Info on the torque vectoring AWD system posted by Ford
1 - 19 of 19 Posts
Joined
·
89 Posts
Ford Focus RS – Ford Performance All-Wheel-Drive
The innovative Ford Performance All-Wheel-Drive system with Dynamic Torque Vectoring introduces a new level of handling capability and driver enjoyment, combining outstanding traction and grip with unmatched agility and cornering speed.
The Ford Performance AWD system has been tuned to deliver exceptional grip – with lateral acceleration exceeding 1 g – and class-leading cornering speed and acceleration out of a bend. With neutral and adjustable limit handling, and the ability to achieve controlled oversteer drifts at the track, the system helps delivers the ultimate fun-to-drive experience.
Torque Vectoring AWD in Action
The ground-breaking Ford Performance AWD system features innovative technology to deliver outstanding driving dynamics:
• twin electronically-controlled clutch packs on each side of the rear drive unit (RDU) manage the front/rear torque split – and the side-to-side torque distribution on the rear axle
• independent RDU control unit continuously varies the front/rear and side-to-side torque distribution to suit the current driving situation
• intelligent system monitors multiple vehicle sensors 100 times per second
• a maximum of 70 per cent of the drive torque can be diverted to the rear axle; up to 100 per cent of the available torque at the rear axle can be sent to each rear wheel
• during cornering, the RDU pre-emptively diverts torque to the outer rear wheel immediately based on inputs such as steering wheel angle, lateral acceleration, yaw and speed
• AWD system is tuned to offer multiple modes, including a unique drift setting to help achieve controlled oversteer drifts in track conditions
• to optimise handling and stability, the car’s brake-based Torque Vectoring Control is tuned to work in parallel with the torque vectoring AWD system
• AWD hardware is compact and weight-efficient to maximise vehicle performance
Ford Performance AWD v Conventional AWD:
• More agile and adjustable handling
• Reduced understeer
• Increased corner exit speed
• More fun to drive!
What is Torque Vectoring?
Torque vectoring is the ability to vary the amount of torque being delivered to each side of a drive axle, so that one side receives a greater proportion of the available torque.
This effect – which can be achieved by special axle units or by brake-based systems – can achieve significant benefits for vehicle dynamics.
During cornering, transmitting increased torque to the outer drive wheel helps to improve agility, stability and avoid understeer.
AWD system monitors inputs from vehicle sensors 100 times per second:
• steering
• throttle
• engine output/speed
• yaw rate
• lateral/longitudinal accelerations
• brake/ESC system
• wheel speeds
• PTU and RDU temperatures
Focus RS: Example of torque distribution during cornering (left hand bend):
Torque distribution helps drive car around bend
90% of rear wheel torque to outer wheel
55% of torque to rear wheels
10% of rear wheel torque to inner wheel
Attachments
Joined
·
3 Posts
Can't weight for weight numbers
Joined
·
604 Posts
Same here!
Joined
·
288 Posts
If 70% of the total system torque can be sent to one rear wheel, and that torque delivery is controlled by one clutch pack in the RDU, isn't it safe to say that the other identical clutch pack in the RDU could clamp down with equal force at the same time, which would deliver 100% torque rearward? (140% if applicable, which it is not, because physics).
Correct me if i am wrong;
The transmission is connected to the PTU which is basically a closed diff in reverse, the power flows from the crown wheel to the pinion on the drive shaft.
The drive shaft is connected to the pinion in the RDU which spins the crown wheel of the RDU. The gears in the RDU will always be spinning if the transmission is spinning which means that the driven side of each clutch pack is spinning all the time.
Torque is then transferred to each rear wheel individually based on which clutch pack clamps down. In the event that torque is not needed at the rear (for example streight calm highway driving), the clutch packs will open, however the PTU, Drive-shaft, and driven gears of the RDU will still spin.
I totally understand the need for marketing hype ( try to get an allocation at MSRP right now), but talking in percentages is kinda silly because the torque that the PTU sees from 1st gear and 6th gear are orders of magnitude different at WOT. In addition the PTU can not pick how much torque gets sent rearward, that is decided by the RDU.
Anyone have any insight?
Is my thinking way out of line?
The engineers obviously killed it with this one regardless...
Correct me if i am wrong;
The transmission is connected to the PTU which is basically a closed diff in reverse, the power flows from the crown wheel to the pinion on the drive shaft.
The drive shaft is connected to the pinion in the RDU which spins the crown wheel of the RDU. The gears in the RDU will always be spinning if the transmission is spinning which means that the driven side of each clutch pack is spinning all the time.
Torque is then transferred to each rear wheel individually based on which clutch pack clamps down. In the event that torque is not needed at the rear (for example streight calm highway driving), the clutch packs will open, however the PTU, Drive-shaft, and driven gears of the RDU will still spin.
I totally understand the need for marketing hype ( try to get an allocation at MSRP right now), but talking in percentages is kinda silly because the torque that the PTU sees from 1st gear and 6th gear are orders of magnitude different at WOT. In addition the PTU can not pick how much torque gets sent rearward, that is decided by the RDU.
Anyone have any insight?
Is my thinking way out of line?
The engineers obviously killed it with this one regardless...
Joined
·
556 Posts
Almost. 70% of torque can be applied to the rear drive unit (RDU). 100% of the 70% torque can be applied to the left or right (as you mentioned) via locking the clutch.
E.g. locked fully on right, open left, 70% of systems entire torque is sent to right rear wheel. Vice versa if locked fully left, open right.
If both left and right clutches are fully locked, then it is effectively 50:50, or in 'whole system' speak, 35% to each rear wheel.
Here's how the Focus RS awd system works
Joined
·
288 Posts
Is that using the assumption that the 1.8% over driven rear wheels bring the torque split from 50:50 to 70:30 on flat ground in a straight line?
My thought is that any over-driving should bring the split to 100:0.
Does The RDU have the capability to actuate each clutch fully independently?
Joined
·
1,878 Posts
Your understanding of the mechanics of the system is correct. The goal with expressing torque as a percentage is due to torque splits. You have the legendary RS200 with selectable rear-biased torque splits on one end of the spectrum and Honda's part time AWD with a maximum of something like 15% torque to the rear at the other. The goal with percentages is to show that the RS can drive like a rear-biased car, making it much more fun and lively than its FWD-based competitors. That's where the "70% to the rear" comes from. The "100% to either side" bit shows how this is far more sophisticated than an LSD at the rear because the two rear wheels are completely independent of each other. They are independent data points expressing different characteristics of the powertrain. I am running under the assumption that the 70% to the rear limit involves much more than just the RDU. The PTU has a torque limit that some have claimed is impressively low, which would allow only 70% of the engine's torque to the distributed to the rear regardless of which wheel puts it down. In theory, yes, if each clutch pack can hold 70% of the peak torque then both combined would be able to handle 100% of the torque. But the AWD system is part of a bigger picture with more dependencies than just that.
There is no reason that both clutches couldn't just lock, but they are software limited to a maximum amount of clamping force to protect the rest of the driveline components. It's likely a low limit for longevity as opposed to only leaving a narrow margin in order to prevent immediate failure, and it will be interesting to see what happens when tuners start messing with that limit. Until then we're stuck with the 70% overall to the rear number. For safety.
The most recent figure that I have heard is 2%, not that it matters much.
You have to keep in mind that torque split is absolutely not static. Technically, by overdriving the rear axle you're lessening the torque that the rear axle puts down relative to a simple three diff system. Higher speed means lower torque. The only reason that you get a more rearward split than 51:49 is because overdriving the rear wheels means that you're putting less load on the front axle because torque only exists in the presence of a resisting force. And if you think of it in an incredibly simplified sense, 100% load at the front is a baseline. 100% load on the rear axles would mean that the car would be moving 1.8-2% faster and be putting 1.8-2% LESS torque to the ground overall. So in a static sense there can never be 100% torque to the rear as it is limited to ~98%. And since the absolute torque value varies in each gear the practical torque split limit is less than 98% to the rear due to hardware capacity. Conceivably with a more robust system you could claim close to 100% torque to the rear but that would make it much heavier and more expensive than it already is.
Joined
·
288 Posts
Gotcha,
I just thought of a silly scenario trying to wrap my head around the whole thing;
Lets say the rear is over driven by 2%, with welded diffs all around. if you had tons of grip at the tires than the system would see crazy internal forces as the front wheels fought the back wheels through the driveline. This is regardless of how much power you are trying to put down from the engine.
I assume this is the cause of the problems they were running in to when they were first trying to develop the rear bias with a haldex system.
Joined
·
1,878 Posts
There's only one diff in this car. I assume that you mean the RDU is locked. And yes. That's why locking the RDU doesn't make sense. You can get away with it in situations where you're forcing the tires to break loose like drift mode or potentially launch control, but under normal driving the car will (eventually) rip itself apart. And once you go to something like race slicks even launching gets questionable. The forces aren't really any more than a traditional car with welded diffs all around trying to turn sharply, but you spend a lot more time going straight than you do turning.
I am not as familiar with Haldex's Gen V system. It's made to slip a bit, but I would guess that it's nowhere near as robust as the clutches on the GKN unit which are made to slip forever, and that's why it blew when overdriven. Haldex advertises that their unit can handle scenarios like mismatched tires without issue, so my guess is that it's mostly a robustness issue in combination with more torque than it's designed to handle on a regular basis.
Joined
·
423 Posts
"Highway Mode" as you have described it, is the relaxed state of the system. When cruising in a straight line with no wheel slip present, the rear clutches disengage, yielding an effective 100:0 ratio as you've described.
I would've loved a persistent 50:50 split "Snow/Gravel Mode". Basically the same as Normal, but with a forced minimum of 50% going to the rear.
Joined
·
2,063 Posts
at a 50/50 split you have the most clutch slip possible, the higher the rear bias gets the more you end up with these binding internal forces that have been mentioned. these forces aren't as bad as it seems. the open diff in the front cuts these forces in half cuz as the rear overtakes the front it only has to push one tire. you guys are looking to far into it. how does the driveline cope with the overdrive??? it will eat tires, simple as that
Joined
·
141 Posts
Joined
·
288 Posts
You must be new hereWow, talk about necro'ing a thread...layful:
people get chewed apart for making duplicate threadsI am busy building a Quaife front LSD into the car. It s a crazy job to build it in just plain crazy. I am crazy doing it.
I can tell you this. I am fed up with car manufactures building cars and doing it the easy way with delivering sporty cars with electronic e Diffs , a luxury word is Torque Vectoring for it.
I have to put incredible time and effort into my ford to put an quaife into it because at ford they are to lazy the make it right the first time. A quaife diff costs around 750 euro and if ford buys them in bulk they cost even less. And it brings so much more fun. If you put on open diff or LSD in the gearbox that s the same work.
What would it be laugh if you buy an GT3 RS or BMW M car with an electronic brake diff.
Real sporty cars have mechanical diffs period.
For me the Ford is my last car i will ever buy to have electronic brake diffs onboard. If a manufacturer can not build sporty cars properly they can keep them.
I can tell you this. I am fed up with car manufactures building cars and doing it the easy way with delivering sporty cars with electronic e Diffs , a luxury word is Torque Vectoring for it.
I have to put incredible time and effort into my ford to put an quaife into it because at ford they are to lazy the make it right the first time. A quaife diff costs around 750 euro and if ford buys them in bulk they cost even less. And it brings so much more fun. If you put on open diff or LSD in the gearbox that s the same work.
What would it be laugh if you buy an GT3 RS or BMW M car with an electronic brake diff.
Real sporty cars have mechanical diffs period.
For me the Ford is my last car i will ever buy to have electronic brake diffs onboard. If a manufacturer can not build sporty cars properly they can keep them.
1 - 19 of 19 Posts
