Rolling Roads vs AWD cars.

[Leadfoot]

I have always wondered why most awd cars don't normally meet their quoted claimed power and torque output on rolling roads compared to rwd or fwd car.

To quote a very well established company WRC how do the dynoing for EVO magazine. 'Four wheel drive system are slightly confused by rolling roads, constantly shuffling power in a search for grip'.

I was wondering does this explain why Audis with their Quattro system produce less than quoted, all this shuffling between the front and rear diffs meaning some of those horsepowers sending time in limbo between the four wheels.

I sure someone on this site can explain away this as nonsense, but it's interesting none the less.:thumb:

[Klint]

You also need to remember that alot of power is lost as heatsoak and friction in the drivetrain, this is (obviously) alot more on a 4WD vehicle than a RWD vehicle.

[Leadfoot]

Agreed Klint,

But I think we are all in agreement that the bulk of the lose for any car is through the gearbox itself and to a smaller degree the diff. If this is indeed the case then the extra diff in an awd system will only account for the small difference between the two, but all have seen the diagram of the S4 and RS4, the difference is more than just a little between them and the similar powered rwd cars.

Maybe what WRC are saying has some substance.

[SuperstarDriver]

i do not agree with none of you, sorry guys but you're wrong!Quattro 4WD is so perfect built that puts EXACTLY 100% of engine power to the road through the drivetrain...so get lost with stupid traction like RWD...that's a bullshit...spinning every second nonetheless that's an very stupid traction...4WD are 4 super cars not stupid drifting cars...

[Klint]

i do not agree with none of you, sorry guys but you're wrong!Quattro 4WD is so perfect built that puts EXACTLY 100% of engine power to the road through the drivetrain...so get lost with stupid traction like RWD...that's a bullshit...spinning every second nonetheless that's an very stupid traction...4WD are 4 super cars not stupid drifting cars...
Ok Superstardriver, find a dyno plot of a quattro achieving 100% HP and torgue figures of what Audi claims at the flywheel, then i'll believe you.

P.S Make sure the rolling road dyno plot doesn't take into account drivetrain loses.

[Klint]

Agreed Klint,

But I think we are all in agreement that the bulk of the lose for any car is through the gearbox itself and to a smaller degree the diff. If this is indeed the case then the extra diff in an awd system will only account for the small difference between the two, but all have seen the diagram of the S4 and RS4, the difference is more than just a little between them and the similar powered rwd cars.

Maybe what WRC are saying has some substance.
Leadie,

You need to remember some firms who offer dyno facilities calculate drivetrain loss and add it to the dyno figures. There is no proper way to calaculate such loses but there are equations out there, if my memory's correct mechanical 4WD systems, such as the Subaru system can lose as much as 45% of flywheel horsepower, electrical 4WD systems such as BMW's X5, can lose as much as 35% of the flywheel horsepower, whereas the front engined rear wheel drive layout BMW has been using has been known to lose 15% of flywheel horsepower and FWD cars lose around 25%, these are numbers based on my poor memory on the subject and all makes and models of cars are just examples.

There's always going to be a difference between flywheel horsepower and wheel horsepower. in the real world it's the wheel horsepower that counts.

[Klint]

Leadie,

You need to remember some firms who offer dyno facilities calculate drivetrain loss and add it to the dyno figures. There is no proper way to calaculate such loses but there are equations out there, if my memory's correct mechanical 4WD systems, such as the Subaru system can lose as much as 45% of flywheel horsepower, electrical 4WD systems such as BMW's X5, can lose as much as 35% of the flywheel horsepower, whereas the front engined rear wheel drive layout BMW has been using has been known to lose 15% of flywheel horsepower and FWD cars lose around 25%, these are numbers based on my poor memory on the subject and all makes and models of cars are just examples.

There's always going to be a difference between flywheel horsepower and wheel horsepower. in the real world it's the wheel horsepower that counts.
Also just to add to the original post about 4WDs getting confused on rolling roads...Unless there is tyre slip i can't imagine the 4WD system getting confused as the car doesn't know any better, whether it's actually being driven down the road or is on a rolling road.

However you do find some manufacturer's do put 'restraints' in place to prevent people from putting their cars on rolling roads, Mercedes is one of the manufacturers that comes to mind, a simple pull of a fuse can 'confuse' the stability programme into thinking the car's being driven down the road.

So really it all depends on the how the manufacturer has programmed the stability programmes.

As far as i know, Audi's ESP system can be disengaged completely, thus not interfearing with rolling road tests.

[skratch]

Its all about the driveline,The audi will lose alot more because it has a beffier (heavier driveline)BMW uses a verylight driveline and uses as many shortcuts they can to get the power to the ground...aka electric fans,electric water pumps,aka now even disconecting the alterantor while on the throttle in the new M3.These all with a light tranny alow the car to put down alot more power than running threw an extra 300lb quattro system.

You should read up on the new tranny's bmw is using thats giving them (from memory)3-5% more efficiant at putting power threw them.The 335 is a perfect example.

Or Audi could just be under powering there cars lol but IM sure there not

[Leadfoot]

Klint and Skratch,

I am no expert on the subject, I was only reporting what the representative of WRC said on the subject of awd cars on rolling roads. I is under the impression that what ever they show on the display is less than they are really achieving, how much if any is up for debate.

Don't bust my balls if I am wrong in this, but if EVO magazine are using them they must know what they are talking about what with the chance of a manufacturer suing them for write the wrong figures.

[SuperstarDriver]

should i show you the episode where Clarkson explains what happen with an 4WD when is pushed to pedal to the max and the toque is killing the traction and tires EVERY SINGLE SECOND and is not able to put power on ground at all?It's about the ALL NEW BRABUS SL65 730HP with RWD...this stupid TRACTION FOR STUPID DRIVERS...BURNING TIRES ON AND ON AND ON AND ON AND ON AND ON AND ON UNTIL IS NOT LEFT ANYTHING...Ahhh...RWD BETTER THAN 4WD?DREAM ON...LOOK ON RS4 AT NURBUGRING IS KILLING M6 AT TIMES...AND IT HAS 4WD AND 87HP LESS...LOOK AT THE R8 WHO HAS ALSO BETTER TIME THAN THE M6...YEAHHH RWD BETTER...WHERE DO YOU LIVE?IN CONGO?RWD IS DRIFT TRACTION, THAT'S IT...NO SPORTY TRACTION...OR IS FWD OR 4WD, NO RWD...CAUSE RWD IS A BULLSHIT, A SUPRAVIRATION BULLSHIT...sorry for my language but i'm nervous...this topics like this is make me nuts...stupid ideas...

[Leadfoot]

It one of high lights to my day moments.

:applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause:

Thanks SuperstarDriver.:thumb:

[SuperstarDriver]

thank you Leadfoot, i needed to make my come cause somebody i think is a bmw fan on this forum and is not right...for me bmw is a stupid machine, i invented also the acronim of the name...BMW=BAVARIAN MOTHERFUCKIN' WORKSHIT...like it?:D and i am right to do that destroying BMW cause it deserves...bmw is a shit...

[sticky]

thank you Leadfoot, i needed to make my come cause somebody i think is a bmw fan on this forum and is not right...for me bmw is a stupid machine, i invented also the acronim of the name...BMW=BAVARIAN MOTHERFUCKIN' WORKSHIT...like it?:D and i am right to do that destroying BMW cause it deserves...bmw is a shit...
Why do the moderators although this type of BS but get on peoples backs when they provide a view that goes against the Audi majority of the board? If this type of posting was made in favor of Audi's competition the person would be banned immediately, what is with the hypocrisy?

[Klint]

Yes, i agree. BMW is the shit. :D

[Lateknight]

This 4 page article gives an insight into 4wd rolling road outputs.

http://www.dialynx.co.uk/reviews_rolling_road.htm

(click on each of the seperate pages to expand)

[Lateknight]

It one of high lights to my day moments.

:applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause: :applause:

Thanks SuperstarDriver.:thumb:

You must have some pretty dull days !!

[SuperstarDriver]

Audi is like GOD you know is there and is protecting you against all mistakes you made as a driver, BMW is killing you in the first minute you make a mistake and is a pain death...RWD will never be safe, sport, 100%grip or powerfull drivetrain traction...no way...or is it FWD or the much much better 4WD which is the best and the sportier traction in the world! By the way guys why the hack in the world do you say that 4WD is not putting 100% to the ground at any time?did i must say again avout the new S5 with TORQUE VECTORING almost the same like as the system from ProDrive? Did anyone saw that episode with Prodrive at TopGear?Well...Clarkson has been testing itand vomiting after because he was moving in cercles and he said the car was not under or oversteering at all at any speeds, at any position of the acceleration pedal, it's like an Quattro...you barely make an quattro to understeer and oversteering an Quattro is almost impossible...so get lost with those stupid articles, the facts are the facts...that's it!

[Leadfoot]

sticky & Lateknight,

Surely you know sarcasm when you see it.

Well that was me there. :D

Thanks for that Lateknight, it explains a lot.:thumb: