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

Re: The Porsche Taycan's Two-Speed Gearbox

#51

Post by [deleted] » Fri, Sep 06, 2019, 9:33 PM UTC

newnewpdro wrote: post #45

dragontamer wrote: post #40

Earlier quoted context omitted.

> 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…

> The only reason to push 0-60 times is for drag-racing really. Wat? Most people care about accelerating from a standstill to the average legal speed limits. 0-60 captures that perfectly. It's incredibly relevant to the general public's driving patterns.

[deleted]

Re: The Porsche Taycan's Two-Speed Gearbox

#52

Post by johnvanommen » Fri, Sep 06, 2019, 9:34 PM UTC

mprovost wrote: post #17

Interesting fact about ZF: it was founded in 1915 to make gearboxes for zeppelins.

TIL:

"ZF Friedrichshafen is more than 90% owned by the Zeppelin Foundation, which is largely controlled by the town of Friedrichshafen."

Re: The Porsche Taycan's Two-Speed Gearbox

#53

Post by mywittyname » Fri, Sep 06, 2019, 9:35 PM UTC

madmulligan wrote: post #15

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…

The main advantage of the eCVT is the ability to seamlessly combine the power from two motor-generator units and an ICE (as in the Prius) while holding the ICE in the RPM range you want it. Here, there is only one electric motor and keeping it at a certain RPM range (other than below it's max) isn't really important. While a CVT will get you smooth ratio changes, you are still constrained by a minimum and maximum gea…

> and keeping it at a certain RPM range (other than below it's max) isn't really important.

Yeah it is, because electric motors have RPM bands where they are most efficient. The whole point of a adding a two-speed transmission in the first place was to increase efficiency, range, and top speed. If they managed a 5% improvement with a two-speed, I'm betting they could at least double that with an eCVT.

Re: The Porsche Taycan's Two-Speed Gearbox

#54

Post by rhinoceraptor » Fri, Sep 06, 2019, 9:35 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.

That could simply be due to the fact that CVTs have never been really used and developed for high performance applications, since car enthusiasts hate them. But there was an F1 car with a CVT before they were banned.

Re: The Porsche Taycan's Two-Speed Gearbox

#55

Post by _ea1k » Fri, Sep 06, 2019, 9:36 PM UTC

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…

I think this is a benefit only at higher speeds, tbh. The Tesla single speed setup seems to be really tuned towards low end acceleration, which admittedly is a logical thing to tune for in a premium family sedan.

We've already seen some pretty good hints that the next Tesla Roadster may have at least a two speed gearbox, probably for similar reasons.

Re: The Porsche Taycan's Two-Speed Gearbox

#56

Post by kenhwang » Fri, Sep 06, 2019, 9:40 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.

I'm skeptical Tesla can even roll out the Model Y before 2021. Meeting deadlines has never been their strong suit.

Rimac pretty much stole the show in the electric supercar segment already.

Re: The Porsche Taycan's Two-Speed Gearbox

#57

Post by mywittyname » Fri, Sep 06, 2019, 9:41 PM UTC

aidenn0 wrote: post #3

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…

Wouldn't an eCVT require an additional motor?

Yes, but only two small ones to control the rotational speed of the ring / planet gears.

Re: The Porsche Taycan's Two-Speed Gearbox

#58

Post by AndrewBissell » Fri, Sep 06, 2019, 9:46 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.

Tesla's capex spending is lower than their depreciation, meaning they're not investing enough to maintain their existing production lines. There is no way they will be rolling out any new models any time soon.

Re: The Porsche Taycan's Two-Speed Gearbox

#59

Post by dragontamer » Fri, Sep 06, 2019, 9:49 PM UTC

newnewpdro wrote: post #50

Ididntdothis wrote: post #47

Earlier quoted context omitted.

People rarely do a full power 0-60 with a car that can do it under 5 seconds. More likely they go from 30-60 or similar.

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 freeway, so I'd like to make sure I can accelerate in an adequate amount of time: to the point where I've (occasionally) downshift to 2nd, even in standard traffic, to get to 60mph asap.

Re: The Porsche Taycan's Two-Speed Gearbox

#60

Post by mtw » Fri, Sep 06, 2019, 9:50 PM UTC

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…

Porsche are experts in transmissions and gearboxes, but are starting (almost) from scratch for batteries. Give them a few years, they'll catch on.