sti v5 Type r centre diff control
26 November 2000, 11:21 AM
#3
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Hi buddy
IMHO the centre diff control is an incredibly important driving control.
The Type R's have a very agressive rear diff, so need this control to off safety and stability under power in slippy conditions.
In the full back (open) position the centre diff is very open (perhaps someone can confirm whether it is fully open (it feels it)), which (due to the rear torqe bias) effectively means the car will be almost RWD.
BUT, it is not as simple as that, as nobody in the world would put the rear diff of a type r in a powerful RWD road car, as they would be way too difficult to control for the average driver.
The more you move the diff control forward (tighter) the more you limit the amount of torque that can escape to the rear diff. This means that you are effectively moving the bias forward. This continues up until the point that you lock the centre diff which basically means 50:50 torque split.
On the road the only really useable range is from full back (open) to the point where the first orange light comes on.
In completely dry conditions I have the diff full back.
If it is wet on the ground I'll set it to around the point where the second green light comes on.
If it is raining and there is a lot of wet or grease, I'll set it to the point where the first orange light comes on.
But remember that the control is an analogue control in that the lights are only there as a guide, so in truth I am altering it all the time while driving.
Also, if you have it set forward a bit, remember to roll it back for tight slow corners, otherwise you'll hear that noise that all type r owners love so much!!
Another thing worth mentioning, is that the more you roll the diff forward the more you are likely to promte slight understeer. Don't be a hero though and think "nah, I'll leave it all the way back for serious sideways action!!"
because it will bite you.
The Type R is fabulous version of impreza (IMHO the best - although the judges are back out on the 22B since finding another one that I like (thanks chuckster)) but the diff set-up if far better suited to gravel than the road.
You can't be as carefree with it as you can the UK, WRX or Standard STi, as they require a lot more *driving*. But the pleasure for me is that the diff control basically means you have many totally different handling cars in one.
Hope this helps
Cheers
Simon
IMHO the centre diff control is an incredibly important driving control.
The Type R's have a very agressive rear diff, so need this control to off safety and stability under power in slippy conditions.
In the full back (open) position the centre diff is very open (perhaps someone can confirm whether it is fully open (it feels it)), which (due to the rear torqe bias) effectively means the car will be almost RWD.
BUT, it is not as simple as that, as nobody in the world would put the rear diff of a type r in a powerful RWD road car, as they would be way too difficult to control for the average driver.
The more you move the diff control forward (tighter) the more you limit the amount of torque that can escape to the rear diff. This means that you are effectively moving the bias forward. This continues up until the point that you lock the centre diff which basically means 50:50 torque split.
On the road the only really useable range is from full back (open) to the point where the first orange light comes on.
In completely dry conditions I have the diff full back.
If it is wet on the ground I'll set it to around the point where the second green light comes on.
If it is raining and there is a lot of wet or grease, I'll set it to the point where the first orange light comes on.
But remember that the control is an analogue control in that the lights are only there as a guide, so in truth I am altering it all the time while driving.
Also, if you have it set forward a bit, remember to roll it back for tight slow corners, otherwise you'll hear that noise that all type r owners love so much!!
Another thing worth mentioning, is that the more you roll the diff forward the more you are likely to promte slight understeer. Don't be a hero though and think "nah, I'll leave it all the way back for serious sideways action!!"
because it will bite you.The Type R is fabulous version of impreza (IMHO the best - although the judges are back out on the 22B since finding another one that I like (thanks chuckster)) but the diff set-up if far better suited to gravel than the road.
You can't be as carefree with it as you can the UK, WRX or Standard STi, as they require a lot more *driving*. But the pleasure for me is that the diff control basically means you have many totally different handling cars in one.
Hope this helps
Cheers
Simon
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27 November 2000, 03:30 PM
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Buddy,
I would re-iterate what Simon has said on this one. I never use my diff-lock more that two notches up, i.e first amber( I think).
This makes it handle more predictably in the wet. I swear that the steering even becomes slightly heavier!
Don't leave it like that when you tight turn though, otherwise you'll get the diff to wind up. Not a bad thing, but it sounds awful!
Above all, enjoy!
Matt
I would re-iterate what Simon has said on this one. I never use my diff-lock more that two notches up, i.e first amber( I think).
This makes it handle more predictably in the wet. I swear that the steering even becomes slightly heavier!
Don't leave it like that when you tight turn though, otherwise you'll get the diff to wind up. Not a bad thing, but it sounds awful!
Above all, enjoy!
Matt
28 November 2000, 02:57 PM
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Sorry, but can you guys explain 2 things:
1) what do you mean by 'wind up' ? What does it actually do ?
2) Why, if more drive is at the front does it understeer more ?
I havent been brave enough to use the diff control yet, as I just wasnt sure what it would do to the cars behaviour.
1) what do you mean by 'wind up' ? What does it actually do ?
2) Why, if more drive is at the front does it understeer more ?
I havent been brave enough to use the diff control yet, as I just wasnt sure what it would do to the cars behaviour.
29 November 2000, 09:49 AM
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TRIGGER:
1) When you go around a corner, each wheel drives along an arc of a different radius, which makes them rotate at a different speed. Imagine doing a tight 180' without skidding or spinning your wheels, the outer wheels are on a larger arc of a bigger radius, so they travel further, so they rotate faster than the inner wheels.
There is a similar difference between the front & rear wheel speeds, although it is less pronounced.
Windup occurs in the driveshaft when the wheel(s) at one end try to turn faster than the wheel(s) at the other end. It is literally the effect of the driveshaft being wound up (twisted) like the elastic band in a model aeroplane.
The diff allows the wheels to both receive torque from the engine, while still being free to rotate at different speeds.
A fully open diff would let one wheel turn as fast as it wanted while the other was stationary. A "Limited Slip Diff" (LSD) allows a limited amount of slip, or difference between the wheel speeds. A locked diff allows no slip, just like a solid axle.
On loose surfaces, such as mud or gravel, windup isn't a problem, because any windup torque is dissippated by the wheels spinning.
2) Because more drive is at the front!
More torque at the rear makes the car oversteer, move it to the front and it makes the car oversteer less, to the point that it begins to understeer.
[This message has been edited by DavidRB (edited 29 November 2000).]
1) When you go around a corner, each wheel drives along an arc of a different radius, which makes them rotate at a different speed. Imagine doing a tight 180' without skidding or spinning your wheels, the outer wheels are on a larger arc of a bigger radius, so they travel further, so they rotate faster than the inner wheels.
There is a similar difference between the front & rear wheel speeds, although it is less pronounced.
Windup occurs in the driveshaft when the wheel(s) at one end try to turn faster than the wheel(s) at the other end. It is literally the effect of the driveshaft being wound up (twisted) like the elastic band in a model aeroplane.
The diff allows the wheels to both receive torque from the engine, while still being free to rotate at different speeds.
A fully open diff would let one wheel turn as fast as it wanted while the other was stationary. A "Limited Slip Diff" (LSD) allows a limited amount of slip, or difference between the wheel speeds. A locked diff allows no slip, just like a solid axle.
On loose surfaces, such as mud or gravel, windup isn't a problem, because any windup torque is dissippated by the wheels spinning.
2) Because more drive is at the front!
More torque at the rear makes the car oversteer, move it to the front and it makes the car oversteer less, to the point that it begins to understeer.[This message has been edited by DavidRB (edited 29 November 2000).]
29 November 2000, 11:08 AM
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This is all great stuff about the diff control, thanks guys. But one comment hasn't been answered that definitely interests me.
That is: Can the diff control be used while in motion?
At the moment I only adjust it when I am stationary. Does anyone know the official line on this? And maybe even the technical reasoning behind the answer?
If you excuse the Pun, it will make a difference as to how much I use it when I drive.
Julian
That is: Can the diff control be used while in motion?
At the moment I only adjust it when I am stationary. Does anyone know the official line on this? And maybe even the technical reasoning behind the answer?
If you excuse the Pun, it will make a difference as to how much I use it when I drive.
Julian
29 November 2000, 11:28 AM
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I haven't encountered any problems moving it while in motion. Not a good idea to change it when stationary as if pulling out of a junction, with the dial rolled forward, it will cause the diffs to complain (Knock knock crunch tap.)
I think the rear bias is 60:40 or 63:37 something like that - and then as you wind it forward the ratio's will go down to 50:50 (locked.) The only road driveable settings are Super green, green, first amber IMO.
I think the rear bias is 60:40 or 63:37 something like that - and then as you wind it forward the ratio's will go down to 50:50 (locked.) The only road driveable settings are Super green, green, first amber IMO.
29 November 2000, 11:47 AM
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A bit off topic but....
Do all cars equiped with the electronic centre diff have mechanical front and rear diffs? (i believe the straight Sti has a viscous front diff and ABS?)
I tend to find that the rear "skips" a little out of tight junctions even with the diff right back... but that is fairly normal in my experience with RWD cars equipped with lsd's.
Personally, i constantly play with the diff if its streaming wet, whilst i'm moving. However, moving it just one click forward makes a huge difference and i rarely go to the amber setting.
Cheers
Rus
Do all cars equiped with the electronic centre diff have mechanical front and rear diffs? (i believe the straight Sti has a viscous front diff and ABS?)
I tend to find that the rear "skips" a little out of tight junctions even with the diff right back... but that is fairly normal in my experience with RWD cars equipped with lsd's.
Personally, i constantly play with the diff if its streaming wet, whilst i'm moving. However, moving it just one click forward makes a huge difference and i rarely go to the amber setting.
Cheers
Rus
29 November 2000, 01:49 PM
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Russ,
As I understand it, very few imprezas have come from the factory with an LSD front diff. This is an option on certain models (R/RA?) that had to be specifically requested on ordering the car.
Fitting the right type of diff to the front of a scooby makes an incredible difference to the handling and grip.
Moray
As I understand it, very few imprezas have come from the factory with an LSD front diff. This is an option on certain models (R/RA?) that had to be specifically requested on ordering the car.
Fitting the right type of diff to the front of a scooby makes an incredible difference to the handling and grip.
Moray
29 November 2000, 06:00 PM
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Moray
So What's the"right" type of diff?
My V5-Limited doesn't have ABS, as it was explained to gullible old me, this meant it was almost certainly a mech lsd in there.
The scrubbing at low speed and noisier rear axles on Type RA's seems ro be present in all that i've driven (all three that is!) which i thought was a good indication but is there any way of telling?
Rus
So What's the"right" type of diff?
My V5-Limited doesn't have ABS, as it was explained to gullible old me, this meant it was almost certainly a mech lsd in there.
The scrubbing at low speed and noisier rear axles on Type RA's seems ro be present in all that i've driven (all three that is!) which i thought was a good indication but is there any way of telling?
Rus
