Viscous vs Electronic Transfer Clutch?

[Gloyale]

That run was tested on bitumen.

 

I found no difference between 1, 2, 3 and D

 

That display was measuring duty cycle. So it is the ratio of on and off periods.

 

0% duty cycle would mean zero pressure to the MPT and thus a torque split of 100% front and 0% rear.

 

50% duty cycle means there half pressure to the MPT and a torque split would be 75% front and 25% rear.

 

100% duty cycle will give full pressure to the MPT and a torque split of 50 50

 

.

 

Backwards.

 

0% duty cycle = no pressure drain off = locked 4wd (this is why simply "cutting" the power wire to the Duty C works for a "lock switch")

 

100% duty cycle = maximum pressure drain off = no rear drive. this is the state when you insert the FWD fuse.

 

 

Unless there is some difference in how the AUS spec trannies use the Duty solenoid.

[nipper]

Backwards.

 

0% duty cycle = no pressure drain off = locked 4wd (this is why simply "cutting" the power wire to the Duty C works for a "lock switch")

 

100% duty cycle = maximum pressure drain off = no rear drive. this is the state when you insert the FWD fuse.

 

 

Unless there is some difference in how the AUS spec trannies use the Duty solenoid.

 

Well they are upside down and drive on the wrong side of the road

[zyewdall]

having driven dozens of different subaru's as daily drivers i've never really noticed much difference. it's negligible for me since snow tires or studs are the real solution for those of us that have serious conditions (meaning economically destitute states that can't afford to/don't maintain snow packed mountain roads :lol:) to cover.

 

LOL. Better than the states that cover those roads in rock salt. I'd rather buy studded snow tires every two years, than buy a new car every 10 years because the metals rusting away....

 

I've never noticed much difference either... in snow handling at least. I can't stand the automatics in the mountains because they are shifting gears instead of me and are always in the wrong gear (unless I just manually shift them, which is what I end up doing).

[CNY_Dave]

Backwards.

 

0% duty cycle = no pressure drain off = locked 4wd (this is why simply "cutting" the power wire to the Duty C works for a "lock switch")

 

100% duty cycle = maximum pressure drain off = no rear drive. this is the state when you insert the FWD fuse.

 

 

Unless there is some difference in how the AUS spec trannies use the Duty solenoid.

 

Without knowing the waveform and the details of the meter it's tough to say how any given duty-cycle meter will 'read' it.

 

But yes, that's how that gen works, but they changed that around in later years I heard?

 

Dave

[idosubaru]

How can I get mine to give %110 like those Nike adds?

[ausubaru92]

Backwards.

 

0% duty cycle = no pressure drain off = locked 4wd (this is why simply "cutting" the power wire to the Duty C works for a "lock switch")

 

100% duty cycle = maximum pressure drain off = no rear drive. this is the state when you insert the FWD fuse.

 

 

Unless there is some difference in how the AUS spec trannies use the Duty solenoid.

 

 

You are right.

 

I set the duty cycle meter up to display the duty cycle backwards as it makes it easier to interpret the data. So i explained the operation of the solenoid to match the readings in the video.

 

Is there any reason why the AWD manual Subarus are always mechanical AWD?

 

And how about the STI? I know that's a huge can of worms I'm opening, but what is it more related to; the manual (viscous center diff) or the automatic (electronic transfer clutch)?

The manual AWD use a mechanical centre diff because its cheap and effective. And because the manual gearbox doesnt have a high pressure oil supply like the automatics do.

 

As for the STI (which i assume you mean the DCCD gearbox)

They use a planetary centre diff like the normal manual, but it has a mismatched ratio to give it a 35/65 front/rear bias.It has a series of clutch plates that are actuated by an electric solenoid to behave like a LSD with a variable lock between 35/65 open and 50/50 locked. (think of the RX FT4WD 5speed, it has a 50/50 open diff, that can be switched to 50/50 locked, except it only has 2 modes of operation, the DCCD is variable)

The DCCD control unit uses throttle, brake and G force sensors to control the clutch when in auto mode, or several stages of set lock can be applied when the driver places the DCCD knob in manual mode.

 

The VTD (variable torque distribution) auto, uses a very similar system to the STI above, only it uses oil pressure to control the centre diff instead of the electric solenoid.

Edited February 9, 2010 by ausubaru92

[barry1956]

You are right.

 

... The manual AWD use a mechanical centre diff because its cheap and effective. And because the manual gearbox doesnt have a high pressure oil supply like the automatics do.

 

As for the STI (which i assume you mean the DCCD gearbox)

They use a planetary centre diff like the normal manual, but it has a mismatched ratio to give it a 35/65 front/rear bias.It has a series of clutch plates that are actuated by an electric solenoid to behave like a LSD with a variable lock between 35/65 open and 50/50 locked. (think of the RX FT4WD 5speed, it has a 50/50 open diff, that can be switched to 50/50 locked, except it only has 2 modes of operation, the DCCD is variable)

The DCCD control unit uses throttle, brake and G force sensors to control the clutch when in auto mode, or several stages of set lock can be applied when the driver places the DCCD knob in manual mode.

 

The VTD (variable torque distribution) auto, uses a very similar system to the STI above, only it uses oil pressure to control the centre diff instead of the electric solenoid.

 

I have an 05 manual 2.5 Outback. My interest is driving fire trails. Would the dccd give me an improvement over the stock VLSD centre diff in thes circumstances. i.e. which will provide a better centre 'lock'?

Edited February 7, 2011 by barry1956