RE: McLaren P1: Driven
Discussion
Max_Torque said:
Oh my. Oh my oh my.
That. Is going to be good.
Cobnapint said:
Max_Torque said:
Oh my. Oh my oh my.
That. Is going to be good.
It just looks so damn chuckable, which of course it 100% should not be. And the speed at which it accelerates towards that bridge...
Edited by loudlashadjuster on Monday 17th February 23:32
E-diff topic.
This is like when Harris made the video about the Focus RS with left foot braking to get the diff working before a corner on the road or some such wrongness, despite the differential being a mechanical type and reacting at the instant there was a torque differential anyway. Never mind the issue of having the left foot over the brake into a corner on a public road. Hmmm.
McLaren have followed their ethos for the P1, but for observers to make any judgements on anything but the final result is pointless, because it's all about the package and design.
But do brakes need to be bigger at the back to manage the extra energy they receive from e-diff operation? More inertia, more weight? More things removing a mechanical diff in the first place are meant to save you?
BMW and Ferrari fit electronically controlled locking differentials, not just brake wheels to send torque to the other one. That is a good solution.
You get full torque output AND torque balancing, rather than reduced torque output.
Does it really matter in the end?
This is like when Harris made the video about the Focus RS with left foot braking to get the diff working before a corner on the road or some such wrongness, despite the differential being a mechanical type and reacting at the instant there was a torque differential anyway. Never mind the issue of having the left foot over the brake into a corner on a public road. Hmmm.
McLaren have followed their ethos for the P1, but for observers to make any judgements on anything but the final result is pointless, because it's all about the package and design.
But do brakes need to be bigger at the back to manage the extra energy they receive from e-diff operation? More inertia, more weight? More things removing a mechanical diff in the first place are meant to save you?
BMW and Ferrari fit electronically controlled locking differentials, not just brake wheels to send torque to the other one. That is a good solution.
You get full torque output AND torque balancing, rather than reduced torque output.
Does it really matter in the end?
These cars are so powerful , normal rules do not apply . These are f1 plus power levels put into the hands of joe public who is not automatically Walter rohrl . Few can truly tame such performance unaided . What these cars do is almost simulate the drivers car . . Especially on the roads , be under no illusion it's partly the computers keeping you going the right way. It's a simulated interaction .
So with this being the case , does it really matter if a car has a slippy diff or not ? Not really IMO .
Same with the 918 being 4wd , it's not ideal but with 950 plus pounds feet of torque it's bloody necessary ! You could see Chris struggling with the systems ON , let alone with the systems off . Cars are too powerful now to be analogue , they MUST be digital , the computers react better in this manner . I would still prefer a e controlled diff like Ferrari and Porsche use but mac don't like them no big deal tbh .
It's a pity but it's a fact . The true analogue drivers car is dead , now is the era of the electronic , digital almost simulated drivers car . track times and acceleration figures . Unfortunate or not ( depends on your point of view ) that is the fact of it .
Even Chris sliding about like that , I'd love to know how " off " the systems really were and how much the brake steer and tc was still intervening . I suspect a lot more than even mr Harris could feel . Usually that would be a bad thing but I think with so much power there is no other way .
On things like the 12 c etc however I firmly believe a slippy or an e controlled diffy is better . At least this newer software for the mac no diff rear end .
So with this being the case , does it really matter if a car has a slippy diff or not ? Not really IMO .
Same with the 918 being 4wd , it's not ideal but with 950 plus pounds feet of torque it's bloody necessary ! You could see Chris struggling with the systems ON , let alone with the systems off . Cars are too powerful now to be analogue , they MUST be digital , the computers react better in this manner . I would still prefer a e controlled diff like Ferrari and Porsche use but mac don't like them no big deal tbh .
It's a pity but it's a fact . The true analogue drivers car is dead , now is the era of the electronic , digital almost simulated drivers car . track times and acceleration figures . Unfortunate or not ( depends on your point of view ) that is the fact of it .
Even Chris sliding about like that , I'd love to know how " off " the systems really were and how much the brake steer and tc was still intervening . I suspect a lot more than even mr Harris could feel . Usually that would be a bad thing but I think with so much power there is no other way .
On things like the 12 c etc however I firmly believe a slippy or an e controlled diffy is better . At least this newer software for the mac no diff rear end .
Edited by wtdoom on Thursday 20th February 12:43
As Mr Harris said earlier in this thread, locking diffs do all sorts of undesirable things, locking up the rear axle and compromising its independence, inducing understeer etc. I'm sure McLaren know what they're doing and are keeping the weight down with those silicon-carbide brakes... and if you want an analogue hypercar, Noble, Koenigsegg and Pagani will gladly do you one. The Pagani Huayra is similarly powerful to the P1 (minus the 'leccy motor) and doesn't have overly intrusive systems. The Noble has bugger all systems, full stop, yet even at full chat on 650hp it's said not to be scary to drive. The Koenigseggs have quite sophisticated traction control but again you don't hear reviewers moaning about that. Again, if McLaren can keep things in check and save you from an expensive 1-of-375, 217mph fireball, without the systems being intrusive, I don't think that need be a problem. If you really want to keep it simple, the Noble M600 is very analogue and quite fast enough, even if it wouldn't see which way the McLaren went at Le Mans or even the Nordschleife. How many drivers will ever use their P1s in real anger? Not many, I suspect - and more's the pity.
Edited by RoverP6B on Thursday 20th February 12:48
wtdoom said:
These cars are so powerful , normal rules do not apply . These are f1 plus power levels put into the hands of joe public who is not automatically Walter rohrl . Few can truly tame such performance unaided . What these cars do is almost simulate the drivers car . . Especially on the roads , be under no illusion it's partly the computers keeping you going the right way. It's a simulated interaction .
So with this being the case , does it really matter if a car has a slippy diff or not ? Not really IMO .
Same with the 918 being 4wd , it's not ideal but with 950 plus pounds feet of torque it's bloody necessary ! You could see Chris struggling with the systems ON , let alone with the systems off . Cars are too powerful now to be analogue , they MUST be digital , the computers react better in this manner . I would still prefer a e controlled diff like Ferrari and Porsche use but mac don't like them no big deal tbh .
It's a pity but it's a fact . The true analogue drivers car is dead , now is the era of the electronic , digital almost simulated drivers car . track times and acceleration figures . Unfortunate or not ( depends on your point of view ) that is the fact of it .
Even Chris sliding about like that , I'd love to know how " off " the systems really were and how much the brake steer and tc was still intervening . I suspect a lot more than even mr Harris could feel . Usually that would be a bad thing but I think with so much power there is no other way .
On things like the 12 c etc however I firmly believe a slippy or an e controlled diffy is better . At least this newer software for the mac no diff rear end .
You can still have a highly electronically controlled conventional limited slip diff. Ferrari have recently enhanced theirs with great effect.So with this being the case , does it really matter if a car has a slippy diff or not ? Not really IMO .
Same with the 918 being 4wd , it's not ideal but with 950 plus pounds feet of torque it's bloody necessary ! You could see Chris struggling with the systems ON , let alone with the systems off . Cars are too powerful now to be analogue , they MUST be digital , the computers react better in this manner . I would still prefer a e controlled diff like Ferrari and Porsche use but mac don't like them no big deal tbh .
It's a pity but it's a fact . The true analogue drivers car is dead , now is the era of the electronic , digital almost simulated drivers car . track times and acceleration figures . Unfortunate or not ( depends on your point of view ) that is the fact of it .
Even Chris sliding about like that , I'd love to know how " off " the systems really were and how much the brake steer and tc was still intervening . I suspect a lot more than even mr Harris could feel . Usually that would be a bad thing but I think with so much power there is no other way .
On things like the 12 c etc however I firmly believe a slippy or an e controlled diffy is better . At least this newer software for the mac no diff rear end .
BMW have been offering their's for years to allow hooligan slides but also a safe envelope of control.
The power argument is a bit iffy too. There have been powerful cars for years.
Analogue and digital? Another complete bunch of junk written by cretinous journalists who have no idea what they are talking about at the best of times.
Cars are both, and always have been.
If the P1 really was a digital car, it'd have two throttle states. On and off. I'd much prefer an analogue throttle in a powerful car
Stop reading what journalists write. They don't know what to say about the tech so they just write complete junk which is meaninless and stupid.
We still keep seeing them talking about torque like it's an absolute comparable figure, forgetting entirely about gearboxes!
Journalists are good for telling you how things feel, the sensations and feelings, things we can't feel. But for how they convey technical things, hmmm, no. Just no
Dave
RoverP6B said:
As Mr Harris said earlier in this thread, locking diffs do all sorts of undesirable things, locking up the rear axle and compromising its independence, inducing understeer etc. I'm sure McLaren know what they're doing and are keeping the weight down with those silicon-carbide brakes... and if you want an analogue hypercar, Noble, Koenigsegg and Pagani will gladly do you one. The Pagani Huayra is similarly powerful to the P1 (minus the 'leccy motor) and doesn't have overly intrusive systems. The Noble has bugger all systems, full stop, yet even at full chat on 650hp it's said not to be scary to drive. The Koenigseggs have quite sophisticated traction control but again you don't hear reviewers moaning about that. Again, if McLaren can keep things in check and save you from an expensive 1-of-375, 217mph fireball, without the systems being intrusive, I don't think that need be a problem. If you really want to keep it simple, the Noble M600 is very analogue and quite fast enough, even if it wouldn't see which way the McLaren went at Le Mans or even the Nordschleife. How many drivers will ever use their P1s in real anger? Not many, I suspect - and more's the pity.
The only reason they put electrics on is to widen the appeal to less capable drivers.Edited by RoverP6B on Thursday 20th February 12:48
They can make the car more focussed at one end for higher performance, and fill in skill gaps with electronic systems for people with less skill, or in poorer road conditions.
That is a good thing.
But nothing is digital/analogue. Using that argument you could say the F50 was a 'digital' car because it had an engine ECU and electronic dampers. Enough to cover most of the things you interface the car and road through!
Locking diffs don't usually cause undesirable things when set up as part of a package.
And people like Ferrari fully control their diff electronically any way, so it's all the advantages without most of the disadvantage, along with a whole load of new advantages because it can be varied constantly.
The P1 system offers no benefits except reduced weight. Everything else it does a Ferrari could do via braking too via the ESP and related TCS systems, AND use it's differential on top!
But Ferrari don't do that because it's ultimately costing you torque and sending engine power, or charged power, into heat in the brakes. Not quite so efficient.
As said, it's just a different solution. Better in some ways, worse in others. Different. Not better or worse. And not bloody digital!
Mr Whippy said:
And people like Ferrari fully control their diff electronically any way, so it's all the advantages without most of the disadvantage, along with a whole load of new advantages because it can be varied constantly.
The P1 system offers no benefits except reduced weight. Everything else it does a Ferrari could do via braking too via the ESP and related TCS systems, AND use it's differential on top!
But Ferrari don't do that because it's ultimately costing you torque and sending engine power, or charged power, into heat in the brakes. Not quite so efficient.
As said, it's just a different solution. Better in some ways, worse in others. Different. Not better or worse. And not bloody digital!
Would it be possible to give us more information on how the conclusion of "not better or worse" was reached? For example, under what conditions was one system better than the other and by what percentage?The P1 system offers no benefits except reduced weight. Everything else it does a Ferrari could do via braking too via the ESP and related TCS systems, AND use it's differential on top!
But Ferrari don't do that because it's ultimately costing you torque and sending engine power, or charged power, into heat in the brakes. Not quite so efficient.
As said, it's just a different solution. Better in some ways, worse in others. Different. Not better or worse. And not bloody digital!
I find PH great for subjects that I have a very basic grounding in, often an expert will put flesh on the bones in a way that clears up some of the opinions offered up as fact.
This for example..
Max Torque said:
People like Tom believe a conventional mech (or electro-mech) diff to be "optimum" because it allows you to do big, smokey, and easily controlled skids. Which to a large degree it does. However, whilst you are doing those aformentioned big skids, the driving tyres are effectively locked together, and the more torque you want to shuffle across to the outside (more heavily loaded) tyre, the more locked-together those tyres are (and hence the lower the speed differential across them). That means that during that time, neither tyre can be held close to it's optimum dynamic slip ratio, and as such, the perfect absolute longitudinal acceleration of the vehicle for that surface friction cannot actually be achieved.
However, by using a conventional open differential, and a high band width speed controller using the rear brakes to torque balance, the brake steer system can both maximise drive torque across the axle AND optimise the dynamic slip ratio at EACH individual rear tyre.
However, by using a conventional open differential, and a high band width speed controller using the rear brakes to torque balance, the brake steer system can both maximise drive torque across the axle AND optimise the dynamic slip ratio at EACH individual rear tyre.
The Vambo said:
Mr Whippy said:
And people like Ferrari fully control their diff electronically any way, so it's all the advantages without most of the disadvantage, along with a whole load of new advantages because it can be varied constantly.
The P1 system offers no benefits except reduced weight. Everything else it does a Ferrari could do via braking too via the ESP and related TCS systems, AND use it's differential on top!
But Ferrari don't do that because it's ultimately costing you torque and sending engine power, or charged power, into heat in the brakes. Not quite so efficient.
As said, it's just a different solution. Better in some ways, worse in others. Different. Not better or worse. And not bloody digital!
Would it be possible to give us more information on how the conclusion of "not better or worse" was reached? For example, under what conditions was one system better than the other and by what percentage?The P1 system offers no benefits except reduced weight. Everything else it does a Ferrari could do via braking too via the ESP and related TCS systems, AND use it's differential on top!
But Ferrari don't do that because it's ultimately costing you torque and sending engine power, or charged power, into heat in the brakes. Not quite so efficient.
As said, it's just a different solution. Better in some ways, worse in others. Different. Not better or worse. And not bloody digital!
I find PH great for subjects that I have a very basic grounding in, often an expert will put flesh on the bones in a way that clears up some of the opinions offered up as fact.
This for example..
Max Torque said:
People like Tom believe a conventional mech (or electro-mech) diff to be "optimum" because it allows you to do big, smokey, and easily controlled skids. Which to a large degree it does. However, whilst you are doing those aformentioned big skids, the driving tyres are effectively locked together, and the more torque you want to shuffle across to the outside (more heavily loaded) tyre, the more locked-together those tyres are (and hence the lower the speed differential across them). That means that during that time, neither tyre can be held close to it's optimum dynamic slip ratio, and as such, the perfect absolute longitudinal acceleration of the vehicle for that surface friction cannot actually be achieved.
However, by using a conventional open differential, and a high band width speed controller using the rear brakes to torque balance, the brake steer system can both maximise drive torque across the axle AND optimise the dynamic slip ratio at EACH individual rear tyre.
However, by using a conventional open differential, and a high band width speed controller using the rear brakes to torque balance, the brake steer system can both maximise drive torque across the axle AND optimise the dynamic slip ratio at EACH individual rear tyre.
Ultimately it's all about torque control at the wheels vs what is desired by the driver, or assumed to be desirable by the people setting up the system for a range of drivers with different buttons pressed (ie, brass balls mode, or useless driver mode)
Any car with a modern ESP system can probably implement a brake force torque biasing effect. I can do it in my old Z4 with the handbrake.
Ferrari could have done it but chose to use an electronically controlled mechanical visco limited slip differential iirc.
McLaren decided to save some weight, drive-train inertia and money and simply make the brakes at the back do things based on the user inputs and the wheel speeds.
Ultimately the cost is that they put energy into brake discs/pads/calipers, that has been generated by the engine or energy recovery systems. That is inefficient in the biggest sense of hybridisation.
Since there is only one electric motor there is no way to trim the torque that it provides to just one wheel. Thus energy via this system is wasted and ultimately the cars performance suffers vs an electronically variable mechanical differential... which if it wanted could *still* use brake controls too.
Everything has a list of pros and cons associated with it. From a solid rear axle to an open differential, everything has it's place dependent upon the vehicle designers brief.
In the end the P1 might be better with it's differential because everything else has been designed with it in mind. Just as the LaFerrari will be better with it's diff because other things are designed around it.
Really I don't get why McLaren didn't just use an open diff and a motor on each output shaft that could apply positive and negative torques. Then they could brake and regenerate, bias and regenerate, trim torque to control traction to a point and so on.
Having the electric motor simply adding to an open differential and then having to trim it back with braking at the wheels seems a bit crude... well that is my opinion given their blank sheet of paper opportunity.
Dave
I think the reason they use an E-LSD instead of a mechanical limited slip differential is that it is SUPERIOR to any mechanical LSD. It's a completely variable locking across the axle electronically controlled clutch system that works in the same way as the active 'VAQ' Haldex like across the axle clutch in the new Golf Gti. It's not an OPEN diff! Also it ISN'T an 'E-lsd' which just uses the brakes with clever calibration and the wheel speed sensors to mimic the effects of an LSD.
Using this system it varies the locking precisely and extremely fast, much faster than a conventional LSD. It then uses braking as a last resort on the inside tyre once locking is already at 100% to make the car easier to drive before then cutting engine power if braking is not enough due to being on ice/snow. Using this system both axles get the best traction that they can get in all conditions.
This 'LSD creates understeer' thing I don't get. From racing games, etc as I understand it an LSD just provides more traction at either driven axle because it locks the inside tyres torque to a set percentage or ratio below the outside tyres torque. I don't understand how it can create understeer except on a FWD car. On a FWD car yes if you use too much locking like for like get understeer instead of wheel spin but only if there's enough power and traction to create the push understeer.
All else being equal a RWD car with an LSD will have greater traction but then will oversteer more once the traction limit is reached. Therefore when using an LSD a manufacturer will deliberately make the rear end stiffer to compensate for the greater traction and increase the predictability once it does break free.
All of the above could be wrong but that's the way I understand it.
Source for VAQ diff:
http://drivelinenews.com/news/electronic-locking-d...
Using this system it varies the locking precisely and extremely fast, much faster than a conventional LSD. It then uses braking as a last resort on the inside tyre once locking is already at 100% to make the car easier to drive before then cutting engine power if braking is not enough due to being on ice/snow. Using this system both axles get the best traction that they can get in all conditions.
This 'LSD creates understeer' thing I don't get. From racing games, etc as I understand it an LSD just provides more traction at either driven axle because it locks the inside tyres torque to a set percentage or ratio below the outside tyres torque. I don't understand how it can create understeer except on a FWD car. On a FWD car yes if you use too much locking like for like get understeer instead of wheel spin but only if there's enough power and traction to create the push understeer.
All else being equal a RWD car with an LSD will have greater traction but then will oversteer more once the traction limit is reached. Therefore when using an LSD a manufacturer will deliberately make the rear end stiffer to compensate for the greater traction and increase the predictability once it does break free.
All of the above could be wrong but that's the way I understand it.
Source for VAQ diff:
http://drivelinenews.com/news/electronic-locking-d...
Edited by iloveboost on Friday 21st February 10:51
iloveboost said:
I think the reason they use an E-LSD instead of a mechanical limited slip differential is that it is SUPERIOR to any mechanical LSD. It's a completely variable locking across the axle electronically controlled clutch system that works in the same way as the active 'VAQ' Haldex like across the axle clutch in the new Golf Gti. It's not an OPEN diff! Also it ISN'T an 'E-lsd' which just uses the brakes with clever calibration and the wheel speed sensors to mimic the effects of an LSD.
Ah so it's not an e-diff or an open differential.This is why I need to stop reading articles by journalists and read proper engineering articles.
Well given that piece of information it's pretty nice then.
And technically it's still a mechanical differential with electronic control.
But in the end many modern differentials in cars are visco or haldex types or hybrids with various electronic interference to trim behaviours.
In the end it's still all about what the engineer writes down on his 'wish list' and then finds something to fit those parameters.
A diff like BMW M use for example might be perfectly fine for the engineers wish list under 99% of the time and operating conditions, so why spec, develop and have to fill calibration tables full of values to get the desired behaviours, and possibly have a unit that requires more costly maintenance and costs more to install etc etc...
So I have a new appreciation for the P1's diff.
But it still doesn't change the point that it's just a device to do what the engineers want. Their ethos and design will determine what the end outcome will be.
I'm still wondering why no one has made a car like this but with 4 leccy motors, but NOT just battery powered only. Ie, petrol-electric 4wd with absolute per-wheel torque control.
Dave
Gassing Station | General Gassing | Top of Page | What's New | My Stuff