The Porsche Taycan's Two-Speed Gearbox • Hacker News Board

Re: The Porsche Taycan's Two-Speed Gearbox

#61

Post by tomatocracy » Fri, Sep 06, 2019, 9:52 PM UTC

dragontamer wrote: post #40

gleglegle wrote: post #5

It's a little surprising that even with a two-speed Gearbox the Taycan has neither better range nor low range 0-60 acceleration than the Tesla P100D (which has the same size battery). Obviously spec comparisons aren't the whole story and the handling and high-range acceleration may be better on the Taycan. Looking forward to seeing more comparisons and already glad to see more EV models in this category. Edited incor…

> It's a little surprising that even with a two-speed Gearbox the Taycan has neither better range nor low range 0-60 acceleration than the Tesla P100D (which has the same size battery). 0-60 times probably don't matter on the track. Its probably more important to optimize the 60 to 120mph time, which is where the torque of a (single gear) electric motor begins to taper off. I bet that Taycan has superior 60-to-120mph…

On a track, the lateral G force the car can maintain traction at and the deceleration time matter a lot too.

Re: The Porsche Taycan's Two-Speed Gearbox

#62

Post by tomatocracy » Fri, Sep 06, 2019, 9:56 PM UTC

Cshelton wrote: post #43

rconti wrote: post #35

Earlier quoted context omitted.

Sure, and it's an ancient car, by EV standards. I'd hope that a Porsche that nobody has taken delivery of yet and costs way more is better. Last time I was at the track (in my BMW M car, mind you) we had a couple of Model 3 Performance cars, and a couple of Model S. I could pass the Model S with ease. I couldn't get close to the Model 3 Performance.

Which seems pretty reasonable...large family sedan vs a sports sedan. Besides, when the new Tesla roadster rolls out in 2020/2021, it is game over for everyone else anyway. At a price point of ~$200k, it'll kind of make the Porsche Taycan a joke. Unless you are a Porsche only individual. Which, to their credit, is a fairly sizable market.

Replying here because I can't to child.

Tesla's capex being lower than depreciation doesn't mean that they're not maintaining their production lines (but neither does it mean they're not - the two are largelty unrelated).

Depreciation is set by accounting policy, not by how much maintenance capex you'd need to spend to keep the facility in the same condition.

Re: The Porsche Taycan's Two-Speed Gearbox

#63

Post by mywittyname » Fri, Sep 06, 2019, 9:56 PM UTC

efraim wrote: post #10

mywittyname wrote: post #2

I'm surprised ZF/Porsche didn't turn this into an eCVT, as an eCVT (a la Prius) has probably the same complexity, but with the added benefit of having more ratios. I suspect it would also reduce shock loads on the transmission as a result of shifting. I wish the article would have gone into this, because I suspect Porsche said no more for marketing reasons rather than technical ones, as CVTs are universally hated in…

A CVT can't handle as much torque as a gear-based transmission.

CVT != eCVT

An eCVT is a planetary gearbox which uses a pair of electric motors to control the rotational speed of the ring and planetary gears to achieve an overall gear ratio anywhere between a minimum and maximum ratio.

It's largely the same thing as what this two-speed gearbox is, but it leverages electric motors to provide a smooth transition between two ratios, instead of using (presumably) a set of clutches and auxiliary gears to select one of two fixed ratios.

This is why this question jumped out at me immediately. On the surface, they are going with a really, really archaic, complex design over a more simple, all-electric design which is ideally suited for their application.

I can't help but think ZF started with an eCVT, then retrofited it back to being a two-speed. They must have had a good reason for this. And I wonder if it's a patent/license issue, or if there's some technical reason this wouldn't work. And I'm disappointed the article doesn't go into details on this.

Re: The Porsche Taycan's Two-Speed Gearbox

#64

Post by kenhwang » Fri, Sep 06, 2019, 10:00 PM UTC

rconti wrote: post #16

Mikeb85 wrote: post #14

Earlier quoted context omitted.

Porsches have never really been about straightline speed. Always about overall performance and a sports-car feeling. I'm guessing they optimized things like power, gearing and weight placement to offer good acceleration through a range of speeds with amazing handling and decent range at speed.

True, and the Taycan may well be a better car in many ways. But a discussion of the gearbox has nothing to do with handling or sports car feeling. I'm wondering what we're missing here. 5% efficiency improvement at high speeds isn't anything to write home about today. The transmission is a known quantity -- it's just gears, it won't get more efficient as they develop it. The efficiency of the whole system (battery/dr…

Mazda dumped a bunch of R&D and complexity into their transmission for "only" a 4-7% (AT)¹ and 1% (MT)² efficiency improvement. I guess in the automotive world, you're fighting for every last %.

¹ https://www.mazda.com/en/innovation/technology/skyactiv/skya...

² https://www.mazda.com/en/innovation/technology/skyactiv/skya...

Re: The Porsche Taycan's Two-Speed Gearbox

#65

Post by pixelbash » Fri, Sep 06, 2019, 10:04 PM UTC

dragontamer wrote: post #59

newnewpdro wrote: post #50

Earlier quoted context omitted.

When a car does it silently without being overtly antisocial they do it far more often.

Leaving all the other cars next to you in the dust is quite antisocial behavior actually. For the most part, I want to accelerate with everyone else when that green light goes off (except for Trucks: I wanna leave Trucks in the dust and get away from them ASAP). The 30mph to 60mph acceleration of off-ramp into freeway cruising speed however, is pretty important. A lot of things are going on when I merge onto a freewa…

> Leaving all the other cars next to you in the dust is quite antisocial behavior actually.

As a motorcycle rider I disagree, it's the safest option for us.

I get that not everyone is pleased about it, though.

Re: The Porsche Taycan's Two-Speed Gearbox

#66

Post by dragontamer » Fri, Sep 06, 2019, 10:06 PM UTC

pixelbash wrote: post #65

dragontamer wrote: post #59

Earlier quoted context omitted.

Leaving all the other cars next to you in the dust is quite antisocial behavior actually. For the most part, I want to accelerate with everyone else when that green light goes off (except for Trucks: I wanna leave Trucks in the dust and get away from them ASAP). The 30mph to 60mph acceleration of off-ramp into freeway cruising speed however, is pretty important. A lot of things are going on when I merge onto a freewa…

> Leaving all the other cars next to you in the dust is quite antisocial behavior actually. As a motorcycle rider I disagree, it's the safest option for us. I get that not everyone is pleased about it, though.

> As a motorcycle rider I disagree, it's the safest option for us.

Things are different if you're in a 4000+lb electric vehicle. The bigger the vehicle, the more polite it is to stick with the rest of traffic (or even let people pass you).

Re: The Porsche Taycan's Two-Speed Gearbox

#67

Post by nraynaud » Fri, Sep 06, 2019, 10:06 PM UTC

AgloeDreams wrote: post #8

As I understand it, this gearbox type is key on Porche's intent to make it able to maintain performance over use rather than overheat, notably it improves acceleration and efficiency at high speed. I would expect the Taycan to use less energy to maintain 150mph.

don't you have a ton of cooling air at 150mph?

Re: The Porsche Taycan's Two-Speed Gearbox

#68

Post by nraynaud » Fri, Sep 06, 2019, 10:08 PM UTC

just to be sure: should I be in awe in front of a 2 speeds automotive gearbox from a 100 years old manufacturer?

it's been a few minutes and I still don't feel the tingling.

Re: The Porsche Taycan's Two-Speed Gearbox

#69

Post by Diederich » Fri, Sep 06, 2019, 10:10 PM UTC

dragontamer wrote: post #59

newnewpdro wrote: post #50

Earlier quoted context omitted.

When a car does it silently without being overtly antisocial they do it far more often.

Leaving all the other cars next to you in the dust is quite antisocial behavior actually. For the most part, I want to accelerate with everyone else when that green light goes off (except for Trucks: I wanna leave Trucks in the dust and get away from them ASAP). The 30mph to 60mph acceleration of off-ramp into freeway cruising speed however, is pretty important. A lot of things are going on when I merge onto a freewa…

> Leaving all the other cars next to you in the dust is quite antisocial behavior actually

Honest question: can you expand on that? Assuming it's a safe thing to do, why is it antisocial?

Re: The Porsche Taycan's Two-Speed Gearbox

#70

Post by Zanni » Fri, Sep 06, 2019, 10:12 PM UTC

dragontamer wrote: post #59

newnewpdro wrote: post #50

Earlier quoted context omitted.

When a car does it silently without being overtly antisocial they do it far more often.

Leaving all the other cars next to you in the dust is quite antisocial behavior actually. For the most part, I want to accelerate with everyone else when that green light goes off (except for Trucks: I wanna leave Trucks in the dust and get away from them ASAP). The 30mph to 60mph acceleration of off-ramp into freeway cruising speed however, is pretty important. A lot of things are going on when I merge onto a freewa…

Serious question: how is this antisocial behavior? I understand wanting to stick with the flow of traffic when you're part of the pack, but if you're in front of the pack, what's the advantage (to anyone) of hanging back?