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tonybelding
Active Member
Virtual Gear Shift
I thought about this a little, and I have to disagree. I really hope they keep the shifter. Remember, it was only an electrical switch to begin with. But it's a quite nifty switch. So I say, let's put it to good use. It should be possible to program it to simulate the kind of performance we expected from the two-speed system.
When you put it in 1, it should allow full power to the motor and an aggressive regen profile. It could be made to perform much the way 1st gear would have, only without having to stop at 60 MPH!
When you put it in 2, then it should limit power to the motor and use a more relaxed regen profile. So it will be good for casual everyday driving where you don't want to accidentally break loose the rear tires.
Switching between the two positions would be the quickest and smoothest shift in the world: a virtual gear shift.
I thought about this a little, and I have to disagree. I really hope they keep the shifter. Remember, it was only an electrical switch to begin with. But it's a quite nifty switch. So I say, let's put it to good use. It should be possible to program it to simulate the kind of performance we expected from the two-speed system.
When you put it in 1, it should allow full power to the motor and an aggressive regen profile. It could be made to perform much the way 1st gear would have, only without having to stop at 60 MPH!
When you put it in 2, then it should limit power to the motor and use a more relaxed regen profile. So it will be good for casual everyday driving where you don't want to accidentally break loose the rear tires.
Switching between the two positions would be the quickest and smoothest shift in the world: a virtual gear shift.
I should think this is an excellent idea! Under normal conditions I don't want the extreme performance and squeeling tires that come with it. In second "gear" you can simply limit the torque at low rpm.
Does anybody from Tesla read this?
Traction control can limit tire squeal and other such issues if you want it to.
That could work in any gear, so no need to burden the motor with a taller gear just to get that.
Absolutely they do, but they seem to avoid posting except in rare circumstances. (Daryl might chime in if he thinks there is a good opportunity to add some witty comment that doesn't say too much that they should otherwise be saving for a press release).
I do like the idea of keeping the shifter just as a regen control.
I really do not see why accelerator and brake pedal could not be better used for that. Just set the brake pedal in a way that first third of travel only increases the regen level and only after that brakes starts to grip. With stronger PEM, maximum posible regen gets higher.
So, 2 other big transmission companies were not able to come up with reliable and durable designs after all. I don't blame them, power surges are just to high.
Tesla is calling this transmission 1.5. I speculate that means they will set the fixed gear ratio somewhere inbetween current 1. and 2. gear. With increased torque they will be able to get that advertised 4 second time and with liquid cooling they will be able to move the motor redline towards 15000 rpm and retain that advertised top speed. Liquid motor cooling should also add some additional motor noise insulation.
This all in all is good news. Too bad it took so long time and so much pain for them to arrive.
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tonybelding
Active Member
According to the email from Tesla, top speed with the interim transmission will be 125 MPH. Logically you have to expect it should be just as high, if not higher, with the liquid cooled motor.
W8MM
R1.5 #325 + Mdl S #01380
I agree.
IIRC, Tesla's reason for lowering the top speed from 135 to 130 for the 2-speed configuration was motor heat safety margin. If better motor cooling is available, then I would expect the top speed to return to 135.
No, top speed could not be limited to 100 without a loss in quarter mile time. They indicated a quicker quarter mile time.
Excellent Idea! I think all owners should support this in the owners forum. Without this it really isn't the vehicle we bought!
Not necessarily. I suspect them to tweak the reduction ratio. The old second gear had a total reduction ratio of 1:7.4. (1st: 1:14.32). By slightly increasing the 1:7.4 ratio to 1:7.6 or so you shave of 0.15 secs or so of your 0-60 time. Collateral damage: top speed falls 6mph (using the 7.6/7.4 numbers).
tonybelding
Active Member
I hadn't thought of it that way.
If it was up to me, I'd like a little more top end and sacrifice a bit of 0-60 MPH time. However, I doubt whether there's any way Tesla could do that since they've staked so much on the promise of 0-60 MPH in 4 seconds.
tonybelding
Active Member
Shot Down in Flames
It appears my idea for a "virtual gear shift" has already been shot down by Tesla.
Following is Darryl's response from the owners' forum:
Tony - since we are going to a single speed, we have regulatory requirements for PRNDL settings (park, reverse, etc). It's annoying because it is a strange requirement but we don't have a choice. I like your ideas about different modes. It would be easy to implement in the firmware (in fact we have some driving modes already) but that isn't easy to change on the fly. I have been advocating for mechanical controls that allow you to change regen and other settings on the fly but introducing design changes this late in the game isn't a good idea. perhaps something we can do on an aftermarket basis for those who want it. Having driven the car a lot, it is quite easy to modulate performance (even regen) with the pedla once you get used to it. If you don't want regen as you are coasting you just keep the pedal at the zero point. If you want full regen you take your foot off the pedal (not literally)
Hmm. . . PRNDL. . . L? And why is this prescribed by regulations anyhow?
It appears my idea for a "virtual gear shift" has already been shot down by Tesla.
Following is Darryl's response from the owners' forum:
Tony - since we are going to a single speed, we have regulatory requirements for PRNDL settings (park, reverse, etc). It's annoying because it is a strange requirement but we don't have a choice. I like your ideas about different modes. It would be easy to implement in the firmware (in fact we have some driving modes already) but that isn't easy to change on the fly. I have been advocating for mechanical controls that allow you to change regen and other settings on the fly but introducing design changes this late in the game isn't a good idea. perhaps something we can do on an aftermarket basis for those who want it. Having driven the car a lot, it is quite easy to modulate performance (even regen) with the pedla once you get used to it. If you don't want regen as you are coasting you just keep the pedal at the zero point. If you want full regen you take your foot off the pedal (not literally)
Hmm. . . PRNDL. . . L? And why is this prescribed by regulations anyhow?
Exactly! Isn't this in essence all we need? D for normal and L for more aggressive regen.
Toyota/Lexus have this on the hybrids.
tonybelding
Active Member
Do they? Hmm, I don't know. . . I'll just have to wait and see what they come up with.
I'm pretty sure my girlfriend's Audi A4 (with an automatic transmission) has PRNDS.
S stands for 'sport mode' and I think is pretty much analogous to what Tony is talking about.
Tony, why don't you make your suggestion again with your 'virtual shift' occurring between two driving modes, D and S.
From what Darryl had to say, it sounds like they are now required to have a shifter arrangement that more closely resembles an automatic. I wonder if they'll have to have that dorky safety button on the shifter knob too.
S stands for 'sport mode' and I think is pretty much analogous to what Tony is talking about.
Tony, why don't you make your suggestion again with your 'virtual shift' occurring between two driving modes, D and S.
From what Darryl had to say, it sounds like they are now required to have a shifter arrangement that more closely resembles an automatic. I wonder if they'll have to have that dorky safety button on the shifter knob too.
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Zooming through hills, I would prefer to control speed up and down hills just using the accelerator pedal only. If I can pick a heavier regen profile then I can get by on the downhills just by easing up on the one pedal. This makes driving a lot more fun and enjoyable on rolling "switchback" hills which (IMHO) is the forte of the roadster.
From what I can tell, Tesla has avoided tying the brake pedal travel into the regen system. Cars like the Prius may well use initial brake pedal movement for regen only, but Tesla seems to have opted to not mix the two (regen & braking) on the same pedal to avoid all the related design, test and safety considerations that would have added scope to their already intense project schedule. Besides, I would prefer to save the brake pedal for cases where I really want to stop, and instead just have enhanced regen option selectable for cases where you let off of the accelerator pedal to slow down a little.
This is what I (and probably many others) had been suggesting that they do all along. I don't know what their current thinking is in terms of gear ratios. Between old 1st ratio and old 2nd ratio would seem like a good idea to me, but what do I know?
Yes!
I am not so sure of that. 13,000 RPM limit may not have just been due to heat. There are other controller, bearing and balance issues to contend with if you try to rev higher. It wouldn't surprise me if redline is the same, and top speed comes down a bit.
Yeah, I thought of that too. Noise with existing motor was fairly minimal so this would be only a minor benefit.
Yeah, no kidding!
I am of the different opinion. I would like to keep the 0-60 time, but would be willing to forgo the top end. As long as it could get to 100MPH I would be satisfied.
FYI, my ranger EV (with a single fixed gear ratio) has PRNDE
Where "E" is Economy mode that switches controller profile for
#1: More regen
#2: Reduced top speed
Are we mixing up "interim transmission" with the new PEM/eMotor combination "final fix"?
Unless I am mistaken, the first batch of Roadsters will have the old PEM & eMotor with a variant of the old transmission effectively locked in 2nd gear. This is the one with the 125 MPH top speed, and 13,000 redline (reduced from 13,500 for reliability reasons).
It may be that the new PEM and liquid-cooled eMotor and gear reduction has a different top speed. I might be wrong, but I think we might be mixing up specs of the different variants.
Original prototype specs:
2 speed
0-60 < 4s
130 MPH+
13,500 RPMs
250mile+ range
1st spec revision:
2 speed
0-60 < 4s
125 MPH
13,000 RPMs
> 200 mile range (briefly reported as 245miles)
2nd spec revision (preliminary production model)
1 speed (effectively old trans locked in 2nd)
0-60 ~= 5.7s
125 MPH
13,000 RPMs
220 mile range
3rd spec revision (planned retrofit to early cars, and planned future standard)
1 speed (possibly a new ratio between old 1st and 2nd)
0-60 < 4s
??? top speed
??? RPMs
> 220 mile range (reportedly efficiency has improved)
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