the RWD vs 4WD debate... [Archive]

TomM

11-06-2003, 19:44

I was having a pissed late-night argument with a mate a while back. (He has a Scooby.)

I was saying that in the dry, around a track, there is little advantage to having a 4WD car - a well driven RWD would be just as fast.

He thought the opposite - that being 4WD, you'd have less 'power per wheel', so would be less likely to reach the limit of your tyres' grip. I decided this was a limited view :)

There's obviously lots of variables - gearing, car weight, 4WDs weigh more than RWDs due to the extra diffs, and given identical flywheel powers, RWDs will have far more at the wheels due to lower drivetrain loss.

But taking this as read, which layout is the best for track driving? And basically, given similar engine powers, who'd win around a track ;) :D

11-06-2003, 19:48

I'm not a techy person so I'm sure someone will prove me wrong but doesn't 4wd offer better traction, not grip.

On a dry track with similar engine power rear wheel dive would win cos it'll be lighter and the transmission losses will be less.

Plus:

RWD = proper sports car
4WD = agricultural vehicle

;)

arry

11-06-2003, 19:49

i never thought much of 4wd cars to be honest until driving a pulsar recently - have to say the thing is incredible round bends and i dont think, regardless of conditions, i'd stand a chance of keeping up with one round a track.

Having said that, i think if you get someone who REALLY knows what they are doing in a rwd car they can be formiddable

Psycosis

11-06-2003, 19:51

I agree with the Pulsar thing, almost unstoppable.

Gee

11-06-2003, 20:05

I recently did a trackday at Knockhill in my Pulsar GTi-R and I think that my old S13 would be quicker round the bends than my 'R.

There is far too much understeer for my liking with the Pulsar as I prefer the sticky front end and light back end that I had with my 2***** which I think I would be faster with.

Apparently the Pulsar's understeer can be eliminated by fitting the Whiteline handling kit.

SteveCarter200

11-06-2003, 20:16

Taking it pretty much to the extreme for a road going type of car think back to the BTCC when the Audis were competing. In the dry, not much difference between RWD, FWD or 4WD. In the wet, 4WD kicked ass.

Psycosis

11-06-2003, 20:33

Yeah the whiteline kit fixes most of that understeer.
So you can accelerate even more round corners.

I need to be in a great handling 200 so i know what they are capable of, so far i haven't been in one when someone has given it some real stick round corners (without sliding)

Martin T

11-06-2003, 21:34

Funny if 4wd is so much better that all of the proper race cars use RWD.

Why does Ferrari not use 4WD?
Answer: They will use 4WD when it gets their cars better track times.

voodoo_melon

11-06-2003, 21:36

Lamborghini use 4wd in both the Diablo and the Murcielago.

Ferrari prolly don't use it because of the weight and added complexety and cost.

GenerationNexus

11-06-2003, 21:36

Originally posted by Tombs

I was saying that in the dry, around a track, there is little advantage to having a 4WD car - a well driven RWD would be just as fast.

He thought the opposite - that being 4WD, you'd have less 'power per wheel', so would be less likely to reach the limit of your tyres' grip. I decided this was a limited view :)

I have saw one video with an RX7, NSX, GTR34, Sub STI (and something else) all driven by pro jap drivers and all stock power. NSX led most of the way, followed by the RX7, who took the NSX after a few laps. Now different tracks would suit diff cars. Be careful when drawing comparisons as with two not brilliant drivers, they would prob be a lot quicker round the bends and twistys with 4X4, but if you have the skill to handle RWD ...

arry

11-06-2003, 21:36

Originally posted by Martin T
Funny if 4wd is so much better that all of the proper race cars use RWD.

Why does Ferrari not use 4WD?
Answer: They will use 4WD when it gets their cars better track times.

thats the nail hit i think - ferrari are REAL sports cars expected to be driven by REAL sports drivers - hence they are faster than 4wd jobbies. I think 4wd cars are a lot more forgiving on inexperienced drivers

Martin T

11-06-2003, 21:37

They dont claim better track times for it, though.

Lewis

12-06-2003, 08:32

If you had a RWD & a AWD car with the same weight, power @ flywheel etc the AWD would generally be slightly quicker. Anything else would be down to differences in the car ( weight, power etc ).

If RWD is bettter why is the world best new supercar going to be AWD. When we try running in RWD mode the car just spins around, but in AWD all 4 tyres stop spinning at about 50mph as it changes to 2nd gear :)

Ferrari don't use AWD becasue ATM they can't do it properly.

Jeffers_S13

12-06-2003, 08:33

Originally posted by GenerationNexus
I have saw one video with an RX7, NSX, GTR34, Sub STI (and something else) all driven by pro jap drivers and all stock power. NSX led most of the way, followed by the RX7, who took the NSX after a few laps. Now different tracks would suit diff cars. Be careful when drawing comparisons as with two not brilliant drivers, they would prob be a lot quicker round the bends and twistys with 4X4, but if you have the skill to handle RWD ...

I've seen a bunch of these videos, my mates downloaded shed load of them. Every one is very similar, they get a selection of Japanese cars as listed above and just race them round a track ! do donuts, do drag runs, they have loads of detail about the spec of the cars etc and cars get eliminated throughout the program I think. Its about an hour long, they should get something like it over here ! its excellent ! BTW the NSX's always seem to do really well.

dunc

12-06-2003, 08:53

Like lewis said, if all other things were similar between a 2wd and 4wd car (power @ wheels, power to weight ratio) then having drive to an extra couple of wheels can only be an advantage. I don't think either 4wd or 2wd is vastly supperior in a fast corner in the dry. Any differences in this could be put down to setup.

F1 rules have strict guidelines that are biased to RWD (stating slim front wheels and wide rear wheels etc), if it wasn't for this I don't see why F1 cars wouldn't try out 4WD. Anyone remember the 6 wheel jobbie that was used to get more grip? It was banned as would a 4WD setup I believe.

Dunc.

Pete C

12-06-2003, 09:44

I'd say it depends on what kind of 4WD it is, if it's 'proper' permanent 4WD with a RWD bias, like my old Sierra XR4X4 which was 37% FWD, 63%RWD, then the handling around corners should be a lot better than a RWD car with similar tyres, suspension, etc :D

BUT in cars with non-permanent 4WD, like my mate's Calibra Turbo, which has a FWD bias, and switches to 2WD every time you hit the brakes, well, his car understeers like hell, and I'm pretty sure mine would outhandle his in the dry :)

However, in the wet, any kind of 4WD has a massive advantage.

TomM

12-06-2003, 10:50

Originally posted by dunc
...power @ wheels...
Unfair comparison, 'cos the 4WD car would be significantly more powerful to deliver this.

Why (in the dry, good suspension, good tyres, etc) is AWD inherently better?

Kes

12-06-2003, 11:48

I've owned both, and there's no right or wrong answer.

Firstly, the track - Long straights and fast sweepers or tight and twisty? Tight and twisty suits 4wd, long straights and sweepers would favour RWD. 4wd only benefits traction.

Secondly, the drive - We all prefer different handling characteristics, some people actually like understeer :eek: This means in differing cars, one driver may be faster than another. It's all down to taste.

To be honest, on road cars in most conditions, 4wd on a powerful car just gives you the opportunity to use the power more, and makes it easier on the driver to do so. Round a track, it comes more down to chassis set up and driver than just rwd / 4wd. Look at the new scoob STI and EVO 8, both similar power / torque / weight, but the EVO is quicker round a track, it's not just down to 4wd...

I loved my 200SX, I used to live 2 miles from work, 5 mins in the car of which each day I would spend at least 25% travelling sideways with a big grin on my face :D It was easy and very addictive. My Mazda goes sideways, but not as easily and has to be travelling a bit quicker to do it, so there's a lot more risk - I don't go sideways as often now :( But! on the crappy things we have for roads in this country, and the crappy weather we get, I can use more of the performance more of the time, and it makes a big change from the 200. I'm still tempted to get another 200 for the fun factor, the 323 is more usable and quicker on the road. As for quicker round a track, I'll find out when I meet a 200 on a track day ;) 1 Min 27 secs round Castle Combe at Japfest within 5 laps and my first time there, I think that's ok.

dunc

12-06-2003, 12:11

Originally posted by Tombs
Unfair comparison, 'cos the 4WD car would be significantly more powerful to deliver this. - ONLY UNDER THE BONNET, WHATS LOST IN TRANSMISSION MEANS NOTHING IN THIS DEBATE. WHEELS POWER IS THE ONLY FAIR COMPARISON IMO.

Why (in the dry, good suspension, good tyres, etc) is AWD inherently better? BECAUSE A 4WD DOING A 4WD DRIFT CREATES MUCH MORE TRACTION AS A 2WD DOING AN OVER STEER DRIFT. ADMITTEDLY SLIDING OR DRIFTING IS NOT IDEAL IN MOST CIRCUMSTANCES BUT WHY WOULD YOU COMPROMISE THE ABITITY IN THESE SITUATIONS

In a situation during a corner when you were just coasting around it (not using any power) then 4WD and 2WD would be identical, this is never the case though is it? The way the power goes down does not only come into effect on straight line traction.

Just MO :)

dobergoose

12-06-2003, 12:42

Originally posted by Martin T
Why does Ferrari not use 4WD?

Clutches

ScoobyDoo

12-06-2003, 12:58

AWD everytime for me:thumbs:

The key benefit of All-Wheel Drive is greater traction. To understand the reasons for this you must start with the basics.

Traction is the force that keeps tyres in stable contact with the road surface during take-off, acceleration, hill climbing and running. The better a car's traction, the safer it is. Safe running depends on constant stable traction and tractional stability is largely determined by the car's drive method.

Distributing power to each of the four wheels, All-Wheel Drive achieves much better traction than either of the two wheel drive methods (Front or Rear Wheel Drive). To understand the reasons for this you have to realise that car tyres slip when the maximum value of the frictional force between the tyres and road surface is exceeded.

For example, if the maximum frictional force of a tyre is 30HP and the engine has an output of 100HP, a 2WD car would deliver 50HP to each of the driving tyres which would be 20HP beyond their capability. The excessive horsepower would then cause the tyres to slip. However, an AWD car would distribute the horsepower equally to all four tyres (25HP per tyre) thus falling below the threshold of 30HP. Accordingly they would fail to slip. Because AWD obtains twice the traction of 2WD, the difference becomes even more significant the more slippery the road surface.

So there you have, twice the traction than a two wheel drive car, Audi, Lamborgini, Mitsubishi, Subaru, Nissan, Bugatti to name a few all seem to think its a good idea too.

dobergoose

12-06-2003, 17:33

Safety sells cars these days.

Most people who have made the switch from RWD to 4WD miss the fun of RWD.

Marty_t3 sold his WRX to come back to a S13
KennethM told me the other day at a trackday that after watching the RWD cars sliding through corners his WRX feels a bit sterile although he loves it.

Kenny had the same lap times in his WRX as Mike did in his S13, both with similar power at Knockhill last tuesday in the dry, sure there would be miles between them in the rain but who wants to be praying for rain when they go out a drive.

Martin T

12-06-2003, 17:45

Using the argument that the Bugatti 16/4 Veyron uses 4WD dont hold that much water, since the Mclaren F1 used RWD.
I suspect that they used 4WD on the bugatti was because its the only way to get 1000BHP down to the road properly.

Martin T

12-06-2003, 17:48

I suppose the main advantages with 4wd are that once you got past the apex of the corner, you can put more power down earlier, but due to the losses, the RWD car can put more power down once its got the grip once the corner's finished/nearly finished.

ScoobyDoo

12-06-2003, 23:15

I got my new WRX delivered today, very sweet :cool:

Bad thing is Ive been told I should keep it below 4000rpm for first 1000miles, is this true?:confused:

voodoo_melon

12-06-2003, 23:31

I'd have thought so, yeah. If it's a brand new engine or got new parts like pistons it's prolly a good idea to take it easy for a while just to get everything run in properly.

AshT_200

12-06-2003, 23:58

Originally posted by voodoo_melon
Lamborghini use 4wd in both the Diablo and the Murcielago.

Ferrari prolly don't use it because of the weight and added complexety and cost.

Plus with Ferraris, less parts means less to go wrong.

AshT_200

13-06-2003, 00:00

Originally posted by Martin T
Funny if 4wd is so much better that all of the proper race cars use RWD.

That is not totally true.

There are a lot of FWD cars in BTCC and for quite a while they have been kicking the asses of the RWD cars.

Take Nissan with the Primera. Ok it might be ugly, but when they were seriously competing as a works team, they dominated it.

ScoobyDoo

13-06-2003, 00:04

Originally posted by voodoo_melon
I'd have thought so, yeah. If it's a brand new engine or got new parts like pistons it's prolly a good idea to take it easy for a while just to get everything run in properly.

cheers voodoo, its a brand new car - no fun for 1000 miles then :(

TomM

13-06-2003, 00:19

Originally posted by ScoobyDoo
cheers voodoo, its a brand new car - no fun for 1000 miles then :(
Not sure if this's directly relevant/comparable, but I remember reading about Clio 172s - giving the car a gentle running-in period (like the one you're suggesting for your Scoob) resulted in a less powerful car afterwards, compared to one thrashed from day one. This was apparantly proven several times.

Dunno what the engine life was like in the non-run-in one, though :eek:

TomM

13-06-2003, 00:27

This was exactly the theory put forward by my Scooby-owning mate!

Originally posted by ScoobyDoo
For example, if the maximum frictional force of a tyre is 30HP and the engine has an output of 100HP, a 2WD car would deliver 50HP to each of the driving tyres which would be 20HP beyond their capability. The excessive horsepower would then cause the tyres to slip. However, an AWD car would distribute the horsepower equally to all four tyres (25HP per tyre) thus falling below the threshold of 30HP. Accordingly they would fail to slip. Because AWD obtains twice the traction of 2WD, the difference becomes even more significant the more slippery the road surface.
This is a good explanation of why a 4WD would be faster at standing starts - better traction, so you can use more power before reaching the limits of the tyres. However, I reckon there's a lot more to fast driving 'round a track than the traction - as someone said above, grip (ie lateral forces as well, and not just accelerative forces) is something different.

When you're cornering hard, yes, you're trying to approach the maximum grip of the tyres without exceeding it - this would give the best grip, and therefore the highest cornering speed. But on a dry track, with two well-set-up cars, and good tyres, I can't understand why having an extra component to the force put through the front tyres (ie the accelerative force from the engine in a 4WD, as well as the lateral cornering force) would make the car grip the road better.

Not being awkward - just want to understand :)

voodoo_melon

13-06-2003, 00:31

Not sure if this's directly relevant/comparable, but I remember reading about Clio 172s - giving the car a gentle running-in period (like the one you're suggesting for your Scoob) resulted in a less powerful car afterwards, compared to one thrashed from day one. This was apparantly proven several times.

Dunno what the engine life was like in the non-run-in one, though

Interesting, wonder what causes that, anyone know?

Back on topic though I can't really comment cos my sx is the only non-fwd car I've driven :| and hopefully the first of many with turbos :) it's so much better than my Astra it's unbelievable (although it was an '88 1.3L so I was hoping it'd be a bit better). Finally I can overtake people! hurrah! :)

dunc

13-06-2003, 08:53

Originally posted by Tombs
Not sure if this's directly relevant/comparable, but I remember reading about Clio 172s - giving the car a gentle running-in period (like the one you're suggesting for your Scoob) resulted in a less powerful car afterwards, compared to one thrashed from day one. This was apparantly proven several times.

Dunno what the engine life was like in the non-run-in one, though :eek:

We noticed this with our curtisy (sp?) cars, they were brand new but as we all know there's no chance anyone's going to even consider taking it easy in a hire car/curtisy car. Anyway the difference in performance was so extreme that our customers were actually complaining that their cars were so slow and thought there was something wrong with their car!

Dunc.

Fizzy

13-06-2003, 10:00

On a tarmac track, then RWD "should" have a slight advantage over 4WD because of the reduced transmission loss. As someone mentioned, the super cars that use 4wd is basically so they can get all those horses onto the road. Look at the Skylines in the JTCC. They're RWD. The advantage of 4WD on a track is being able to accelerate out of bends earlier. But RWD cars have the advantage of being able to turn in quicker, because of less understeer. But don't forget Audi's domination of the BTCC in their Quattros a few years ago. But then we all know what the British weather is like ;)