RWD - FWD - LSD - No of Cyls. Can You Really Tell?

[Hungrymc]

RobM77 said:

spoke to a BMW salesman about this once and he said the majority of people remark on the better poise and balance in the corners when they test drive a BMW compared to the other cars they've looked at or own, but they won't necessarily know that this is because BMWs are rear wheel drive. That latter point was proven by a survey BMW undertook before deciding to re-design the 1 series as FWD; the former point clearly passed them by

Thats just marketing talk surely ? I think BMW have a lot of work to do on calibration of their stability control. It intervenes very early for cars that are meant to be able to deliver RWD handling attitude.

[RobM77]

Hungrymc said:

RobM77 said:

spoke to a BMW salesman about this once and he said the majority of people remark on the better poise and balance in the corners when they test drive a BMW compared to the other cars they've looked at or own, but they won't necessarily know that this is because BMWs are rear wheel drive. That latter point was proven by a survey BMW undertook before deciding to re-design the 1 series as FWD; the former point clearly passed them by

Thats just marketing talk surely ? I think BMW have a lot of work to do on calibration of their stability control. It intervenes very early for cars that are meant to be able to deliver RWD handling attitude.

Two comments on that if I may:

1) Stability control is only supposed to intervene at high slip angles, around or beyond the point of maximum grip. This feeling of balance comes in way before then.

2) My E46 had very nannying stability control, but in my current E90 I can quite happily get it neutral, and even with a little oversteer, without any DSC intervening at all, provided you're smooth and the road is smooth.

[Dr Jekyll]

M4cruiser said:

Yes I can - there are loads of 3-cylinder cars now, compared with say 10 years ago, and most of them have awful engines.

The strange thing is that when BMW made two bikes with 3 and 4 cylinder versions of what were basically similar engines (K75 and K100) the three cylinder bike was noticeably smoother.

[Moonpie21]

So I reckon most people are clueless, they either like the way it drives or they don't. For Mr or Mrs Average on todays road it's probably more about the other peoples perception, seating position/type, toys and expected ride (sporty a bit jiggily or luxury being wafty stable cossetedness), maybe the noise it makes, but that can be piped in and not in relation to number of cylinders.

Realistically the above attributes probably drive their choice and advertising or reading up on something let them justify it in a supposedly knowledgeable manner.

Being honest with myself I probably lean more towards this type of person than I'd like to admit. I have had the benefit of a few track days and driven a wide variety of cars and being a bore I can tell you what each one of them had in terms of the original topic and what each bit did/how it should impact me. I've liked some more than others and at different ages have had different preferences. Knowing what I know and what I've driven could I tell you the perfect setup/combination is... no I can't.

For example I have an MX-5 NA and an A45 at the moment, I enjoy driving both, but as their complete packages. Would more power for the MX-5 make it more fun, no probably not, might even spoil it. Would more rear wheel bias make the Merc more engaging, maybe I'd never find out though. I like them both for what they are and in my ignorance believe that the engineers who designed them achieved their goals and the cars do the jobs they were designed for and I don't need to understand how.

I guess that makes me a bit of a superficial idiot bore? Maybe in general 90% people are the first variety, 5% are me in the middle in some way and then 5% truly know what they are talking about and can tell you the best solution for the job.

[Gary C]

ecsrobin said:

My new car is FWD with LSD I felt like I could feel an LSD but half of me felt it was just a placebo, yesterday the heavens opened and that's when I realised that I definitely could tell an LSD was fitted I could just apply power all the time. Other cars without I'd have been loosing traction the whole journey.

Or just traction control via the ABS


Could you spin up both wheels ?, I doubt it as torsens dont work like that, and I dont know of any road car this side of an older 911GT3 that comes with plated diffs.

Easy way to tell, put car on full lock, then drive forward slowly. An LSD often causes the car to crab slightly (though this is more pronounced on plated diffs, but will do it on torque sensing types too)

[Gary C]

bennyboysvuk said:

Thanks CABC. I've become more and more fascinated by the GT86, but I still might go the other way and get an old 911, just for the NVH and experience.

Rob, it's quite true. Slightly tongue-in-cheek, but on the road the very fastest cars cannot fit into the gaps that bikes can, not even the Twizy.

Get an old 911 !

What i really noticed, when driving a 997 GT3, was how much like my old 3.2 carrera, the handling is. So raw but delicate too. Bit slower though

And so much warmer !

[motco]

CABC said:

With less power, you might feel the LSD less on track as you're carrying more speed through the corner and so not losing the inside wheel. Different in a 200hp Caterham obviously.
On the road it could be that with more cautious cornering but an early boot full the LSD would help.
I'm not championing no LSD, but enjoy a good blat on my favourite roads that I know well . On today's roads I can see hustling a balanced 1.5 could be great fun. The 2l is heavier, lees sweet and obviously more expensive. Price does come into it otherwise it'll be a 458 Speciale.

Btw the Twingo is a packaging solution and will have had its rwd 'characteristics' dialled out for shopping duties. Goes back to the point often made here that rwd does not necessarily make a good car.

Someone I know span and wrecked a Westfield on the exit from a damp roundabout and it was almost certainly make more likely by the LSD. With an open diff the inner wheel would likely have spun and 'wasted' the excess power that the inexperienced foot was trying to deliver. I have a similar Westfield but with an open diff (not my build) and it spins up the unloaded wheel on a fast, gentle, full throttle left hand bend - on track of course. With a passenger aboard on the same bend the wheel just about stays in sufficient contact.

[Gary C]

motco said:

CABC said:

With less power, you might feel the LSD less on track as you're carrying more speed through the corner and so not losing the inside wheel. Different in a 200hp Caterham obviously.
On the road it could be that with more cautious cornering but an early boot full the LSD would help.
I'm not championing no LSD, but enjoy a good blat on my favourite roads that I know well . On today's roads I can see hustling a balanced 1.5 could be great fun. The 2l is heavier, lees sweet and obviously more expensive. Price does come into it otherwise it'll be a 458 Speciale.

Btw the Twingo is a packaging solution and will have had its rwd 'characteristics' dialled out for shopping duties. Goes back to the point often made here that rwd does not necessarily make a good car.

Someone I know span and wrecked a Westfield on the exit from a damp roundabout and it was almost certainly make more likely by the LSD. With an open diff the inner wheel would likely have spun and 'wasted' the excess power that the inexperienced foot was trying to deliver. I have a similar Westfield but with an open diff (not my build) and it spins up the unloaded wheel on a fast, gentle, full throttle left hand bend - on track of course. With a passenger aboard on the same bend the wheel just about stays in sufficient contact.

we keep talking about 'lsd's' as if they are one thing !

An open diff transmits the same torque to both wheels at all times regardless of the wheel speed

A torque biasing diff, biases more torque to the slower wheel, normally at a ratio of approx 5-1. So as the speed differential increases, so more of the torque is transfered to the slower wheel, but they never lock up.

A 'plated' diff will transmit torque to the slower wheel upto 100% lockup but can also be designed to transfer that torque if its come from the engine only (1-way) or from the engine or back from wheels themselves (2-way). these are not often used on 'normal' road cars as they affect braking stability, and the plates wear out.

With a torque biasing diff, with one wheel on ice for example, you can only transmit about 5x the torque of the wheel with low traction (ie the faster spinning wheel), to the other wheel which in this example is 5x bugger all = bugger all, so you still dont move and still just spin the one wheel. however a modern car can use its ABS in reverse to brake the spinning wheel, and thus develop enough torque to transfer to the wheel with traction.

Just saying "my car has an LSD" is insuficient.

There are others

In another example, the EVO V has an open rear diff in its simplest, however the AYC clutch pack progressively locks up one rear wheel to one of two hollow driveshafts, one running 15% faster, and one running 15% slower, and this allows it to program rear wheel steering effect as well as an LSD function.

Whereas Opel used to fit a friction diff to some road Manta's (very rarely) that used a simple preloaded friction plate between the output shafts of the diff such that some torque transfer occured when spinning at different speeds.

Complicated world.

A plated diff with sufficient pre-load and aggressive ramps can lockup fully, and these really do allow both rear wheels to be spun up.

Edited by Gary C on Wednesday 19th October 12:07

[motco]

The Westfield that was wrecked had the diff from a Sierra XR4i as far as I know, but exactly what type that was I don't know. I have yet to discover whether a Torsen type should be allowed on MOT brake rollers.

[ikarl]

motco said:

The Westfield that was wrecked had the diff from a Sierra XR4i as far as I know, but exactly what type that was I don't know. I have yet to discover whether a Torsen type should be allowed on MOT brake rollers.

Why wouldn't it be allowed?

Never heard of any problems with an MX5 going on the brake rollers

[motco]

ikarl said:

motco said:

The Westfield that was wrecked had the diff from a Sierra XR4i as far as I know, but exactly what type that was I don't know. I have yet to discover whether a Torsen type should be allowed on MOT brake rollers.

Why wouldn't it be allowed?

Never heard of any problems with an MX5 going on the brake rollers

Because some types of LSD are damaged by the rollers turning one wheel at a time. I understand that some LSDs are safe but others not, but the MoT station don't know for sure so they use the Tapley device instead. I was hoping for a definitive answer on here.

[Hungrymc]

bennyboysvuk said:

RobM77 said:

CABC said:

bennyboysvuk said:

Right, I'm off to buy a GT86.

i think you'd understand the 86 more than most. all about feel and connection. no car will compete in pace with your R1, best thing a car can do is be delicate, adjustable and feelsome.

That's not quite true though is it? Plenty of road cars are quicker in terms of lap times and top speed. I presume you mean purely in terms of acceleration?

Thanks CABC. I've become more and more fascinated by the GT86, but I still might go the other way and get an old 911, just for the NVH and experience.

Rob, it's quite true. Slightly tongue-in-cheek, but on the road the very fastest cars cannot fit into the gaps that bikes can, not even the Twizy.

In a thread about feeling the impact upon dynamics from different attributes of car, I think its absolutely true that no car will compete with an R1 (pace is less clear cut in exceptional circumstances). If we're talking about balance and the reaction of a car to things such as application of throttle etc. Bikes are a different league of engagement and feel. That's not to say bikes are "better", but if your search is for ultimate feel and direct influence over what's happening, bikes are very different.

[RobM77]

Hungrymc said:

bennyboysvuk said:

RobM77 said:

CABC said:

bennyboysvuk said:

Right, I'm off to buy a GT86.

i think you'd understand the 86 more than most. all about feel and connection. no car will compete in pace with your R1, best thing a car can do is be delicate, adjustable and feelsome.

That's not quite true though is it? Plenty of road cars are quicker in terms of lap times and top speed. I presume you mean purely in terms of acceleration?

Thanks CABC. I've become more and more fascinated by the GT86, but I still might go the other way and get an old 911, just for the NVH and experience.

Rob, it's quite true. Slightly tongue-in-cheek, but on the road the very fastest cars cannot fit into the gaps that bikes can, not even the Twizy.

In a thread about feeling the impact upon dynamics from different attributes of car, I think its absolutely true that no car will compete with an R1 (pace is less clear cut in exceptional circumstances). If we're talking about balance and the reaction of a car to things such as application of throttle etc. Bikes are a different league of engagement and feel. That's not to say bikes are "better", but if your search is for ultimate feel and direct influence over what's happening, bikes are very different.

That's a very good point. For starters, you are holding the steering mechanism in your bare (or gloved) hands, there's no gears or mechanism and there's certainly no assistance. The latest developments in DBW on bikes are quite worrying (I read a test a few years ago where a famous racer they'd drafted in for the test said he couldn't ride the bike due to the lag on the throttle), but they certainly remain a step ahead of cars inherently, due to the concept of straddling an engine with a wheel at either end. It's not just inherent, either, as a much greater proportion of bikes (compared to cars) are built for sheer pleasure and for track performance. A Fireblade or R1 is like a two wheeled Radical SR8 or Ariel Atom basically - imagine having five or six of those types of cars to choose from for around £12k

[Gary C]

motco said:

ikarl said:

motco said:

The Westfield that was wrecked had the diff from a Sierra XR4i as far as I know, but exactly what type that was I don't know. I have yet to discover whether a Torsen type should be allowed on MOT brake rollers.

Why wouldn't it be allowed?

Never heard of any problems with an MX5 going on the brake rollers

Because some types of LSD are damaged by the rollers turning one wheel at a time. I understand that some LSDs are safe but others not, but the MoT station don't know for sure so they use the Tapley device instead. I was hoping for a definitive answer on here.

Lol 'definitive' answer on PH

Anyway, my view is

Simple Torsen Ok on roller brake tester,

not sure about the Togichi LSD on MX5's and RX8's. They seem to break the tabs really easy

Car with center viscous coupling, No apparently but havent done anything with them to know myself

two way plated diff with 100% lockup, the rollers dont stand a chance

Took my EVO V to the local tester, it had the optional big brembo brake kit. Tester didnt even bother to run it on the rollers or tapley. Whereas the 911 when testing the rears just stops the rollers turning

[C70R]

CharlesdeGaulle said:

Another thread got me thinking about how many people really can tell the difference in a car's performance based on what fuel they put in it. Does the expensive stuff really make a difference; can you honestly tell? Really?

Furthermore, can most people genuinely differentiate between a rear wheel drive and a front wheel drive car in normal use? Is the difference that marked that people with average driving ability and experience - which by definition is nearly all of us - could tell by themselves, without having done research or asked? I suspect most people know what ABS is, but not necessarily what it does, but what about a LSD? And as for cylinders, can the average driver honestly tell how many cylinders are under the bonnet: 3, 4, 5 or 6? Maybe he might be able to tell an 8 from a 4, but from a 6? Could most tell the difference between 8 and 12?

I realise that many here will claim they can. I'd like to think I can. I suspect that the collective 'PH-we' might be better than most, but I bet we're not as discriminating or knowledgeable as we like to think we are.

Ultimately, as a bunch of human-beings and consumers, we like to post-rationalise and self-justify/-affirm the decisions we've made. Choosing and buying cars is no different. We create mental hypotheses and justify favourable, positive outcomes to ourselves. It's a simple mechanism of behavioural economics.
In the instance of cars, we aren't helped by the b*llocks, hyperbolic media reviews. Suddenly everyone is an expert - and we find ourselves looking at Readers' Cars threads where the owner of a 1.4 Fabia is telling everyone how great its "body control" is.

Let me give you an example... I'd prefer to spend less on a nearly-new Boxster than a brand-new one - in the back of my mind, I'm also aware that the new Porsche has lost a couple of cylinders. Therefore, I create a smokescreen of reasons about why the 6cyl motor is 'purer', how it sounds better, how it drives better etc., which are (of course) confirmed 100% by my test-drive. We conveniently ignore the fact that most impartial observers have raved about how the new car drives.

Another great example came in a recent thread here, regarding the E46 3-series. We had people who spoke with such authority about "driving dynamics" and "weight distribution", that it would be hard to see how they could be anything other than absolutely correct.
The subject in question? Whether you could 'tell' the difference in the equivalent weight-saving of a tank of petrol when moving between 4cyl and 6cyl cars. There were numerous laughable protestations of "improved turn-in" and "less understeer", driven by people's desire to reinforce their preconceived hypothesis.

It's fairly straightforward, in truth. It's a matter of self-awareness.

[CABC]

C70R said:

Ultimately, as a bunch of human-beings and consumers, we like to post-rationalise and self-justify/-affirm the decisions we've made. Choosing and buying cars is no different. We create mental hypotheses and justify favourable, positive outcomes to ourselves. It's a simple mechanism of behavioural economics.
In the instance of cars, we aren't helped by the b*llocks, hyperbolic media reviews. Suddenly everyone is an expert - and we find ourselves looking at Readers' Cars threads where the owner of a 1.4 Fabia is telling everyone how great its "body control" is.

Let me give you an example... I'd prefer to spend less on a nearly-new Boxster than a brand-new one - in the back of my mind, I'm also aware that the new Porsche has lost a couple of cylinders. Therefore, I create a smokescreen of reasons about why the 6cyl motor is 'purer', how it sounds better, how it drives better etc., which are (of course) confirmed 100% by my test-drive. We conveniently ignore the fact that most impartial observers have raved about how the new car drives.

Another great example came in a recent thread here, regarding the E46 3-series. We had people who spoke with such authority about "driving dynamics" and "weight distribution", that it would be hard to see how they could be anything other than absolutely correct.
The subject in question? Whether you could 'tell' the difference in the equivalent weight-saving of a tank of petrol when moving between 4cyl and 6cyl cars. There were numerous laughable protestations of "improved turn-in" and "less understeer", driven by people's desire to reinforce their preconceived hypothesis.

It's fairly straightforward, in truth. It's a matter of self-awareness.

i remember you post rationalising your own viewpoint in that thread.
Several of us tried to explain that it's where the weight is rather than how much.
The 6 pot E36 (my own reference point) was clearly front heavy compared to the 4 pot.
Having several kilos forward of the front axle is one factor that makes Audis such bad handling cars.
And no, i can't tell at all if a tank is empty or full from the weight.

[RobM77]

I'm sure that C70R's point is true for a proportion of people, yes, not all though obviously.

I realise this wasn't central to his argument, but regarding the weight issue, it's a lot more than a tank of fuel's worth between a 4cyl and 6cyl Beemer (eg 330d saloon is 1615kg, and the 320d 1505kg, so almost double that for a tank of fuel), but the crucial thing is where the weight is. It's laughably easy to feel a 110kg lard arse passenger in a 3 series, or similarly even less than that on the roof. Incidentally, in a Caterham, removing the spare wheel (10kg maybe?) makes a huge difference to ride and handling, because it's mounted so high, but brimming the tank with more weight makes much less difference - again, it's where it is that counts.

Edited by RobM77 on Wednesday 19th October 17:09

[nickfrog]

C70R said:

Let me give you an example... I'd prefer to spend less on a nearly-new Boxster than a brand-new one - in the back of my mind, I'm also aware that the new Porsche has lost a couple of cylinders. Therefore, I create a smokescreen of reasons about why the 6cyl motor is 'purer', how it sounds better, how it drives better etc., which are (of course) confirmed 100% by my test-drive. We conveniently ignore the fact that most impartial observers have raved about how the new car drives.

.

Bloody hell mate. You're living on the edge. I hope he is not reading this or you're gonna get both barrels to the tune of the usual broken record that goes something like : "shiny, shiny, new, new, nasp, clueless people, all turbos are crap, I know better, shiny, shiny, new, new, primary controls, ad hominem, nasp, etc etc"

[bennyboysvuk]

RobM77 said:

That's a very good point. For starters, you are holding the steering mechanism in your bare (or gloved) hands, there's no gears or mechanism and there's certainly no assistance. The latest developments in DBW on bikes are quite worrying (I read a test a few years ago where a famous racer they'd drafted in for the test said he couldn't ride the bike due to the lag on the throttle), but they certainly remain a step ahead of cars inherently, due to the concept of straddling an engine with a wheel at either end. It's not just inherent, either, as a much greater proportion of bikes (compared to cars) are built for sheer pleasure and for track performance. A Fireblade or R1 is like a two wheeled Radical SR8 or Ariel Atom basically - imagine having five or six of those types of cars to choose from for around £12k

Which is probably why commuting in the M135i feels slow and incredibly refined compared to commuting on the R1.

[RobM77]

bennyboysvuk said:

RobM77 said:

That's a very good point. For starters, you are holding the steering mechanism in your bare (or gloved) hands, there's no gears or mechanism and there's certainly no assistance. The latest developments in DBW on bikes are quite worrying (I read a test a few years ago where a famous racer they'd drafted in for the test said he couldn't ride the bike due to the lag on the throttle), but they certainly remain a step ahead of cars inherently, due to the concept of straddling an engine with a wheel at either end. It's not just inherent, either, as a much greater proportion of bikes (compared to cars) are built for sheer pleasure and for track performance. A Fireblade or R1 is like a two wheeled Radical SR8 or Ariel Atom basically - imagine having five or six of those types of cars to choose from for around £12k

Which is probably why commuting in the M135i feels slow and incredibly refined compared to commuting on the R1.

Yeah, just a bit! I'm surprised you bother with a 135i to be honest - after the R1 doesn't that just feel similar to a 120i? Personally I find that after driving a single seater, road cars just all feel slow and unresponsive, regardless of whether they're a 'fast' model or a slow model.