearboxes. 20kgf/100rpm heavy duty viscous units provide considerably more responsive torque transfer action then the stock 4kgf/100rpm center diff. Increased clutch plate quantity and oil viscosity withstands greater abuse. Kaaz and Cusco units provide torque sensitive LSD action as opposed to the speed sensitive action of the viscous units therefore maximizing wheel slip control. The upgraded center diff. is the best place to start when seeking to optimize the AWD traction of the Subaru as this allows more instantaneous torque transfer to the axle with more grip when wheelspin is encountered.
RST-1215 STi 20kgf Center LSD for MY99-02 5MT -- $878
RST-1212 STi 20kgf Center LSD for MY90-98 5MT -- $711
RST-1219 STi 20kgf Center LSD for STi 6MT -- $946
KZ-2020 Kaaz Center 1.5way LSD for MY90-98 5MT -- $1360
CU-187F Cusco Center 2way RS-type LSD for 6MT -- $1383
CU-1200 Cusco Tarmac Gear (rear biased center differential) -- $1464
26 December 2003, 11:16 AM
#51
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This make very interesting reading, although I do not understand much of it yet!!
What would I need to do to make my STi 8 (no DCCD, standard suretrac LSD front and rear) into a good drift and gymkhana car like the cusco EVO 6 demonstrator? I have thought about installing a DCCD gearbox, but this requires new wiring looms etc. This Cusco 35/65 centre differential sounds good (even if it is permanent 35/65 split), but from the sounds of it I will need to replace the suretrac LSD's, but with what?
rupert
What would I need to do to make my STi 8 (no DCCD, standard suretrac LSD front and rear) into a good drift and gymkhana car like the cusco EVO 6 demonstrator? I have thought about installing a DCCD gearbox, but this requires new wiring looms etc. This Cusco 35/65 centre differential sounds good (even if it is permanent 35/65 split), but from the sounds of it I will need to replace the suretrac LSD's, but with what?
rupert
27 December 2003, 09:59 AM
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you guys seem to no alot about this subject
ive bought a 95sti-ra from japan that was used as some kind of track car
its apparently got 3 times cusco lsd's in it
i no the front and rear are quite tight similar to my old mk1 escorts ZF motorsports unit
but ive no idea what the centre is as ive not took it to pieces yet its still got a eleci wire going to the centre diff so it could be just std
car also had the os giken twin plate paddle clutch and flywheel combination and a nice set of 8"-17" rays racing alloys and dunlop formula r's
my idea is to stage rally it(in forests) but from what hrubago says ive probly got diffs more suited to tarmac
one question what diff and gearbox oil should i use with the diffs
the oil at the mo is red in colour
should i drain this and use something like castrol b373 oil or is this not suitable for the cusco diffs
ill be puttin a dog kit in the box if that helps you decide the best oil
cheers for any info
Darbo
ive bought a 95sti-ra from japan that was used as some kind of track car
its apparently got 3 times cusco lsd's in it
i no the front and rear are quite tight similar to my old mk1 escorts ZF motorsports unit
but ive no idea what the centre is as ive not took it to pieces yet its still got a eleci wire going to the centre diff so it could be just std
car also had the os giken twin plate paddle clutch and flywheel combination and a nice set of 8"-17" rays racing alloys and dunlop formula r's
my idea is to stage rally it(in forests) but from what hrubago says ive probly got diffs more suited to tarmac
one question what diff and gearbox oil should i use with the diffs
the oil at the mo is red in colour
should i drain this and use something like castrol b373 oil or is this not suitable for the cusco diffs
ill be puttin a dog kit in the box if that helps you decide the best oil
cheers for any info
Darbo
27 December 2003, 01:27 PM
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Can you agreee that best combination is (for the Classic UK turbo or STi except RA or type R):
1) front 1-way plate type LSD or torsen ATB + rear 2- or 1,5 way plated diff.
2) then its time to think about DCCD.
1) front 1-way plate type LSD or torsen ATB + rear 2- or 1,5 way plated diff.
2) then its time to think about DCCD.