Audi R8 Forums banner
1 - 20 of 23 Posts

·
Registered
Joined
·
26 Posts
Discussion Starter · #1 · (Edited)
In Manila when they say a storm is coming a storm will really come. It gets really slippery here when its rainy. I am gonna get my R8 next year but I just wanna know if the R8's quattro AWD system will still keep me out of trouble even if it is rear biased. :(

Why are AWD cars with really close specs to it's RWD opponent (e.g. Porsche 911 Carrera S and Audi R8 4.2) somewhat slower in a drag race. And what do they mean when they say the AWD system will bog down?
 

·
Premium Member
Joined
·
1,034 Posts
I'm no engineer, but I'll attempt some of your questions.

Audi literature says power distribution to the front wheels is normally 15% but can vary between 10% and 35%. Probably quite adequate for that "planted on the ground" feeling you get with other Quattro Audis in wet or slippery conditions.

My R8 driving experience is limited to a track day @ Infineon Raceway with the Audi Sportscar Experience. During some of the skidpad exercises before we went onto the track, it was interesting to see that efforts to provoke wheelspin on dry pavement typically broke all 4 loose at once!

From my dry track experience and what I've read, I suspect most of the owners will tell you that their R8's are solid as a rock in the rain. Of course,
all cars with wide performance tires need to be wary of hydroplaneing in standing water.

I think the "bogging down" on take-off from a standstill is, at least to some slight degree, a feature of ALL all-wheel drive cars, in comparison to otherwise similar cars with rear-wheel drive. There's just twice as much drive-line rotating mass to get spun up. Again, from my experience at Infineon in 6-speed manuals, the R8 doesn't seem to suffer much "bog" if you "launch" with
reasonably high revs. A rear wheel drive R8 would probably do 0-60 in 0,5 sec less than the real thing with awd. If drag racing is your thing, buy a Dodge Viper or ZR1 Corvette, not an R8. The R8 is built for driving, not straight line acceleration.
 

·
Premium Member
Joined
·
1,611 Posts
In Manila when they say a storm is coming a storm will really come. It gets really slippery here when its rainy. I am gonna get my R8 next year but I just wanna know if the R8's quattro AWD system will still keep me out of trouble even if it is rear biased. :(

Why are AWD cars with really close specs to it's RWD opponent (e.g. Porsche 911 Carrera S and Audi R8 4.2) somewhat slower in a drag race. And what do they mean when they say the AWD system will bog down?
4 wheel drive cars bog down because they have inherently better traction than a 2 wheel drive car. To get the spectacular 0-60 times the car has to be heavily abused, typically these times are obtained by putting very high revs and 'dumping' the clutch and getting the 'right' amount of wheelspin. Often in these attempts they get too much and spin the wheels too much and end up with a slower time, or they get too little wheelspin and the car 'bogs' down i.e. the revs drop below the wheelspin torque threshold and you have to wait for the revs to build again. The Porker being rear engined and rear wheel drive has inherently good traction off the line if you get the revs right.
 

·
Registered
Joined
·
5,121 Posts
Or...drive it like you stole it !!! :D
 

·
Premium Member
Joined
·
1,363 Posts
The AWD is easily superior to RWD or FWD in the rain, no matter how wet. But the element that you do control directly is what tires you use. If you have a serious Monsoon season, maybe use a pair of serious rain tires just for that season. Bon Chance!
 

·
Registered
Joined
·
711 Posts
Aquaplaned last Friday in a flashflood at 80mph on M6 toll road. Not much traffic and I eased over but had next to no control. Was swiftly overtaken by a couple of BMW's with, presumably, narrower tyres. I am not sure winter tyres would have helped as we were just floating. Watch out!
 

·
Registered
Joined
·
134 Posts
Aquaplaned last Friday in a flashflood at 80mph on M6 toll road. Not much traffic and I eased over but had next to no control. Was swiftly overtaken by a couple of BMW's with, presumably, narrower tyres. I am not sure winter tyres would have helped as we were just floating. Watch out!
I've had this happen twice in mine. Scared the crap out of me! I wonder if it's the tyres, as I've read about Gallardo's suffering too, and they have the same boots ?
 

·
Registered
Joined
·
5,121 Posts
The R 8s' tires are so wide !! Is there a decent rain tire in these sizes??:eek:
 

·
Registered
Joined
·
935 Posts
Correct. I broke traction last night accelerating flat-out in 3rd on the motorway during some rain!!! :) Bit scary.

I think it's a combo of wide tyres, speed and aquaplaning. It's a good idea to keep speeds under 60MPH/100KM/H during heavy rain.

PS: Disable ASR and see how the R8 behaves in the rain. It's not a safe, simple to drive AWD A4. It's a smooth, progressive and fun RWD sportscar!!! :)
 

·
Registered
Joined
·
82 Posts
I'm no engineer, but I'll attempt some of your questions.

Audi literature says power distribution to the front wheels is normally 15% but can vary between 10% and 35%. Probably quite adequate for that "planted on the ground" feeling you get with other Quattro Audis in wet or slippery conditions.
So it's definitely not a "fixed" 15/85, but it is variable to a degree? And is it a viscous coupling, Torsen, or what TYPE of AWD in the '12 R8? Even though I don't have a clear understanding of the differences - I would love to know so then I can read all about it!
 

·
Registered
Joined
·
4,798 Posts
Taken from the technical manual:

In the Audi R8, drive power is transmitted dynamically to the front axle through a viscous coupling. Power to the rear axle is transmitted through a limited slip
differential which improves rear axle traction under high transverse acceleration. Two transmission choices are available to the customer: a 6-speed manual transmission featuring a double dry-plate clutch or the fully automatic R tronic transmission. An innovative selector mechanism in the R tronic version allows the driver to choose between fully automatic operation or manual gear selection. With the R tronic, the driver can also opt for Sport mode.

The quattro all-wheel drive system is based on a 44:56 weight distribution favoring the rear axle. If needed, up to 310 lb ft (420 Nm) of torque can be transmitted
to the front wheels through the viscous coupling.
 

·
Registered
Joined
·
248 Posts
I have yet to really test the car in inclement weather, but I suspect this will not be the kind of AWD tank-like drive you get in other Audi's or Subaru's. In extreme weather I would be quite careful about taking to many liberties on the assumption the AWD system will come to the rescue. I remember what I had my Audi RS5 before the R8, and the quattro system on that one was truly quite astonishing. Of course, with that came understeer and the car was heavy, so on track you'd feel its downsides, although the sport differential made a big difference (something the R8 doesn't have, at least I don't think so).

This article mentions the gen. 2 R8 having improved the AWD system from the gen. 1 models, from viscous to a more direct clutch system: http://www.themotorreport.com.au/63040/2016-audi-r8-v10-plus-track-test-review
 

·
Registered
Joined
·
367 Posts
The viscous clutch in the gen 1 R8 is the same as the awd 996/997 Porsches, in other words barely awd. Minimal power is transmitted to the front wheels - plenty of videos out there with spinning rear wheels and the fronts doing... nothing. It certainly adds a degree of traction and stability to the vehicle, but don't depend on it to extract you from a snow bank!
 

·
Registered
Joined
·
82 Posts
Taken from the technical manual:

In the Audi R8, drive power is transmitted dynamically to the front axle through a viscous coupling. Power to the rear axle is transmitted through a limited slip
differential which improves rear axle traction under high transverse acceleration. Two transmission choices are available to the customer: a 6-speed manual transmission featuring a double dry-plate clutch or the fully automatic R tronic transmission. An innovative selector mechanism in the R tronic version allows the driver to choose between fully automatic operation or manual gear selection. With the R tronic, the driver can also opt for Sport mode.

The quattro all-wheel drive system is based on a 44:56 weight distribution favoring the rear axle. If needed, up to 310 lb ft (420 Nm) of torque can be transmitted
to the front wheels through the viscous coupling.
Thank you Trev!! I suspected viscous coupling because that's what the Lambo had.
 

·
Premium Member
Joined
·
389 Posts
Where is the viscous coupling located? Maybe in the rear of the car?
Thought this might help.
Copied from website, link below.

2007: The viscous coupling in the Audi R8

The Audi R8 high-performance sports car occupies a special position in the Audi model range – and this extends to its packaging and its drive system. The mid-mounted engine is arranged longitudinally at the rear of the car in front of the rear axle, with the gearbox right behind it. It also includes an auxiliary drive for a prop shaft running past the engine on the side and up to the front axle.
There a viscous coupling distributes the power between the front axle and the rear axle, which is equipped with a locking diffrential. Under normal driving conditions, the coupling sends only about 15 percent of the torque to the front axle – the R8 has an extremely pronounced rear bias. If the rear wheels begin to spin, an additional 15 percent almost immediately flows to the front.
The primary component of the viscous coupling is a package of round clutch disks, each with different gearing. One of each is connected to the prop shaft via the housing; the other is connected to the output shaft to the front axle. The clutch plates rotate in a viscous fluid. If they rotate at greatly different speeds due to a loss of traction at the rear axle, the oil becomes more viscous as a result of its internal friction and an increased torque is delivered to the output shaft to the front axle.

Here is a link to this PDF and a short animation showing the coupling position within the drive train.

http://m.audi-quattro-highlights.de/en/aqh/Technologies/Viscous-coupling
 
1 - 20 of 23 Posts
Top