AWD Power Loss

[The Artist]

Hey guys i just read some thread wich said that cars with AWD loose more in delivering power to the wheels than RWD cars..
so my question is..

Would a similar weight Audi with 500hp be as fast as a BMW?

I think our question will be answerd somewhat when the new M3 comes along..
Both the RS4 and M3 has 420hp.. so that will indeed be interesting..

And if so is the case.. the 580hp of the upcoming RS6 might not kick up a huge gap compared to the M5 and E63 as it should given the power advantage of nearly 80hp...

Whats your take on this?
Are audi forced to have huge HP nr´s to keep up.. beacuse of the quattro
Or is it the theory just BS..

[monster]

Originally Posted by The Artist

Hey guys i just read some thread wich said that cars with AWD loose more in delivering power to the wheels than RWD cars..
so my question is..

Would a similar weight Audi with 500hp be as fast as a BMW?

I think our question will be answerd somewhat when the new M3 comes along..
Both the RS4 and M3 has 420hp.. so that will indeed be interesting..

And if so is the case.. the 580hp of the upcoming RS6 might not kick up a huge gap compared to the M5 and E63 as it should given the power advantage of nearly 80hp...

Whats your take on this?
Are audi forced to have huge HP nr´s to keep up.. beacuse of the quattro
Or is it the theory just BS..

AWD in general looses more power in the drivetrain simply because there are more components in the drivetrain to move, and there are increased frictional lose in the drivetrain because of those additional components

In a pure straight line acceleration comparison if the Audi and the BMW has the same power and weight, thus same power to weight ratio, same gear ratios, same tyres and size, same weight distribution, the Audi will have a quicker start because the car as more grip in the beginning, there will be no energy wasted on wheel spin.

The upcoming RS6 has 580hp party because the car will be heavier than the competition, and partly because Audi wants to have the most powerful car in its class, just like the previous RS6. I am sure Audi do consider the additional drivetrain power loss through the Quattro system, but that is not of its main concern.

[The Artist]

^cool ..
like i belived then.. there is a power loss in theory..but its so small that it doesent matter.. or gets dealt with by the quattro system not loosing traction..

PS
I dont think the RS6 will be much heavier than the E63/M5 i guess its just about audi taking it to the next level then

so now ppl cant use this as an excuse?

or can they

The tread is still open..lol

[monster]

Originally Posted by The Artist

I dont think the RS6 will be much heavier than the E63/M5 i guess its just about audi taking it to the next level then

so now ppl cant use this as an excuse?

or can they

The tread is still open..lol

The RS6 will have a heavy engine. The twin turbo, bigger radiator, the intercooler, as well as extra reinforcements for the engine block to cope with the stress and strains from the extra energy generated from the combustion process will add weight to the car. I am sure the gearbox and drive shafts will need to be upgraded to handle the 1000Nm plus of torque. The Quattro system adds another 200kg to the cars weight i think.

Unless Audi offset this weight increase by using lightweight body panels and suspension parts, this RS6 will become a heavy beast.

[The Artist]

1000NM?? are you sure??
DAYYMN in that case

[monster]

Bartek Sikorski got the info from this site - ONLY REGISTERED AND ACTIVATED USERS CAN SEE ALL LINKS - CLICK HERE TO REGISTER

I was reading this thread http://www.germancarzone.com/a6-s6-r...s-info-66.html and got the figures from there

[The Artist]

the swedish AMG article says that the Gearbox will be capable of 1000nm..not that the car will have 1000nm

[martinbo]

Oo hoo - nice contentious topic Artist.

There are a great many misconceptions about AWD and the benefits it provides.

monster is right, AWD drivetrains have more components: 3 differentials instead of one, two propshafts and two extra driveshafts in its simplest form. In essence, some of the power produced by the engine is consumed by the rotational masses and frictional (more gears, more teeth, more friction) losses know as driveline drag. In effect this means that a car with AWD is less efficient at putting power to the road - especially at higher speeds than a two-wheel drive car. This is a primary reason why the best supercars are rear-wheel drive and why a car like the Veyron needs 1000 horses.

All-wheel drive cars are only faster off the mark if the driver pulls away:
a. without bogging the engine down
b. without slipping the clutch

It must be noted that for the optimum launch in any car just the right amount of wheelspin needs to be generated to avoid bogging the engine down. It's simple: too little wheelspin and grip on the surface overcomes the engine torque, too much wheelspin and you waste valuable seconds trying to grip the road enough to translate into meaningful forward acceleration.

There are several ways to launching an all-wheel drive car for optimum get up and go:

a. A the clutch side-step method. Get the revs up to around 5500 rpm and slide your foot leftways off the clutch. [Wince] Here the idea is to "shock" the tyres into letting go for just an instant so that all the engine power can be translated into forward motion without getting bogged down. The problem with this method is that one can smash first gear and/or its synchromesh to smithereens or, if the torque does somehow make it past the transmission, then the centre and rear differentials take up all of the driveline shock and they can end-up being a little less than "round". A little bit of wheelspin is thus essential. If not then this has to be the most mechanically unsympathetic launch method, it sounds terrible and makes the most awful "BDWANGGG" sound. The preferred method for launching an RS4 quickly.

b. The handbrake-friction point method. Getting the revs up to around 4000 rpm hold the car using the handbrake whilst simultaneously engaging friction point. Stomp on the gas, drop the clutch and the handbrake in one go and hey presto. Burns clutches quicker than Grandma burns the chips if done by an amateur. Preferred method for launching EVOs and STIs.

c. The auto-tranny two footed pullaway. In performance cars with a high stall speed torque convertor automatic hold the car with the left foot on the brake and dial up the rpm. Release the foot brake and mash the accelerator to the carpet. A fine way to break an automatic transmission if not done with a measure of precision and mechanical circumspection. NOT recommended for DSG's, SMGs and CVTs.

In more cases than not the AWD driver actually loses out to a less powerful two wheel drive car because they didn't dial up the right amount of rpm and ended up trying to race off 3000 rpm.

The same will apply to FWD vs RWD, the FWD system being slightly more efficient in terms of placing the maximum amount of power at the wheels. This is oft negated by the poor traction on the front wheels from pullaway as a result of weight transfer to the rear on take off and the diminished available grip on the front wheels.

[Just_me]

Above 200km/h a M5 E60 is faster than a Gallardo
Above 200km/h M5 E39 is faster than RS6 with 450 hp

Thats the conclusion m5board.com done during various races.
I think AWD is one of the reasons for the losses?

[martinbo]

Well it's obvious, really. At lower speeds the engine power is consumed only by the AWD system. So 0-100 km/h, AWD cars put in a good showing. However, at higher speeds aerodynamic drag starts to consume more and more engine power as a greater portion of the output is put to work in overcoming this aerodynamic resistance. The added resistance of an AWD car merely compounds this wasteful consumption of power.