165 replies to this topic

[24gerrard]

http://www.youtube.c...player_embedded

Here we see the powertrain of the new Ferrari FF BMW clone.
The torque loss from all these gears and slipping clutches must be enourmous but then Ferrari has never been energy frugal.

The old Jensen FF was a far better system. Just needed a lock up converter and electronic control.

Edited by 24gerrard, 03 April 2011 - 10:14.

[cheapracer]

In this day and age with crash worthy'ness requirements weight is a huge problem and Ferrari have gone with a system that adds 25 kgs in the driveline and probably 100kgs in the shell to absorb the energy of that 20 kgs.

If they added a larger drive system such as the Jenson had then the extra engineering and weight to absorb impact energy as well as suspension upgrading may be beyond reasonable limits.

[24gerrard]

In this day and age with crash worthy'ness requirements weight is a huge problem and Ferrari have gone with a system that adds 25 kgs in the driveline and probably 100kgs in the shell to absorb the energy of that 20 kgs.

If they added a larger drive system such as the Jenson had then the extra engineering and weight to absorb impact energy as well as suspension upgrading may be beyond reasonable limits.

The Jensen FF had a transfer box on the back of an inline Torqueflite eight automatic.
An extra prop shaft to a front diff and two shafts to the front hubs.
With the upgrade of electricaly controlled wet clutches in a slipper front diff, rear diff and center diff, the Jensen would offer far more.
The TF8 would need a lock up clutch and would obviously be replaced with probably an eight speed ZF.
Either way the only extra gearing in the Jensen FF is the front diff and an auto box runs a central shaft with balanced burst loads and far less torque loss than a dual shaft or dual clutch layshaft gearbox, which has offset burst loads and higher oil windage.
Typical Ferrari, sledge hammer to crack a nut.

[primer]

The torque loss from all these gears and slipping clutches must be enourmous

As compared to what? Some RWD car? Or a cruder circa World War II 4WD system that distributes 25% torque to each wheel irrespective of available traction?

Quite amazing how you also figured out that there must be constant clutch slippage to cause loss of efficiency. Anyone else would deduce that there would be no to very little loss when the car is travelling in straight line or steady speeds, which would be >~90% of the car's typical usage. But Ferrari are wicked. They burn through clutch plates every 500 miles because that way they make more money from service and parts. Not to mention it helps their car consume more fuel, which is their company goal.

but then Ferrari has never been energy frugal.

Indeed, the brand is all about performance and technology. And burning fuel inefficiently. If outright frugality is your thing perhaps you should buy a Fiat...wait, you have a problem with Fiat too, don't you?

The old Jensen FF was a far better system. Just needed a lock up converter and electronic control.

lol yeah and that 'lock up converter' and 'electronic control' would have allowed all the seemless, near instantaneous torque vectoring of the FF system, with no weight or packaging penalty. Ferrari clearly went with a more inefficient solution because that's how they roll, those kitten killing bastards.

[Todd]

While the contempt for Ferrari was ladeled on kind of thick, the points about this drivetrain are pretty valid. The Jensen FF system was likely to be far more robust and also more efficient any time 4wd is actually an advantage. Provided western civilization survives the Obama regime, this will be proven out when used Ferrari FF's are sale proof.

It might be interesting to compare this drivetrain to the complex and heavy front engine, rear transaxle AWD used by Nissan in their own obese hunk of crap, the GT-R. Me thinks the problem is in combining AWD with FE/RT. It would be better to use a front-mid engine location mounted in tandem with the transmission aft of the front axle. You'd still end up with a huge car, but it would be balanced, lighter, more durable, and more efficient than the Ferrari FF or Nissan GT-R.

[24gerrard]

Hybrid gives the best answer. The Porsche GT3 Hybrid uses an energy recovery system that charges a battery pack and this applies part time 4 wheeled drive by adding the electric powewr to the front axle motor/generator. This gives a performance boost in the same way F1 Kers does but also improves handling by giving torque control on the front wheels during cornering. It can also be used 4x4 in low grip conditions.
Energy storage uses a flywheel in a vacuum charged and discharged through induction.
Because the Porsche is part time drive to the front axle in reality and does not have the power station gearing like the Ferrari, the front suspension and crash structure does not need to be anywhwere near as heavy either.

A modern version of the Jensen Ferguson 4x4 system would have complete modern electronic torque balance and could easily disengage the front shafts at the front diff and the front propshaft at the center diff. The Ferrari still has all those gears whirling round on the front of the engine.
Please dont mention the word seamless. It is purely marketing hype. No stepped ratio gearbox or transfer box is seamless. Even with the fastest possible shift, which is still a skilled driver with a racing dog clutch box, there is still a gap between the gear ratios. Dual shaft or dual clutch layshaft gearboxes are less efficient than a conventional single shaft layshaft gearbox when it comes to transfering torque from input to output.

[24gerrard]

Oh and 90 percent of most Ferrari usage has always been trolling around places like Monarco at 30 mph wasting fuel.
Which is why Montezemolo has already admited that all Ferraris in the future will have to be electric hybrids, so they can troll around Town with the gas guzzler turned off solely to meet the emmision regulations.
Not much future there then.

[primer]

While the contempt for Ferrari was ladeled on kind of thick, the points about this drivetrain are pretty valid. The Jensen FF system was likely to be far more robust and also more efficient any time 4wd is actually an advantage.

Depends on the application. You wouldn't use the FF system on a Land Cruiser, but then again for this GT the two front gears will provide adequate AWDness that the owners might require. If there's any criticism for the FF, it is that they have only two gears and that might not provide the fine granularity in certain conditions. This I suspect is mostly because how large and heavy a 4 ratio DSG type box would become, so they had to limit to two ratios.

Perhaps if & when they move to a Zeroshift type transmission they will introduce more gears for the front wheels.

Provided western civilization survives the Obama regime, this will be proven out when used Ferrari FF's are sale proof.

The type of AWD/4WD offered on this car will play no role in the sales figures of this kind of lifestyle vehicle.

It would be better to use a front-mid engine location mounted in tandem with the transmission aft of the front axle. You'd still end up with a huge car, but it would be balanced, lighter, more durable, and more efficient than the Ferrari FF or Nissan GT-R.

This is precisely the system in the FF! For the front wheel's drive they have a compact, PTO type output through a two gear DSG type gerarbox for the front wheel. It is front mid-engined, there was a nice shot of mechanicals when it was released that demonstrated this layout nicely.

Hybrid gives the best answer. The Porsche GT3 Hybrid uses an energy recovery system that charges a battery pack and this applies part time 4 wheeled drive by adding the electric powewr to the front axle motor/generator. This gives a performance boost in the same way F1 Kers does but also improves handling by giving torque control on the front wheels during cornering. It can also be used 4x4 in low grip conditions.
Energy storage uses a flywheel in a vacuum charged and discharged through induction.
Because the Porsche is part time drive to the front axle in reality and does not have the power station gearing like the Ferrari, the front suspension and crash structure does not need to be anywhwere near as heavy either.

24gerrard, a madman's thought process might never make sense but is almost always entertaining to hear. You have problems with this type of 4WD but think that a flywheel whirring at tens of thousands of RPM next to pax is a good idea. I am sure that the flywheel would still be whirring when the owner takes out his FF for it's one monthly stroll and encounters low grip condition right out of his garage.

I also love how batteries -when used in any 'hybrid' application- become these wonderful massless, weightless entities. Ma nature gives them a discount on gravity on account of being so green. I have seen the light. I like the Porsche Perpetual Energy (PPE, $39,000 option in select models) concept, too.

A modern version of the Jensen Ferguson 4x4 system would have complete modern electronic torque balance and could easily disengage the front shafts at the front diff and the front propshaft at the center diff.

Screw your Jensen. A system that copies the Mitsubishi Lancer Evoution WRC car would (theoretically) be best of all, but Ferrari thought of long term reliability and maintenance. Gears are bomb proof. They don't have to worry about how the owner uses the car, you could rallycross on ice all day and the FF would be more reliable than most all other type of 4WD/AWD system.

The Ferrari still has all those gears whirling round on the front of the engine.

The car deactivates the 4WD in gears 5, 6 and 7.

Please dont mention the word seamless. It is purely marketing hype. No stepped ratio gearbox or transfer box is seamless. Even with the fastest possible shift, which is still a skilled driver with a racing dog clutch box, there is still a gap between the gear ratios.

Agree that this first gen might not have enough ratios for a true seamless experience in all modes.

Dual shaft or dual clutch layshaft gearboxes are less efficient than a conventional single shaft layshaft gearbox when it comes to transfering torque from input to output.

FF will not live or die on some perceived disadvantage in efficiency of it's gearbox that drives the front wheels. You have got a NA V12 with 660 horsepower in a car that costs ~$350,000 and you are arguing about efficiency of the gearbox....

Oh and 90 percent of most Ferrari usage has always been trolling around places like Monarco at 30 mph wasting fuel.
Which is why Montezemolo has already admited that all Ferraris in the future will have to be electric hybrids, so they can troll around Town with the gas guzzler turned off solely to meet the emmision regulations.
Not much future there then.

Wait, what? I thought that electric hybrids were good and the way of the future? Or do they only work in Porsche's future? OMG Ferrari are doomed.

Edited by primer, 04 April 2011 - 04:12.

[cheapracer]

I don't think people appreciate how many of these Ferrari's will actually go to snowfields, thats one market they are aiming at besides obviously wealthy Russians and other Europeans who drive in snow.

The Jenson FF is considerably heavier than the 2WD and longer in the wheelbase immediately reconisable by the dual side air ducts behind the front wheels.

I think my point was missed about weight and relevance of crash testing, the Jenson setup is simply to heavy in this day and age regardless of the advantages/disadvantages of the actual driveline system unless you want a vehicle at 2.5 tonnes plus.

Not sure what the talk about slipping is, millions of vehicles around the world drive everyday with slipping sytems, thats how we have AWD or do people think they just made tyres quieter to suit?

[24gerrard]

Even disengaged the Ferrari has a similar geartrain to a JCB whirling around on the crank nose.
A modern Jensen FF would not need to be as heavy as the original, it could use modern materials and a much lighter eight speed auto box with lock up converter from ZF.
The Fergusen system would soon overtake the complex gear system of the Ferrari.
I am comparing the powertrain concept here not a 1970s car with one in 2011.
It goes to show just how behind the times Ferraris are.

How much of a 4x4 vehicle you want to make a hybrid depends on what energy storage device you choose and how much storage you design in. It is just as easy to use batteries as a flywheel or even a combination of the two.
As I mentioned Ferrari has got to design all its model range in the future to be hybrids anyway, because they will not be legal otherwise.

It does not matter how many gears or gearboxes, there can be no such thing as a seamless stepped ratio gearbox.

I do not care if the latest Ferrari oil tanker has 600 bhp or 6000 bhp the gearbox is a major area where energy can be lost and this FF system looks highly inefficient.
If Ferrari do not wish to be doomed they had better think long and hard.
The current drive for sales in Russia and China will not last forever, ownership of a Ferrari in Europe is becoming more of an embarassment at every motor show.

[meb58]

24gerrard,

I am beginning to think that you don't like Ferrari...

[cheapracer]

How much of a 4x4 vehicle you want to make a hybrid depends on what energy storage device you choose and how much storage you design in. It is just as easy to use batteries as a flywheel or even a combination of the two.

Having made a few trips to the snow in Australia to Bulla etc when it's snowing and icy you have to wear chains and drive slowly for a considerable time to get to your destination.

I haven't been to Euro snowfields but imagine you probably must drive slowly up windy mountain roads for many hours (and back down) therefore the choice of electric assistance in my mind becomes an engineering PIA because of the time factor and note that the Ferrari AWD system is for slow speeds and reverts back to 2WD at normal'ish highway speeds, seemingly designed for said conditions.

I laffed at the JCB comparo

i still want to know what an "enginee" is .....

Edited by cheapracer, 04 April 2011 - 15:49.

[OfficeLinebacker]

i still want to know what an "enginee" is .....

It's the one who gets engined (by the enginer). Duh.

[cheapracer]

It's the one who gets engined (by the enginer). Duh.

[Todd]

I don't think people appreciate how many of these Ferrari's will actually go to snowfields, thats one market they are aiming at besides obviously wealthy Russians and other Europeans who drive in snow.

The Jenson FF is considerably heavier than the 2WD and longer in the wheelbase immediately reconisable by the dual side air ducts behind the front wheels.

I think my point was missed about weight and relevance of crash testing, the Jenson setup is simply to heavy in this day and age regardless of the advantages/disadvantages of the actual driveline system unless you want a vehicle at 2.5 tonnes plus.

Not sure what the talk about slipping is, millions of vehicles around the world drive everyday with slipping sytems, thats how we have AWD or do people think they just made tyres quieter to suit?

Don't Mercedes and BMW use the Jensen FF type AWD systems today? So do others companies that offer AWD derivatives of RWD cars, like Chrysler. Maybe they've added new gimmicks, but 3 differentials and two longitudinal driveshafts are still accounted for. Nissan's GT-R takes it even further with parallel driveshafts going fore and aft.

I won't take on understanding everything the originator of this thread has written, but I believe the concern about wear from slipping has to do with the job the wet multiplate clutches does in the front drive system of the Ferrari FF. Without comparable gear ratios for the front and rear axles, the clutches are slipping to match wheel speeds whenever 4WD is engaged.

[Todd]

The type of AWD/4WD offered on this car will play no role in the sales figures of this kind of lifestyle vehicle.

It won't play a role in new vehicle sales, but I specified that it will be reflected in used sales. If these cars become known for needing mid to high 5 figure services for front clutch replacement, they will be a liability for owners. Insurance fraud is often the end of the road for Ferraris with deferred maintenance, even for attractive 2 seaters. There are actually more Ferraris on the used market than there are interested novices, so the market will reflect whether or not designing a front transmission that is a maintenance part was good for the customers.

[primer]

It won't play a role in new vehicle sales, but I specified that it will be reflected in used sales. If these cars become known for needing mid to high 5 figure services for front clutch replacement, they will be a liability for owners.

The front transmission is just like the regular dual-clutch transmission that drives the rear wheels, but with two gears. Why should it be any more unreliable or require frequent service, then? I have not heard any complaints about transmission on ferrarichat in recent Ferrari models. AFAIK, historically the biggest gripe with Fcars used to be the timing belt replacement, but Ferrari have moved to chain and that too has been a non-issue for many models now.

I won't take on understanding everything the originator of this thread has written, but I believe the concern about wear from slipping has to do with the job the wet multiplate clutches does in the front drive system of the Ferrari FF. Without comparable gear ratios for the front and rear axles, the clutches are slipping to match wheel speeds whenever 4WD is engaged.

This is not my understanding at all.

AFAIK the front clutch only comes into play when there's a gear change, just like in any other transmission. If you were burning the clutch plates constantly to distribute torque why would you have any gears at all......and what has matching wheel speeds got to do with it? It's a torque distribution system, and the distribution to front and rear wheels does not necessarily have to be 50/50 at all times.

Here's how I see it: For every gear the driver (or car) selects in the gearbox, they have two possible values of torque they can distribute to the front wheel, and the proportion of torque distributed between front and rear wheels will depend on the ratio of front gear (there's two of them), as well as the currently engaged ratio in the other gearbox for the rear wheels.

The torque distribution -front to rear- will thus change with every gear selection, ideally providing ~50% torque to the front wheels in first gear and incrementally less as you shift up to second, third, fourth. Of course, they can also disengage the front gears entirely and RWD efficiently* when 4WD is not needed.

Have I understood the FF system incorrectly?


* Don't tell 24gerrard.

[24gerrard]

The two speed FF front gearbox uses the two ratios as you say to roughly balance the torque output range of whichever rear gearbox ratios are selected.
The resulting torque is then further modified to each front wheel by slipping a clutch pack to drive each front drive shaft, A very crude idea.
It does away with a front diff, center diff and front prop shaft (of the Fergusen system) and replaces it with a gear system that is almost the same as one in a JCB.

Hybrid light weight front wheel drive systems used to give part time 4x4, can easily be fed real time electrical energy from a compound turbocharger system (as well as from storage), as projected for the 2013 F1 regulations for engine and powertrain. The turbocharger drives an electrical generator instead of or as well as a compressor for induction. You then have long term slow speed use for traction needs on slippery surfaces.

[primer]

The resulting torque is then further modified to each front wheel by slipping a clutch pack to drive each front drive shaft, A very crude idea.

How often is there a requirement to split the torque unevenly between the two front wheels? Normally they get 50% each, only under very specific conditions would the clutch be slipped and torque vectored between the two wheels. Some other vehicles also vector torque like this, haven't yet seen a thread by you moaning about them.

The idea is not crude, it is sound and suited to the vehicle's intended application.

that is almost the same as one in a JCB.

You've latched on to the term PTO without having a understanding of how the FF system works. It's almost as if you are unhappy that Ferrari managed to make a mechanical system (rather than an unnecessarily complex electro-mechanical system), which is efficient and effective.

Hybrid light weight front wheel drive systems used to give part time 4x4, can easily be fed real time electrical energy from a compound turbocharger system (as well as from storage), as projected for the 2013 F1 regulations for engine and powertrain. The turbocharger drives an electrical generator instead of or as well as a compressor for induction. You then have long term slow speed use for traction needs on slippery surfaces.

There's no evidence that your beloved system would by better in any parameter -weight, performance, packaging, and yes even cost- than the one in FF. The one in FF works and is a mostly mechanical, bomb proof design. It does not need additional batteries, electric motors, flywheels, electrical generators, power cables and the maintenance nightmare that comes with having all this equipment in an exotic car.

All they have is just another mechanical gearbox for the front wheels, similar in concept to one that drives the car's rear wheels. It's simple and brilliant.

Edited by primer, 04 April 2011 - 21:07.

[24gerrard]

How often is there a requirement to split the torque unevenly between the two front wheels? Normally they get 50% each, only under very specific conditions would the clutch be slipped and torque vectored between the two wheels. Some other vehicles also vector torque like this, haven't yet seen a thread by you moaning about them.

The idea is not crude, it is sound and suited to the vehicle's intended application.


You've latched on to the term PTO without having a understanding of how the FF system works. It's almost as if you are unhappy that Ferrari managed to make a mechanical system (rather than an unnecessarily complex electro-mechanical system), which is efficient and effective.


There's no evidence that your beloved system would by better in any parameter -weight, performance, packaging, and yes even cost- than the one in FF. The one in FF works and is a mostly mechanical, bomb proof design. It does not need additional batteries, electric motors, flywheels, electrical generators, power cables and the maintenance nightmare that comes with having all this equipment in an exotic car.

All they have is just another mechanical gearbox for the front wheels, similar in concept to one that drives the car's rear wheels. It's simple and brilliant.

The original Jensen FF system was even simpler and oh so much better.
Of course that one was in the 1970s.
Ferrari has one hell of a long way to go to catch up.

[Todd]

All they have is just another mechanical gearbox for the front wheels, similar in concept to one that drives the car's rear wheels. It's simple and brilliant.

The engine speed is the same for whatever speeds the front wheels and rear wheels are turning at any given time. The wheel speeds themselves are very similar front and rear at any given time. The front transmission has two gears for the engine speed to be reduced by before reaching the front wheels. The rear transmission has more than 2 available gears to reduce the engine speed before it reaches the rear wheels. There are engine speeds, gears, and wheel speeds available to the rear of the car that are not matched by those produced by the front gearbox. The differences between the two ratios available to the front gearboxes and the multiple ratios available to the rear gearbox must be achieved by slipping the clutch packs.

Let's call the front gear ratios FL and FH. FL might be 10:1. For every rotation of the engine's crank, the front axle turns 36 degrees, or a tenth of a rotation. FH might be 4:1. For every engine rotation, the front axle would make a quarter of a rotation.

The rear transaxle has, what? 6? 7? 8 ratios? Suppose R1 works out to 12:1, R2 8:1, R3 5:1 R4 4:1 R5 3:1 R6....

I believe I read that 4wd only engages on the first 4 gears, which makes sense since the front has so few ratios to choose from. It still has to operate at speeds where the gear ratios are different front to back, and that is what wears the clutches and makes your lack of comprehension important to the discussion.

[primer]

Fair enough I'll read on this later.

[primer]

I think this is the best description so far, at last it is clear to me how this sytem works:

Yep, a front-wheel-drive transmission sits at the front of the FF’s V-12 in line with the axles (the engine is located behind the front wheels in a front-mid arrangement) and can handle up to 20 percent of the engine’s total torque output. Driven by a conical gear off the nose of the crankshaft, the front transmission is a helical gearset (like in a conventional manual transmission) with two forward speeds plus reverse.

Ah, you’re thinking, how can a two-speed gearbox in the front work with a seven-speed gearbox in the rear? Well, front first is geared six percent longer than rear second, and front second is geared six percent longer than rear fourth (reverse is geared the same). Got that? So the front transmission’s first gear covers the rear’s first and second, and its second gear covers the rear’s third and fourth.

The system doesn’t work above fourth gear, but Ferrari says the torque delivered to the wheels in fifth gear is easily handled by the rear tires. And besides, the company adds that the system is meant only to make the FF more usable in various conditions, thus furthering the go-anywhere mission of the GT car. That said, we’re willing to bet that 4RM helps on a track. In a standing-start launch, Fedeli says that the system is good for a reduction of two- or three-tenths of a second in the run to 60 mph.

Power is routed through two electronically-controlled, hydraulic wet multiplate clutches off to the driver’s side of the front-mounted transmission, one for each wheel. Depending on the amount of slip in the clutches, the front transmission can match the speed of the rear wheels. It can also use torque vectoring to distribute power side-to-side. All this and 4RM weighs less than 90 pounds, about half that of a conventional four-wheel-drive system.

Wouldn't a CVT be a better choice for the front transmission, provided it could handle the torque?

Edited by primer, 04 April 2011 - 23:21.

[primer]

[Todd]

I think this is the best description so far, at last it is clear to me how this sytem works:

If that is clear to you, then you should see that lots of engine output is being turned into heat by the obscenely tasked front clutches. Imagine having fixed throttle and gear settings while using your clutch to regulate speed and you'll have an idea what life is like for the clutch packs.

[Todd]

And yest, a CVT would seem like a much more elegant and durable design solution, although it might not package as well.

[primer]

If that is clear to you, then you should see that lots of engine output is being turned into heat by the obscenely tasked front clutches. Imagine having fixed throttle and gear settings while using your clutch to regulate speed and you'll have an idea what life is like for the clutch packs.

Yes I see it now, and this statement arouses even more suspicion:

Yep, a front-wheel-drive transmission sits at the front of the FF’s V-12 in line with the axles (the engine is located behind the front wheels in a front-mid arrangement) and can handle up to 20 percent of the engine’s total torque output.

How are they 'restricting' the front transmission to handle only 20% of the torque? The maximum torque that the front transmission will face will come when the car is in first gear (rear) and first gear (front). Surely the 6% longer gearing does not explain it? Do they slip the clutch everytime to restrict the torque to front gearbox? I was under the impression that when it comes to transmission it is usually the clutch that is the weak point (in handling torque), but the liberal way in which Ferrari are using the clutch is a new concept to me.

Edited by primer, 04 April 2011 - 23:45.

[cheapracer]

that is what wears the clutches and makes your lack of comprehension important to the discussion.

The wet clutch pack slipping issue isn't an issue, there's a couple of billion motorcycles past and present to prove the foundation of that and the bikes use cheap shitty linings with cheap contaminated (shared with engine) oils.

I am surprised they didn't keep it exclusively mechanical and just use some simple viscous couplings for the slippage (as used by millions of AWDs) rather than computer controlling for the clutch packs though.

Edited by cheapracer, 05 April 2011 - 05:06.

[Todd]

A slipper clutch on a motorcycle really isn't doing the same job. When it is slipping, it is transferring zero torque, for example. The FF's poor clutches are partially engaging more than anything else. I've seen a VW Rabbit clutch reduced to stink and smoke in 250 feet by someone slipping it between a 67 hp engine and 155 mm wide tires.

[primer]

The wet clutch pack slipping issue isn't an issue, there's a couple of billion motorcycles past and present to prove the foundation of that and the bikes use cheap shitty linings with cheap contaminated (shared with engine) oils.

Which motorcycle models constantly slip their clutch to control torque output for the rear wheel?
As a rider I've only found motorcycles where you use clutch during gearchange, and even then during upshifts clutch usage is optional because you can powershift and save the clutch.

[primer]

Yes Todd, not to mention there's quite a difference in the torque output of motorcycle and a 6 lt V12. Clearly Ferrari have some metallurgical breakthrough, otherwise I don't see how they can burn the clutch constantly in the first four gears and produce a car that is reliable enough for daily driving.

IMO the technical brilliance of the FF solution is blemished by the fact that they have to slip the clutch. If they had four ratios for the front transmission (or a CVT) it would have been so much better.

[kikiturbo2]

While the contempt for Ferrari was ladeled on kind of thick, the points about this drivetrain are pretty valid. The Jensen FF system was likely to be far more robust and also more efficient any time 4wd is actually an advantage. Provided western civilization survives the Obama regime, this will be proven out when used Ferrari FF's are sale proof.

It might be interesting to compare this drivetrain to the complex and heavy front engine, rear transaxle AWD used by Nissan in their own obese hunk of crap, the GT-R. Me thinks the problem is in combining AWD with FE/RT. It would be better to use a front-mid engine location mounted in tandem with the transmission aft of the front axle. You'd still end up with a huge car, but it would be balanced, lighter, more durable, and more efficient than the Ferrari FF or Nissan GT-R.

I recently watched a report on a nice race held in New Zeland... Targa NZ... although held in dry weather, and having all sorts of porsches and a ferrari or two in the race, at the end top ten looked something like: GT-R, EVO, GT-R, EVO, GT-R, EVO... Full time 4wd with an active diff ot two, possibly torque vectoring, makes for an unbelivably fast A to B car..

[primer]

Thus Spoke Autocar:

What is particularly interesting about the FF, though, is how it delivers drive to the road, because unlike a conventional all-wheel drive system, there is no centre differential. Instead, for the majority of the time, the FF is effectively a regular rear-wheel-drive Ferrari, with the power directed to the back wheels via a seven-speed, dual clutch transaxle gearbox.

Only when drive is required at the front axle is power taken directly from the engine into a second gearbox, one with just two forward speeds plus reverse. The fascinating aspect to this system (which Ferrari has patented) is that neither of the two front ratios are a match for those in the rear gearbox. The wheel speed mismatch is then managed by slipping two clutches in the forward gearbox – one for each wheel.

These clutches also provide the role of the front differential, not only to manage traction but also provide torque vectoring for improved handling. The obvious question here is – don’t the clutches overheat if they are constantly slipping? The answer, apparently, is that in practice drive is being delivered to the front axle only for short periods.

The main advantages of the system are that it is compact, light (Ferrari claim it adds just 45kg) and that the absence of a front differential means steering feel corruption is minimised.

Shirley they must have a temperature sensor in the transmission to prevent a conflagration? Too hot, let's 2WD.

[cheapracer]

Yes Todd, not to mention there's quite a difference in the torque output of motorcycle and a 6 lt V12. Clearly Ferrari have some metallurgical breakthrough, otherwise I don't see how they can burn the clutch constantly in the first four gears and produce a car that is reliable enough for daily driving.

IMO the technical brilliance of the FF solution is blemished by the fact that they have to slip the clutch. If they had four ratios for the front transmission (or a CVT) it would have been so much better.

Yes, I can't understand either how Ferrari went and installed a clutch pack from a Honda 250 and just expected it to work.

Obviously the motorcycle clutch example with all the notations such as "foundation", "cheap material" and "contaminated oil" was too far out there for you guys.

I doubt the plates in the packs actually touch, theres some pretty clever oils out there now for these applications such as what they use in viscious clutches and toroidal transmissions, anyway unless we see the plates we don't even know it's not a simple variable viscious clutch pack.

By the way, when you leave traffic lights/ride in heavy traffic on your bike do you slip the clutch or just bash down on the lever and hang on?

[cheapracer]

at the end top ten looked something like: GT-R, EVO, GT-R, EVO, GT-R, EVO... Full time 4wd with an active diff ot two, possibly torque vectoring, makes for an unbelivably fast A to B car..

All with slipping clutches too (viscious and clutch LSD's), how many were on fire?

I think Ferrari need to rethink their "slipping clutch" statements real fast - too many people will just associate that speak with bad experiences even though they probably drive or have a neighbor who drives a car with a "slipping clutch" as standard.

Edited by cheapracer, 05 April 2011 - 08:06.

[gruntguru]

Must agree - this thing looks like a real compromise solution. Worst case:
2nd and 4th gear. At wide-open-throttle 20% of engine torque is transferred to the front wheels (ie 20% of the power) and up to 6% of that power will become heat in the clutches ie 1.8% of engine power.
1st and 3rd gear. At wide-open-throttle 20% of engine torque is transferred to the front wheels (ie 20% of the power) and perhaps 20% of that power (depending on ratio spread 1st/2nd and 3rd/4th) will become heat in the clutches ie 4% of engine power. Doesn't sound like much but 4% of 500kw is 20 kw (imagine 20 hair-dryers heating the front transmission). Of course that heat is wasted energy too - so up to 20kW of energy going down the drain. 20 kW would probably maintain the car at at 70mph or more on a level road.

Limiting the front torque will of course be accomplished by slipping the clutches.

Some posters have mentioned other systems using clutch-packs and viscous couplings. These are normally used to regulate differential speeds between wheels - not transmit the actual drive like Ferrari have done.

I dont think a CVT would be the ideal solution as the engine speed is changing stepwise as the rear transmission shifts. Perhaps a "normal" shaft coming forward from the final drive of the rear gearbox to drive the two clutch packs? Packaging issues no doubt.

[cheapracer]

Some posters have mentioned other systems using clutch-packs and viscous couplings. These are normally used to regulate differential speeds between wheels - not transmit the actual drive like Ferrari have done.

Thats pedantic, in the real world the viscious or clutch pack is slipping constantly whenever you are not driving in a dead straight line and I doubt the Ferrari's clutches close unless it senses rear wheel traction control kicking in.

And even in a dead straight line anyone who has driven an old style 4WD in 4WD (50/50 locked drive) can feel the bind.

[gruntguru]

Thats pedantic, in the real world the viscious or clutch pack is slipping constantly whenever you are not driving in a dead straight line and I doubt the Ferrari's clutches close unless it senses rear wheel traction control kicking in.

Not pedantic at all - there is a serious point of (engineering) difference. Transmitting drive power through a slipping clutch or viscous coupling is generally considered bad engineering. Ferrari is getting away with it in this case for the reasons I stated previously, plus the intermittent need for drive to the front wheels.

I remember 25 years ago, someone discovered viscous couplings and decided to convert a Landcruiser Wagon to full-time 4WD - by inserting a VC in the front tailshaft. I shook my head.

Edited by gruntguru, 05 April 2011 - 08:36.

[Grumbles]

....I doubt the Ferrari's clutches close unless it senses rear wheel traction control kicking in...

You hit the nail on the head Cheapy.
I doubt that Ferraris system is really a kitten killing, globe warming, fuel burning disaster at all. The clutches will be completely disengaged normally and only transmit torque when the rears start to lose traction. Fezza say up to 20% to the front but I doubt the clutches will often have to pass on much at all.
On slippery surfaces when the rears start to slip the front torque (and hence heat etc) will be severely limited by same surface thats making the rears struggle. I imagine the traction control will limit the amount of energy to all corners. And at lower speeds on a good surface the weight transfer to the rear will again severely limit the amount of pressure on the front clutch packs. No traction available = no pressure (and no heat) from that particular pack, just like a glorified old style LSD.
I think that some people are getting all worked up over nothing. It mightn't be the most elegant or technically perfect way to do it but as an engineered compromise it mightn't prove to be so bad after all. Certainly not the end of the world as we know it.

[24gerrard]

Hmmm lots of discusion good.
Slipping clutches wet or dry is not a good thing to overdo because of wear, however Ferrari will be using electronic control to prevent excess wear and to disengage the clutches when needed.
This is not the point. Slipping clutches create 'torque loss' in the powertrain. With over 600 bhp available Ferraris can easily mask this but it is very very wasteful of energy and should not be done in a modern vehicle.

CVT transmissions suffer from two ,major problems that prevent their widespread use.
Fisrst they all have a very narrow practicable ratio range and need extra gearing in practice, Secondly they all require to use extra energy to operate the slidding cones (van doorne) toloroidal disks (perbury) and electromagnetic fields (various), this makes them less efficient than conventional gearboxes.

[kikiturbo2]

Thats pedantic, in the real world the viscious or clutch pack is slipping constantly whenever you are not driving in a dead straight line and I doubt the Ferrari's clutches close unless it senses rear wheel traction control kicking in.

And even in a dead straight line anyone who has driven an old style 4WD in 4WD (50/50 locked drive) can feel the bind.

having read some of the test drive articles, in which FF is not anything like a classic rally 4wd car, I'd seccond your opinion.. I'd say that the front drive is used occasionally to tuck the nose in with help from torque vectoring, and provide additional traction in very low traction environment, like snow, where cluch pack wear might not be an issue..

[cheapracer]

I remember 25 years ago, someone discovered viscous couplings and decided to convert a Landcruiser Wagon to full-time 4WD - by inserting a VC in the front tailshaft. I shook my head.

Did he work for Lamborghini by chance because thats how they do it the difference being that unlike the Cruiser'50/50 the Lambo's 30/70 is slipping 100% of the time.


I knew I had seen a wet multiple clutch pack drive before, I just didn't know that a good bulk of the worlds AWD's use them ...

http://en.wikipedia....Haldex_Traction

Since the late 1998, Volkswagen replaced the viscous-coupling Syncro system with a new system called "4motion". First shown in Audi TT and Golf 4motion, the new system uses a multi-plate clutch center differential developed by a Swedish company, Haldex, and computer software from the Austria 4WD specialist Steyr-Daimler-Puch. At this moment, it is only offered for the transverse-engined Golf IV platform, but there is no technical reason prevents it from applying to Audi's longitudinal-engined models.

The Haldex center differential is similar to Porsche 959's PSK system mentioned in the above, it is only smaller, simpler and cheaper thus making mass production feasible. The center differential is mounted near the rear axle and just in front of the rear differential. As shown in the picture below, its clutch consists of 6 discs ....



They are immersed in oil bath to reduce friction. Actuation is made by hydraulic pressure. Normally the input and output shafts rotate with a speed difference (could be implemented by different final drive ratio), therefore the discs are rotating relative to each other. When no pressure is applied, the clutch is not engaged thus torque will not be transferred to the rear axle. Increase the pressure on the multiplate clutch, the latter will be partially engaged, thus sending torque to the rear axle. The more the clutch engages, the more torque transfers to the rear axle.
Computer determines how much torque to be sent to the rear wheels. Normally it is 50:50, but in tight corners when wheels on one of the axles is slipping, the driver can easily feel the torque is transffering from one to another axle. Volkswagen claimed 100% torque could be sent to either axle.

Compare with 959's unit, Haldex's unit has 7 fewer discs in the clutch. This makes the Haldex unit more compact and cheaper. The down side is not capable to handle as much torque (959 had 369 lbft, Audi TT has 206 lbft). Besides, 959's discs were organised as 6 pairs of independent clutches, each actuated by individual hydraulic actuator. The Haldex has just one actuator acting on all six discs, again, this saves weight and cost. However, I suspect if it could vary the amount of torque split as precise as independent clutches.

Based on the journalists comment about the handling of Audi TT and Golf 4motion, it seems that the 4motion system performs even better than the traditional Torsen-differential Quattro. The age of Torsen Quattro is passing away.

Others ....

Porsche 959's PSK uses a multi-plate clutch instead of center differential. You may call it a "differential clutch" as well. The multi-plate clutch has 6 pairs of frictional plate, each pair is independently controlled by computer and actuated by hydraulic pressure. This simply equals to 6 independent clutches.

To make this system work, the front and rear driveshafts must run at different speed in normal condition. (so 959 adopted a pair of front tyres with 1% larger diameter than the rear's) Because of the speed difference between front and rear driveshafts, the 2 frictional plates of each independent clutch are rotating relatively to each other. When apply hydraulic pressure to the first clutch, a small amount of torque will transfer to the front axle. But note that the two driveshafts cannot be fully locked up unless all 6 clutches are locked simultaneously.

Now, you may see how it works: lock up 2 clutches, 3 clutches ... and the torque to front wheels will be increased, subsequently, torque split could be 50:50 if all the clutches are fully engaged. Of course, all these action is controlled by computer.

This is only for "normal" condition. Like other 4WD systems, when tyre slip occurs, most of the torque could be
sent to either axle.

What about energy loss and wear due to the slipping clutches? As the speed difference is very small, Porsche claimed energy loss is no greater than 0.4% of the power developed by the engine. As for wear, the clutch is dimensioned that it was negligible and caused no problem during the whole life span.


Mercedes 4-Matic is very much like Porsche's PSK, but it works as a part-time 4WD. In normal condition, the clutches are disengaged so that the car runs just like any rear-wheel drive version. When it lose traction, the computer will signal the clutches to engage progressively so to transfer some torque to the front wheels.
This is rather irrational. It costs even more than Torsen system, but only offers part-time 4WD. However, unlike Porsche's PSK, it is not subjected to any energy loss or wear during normaly conditions, so the clutch can be made smaller and cheaper.


Since the R33, Nissan's Skyline GT-R also uses multi-plate clutch instead of conventional center differential, in addition, as rear differential lock too. Normally it is rear-wheel drive, the front wheels only intervene whenever necessary.
What makes the Skyline system catches my heart is its real world behaviour. Without driving it or reading road test reports, you might not discover its maturity.

As I have mentioned earlier, throttle-controllable oversteering is usually more desirable to real drivers than pure neutral steering. However, what a pity most permanent four-wheel drive cars are inherently unable to deliver power oversteering. Porsche 959 was one of the exception because it had 60% weight bias towards the rear, but for a front-engined car like the Skyline GT-R, the best solution is to leave it as rear-wheel drive in normal conditions.

The clever electronic control system is fed by all the information that Porsche 959 had, such as G-force, boost pressure, throttle position etc, in addition, the speed of individual wheels measured by ABS wheel speed sensors. By these information, the computer knows whether the car is running out of cornering limit or not. If not yet, the multi-plate clutches won't intervene, thus the car can power slide through the corner smoothly. In case out of limit, the multi-plate clutch will engage and send torque to front wheels, increasing traction.

This makes Skyline a rare example of 4WD having oversteering ability.


Honda's SH-AWD system is unique in the industry. It does not have any center differential or any limited-slip differential. All the mechanicals is mounted at the rear axle. The drive from propeller shaft is sent to an accelerator first. The latter uses planetary gears to step up the rotation speed, creating a speed difference between the input and output shaft. By applying electromagnetic clutches, the speed difference can transfer driving torque to the rear axle.

The electromagnetic multi-plate clutches are mounted behind the accelerator. There are 2 clutches, each responsible for one rear wheel. When the right clutch engage, more torque will be sent to the left rear wheel via the conventional differential. Vice versa, engage the left clutch will transfer more torque to the right rear wheel. (This theory is the same as Mitsubishi's Active Yaw Control) When both clutches engage, more torque will be sent to the rear axle. In this way, SH-AWD can very the torque split between front and rear axle, as well as between the rear wheels.

For Honda Legend equipped with SH-AWD, it normally runs with 70% torque distributed to the front wheels. Under acceleration and braking, up to 70% may be sent to the rear axle to generate more traction. During cornering, to reduce understeer, more torque will be distributed to the outside rear wheel. At extreme cases, the outside rear wheel can take 70% of the engine output, while the inside rear wheel 0% and the front wheels get the remaining 30%. When braking into corners, to correct the tendency of oversteer, more torque will be distributed to the inside rear wheel, taking advantage of the engine braking to reduce oversteer.

The above information courtesy of www.autozine.org, theres more there to...
http://www.autozine....ction_4wd_2.htm

Edited by cheapracer, 05 April 2011 - 09:39.

[kikiturbo2]

Did he work for Lamborghini by chance because thats how they do it the difference being that unlike the Cruiser'50/50 the Lambo's 30/70 is slipping 100% of the time.

I need to correct you a bit... I haven't taken apart the lambo system, but on Lancia delta integrale transmission, the centre diff has a 60/40 % split, using an epicyclic centre "diff" or torque splitter, and Frguson viscous coupler serving as an LSD part of the diff... under normal circumstances, as it has a epicyclic centre diff, there is no slip in the ferguson unit (only when you have different front/reat axle speeds does the ferguson unit "slip")


On a different matter, Haldex is no fun to drive..

Edited by kikiturbo2, 05 April 2011 - 09:49.

[kikiturbo2]

well I stand corrected... no centre diff it seems.. and viscous coupler in the front diff..

[cheapracer]

This is a Gallardo diff and the viscous clutch pack is in the front hump (left next to drive flange) I believe...



Part number 22 ....

http://www.eurospare...?...;B=43618&S=

On a different matter, Haldex is no fun to drive..

I imagine thats because most are front wheel drive with assistance from the rear rather than the other way around.

Edited by cheapracer, 05 April 2011 - 10:50.

[kikiturbo2]

I imagine thats because most are front wheel drive with assistance from the rear rather than the other way around.

I think it is a bit more, but can not be completely isolated from the suspension setupof the car.. however:

the 4x4 systems that like to understeer at the limit are generally those that tend to lock the centre diff under power.. such as Torsen (audi quattro) and Haldex systems.. I have driven both and they do tend to drive like normal FWD cars but with quite a lot of grip..

The active centre diff on the EVO, on the other hand, (and I am using it as an example because a)it will hang it's tail under power quite a lot and b)I am quite familiar with it) works in a different manner.. Although it is 50/50 fixed, usind epicyclic centre diff, it has an active plate clutch which limits slip between front and rear axles.. Driving straight ahead, under throttle, it will lock, but when you enter a corner, it will first open the diff to promote turn in (and help the monkey behind the wheel initiate oversteer) and then it will start locking. The timing of the opening and closing is programmed according to various sensors and surface type..

[cheapracer]

the 4x4 systems that like to understeer at the limit are generally those that tend to lock the centre diff under power.. such as Torsen (audi quattro) and Haldex systems.. I have driven both and they do tend to drive like normal FWD cars but with quite a lot of grip..

Thats a statement that only has foundation because there has never (?) been a rear engined car with a locked center diff to compare!

I used to store and do some prep work on a Subaru RX Turbo (Subaru's first rally car, had 4WD not AWD), a contender for the Qld State Rally championships at the time and thrash it it around the block occasionally and it would understeer in quite badly even with severe "chucking" in/Euro Flicking mostly due to having an engine and accessories hanging way out in front of the front axle line just as Quattros do - oh and bad oversteer from apex out when the rear LSD finally grabbed and the turbo came on song.

Edited by cheapracer, 05 April 2011 - 13:52.

[primer]

Obviously the motorcycle clutch example with all the notations such as "foundation", "cheap material" and "contaminated oil" was too far out there for you guys.

No, it was your incorrect assertion that billions of motorcycles slip their clutch continously, as this Ferrari does in its first four gears.

By the way, when you leave traffic lights/ride in heavy traffic on your bike do you slip the clutch or just bash down on the lever and hang on?

Yes, and this is no different than using a clutch to change the gear in a manual Civic or a Corolla. Once the gear is changed you do not slip (or use in any way) the clutch until another change is necessary. In this respect both bikes and manual transmission cars are alike.

You can drive for ten miles in a car (or a bike) in third gear, and if you do not change the gear you are not putting any wear on the clutch. This is not the case with the Ferrari FF. The two clutch for front wheels' two gears (...) are continously slipping whenever the car is in 4WD mode. Ever drive a mile in a car with the clutch pedal half pressed and then had to smell that horrible burnt clutch smell?

Even if Ferrari manage to control the clutch wear by using unobtanium clutches, you still have to contend with the heat. I have no idea quite how Ferrari are dissipating that much heat (the front can only 'handle' 20% of max torque, so any extra is being burnt off by the clutches).

No wonder they were eager to show off the FF in snow!

Edited by primer, 05 April 2011 - 16:46.

[cheapracer]

Even if Ferrari manage to control the clutch wear by using unobtanium clutches, you still have to contend with the heat. I have no idea quite how Ferrari are dissipating that much heat (the front can only 'handle' 20% of max torque, so any extra is being burnt off by the clutches).

No wonder they were eager to show off the FF in snow!

I refer you to post #42 pointing out examples of millions of cars running around slipping their clutches every day.

I'm starting to think that the Ferrari is a Haldex without them actually saying they have something so common

[Grumbles]

....The two clutch for front wheels' two gears (...) are continously slipping whenever the car is in 4WD mode.

I seriously doubt that this is the case. More likely the clutches would remain disengaged even in 4wd mode, only being actuated when traction loss is detected at the rears.