Opinions Wanted - A5 v C4S
01-17-2013, 07:25 PM
#31
Drifting
The impression I am getting is that the C4S with traction control off is essentially a RWD car, is this correct ?
Except for conditions that are not very likely to arise normally the C4S, 1999 - up to the 997.2, is/was NEVER capable of coupling more than 5% of the engine drive to the front diff'l.
So in a sense, turning traction control on is like pushing a 4WD button, but that also kills any chance to have fun
4WD "on", traditionally, will always provide some means of coupling drive torque rear to front and vice versa, historically. If you meant to say "like turning 4WD off" then yes. TC will will not allow even the slightest level of driven wheel spin/slip. It will INSTANTLY dethrottle the engine fully and began ABS style "hammering" of the slipping wheel(s).
Is there any known changes that can be done to the VC? Thicker (***) viscosity fluid maybe to provide a lower threshold of engagement ?
The only possible answer I have come up with is maybe a way to HEAT the hermetically sealed VC case and thereby increase the front coupling only while the HEAT is applied. But be aware that any method for sustaining drive coupling to the front might well result in premature driveline component failures. Most especially if drive coupling were inadvertently sustained on a non-slippery roadbed surface.
For the record the 2008-2009 A5 would use the 5th Gen of Quattro which has the
Torsen type 3 (Type "C") centre differential, 40:60 'default' split front-rear,
40:60 F/R torque split would/can get you in BIG trouble quickly were it not for some form of stability control. If the stability control yaw sensor indicates that lateral forces are building to the point of loss of control many new systems (most R/awd systems 997.2 C4S, etc.) can automatically route DRIVE torque AWAY from the front. Whereas all your Audi can do is begin applying braking and simultaneously DE-THROTTLE the engine.
Automatically apportioning up to 80% of the torque to one axle using a 4:1 high-biased center differential.
With the aid of ESP, up to 100% of the torque can be transferred to one axle.
100%...yes via BRAKING to produce an artificial torque load.
Except for conditions that are not very likely to arise normally the C4S, 1999 - up to the 997.2, is/was NEVER capable of coupling more than 5% of the engine drive to the front diff'l.
So in a sense, turning traction control on is like pushing a 4WD button, but that also kills any chance to have fun
4WD "on", traditionally, will always provide some means of coupling drive torque rear to front and vice versa, historically. If you meant to say "like turning 4WD off" then yes. TC will will not allow even the slightest level of driven wheel spin/slip. It will INSTANTLY dethrottle the engine fully and began ABS style "hammering" of the slipping wheel(s).
Is there any known changes that can be done to the VC? Thicker (***) viscosity fluid maybe to provide a lower threshold of engagement ?
The only possible answer I have come up with is maybe a way to HEAT the hermetically sealed VC case and thereby increase the front coupling only while the HEAT is applied. But be aware that any method for sustaining drive coupling to the front might well result in premature driveline component failures. Most especially if drive coupling were inadvertently sustained on a non-slippery roadbed surface.
For the record the 2008-2009 A5 would use the 5th Gen of Quattro which has the
Torsen type 3 (Type "C") centre differential, 40:60 'default' split front-rear,
40:60 F/R torque split would/can get you in BIG trouble quickly were it not for some form of stability control. If the stability control yaw sensor indicates that lateral forces are building to the point of loss of control many new systems (most R/awd systems 997.2 C4S, etc.) can automatically route DRIVE torque AWAY from the front. Whereas all your Audi can do is begin applying braking and simultaneously DE-THROTTLE the engine.
Automatically apportioning up to 80% of the torque to one axle using a 4:1 high-biased center differential.
With the aid of ESP, up to 100% of the torque can be transferred to one axle.
100%...yes via BRAKING to produce an artificial torque load.
*** The base idea behind a VC coupling is that the fluid will normally remain thin/flaccid and therefore not couple very much drive torque. Then under special conditions, conditions that result in HEATING the fluid, it thickens thereby increasing the level of coupling. Use a "base" thicker VC fluid and the latent, flaccid, coupling level rises according, possibly enough to compromise the life cycle of driveline components.
Heating the fluid increases viscosity..what kind of magicians hat trick is this?
No trick at all, heating the fluid would normally result in expansion of the fluid volume. But in the case (no pun itended) of our VC, the fluid is within a hermetically sealed case of a FIXED volume, so the effect is to THICKEN the fluid..
Last edited by wwest; 01-17-2013 at 07:51 PM.
01-17-2013, 07:57 PM
#32
Drifting
TC can be used to indicate that the roadbed is slipperier than the driver might be aware. Once TC activates, turn it off IMMEDIATELY and then use the old tried and true technique of throttle feathering to produce wheel drive torque right up to the "cusp" of wheelspin/slip, not beyond. If that tehnique doesn't get you moving then next as traction, tire chains, or call for a tow.
In cold weather your VC is unlikely to tighten up at all and NEVER for an extended period.
01-17-2013, 08:00 PM
#33
Drifting
I've had quite a few Audis and I'm a huge fan of the brand and their cars. I also love my C4S.
I haven't driven my C4S in the snow,
Yet...
but the AWD 996s are known for being darn good snow cars.
What, WHAT? not that I'm aware of, not of any drivers around here.
Personally, I love the A5s and they're one of my favorite cars on the road right now; but in the end I bought a C4S if that tells you anything.
I haven't driven my C4S in the snow,
Yet...
but the AWD 996s are known for being darn good snow cars.
What, WHAT? not that I'm aware of, not of any drivers around here.
Personally, I love the A5s and they're one of my favorite cars on the road right now; but in the end I bought a C4S if that tells you anything.
01-17-2013, 08:09 PM
#34
Drifting
Yes, but now have a friend hold one front wheel stationary while you hold the other and note how easy that is....engine IDLE!
01-17-2013, 08:22 PM
#35
Drifting
Eric - thanks for the link. I read through that particular one and it has some great info.
My thinking would be that I could get 911 (which is high on the to get list) and be able to enjoy it all year, plus I just dont have any room right now for A5 + a 911
I completely understand the concept that these are 2 different approaches to the AWD concept.
"2 different approaches" ... No a MYRIAD of AWD designs over the past 15 years or so. Unless you mean just F/awd vs R/awd...?
I wouldnt expect the C4S to go through quite as much as say an A4 which is more utilitarian in nature v the performance approach of the C4S.
I'm just not willing to give up AWD for those few times we get a decent snow...its just too much fun channeling Ken Block and Walter Rohl =)
One thing people did seem to mention on RennList is the failure of the VC. If this part has a limited life span I would be conscious of burning it out every time I went out in the white stuff.
Not VC failure, but failure of the VC to work, most likely.
The VC is flaccid, and remains so, so much of the time it would be impossible to "burn out" absent some sort of owner driveline modification, differing circumference tires on the front vs the rear. The Lexus F/awd RX series was marketing and sold for years, RX330-2010 RX350, as having a VC when none actually existed. Nobody seems to have noticed.
rossclifford - As far as salt, proper precautions would be taken for the interior and with regular attention the paint on the A4 looks as good as the day I bought it. No body rust at 162K is pretty good for a NY based car.
One thing that I have found great for other components/fasteners, linkages etc is motorcycle chain lube. Specifically PJ1 Blue Label, really helps prevent rust on the exposed bolts. Goes on thin them forms a film, very effective.
My thinking would be that I could get 911 (which is high on the to get list) and be able to enjoy it all year, plus I just dont have any room right now for A5 + a 911
I completely understand the concept that these are 2 different approaches to the AWD concept.
"2 different approaches" ... No a MYRIAD of AWD designs over the past 15 years or so. Unless you mean just F/awd vs R/awd...?
I wouldnt expect the C4S to go through quite as much as say an A4 which is more utilitarian in nature v the performance approach of the C4S.
I'm just not willing to give up AWD for those few times we get a decent snow...its just too much fun channeling Ken Block and Walter Rohl =)
One thing people did seem to mention on RennList is the failure of the VC. If this part has a limited life span I would be conscious of burning it out every time I went out in the white stuff.
Not VC failure, but failure of the VC to work, most likely.
The VC is flaccid, and remains so, so much of the time it would be impossible to "burn out" absent some sort of owner driveline modification, differing circumference tires on the front vs the rear. The Lexus F/awd RX series was marketing and sold for years, RX330-2010 RX350, as having a VC when none actually existed. Nobody seems to have noticed.
rossclifford - As far as salt, proper precautions would be taken for the interior and with regular attention the paint on the A4 looks as good as the day I bought it. No body rust at 162K is pretty good for a NY based car.
One thing that I have found great for other components/fasteners, linkages etc is motorcycle chain lube. Specifically PJ1 Blue Label, really helps prevent rust on the exposed bolts. Goes on thin them forms a film, very effective.
01-23-2013, 01:03 PM
#36
Pro
Thread Starter
Guys,
Appreciate all the feedback here. I am loosing the fight to resist the allure of the 996. The more I learn and hear about these cars I am getting comfortable with the wintertime abilities. Given that we have had 2 weeks of actual snow here in the NE, I dont think I need the full capability of the Audi system.
And for the rest of the year, I get to enjoy a car I have been wanting for longer than I can remember.
Now the search begins =)
Appreciate all the feedback here. I am loosing the fight to resist the allure of the 996. The more I learn and hear about these cars I am getting comfortable with the wintertime abilities. Given that we have had 2 weeks of actual snow here in the NE, I dont think I need the full capability of the Audi system.
And for the rest of the year, I get to enjoy a car I have been wanting for longer than I can remember.
Now the search begins =)
01-23-2013, 07:36 PM
#37
Instructor
Guys,
Appreciate all the feedback here. I am loosing the fight to resist the allure of the 996. The more I learn and hear about these cars I am getting comfortable with the wintertime abilities. Given that we have had 2 weeks of actual snow here in the NE, I dont think I need the full capability of the Audi system.
And for the rest of the year, I get to enjoy a car I have been wanting for longer than I can remember.
Now the search begins =)
Appreciate all the feedback here. I am loosing the fight to resist the allure of the 996. The more I learn and hear about these cars I am getting comfortable with the wintertime abilities. Given that we have had 2 weeks of actual snow here in the NE, I dont think I need the full capability of the Audi system.
And for the rest of the year, I get to enjoy a car I have been wanting for longer than I can remember.
Now the search begins =)
https://rennlist.com/forums/996-foru...ts-in-oil.html
Sadly, considering the purchase of an A5 or S5 very soon.
Don't want to tromp on your dreams, but do want you to be careful as you look.
Last edited by Quix; 01-23-2013 at 08:52 PM.
01-23-2013, 07:55 PM
#38
Yes, but now have a friend hold one front wheel stationary while you hold the other and note how easy that is....engine IDLE!
But seriously, what is the OP trying to do? They are two completely different cars for different purposes. Get a Jeep Rubicon if you want a true 4wd.
01-24-2013, 10:20 AM
#39
Pro
Thread Starter
Quix - I read through the beginning of your first post. Sorry to hear of the news. Understand how frustrating that can be when you do everything you can to prevent it. That said, I will keep it in mind when I search.
That said, if you do go the Audi route I can give you some points to look for in an A5/S5 from my initial research
Krazy - my initial foray was not to compare how much can a C4S go through, simply how much of a change it would be from what I have been used to. Its easy to get spoiled with Quattro when it comes to inclement weather.
That said, if you do go the Audi route I can give you some points to look for in an A5/S5 from my initial research
Krazy - my initial foray was not to compare how much can a C4S go through, simply how much of a change it would be from what I have been used to. Its easy to get spoiled with Quattro when it comes to inclement weather.
