Discussion
TheDeuce said:
Actually in my bev you can hold on the brake and throttle, it'll bog down on it's springs until you come off the brake and then catapult itself forward. Doing so wipes about half a second off the official 0-60, I suspect because 'officially' such behaviour is a potential warranty issue...
Silly behaviour of course, but a true PH'r has to try these things
Unfortinately mine doesn't, it just result's in warnings on the dash and no power.Silly behaviour of course, but a true PH'r has to try these things
WestyCarl said:
TheDeuce said:
Actually in my bev you can hold on the brake and throttle, it'll bog down on it's springs until you come off the brake and then catapult itself forward. Doing so wipes about half a second off the official 0-60, I suspect because 'officially' such behaviour is a potential warranty issue...
Silly behaviour of course, but a true PH'r has to try these things
Unfortinately mine doesn't, it just result's in warnings on the dash and no power.Silly behaviour of course, but a true PH'r has to try these things
I bet other EV's allow the same sort of launch though... I'm in an i4 again soon, I'll give it a go
Edit: mines the iPace btw, what EV do you have?
Edited by TheDeuce on Wednesday 29th December 21:55
TheDeuce said:
Actually in my bev you can hold on the brake and throttle, it'll bog down on it's springs until you come off the brake and then catapult itself forward. Doing so wipes about half a second off the official 0-60, I suspect because 'officially' such behaviour is a potential warranty issue...
Silly behaviour of course, but a true PH'r has to try these things
It's no warranty issue at all!Silly behaviour of course, but a true PH'r has to try these things
Unlike with an ICE, where the engine power has to go somewhere (into heat in the transmission), at zero wheel speed the power is very small, all you are doing is preloading the powertrain with torque, and this is no really different, as far as the powertrain is concerned, as applying the same torque whilst the powertrain is turning. Without any of the shock loadings comensurate with matching the speed of a spinning, high inertia, engine to a stationary, high inertia, powertrain, when you let off the brakes, the BEV simply rolls away at that torque level!
In reality, the system will be calibrated to NOT let you have maximum torque for a couple of (rather complex) reasons, and also depending on the powertrains target attribute set, ie a shopping car wil lonly let you have enough torque to prevent the vehicle rolling backwards when you come off the brakes, but a sporting car may let you have up to the static traction limit level.
TheDeuce said:
Oh dear - no fun mode!!
I bet other EV's allow the same sort of launch though... I'm in an i4 again soon, I'll give it a go
Edit: mines the iPace btw, what EV do you have?
M3 LR. I bet other EV's allow the same sort of launch though... I'm in an i4 again soon, I'll give it a go
Edit: mines the iPace btw, what EV do you have?
Edited by TheDeuce on Wednesday 29th December 21:55
I guess there is only limited benefit anyway, the electric motor can produce max torque pretty much instantaneously, unlike a ICE.
WestyCarl said:
TheDeuce said:
Oh dear - no fun mode!!
I bet other EV's allow the same sort of launch though... I'm in an i4 again soon, I'll give it a go
Edit: mines the iPace btw, what EV do you have?
M3 LR. I bet other EV's allow the same sort of launch though... I'm in an i4 again soon, I'll give it a go
Edit: mines the iPace btw, what EV do you have?
Edited by TheDeuce on Wednesday 29th December 21:55
I guess there is only limited benefit anyway, the electric motor can produce max torque pretty much instantaneously, unlike a ICE.
Lily the Pink said:
Do people really still care about 0-60 times and traffic light grand prix ? What is surely more interesting is the 40-60 or 50-70 times for the overtake manoeuvre, where the EV scores particularly well.
In an EV any of those is simple: decide, apply throttle max acceleration. It’s that whole preemptive nature that goes out the window, the car is always in a low gear and on cam My basis for this is IPACE and E92 M3 with DCT experience so understand it’s not a catch al comparison.
Max_Torque said:
TheDeuce said:
Actually in my bev you can hold on the brake and throttle, it'll bog down on it's springs until you come off the brake and then catapult itself forward. Doing so wipes about half a second off the official 0-60, I suspect because 'officially' such behaviour is a potential warranty issue...
Silly behaviour of course, but a true PH'r has to try these things
It's no warranty issue at all!Silly behaviour of course, but a true PH'r has to try these things
Unlike with an ICE, where the engine power has to go somewhere (into heat in the transmission), at zero wheel speed the power is very small, all you are doing is preloading the powertrain with torque, and this is no really different, as far as the powertrain is concerned, as applying the same torque whilst the powertrain is turning. Without any of the shock loadings comensurate with matching the speed of a spinning, high inertia, engine to a stationary, high inertia, powertrain, when you let off the brakes, the BEV simply rolls away at that torque level!
In reality, the system will be calibrated to NOT let you have maximum torque for a couple of (rather complex) reasons, and also depending on the powertrains target attribute set, ie a shopping car wil lonly let you have enough torque to prevent the vehicle rolling backwards when you come off the brakes, but a sporting car may let you have up to the static traction limit level.
It's quite possibly the case that the control electronics in the EV simply reduce power to the motor to hold it at the optimum but non damaging point of force I suppose.
All I know for certain is that it's definitely the fastest way to launch the car but it's not mentioned in the manual.
TheDeuce said:
I dunno - the car sits down as I apply power whilst holding it on the brakes so I can only assume the motor is trying to spin but can't, not sure what that does to a digitally controlled DC motor in an EV? For a traditional motor, it would get very hot very quickly and then thermally trip.
It's quite possibly the case that the control electronics in the EV simply reduce power to the motor to hold it at the optimum but non damaging point of force I suppose.
All I know for certain is that it's definitely the fastest way to launch the car but it's not mentioned in the manual.
Traction motors are run in a torque control mode for BEVs, ie just like in a normal ICE, the accelerator pedal is used to demand a certain torque from the motor.It's quite possibly the case that the control electronics in the EV simply reduce power to the motor to hold it at the optimum but non damaging point of force I suppose.
All I know for certain is that it's definitely the fastest way to launch the car but it's not mentioned in the manual.
For an electric machine, phase current is proportional to torque and output power proportional to torque multiplied by output speed. So when you press the accelerator the inverter, the power electronics that control the flow of electrical energy into the motor, applies controls phase current so the motor's output torque matches the demand from the driver. How fast or slow the motor is spinning is effectively irrelevant, the power applied matches the demand. And if the motor isn't spinning, because you've jammed the brakes on, then the motor makes the torque required, but it's effective power output is zero, because it's output speed is also zero. The system just sits there, with the magnetics in the motor pulling on the drivetrain and chassis (via the motor mounts) with a certain torque, and the friction in the brakes reacting that torque back to the chassis.
The motor won't overheat because so little power is being transfered as the system is static
Max_Torque said:
TheDeuce said:
I dunno - the car sits down as I apply power whilst holding it on the brakes so I can only assume the motor is trying to spin but can't, not sure what that does to a digitally controlled DC motor in an EV? For a traditional motor, it would get very hot very quickly and then thermally trip.
It's quite possibly the case that the control electronics in the EV simply reduce power to the motor to hold it at the optimum but non damaging point of force I suppose.
All I know for certain is that it's definitely the fastest way to launch the car but it's not mentioned in the manual.
Traction motors are run in a torque control mode for BEVs, ie just like in a normal ICE, the accelerator pedal is used to demand a certain torque from the motor.It's quite possibly the case that the control electronics in the EV simply reduce power to the motor to hold it at the optimum but non damaging point of force I suppose.
All I know for certain is that it's definitely the fastest way to launch the car but it's not mentioned in the manual.
For an electric machine, phase current is proportional to torque and output power proportional to torque multiplied by output speed. So when you press the accelerator the inverter, the power electronics that control the flow of electrical energy into the motor, applies controls phase current so the motor's output torque matches the demand from the driver. How fast or slow the motor is spinning is effectively irrelevant, the power applied matches the demand. And if the motor isn't spinning, because you've jammed the brakes on, then the motor makes the torque required, but it's effective power output is zero, because it's output speed is also zero. The system just sits there, with the magnetics in the motor pulling on the drivetrain and chassis (via the motor mounts) with a certain torque, and the friction in the brakes reacting that torque back to the chassis.
The motor won't overheat because so little power is being transfered as the system is static
I'll continue to frustrate Porsche drivers when the lights change
TheDeuce said:
Thanks, that makes complete sense - and I pretty much assumed there would be some elegance to the control over the motors.
You can in many ways think of the inverter as the "gearbox" in the system, as it matches the speed of the spinning motors electrical fields to the static DC voltage of the battery ;-)The important thing to understand is that a motor has a characteristic called "back EMF" which is the voltage it produces itself as its magnetic field interacts with the copper wire windings. Any time a magnetic field crosses a conductor a voltage is generated by that movement, so whilst we push voltage into a motor to make it spin round, the same characteristic causes the spining motor to generate its own voltage, one that opposes the input voltage, this is called the back EMF(where EMF = electro motive force)
Th meagnitude of that voltage is directly proportional to the speed at which the magnetic field crosses the conductor, so hopefully it should be obvious that the backEMF is therefore proportional to rotational speed, and at zero speed there is no backEMF, and at max speed the backEMF is at a maximum.
So why is all this important, because the voltage applied to the motor by the inverter is opposed by the backEMF.
Lets say a motor has a backEMF characteristic of 1 volt per rpm: so at 100 rpm, there is clearly 100 volts of backEMF being generated by the motor.
if the inverter applies precisely 100 volts to the motor, the voltages balance, and no current flows, this is effectively "freewheeling" because motor torque is proportional to current, so no current = no torque
If the inverter applies more than 100v to the motor, then current flows into the motor and the motor generates a positive torque (motoring)
if the inverter applies less than 100v to the motor, then current flows out of the motor and the motor generates a negative torque (generating)
The POWER created is equal to the current multipled by the backEMF, which as we know is proportional to rotatonal speed, that means power = torque x speed, which should be familiar from mechanical theory.
With our example motor at 100 rpm (100 volts back EMF) if 1 amp is driven into the motor, we have 100 watts of power being created by the motor (100v x 1A = 100W).
The inverters job is therefore to control the flow of current into and out of the motor to directly control the torque of that motor. Of course with a modern brushless motor the inverter is also required to do the commutation, the phasing of the magnetic field in the fixed stator to the rotating rotor, as well whereas old brushed motors used fixed, mechanical brushes and contacts to do that bit.
Being able to control the phase and magnitude of the voltage it applies opens up many very complex but useful control strategies, and in fact, all modern inverters use a control method called FOC which stands of Field Oriented Control, which as its name suggests, does exatly that, ie it controls the magnetic field in the motor as its primary control methodolgy.
Modern motors and inverters are actually very elegant, and despite there mechancial simplicity, conceal complex requirements :-)
Edited by anonymous-user on Friday 31st December 11:13
mattyprice4004 said:
I love EV drivers, purely for this astounding level of delusion.
Too much special Christmas sauce?
Im a car driver (ie. Drive BOTH) and don’t like to bite at the cranberry sauce but it’s too easy, Good luck beating my IPACE off the lights even if you were primed and ready… Too much special Christmas sauce?
All I was mentioning was normal day to day driving and how much effort to make sensible progress and not dawdling but frankly it’s merits are at most situations.
Edited by JonnyVTEC on Friday 31st December 12:30
JonnyVTEC said:
Im a car driver (ie. Drive BOTH) and don’t like to bite at the cranberry sauce but it’s too easy, Good luck beating my IPACE off the lights even if you were primed and ready…
To be honest Jonny, I'm of the age where I prefer the iPace next to me to march well ahead and clear the junction of errant cyclists, pedestrians and light jumpers for me. 
sjwb said:
Ironic isn’t it? I started this thread to say that I had bought an EV, intending a touch of humour. Well, now it seems to have grown legs of it own and descended into a morass of intellectual masterbation!
But then again, don’t most threads wander?
But then again, don’t most threads wander?
Well that's pissed on your parade lol
Great purchase, why not put some pics up ?
They are brilliant cars and far more fun than anyone expects when they get in one. Ironically they seem to be really appreciated right at the end of their production !
Edited by carl0 on Friday 31st December 16:15
Am I allowed to say that I love our Volvo XC40 P8 Recharge? - every single one of the 408 horsepower? Bonkers fast for a compact SUV. Hilarious. And yet I seem to be averaging 37.8 kWh per 100.
Had it in for recall the other day and was given a diesel V70 Ovlov as a courtesy car. The drivetrain felt antediluvian in comparison (8 speed auto was smooth but a bit slow to react) and clattery and slooooowww. I remember very well the BMW X3 35d we traded it in for - brilliant thing for four years - but felt dim witted in comparison and way slower too.
The 5 speed auto in my 2005 Merc SL is utterly prehistoric and feels it - as much as I love wafting around with the roof down whenever I can, I can’t help thinking that for road focussed cars leccy is just so much better.
Had it in for recall the other day and was given a diesel V70 Ovlov as a courtesy car. The drivetrain felt antediluvian in comparison (8 speed auto was smooth but a bit slow to react) and clattery and slooooowww. I remember very well the BMW X3 35d we traded it in for - brilliant thing for four years - but felt dim witted in comparison and way slower too.
The 5 speed auto in my 2005 Merc SL is utterly prehistoric and feels it - as much as I love wafting around with the roof down whenever I can, I can’t help thinking that for road focussed cars leccy is just so much better.
otolith said:
TheRainMaker said:
What a load of balls 
An EV that does 0-60 in 6 seconds will be no faster off the line than an ICE that will do 0-60 in 6 seconds.
But one that does 0-60 in 6 seconds half a second after the throttle is applied…An EV that does 0-60 in 6 seconds will be no faster off the line than an ICE that will do 0-60 in 6 seconds.
The only way an ICE will leave the lights as sharply is if it's launched... I'm sorry, but no one wants to sit at the lights looking a complete tit with launch control engaged and their engine screaming!
This is pretty much what a Porsche driver would need to do to leave the line as briskly as an EV each time:
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