Capt William

The logic goes that the BMW is a RWD car vs the Audi being FWD with quattro added as an afterthought. Now I don't care to much about how the car started life but I do know this:

I have recently gotten to know a guy from UK that races (heavily modified) Subaru WRX STIs on the rally circuit. He says that AWD cars have an unquestionable advantage over FWD or RWD in racing. In rallying the AWD cars are put at the front of the pack so that they don't have to do risky passes around all the RWD and FWD cars (rallies have staggered starts, the winner has the shortest time). He said on tarmack (road) or on dirt the AWD traction translates to faster speeds.

Of course this doesn't mean that all AWD cars are faster than all RWD or FWD cars but the AWD advantage is not a minor one. I believe that there was a time when Audi used to advertise that quattro was the "unfair advantage". I think that Audis were no longer allowed to compete in some types of racing (or they were handicaped in some way) because they were winning all the races in their class due to the "unfair advantage".

There is no question that BMW, Mercedes, etc. builds some nice feeling cars but I certainly wouldn't say they are better because they were designed to be RWD vs FWD or especially AWD.

Audacious

In the snow, my A6 sure drives like a rear wheel drive car when messing around.. In fact, I would say that the drive bias (if there is any) would be to the rear, although this sensation is most likely dure to less weight in the rear.

In short, you car power the car around a corner with the rear hanging out.. something I dare you to do in a FWD car (without using the parking brake.)

Add a little more power and steering input, and you know it is an AWD car, as you can straighten out your line WITH power on..

When I look at the engine / trans layout in the car, and think of all the things the engineers would have to allow for to get power back to the rear wheels, there is no way that this car was designed FWD first, then AWD added.. that just does not make sense.

Edd W

about 6 or 7 years ago that they were, in line with the rules, forced carry more and more extra weight. In the end they were carrying about 185Kg more than any other cars and so became un-competitive.

The reason for the advantage is two fold and outweighs the extra mechanical losses and weight of the extra drive train. Tyres take a more even load so last the race distance more easily enabling softer compounds than 2wd cars and the drivers can brake through corners and get the power down earlier.

In the wet, they were lapping the whole field in a 20 lap race.

1996 was Audi's first year in touring cars after pulling out of the WRC about three years earlier because they were concerned about overall safety and wanted to move into something nearer where they were marketing their cars.
Drivers at the time were people like Frank Beila,<ul><li><a href="http://tocatour.com/archive/1996_Results/1996_results.html">BTCC archive results</a></li></ul>

Potomac-Greg

Audi's drivetrain is designed to be used for AWD or FWD. That requires the engine to be predominantly ahead of the front axle line. That is why, even with quattro, most Audis have 60% of their weight on the front axle. That number is very similar to the weight distribution on FWD cars.

I'm one of the people who wishes that Audi would get closer to 50/50 distribution; but if you design a base car to be FWD, you'll never get there (unless you bolt 500 lbs. of ballast into the trunk!).

I wouldn't say that quattro is an "afterthought" any more than BMW's AWD is an "afterthought." Both are well conceived systems. Of the two, I think Audi's is better engineered.

Edd W

around since the first Audi's in the early 70's.

When you work on the quattro gearbox, you can tell how the rear drive output is just bolted onto the rear of the FWD box and then the output shaft was changed into a hollow tube with the rear drive as another shaft inside it. This inner shaft connects to the centre diff, then on to the rear diff.

As far as I know, Audi did not start working on 4WD until about 1977 and then it was just experiemntal work with Steyr-Puch.

Potomac-Greg

I wonder why Audi never used this in its advertising.

Potomac-Greg

I think it is wrong to call it an "afterthought" given the extraordinary effort and results. It's a tough system that works very well, and Audi has spent years refining it.

My old 90Q had a button by the parking brake that would lock the differentials (rear). I'm not sure that it was very important, but it seemed kind of cool. I could also turn off ABS with a button on the dash.

Gerry

Hans Stuck coined the term in the early 80's when Audi was dominating the US Trans Am series. Audi marketing did a great job of exploiting the term but Hans was very clear when discussing (ouside of Audi marketing) on a recent Speed channel "Legends" show. The Trans Am cars were extremely high powered rear wheel drive racers and with the RWD cars if they used all their power, all the time exiting turns the tire wear would be so great that the rear tires would not make it to the end of the race in good shape. He said that everyone thought it was a handling advantage (and Audi didn't want him to speak differently at the time) but the real truth was that he was simply the only one who could use all their power any time he wanted and have good tires to the end. Every race simply became a waiting game until the other cars tires went away and then he could pass at will. Made for great excitement at the track,and of course if it rained, that advantage spoke for itself.

Audacious

You don't design and bring to market a car that you have to redesign to allow for a rear differential, and a driveshaft tunnel at a later date..

The A6 was always intended to have AWD, otherwise the engine would have been transverse, and the rear floor would have been flat.

rally

A full on rally car uses active differentials that can lock all four wheels at the same time for unbelievable traction. A street car would not go easily around a corner if all the diffferentials were locked.

My rally car had locked differentials and would not make a sharp turn on tarmac without binding the differentials.

It wasn't too many years ago that the top times on tarmac rally stages were being turned by 2WD cars because they could get through tight corners easier and carried less weight.
The manufacturers eliminated the front wheel drive edge on tarmac by changing two things.

First a cutoff was designed in 1999? (both mechanical and electrical were used) for the center differential. Activating the cutoff just before a tight corner allowed the AWD car to switch to 2WD before the corner to slide the car into and around the corner before releasing the cutoff and applying full AWD power.

The advent of active (computer controlled) differentials allowed the cars to use one or all of the tires at a given time depending on what the computer encountered. Maximum traction with tractability at all times.

You can't get true (Suburu has a semi-active diff in the new STi) active differentials in a street car because the cost is astronomical.

No contest on loose surfaces. The AWD is a missile.