RMR Testing RWD Evo 9- Video
Originally Posted by GDB
The dial varies how early/late the differential locks, as I have said.
*Similar* in function when the ACD switches from Tarmac to Gravel to Snow; varying the lock-rate, NOT the amount of torque transferred.
STi = 35:65 AT ALL TIMES (the new one I believe is 49:51 or something like that)
Evo = 50:50 AT ALL TIMES
Only Honda's SH-AWD and I believe Skyline GT-R's ATTESA varies the torque transferred front/rear.
*Similar* in function when the ACD switches from Tarmac to Gravel to Snow; varying the lock-rate, NOT the amount of torque transferred.
STi = 35:65 AT ALL TIMES (the new one I believe is 49:51 or something like that)
Evo = 50:50 AT ALL TIMES
Only Honda's SH-AWD and I believe Skyline GT-R's ATTESA varies the torque transferred front/rear.
Where are you getting 50:50 AT ALL TIMES? The Tarmac setting is a 50/50 split but the center diff dissengages when the parking brake is engaged and also to aid turn in. In Gravel and Snow it is 60/40 and 70/30 front/rear respectively. This is achieved by pulsing the center diff clutch pack and IS the ammount of torque transfered.
"This is the Center Limited Slip Assembly. It is in the same location on all Evos, but in 03 and 04 it is a viscous coupling. On 05+ Evos it is an active clutch pack that can vary the torque split between front and rear."
"This is the Ring and Pinion set that transmits torque to the rear wheels. You can see here how the ring gear is bolted to the dark blue housing that is connected to the center differential's right spider gear. This is an unusual arrangement because the ring gear is actually driving the smaller pinion gear."
Quotes from Stephen Dorrick Mitsu evo drivetrain diagram+description
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Originally Posted by hank
Where are you getting 50:50 AT ALL TIMES? The Tarmac setting is a 50/50 split but the center diff dissengages when the parking brake is engaged and also to aid turn in. In Gravel and Snow it is 60/40 and 70/30 front/rear respectively. This is achieved by pulsing the center diff clutch pack and IS the ammount of torque transfered.
"This is the Center Limited Slip Assembly. It is in the same location on all Evos, but in 03 and 04 it is a viscous coupling. On 05+ Evos it is an active clutch pack that can vary the torque split between front and rear."
"This is the Ring and Pinion set that transmits torque to the rear wheels. You can see here how the ring gear is bolted to the dark blue housing that is connected to the center differential's right spider gear. This is an unusual arrangement because the ring gear is actually driving the smaller pinion gear."
Quotes from Stephen Dorrick Mitsu evo drivetrain diagram+description
"This is the Center Limited Slip Assembly. It is in the same location on all Evos, but in 03 and 04 it is a viscous coupling. On 05+ Evos it is an active clutch pack that can vary the torque split between front and rear."
"This is the Ring and Pinion set that transmits torque to the rear wheels. You can see here how the ring gear is bolted to the dark blue housing that is connected to the center differential's right spider gear. This is an unusual arrangement because the ring gear is actually driving the smaller pinion gear."
Quotes from Stephen Dorrick Mitsu evo drivetrain diagram+description
I still maintain my stand it is 50/50 though
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https://www.evolutionm.net/forums/sh...0&postcount=22
Unlike a viscous coupled center differential, the ACD is mechanically geared to a 50:50 torque spilt. This is only seen when the diff is in 100% lock mode (typically in straight line driving on tarmac). What changes is the opening/slippage between the clutch plates in the diff itself, varing from a fully open diff (no power to rear wheels) to fully locked.
In Tarmac mode ... which has the highest locking force and least slip of the three, the diff opens up (i.e. slips) instantly on turning the wheel allowing for increased steering response.
In Gravel mode (recommended for wet tarmac) ... which has a lower ultimate locking force value, the diff takes 2-3 secs to unlock. Thus sending more power to the 4 wheels on gravel, but still enabling good steering feedback.
In Snow mode ... the locking force is lowest and takes around 5 secs to release.
Get this : the system behaves differently on different surfaces. CCC magazine once said it was as if the electronics know that you are trying to trick it! For example, putting it into Gravel on Dry Tarmac causes the center diff to remain locked for longer and thus sending more power to the REAR wheels... thus causing the oversteer. On wet pavement, putting the car into Gravel mode (as is recommended) quiets the car down and glues it to the road!
The coolest thing about ACD, is that it unlocks the center diff immediately on application of the handbrake, just like a WRC diff.... no need to dip the clutch for handbrake turns!
Unlike a viscous coupled center differential, the ACD is mechanically geared to a 50:50 torque spilt. This is only seen when the diff is in 100% lock mode (typically in straight line driving on tarmac). What changes is the opening/slippage between the clutch plates in the diff itself, varing from a fully open diff (no power to rear wheels) to fully locked.
In Tarmac mode ... which has the highest locking force and least slip of the three, the diff opens up (i.e. slips) instantly on turning the wheel allowing for increased steering response.
In Gravel mode (recommended for wet tarmac) ... which has a lower ultimate locking force value, the diff takes 2-3 secs to unlock. Thus sending more power to the 4 wheels on gravel, but still enabling good steering feedback.
In Snow mode ... the locking force is lowest and takes around 5 secs to release.
Get this : the system behaves differently on different surfaces. CCC magazine once said it was as if the electronics know that you are trying to trick it! For example, putting it into Gravel on Dry Tarmac causes the center diff to remain locked for longer and thus sending more power to the REAR wheels... thus causing the oversteer. On wet pavement, putting the car into Gravel mode (as is recommended) quiets the car down and glues it to the road!
The coolest thing about ACD, is that it unlocks the center diff immediately on application of the handbrake, just like a WRC diff.... no need to dip the clutch for handbrake turns!
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http://www.lancerregister.com/showth...d+torque+split
When you're driving in a straight line the central diff is locked, meaning the 2 axles are turning at exactly the same rate (useful to travel straight ahead I think you'll agree! ) Then when you turn the wheel depending on what mode the ACD is in different stuff happens.
In tarmac, it allows slip straight away. You're supposed to use this mode on dry tarmac where grip is at its highest and as such sliding even just a little bit is slower. The ACD and the SAYC speak to each other too to make a better job of cornering.
In gravel it takes 2-3 seconds to release the diff, this means a small amount of slide can be had which helps to get the back end round (I think). I believe this is on the count that - less grip = more understeer so this combats it. Use this on wet roads - it feels a LOT more secure In tarmac mode, on wet roads the back end feels real twitchy as the SAYC is pretty much on it's own.
In snow it takes 5-6 seconds to release but I've never tried this. I'm guessing you could get some real good slides with this. I'll give it a go at Llandow tomorrow and let you know!
All the above is what I've gleaned from reading stuff on here and other sites. There are still a lot of people who say ACD transfers torque, they are definitely wrong!!!
When you're driving in a straight line the central diff is locked, meaning the 2 axles are turning at exactly the same rate (useful to travel straight ahead I think you'll agree! ) Then when you turn the wheel depending on what mode the ACD is in different stuff happens.
In tarmac, it allows slip straight away. You're supposed to use this mode on dry tarmac where grip is at its highest and as such sliding even just a little bit is slower. The ACD and the SAYC speak to each other too to make a better job of cornering.
In gravel it takes 2-3 seconds to release the diff, this means a small amount of slide can be had which helps to get the back end round (I think). I believe this is on the count that - less grip = more understeer so this combats it. Use this on wet roads - it feels a LOT more secure In tarmac mode, on wet roads the back end feels real twitchy as the SAYC is pretty much on it's own.
In snow it takes 5-6 seconds to release but I've never tried this. I'm guessing you could get some real good slides with this. I'll give it a go at Llandow tomorrow and let you know!
All the above is what I've gleaned from reading stuff on here and other sites. There are still a lot of people who say ACD transfers torque, they are definitely wrong!!!
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Another quote from the Lancer Register:
Fishmonkey you are correct in you comments, that is how the ACD works. I know this cos Ive asked soooooo many people inc Mitsi UK and EU and they confirmed your explanation. Unless they are incorrect this is my understanding
The VIII in 4WD mode ( straight line ) is always 50:50 the settings on the ACD determine how long the 50:50 drive is locked once the steering wheel has been turned. Effectively the car becomes RWD once you turn the wheel, the longer the ACD is engaged the more amount of 4WD drive you have on lock.
Tarmac = Turn the wheel - ACD Drops traction to the Front immediately = promotes overseer as in the dry the front end has grip and off you go let the SAYC take over
Gravel= Turn the wheel - ACD Drops traction to the Front 2-3 Secs later = you have some front end pull on lock to get you round then the back pushes you round again SAYC comes in to play
Snow= Turn the wheel - ACD Drops traction to the Front 5-6 Secs later = you still have some front end pull on lock to get you round then the back end only has the drive again SAYC comes in to play
My understanding from Mitsi is that the whole system is designed to promote overseer in every scenario as this is deemed to be a better compensator that Understeer when going round corners esp on slippy surfaces.
And don’t forget that this all happens only on turns and as soon as the front wheels return to straight ahead everything goes back to FWD 50:50.
Its a bit mad really cos its all automatic and if you are driving hard around corners or even with a little throttle on cruising all this still is running and working
Fishmonkey you are correct in you comments, that is how the ACD works. I know this cos Ive asked soooooo many people inc Mitsi UK and EU and they confirmed your explanation. Unless they are incorrect this is my understanding
The VIII in 4WD mode ( straight line ) is always 50:50 the settings on the ACD determine how long the 50:50 drive is locked once the steering wheel has been turned. Effectively the car becomes RWD once you turn the wheel, the longer the ACD is engaged the more amount of 4WD drive you have on lock.
Tarmac = Turn the wheel - ACD Drops traction to the Front immediately = promotes overseer as in the dry the front end has grip and off you go let the SAYC take over
Gravel= Turn the wheel - ACD Drops traction to the Front 2-3 Secs later = you have some front end pull on lock to get you round then the back pushes you round again SAYC comes in to play
Snow= Turn the wheel - ACD Drops traction to the Front 5-6 Secs later = you still have some front end pull on lock to get you round then the back end only has the drive again SAYC comes in to play
My understanding from Mitsi is that the whole system is designed to promote overseer in every scenario as this is deemed to be a better compensator that Understeer when going round corners esp on slippy surfaces.
And don’t forget that this all happens only on turns and as soon as the front wheels return to straight ahead everything goes back to FWD 50:50.
Its a bit mad really cos its all automatic and if you are driving hard around corners or even with a little throttle on cruising all this still is running and working
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... and finally some more technical bits on ACD
http://www.btrprep.com/evo_7.htm
http://www.btrprep.com/e7_qa.htm
http://www.btrprep.com/evo_7.htm
http://www.btrprep.com/e7_qa.htm
Originally Posted by GDB
Another quote from the Lancer Register:
Fishmonkey you are correct in you comments, that is how the ACD works. I know this cos Ive asked soooooo many people inc Mitsi UK and EU and they confirmed your explanation. Unless they are incorrect this is my understanding
The VIII in 4WD mode ( straight line ) is always 50:50 the settings on the ACD determine how long the 50:50 drive is locked once the steering wheel has been turned. Effectively the car becomes RWD once you turn the wheel, the longer the ACD is engaged the more amount of 4WD drive you have on lock.
Tarmac = Turn the wheel - ACD Drops traction to the Front immediately = promotes overseer as in the dry the front end has grip and off you go let the SAYC take over
Gravel= Turn the wheel - ACD Drops traction to the Front 2-3 Secs later = you have some front end pull on lock to get you round then the back pushes you round again SAYC comes in to play
Snow= Turn the wheel - ACD Drops traction to the Front 5-6 Secs later = you still have some front end pull on lock to get you round then the back end only has the drive again SAYC comes in to play
My understanding from Mitsi is that the whole system is designed to promote overseer in every scenario as this is deemed to be a better compensator that Understeer when going round corners esp on slippy surfaces.
And don’t forget that this all happens only on turns and as soon as the front wheels return to straight ahead everything goes back to FWD 50:50.
Its a bit mad really cos its all automatic and if you are driving hard around corners or even with a little throttle on cruising all this still is running and working
Fishmonkey you are correct in you comments, that is how the ACD works. I know this cos Ive asked soooooo many people inc Mitsi UK and EU and they confirmed your explanation. Unless they are incorrect this is my understanding
The VIII in 4WD mode ( straight line ) is always 50:50 the settings on the ACD determine how long the 50:50 drive is locked once the steering wheel has been turned. Effectively the car becomes RWD once you turn the wheel, the longer the ACD is engaged the more amount of 4WD drive you have on lock.
Tarmac = Turn the wheel - ACD Drops traction to the Front immediately = promotes overseer as in the dry the front end has grip and off you go let the SAYC take over
Gravel= Turn the wheel - ACD Drops traction to the Front 2-3 Secs later = you have some front end pull on lock to get you round then the back pushes you round again SAYC comes in to play
Snow= Turn the wheel - ACD Drops traction to the Front 5-6 Secs later = you still have some front end pull on lock to get you round then the back end only has the drive again SAYC comes in to play
My understanding from Mitsi is that the whole system is designed to promote overseer in every scenario as this is deemed to be a better compensator that Understeer when going round corners esp on slippy surfaces.
And don’t forget that this all happens only on turns and as soon as the front wheels return to straight ahead everything goes back to FWD 50:50.
Its a bit mad really cos its all automatic and if you are driving hard around corners or even with a little throttle on cruising all this still is running and working
Originally Posted by GDB
... and finally some more technical bits on ACD
http://www.btrprep.com/evo_7.htm
http://www.btrprep.com/e7_qa.htm
http://www.btrprep.com/evo_7.htm
http://www.btrprep.com/e7_qa.htm
