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I'm new to the audi scene with my 90 sedan 20v as my DD. But I've been racing subarus for about 7 years and have a 1998 RHD STi V.4 type RA as my weekend toy/ occasional driver. From what I can tell the subaru and longitudal audi quattro systems are almost the same layout. Both having the motor mounted in front of the front axle while having the awd center diff and front diff being built into the transaxle. Does anyone have any technical drawings of the two systems? From what I can tell they are 95% the same with no advantage to either system.
 

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Biggest difference is in build materials, Audi used metal instead of building them out of glass.
 

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The advantage of Audi is the torsen diff rather than a viscous coupling. They both have their advantages and disadvantages but it's hard to beat the torsen in drivetrain lossses and reaction time to changing conditions.

Plus as mentioned the Audi stuff tends to be much more reliable at higher output. But an sti 6 speed is pretty strong also.

So yes, layout is similar but the mechanicals are not.
 

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Ive owned an older impreza and many older Audies. Although the Subaru was ridiculously reliable,the Audies always seemed to feel more robust,drivetrain wise. If i had a job to destroy cars by beating them to death,id say the audi would outlast the subie.
 

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The one nice thing about a viscous coupling is it will transfer 100% torque when the opposite axle has 0% traction. However, if you do that long enough they overheat and blow up.
 

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123quattro said:
The one nice thing about a viscous coupling is it will transfer 100% torque when the opposite axle has 0% traction. However, if you do that long enough they overheat and blow up.
Viscous couplings won't ever get 100% torque transfer. You need a locked diff for that. From what I read they will only get about 80%
 

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when i compared my 3.0 a6 avant to a ej25 impreza outback.. the subaru didnt have enough horsepower to finish the test...
 

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Which Subaru? Subaru has used every possible layout.

They had manual transmissions that were FWD until you splined the rear driveshaft to the trans. (Some, but not all, of these were dual-range.) They had automatic transmissions that were FWD until an internal clutch pack was engaged to have the same effect. (These are the ones with the underhood fuse you pulled so you could tow it rear wheels down)

Then they had transmissions with center diffs that you could manually lock. Some, but not all, were dual-range - close ratio dual range at that, changed effective final drive from 3.70 to 4.30 or thereabouts. (The 3-door RX Turbo trans)

The common Impreza/Legacy transmissions had VLSDs, not viscous couplings. They were normal bevel diffs that had a viscous limited slip section on the back. These are the diffs were people swap in 12kg or 16kg or 20kg viscous sections. A 20kg is basically just enough slip that you don't break axles - you can drive them with an axle out.

Some automatics (and IIRC some STIs that we didn't get here) had cam and pawl differentials. Look them up, they're a neat concept. The cars with this had a 45/55 torque split.

Some STIs had epicyclic diffs with a computer controlled clutch pack to lock the diff. The cars with these had the differential dial where you could dial in manual lock vs. computer control. Again note that drive was always through gears, the clutch pack is only there as a limited slip device.

IIRC the only Subarus that DID use viscous couplings were Rexes, which we didn't get here because it was a Kei car. IIRC it was no center diff, no rear diff, just a viscous coupling on EACH rear axle. Neat idea (IIRC it was licensed from Ferguson) and you don't need much in a super tiny car with a 660cc engine.

But at no time did they use a torsen... which is why Subarus handle beautifully instead of like dog poo :D
 

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maverick said:
123quattro said:
The one nice thing about a viscous coupling is it will transfer 100% torque when the opposite axle has 0% traction. However, if you do that long enough they overheat and blow up.
Viscous couplings won't ever get 100% torque transfer. You need a locked diff for that. From what I read they will only get about 80%
Ok, fine, whatever their efficiency loss is. They can transfer a lot of torque. I had one in my 1990 Range Rover in the center diff. It worked nicely, until I got stock and blew it up from overheating it. It was replaced with a locking center diff. :)
 

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Noisy Cricket said:
Which Subaru? Subaru has used every possible layout.

They had manual transmissions that were FWD until you splined the rear driveshaft to the trans. (Some, but not all, of these were dual-range.) They had automatic transmissions that were FWD until an internal clutch pack was engaged to have the same effect. (These are the ones with the underhood fuse you pulled so you could tow it rear wheels down)

Then they had transmissions with center diffs that you could manually lock. Some, but not all, were dual-range - close ratio dual range at that, changed effective final drive from 3.70 to 4.30 or thereabouts. (The 3-door RX Turbo trans)

The common Impreza/Legacy transmissions had VLSDs, not viscous couplings. They were normal bevel diffs that had a viscous limited slip section on the back. These are the diffs were people swap in 12kg or 16kg or 20kg viscous sections. A 20kg is basically just enough slip that you don't break axles - you can drive them with an axle out.

Some automatics (and IIRC some STIs that we didn't get here) had cam and pawl differentials. Look them up, they're a neat concept. The cars with this had a 45/55 torque split.

Some STIs had epicyclic diffs with a computer controlled clutch pack to lock the diff. The cars with these had the differential dial where you could dial in manual lock vs. computer control. Again note that drive was always through gears, the clutch pack is only there as a limited slip device.

IIRC the only Subarus that DID use viscous couplings were Rexes, which we didn't get here because it was a Kei car. IIRC it was no center diff, no rear diff, just a viscous coupling on EACH rear axle. Neat idea (IIRC it was licensed from Ferguson) and you don't need much in a super tiny car with a 660cc engine.
Not totally correct:

I used to be a Subaru mechanic at an independent shop in PDX and got to mess with Subaru's sub-standard drive trains on a daily basis.

I'll give you the basic rundown:

Most EA series cars had part time 4wd, either single ratio or dual range. Even the 3AT auto cars had the same part time system as the manuals.

Some of those came AWD, using basically the same system as the later EJ cars...in fact the 4EAT trans used in the EA cars is the same as the EJ with a different bell housing. This trans uses a clutch type center diff that is controlled by a solenoid (specifically the duty C solenoid...the one that causes torque bind) that also allows the AWD to be disabled by use of a fuse in the engine compartment.

The RX (both 3 door and rare sedan) used a dual range, awd trans with a switchable locking center diff...which is probably the closest thing to an 016 Audi trans with a 2 range transfer case. I've never seen the center locker in a non dual range car.

None of these are particularly strong...basically can handle EJ22 power but not much more

The early EJ series manual trans are similar to an 016 without any lockers. Just straight differentials.

Around about the OBDII time the manuals "gained" a viscous center diff...which likes to fail.

Autos were still the 4EAT...a generally boring unit that actually holds a decent amount of power.

Some STi models had AP Suretrac front diffs...which is a quasi-helical (torsen) unit...most others were straight torsen.

The DCCD in the 5 and 6 speed STi trannies are a planetary unit that uses a clutch pack to vary the power distribution between front and rear.

STi had a torsen rear...all the other LSDs were viscous with the exception of the 3.70 unit used in the EA cars (clutch type)

My opinion after looking at Audi and Subaru drivetrain components was that Subaru recognized the good ideas Audi had and decided to use their technology and just make it shittier. (my theory)
 

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rallynz said:
The RX (both 3 door and rare sedan) used a dual range, awd trans with a switchable locking center diff...which is probably the closest thing to an 016 Audi trans with a 2 range transfer case. I've never seen the center locker in a non dual range car.
The GL-10 Turbo supposedly had a single range center/locker. I haven't seen one though.

The RX Turbo sedan did not have a center diff, it was FWD/4WD. That is what mine had. It was the same transmission as my GL wagon except it was a close ratio dual range instead of wide ratio. Also it had the turbo EA82 which was the most fragile Japanese turbo engine ever, which is why I did not own that car for very long. (And I still kick myself for unloading it because it was a RUST FREE RX TURBO)

The DCCD in the 5 and 6 speed STi trannies are a planetary unit that uses a clutch pack to vary the power distribution between front and rear.
It does not vary the power distribution, it varies the differential lockup. Subtle but important difference. The power distribution CAN vary with clutch pack application.

Everyone I know who ever played with a DCCD equipped car on dirt just set the dial out to max lock since a locked diff is more predictable than an open one. I used to think they were nuts until I started playing with 016 equipped cars and, sure enough, I run with the diffs locked because it's more predictable. That's why I think torsen diffs suck, they are open diffs that are even more unpredictable when you're sliding around. And if you're not sliding around, you're driving like a weenie and it doesn't matter what kind of diffs you have or even if you're just 2wd...

That said, my favorite AWD trans is the setup in the GC 2.5RS. They just work perfectly. I've driven them with the 20kg diff installed and it wrecks the handling. The car starts to drive like a locker Audi :) The stock diff is a perfect match of predictability while still being open enough to allow you to drive the car instead of throwing it around, but you CAN throw it around if you want. No matter what your driving style is, the car suits it, it's not a case of having to adapt the driver to the car's quirks because it HAS no quirks. No matter what stupid situation you get yourself into, you can play with the steering and throttle and come out of it unscathed. It's a shame that those cars are soooo expensive to buy. Seems like the going rate for a decent one is $6k-ish, or about 2 WRXs.
 

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kahunaking said:
.Does anyone have any technical drawings of the two systems? From what I can tell they are 95% the same with no advantage to either system.
Take a look at this pdf "Audi Turbo Quattro Coupe Introductory Service Training Information":
http://www.quattro.ca/Urq/urq-IST-Introduction.pdf

Pages 28/29 'conceptual', pages 32/33 detailed transmission cross section..

Lots of other interesting info too, for the mechanics that were to soon be working on the 'urq'.. :D
 

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Noisy Cricket said:
rallynz said:
The RX (both 3 door and rare sedan) used a dual range, awd trans with a switchable locking center diff...which is probably the closest thing to an 016 Audi trans with a 2 range transfer case. I've never seen the center locker in a non dual range car.
The GL-10 Turbo supposedly had a single range center/locker. I haven't seen one though.

The RX Turbo sedan did not have a center diff, it was FWD/4WD. That is what mine had. It was the same transmission as my GL wagon except it was a close ratio dual range instead of wide ratio. Also it had the turbo EA82 which was the most fragile Japanese turbo engine ever, which is why I did not own that car for very long. (And I still kick myself for unloading it because it was a RUST FREE RX TURBO)
So if the RX Sedan only came with a FWD/4WD, then why did we have a dual range, full time awd, center diff lock car at the shop? Explain that to me...and no it was not swapped.

I can understand why the 20kg center diff sucked on the road...it's usually the choice for gravel rally cars.

I always thought the 2.5RS drove like a bag of dicks...not a well balanced car and the power band sucks. My Legacy Turbo felt far more balanced and easy to control...but the noodle-ish nature of the Subaru chassis ruins it all. I think my 4kq is easier to drive in corners...when it lets go I just have to lift throttle and it generally comes back into shape.

I spun my Legacy out a number of times but haven't ever spun an Audi (without trying to :D )
 

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rallynz said:
So if the RX Sedan only came with a FWD/4WD, then why did we have a dual range, full time awd, center diff lock car at the shop? Explain that to me...and no it was not swapped.
Year thing? My sedan was an '85. IIRC the 3 door wasn't produced until 1987 and that was when the lockable diff trans was introduced.

I can understand why the 20kg center diff sucked on the road...it's usually the choice for gravel rally cars.
I've only ever driven it on dirt/mud/gravel. Too much lock to be able to steer effectively, IMO.

I always thought the 2.5RS drove like a bag of dicks...not a well balanced car and the power band sucks. My Legacy Turbo felt far more balanced and easy to control...but the noodle-ish nature of the Subaru chassis ruins it all. I think my 4kq is easier to drive in corners...when it lets go I just have to lift throttle and it generally comes back into shape.

I spun my Legacy out a number of times but haven't ever spun an Audi (without trying to :D )
That's exactly why I prefer the Impreza... you can rotate the car much more neatly.

It was actually somewhat of a downer for me, the one I drove at Nationals this year was the first STOCK one that I'd driven, and I was driving it like it had a super tight diff. Wasted a lot of momentum entering corners by flicking and scrubbing speed instead of just driving through like the car's owner does. Later I got to drive it at a regional and I saw the light - just drive the damn thing without worrying, and it will do what you want it to do. No need to plan a corner three corners in advance in order to get the car's attitude adjusted correctly.


But if you have to rotate it... you can.
 

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The Oregon rally cross champ until a few years ago was a stock 84 4kq with rally tires...no Subaru could even touch his times...even stage cars.

I think Subaru's AWD system is set up more for idiotic soccer moms who can't drive in the snow than competition...I've ridden in a lot of different stage cars and all the Noobarus needed $$$$$$ to make them properly handle in gravel...whereas the 20v Ur quattro I rode in just had locked stock diffs and turned great with left foot braking.
 

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Friend of mine owns a local tuning shop that does a lot of Toyota/Lotus work. He has a RAV4 with a turbo AWD powertrain from pieced together JDM Toyota parts. No one can touch him in rally cross or ice racing. It's about 300awhp. The Subaroo guys get so angry when their caged cars get beat by his daily driver.

 
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