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The Porsche Taycan's Two-Speed Gearbox

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Re: The Porsche Taycan's Two-Speed Gearbox

#161

Post by GhostVII »

phkahler wrote: post #89

Aside from not providing much of any performance benefit, this will introduce difficulty coordinating regenerative braking through the shift point. One of my former employers had a group trying really hard to make a 2-speed for EVs make sense. It just doesn't. If there is an efficiency gain, it's probably better to throw the extra money and weight into the motor. An exception might be if you want to cruise at 120+ mp…

Why don't you think there will be much performance benefit? The Porsche taycan is much faster accelerating than any Tesla at high speeds, probably due to the two speed gearbox. I don't think it is an efficiency thing, electric motors just start loosing power after a certain rpm, and a gearbox helps with this.

Re: The Porsche Taycan's Two-Speed Gearbox

#162

Post by GhostVII »

Dylan16807 wrote: post #156
compiler-guy wrote: post #106

Earlier quoted context omitted.

Are saying that Porsche--which is spending billions of dollars on the Taycan and its transmission--is doing this for no good reason? "People care about range and reliability."--Certainly some, perhaps most people, do. And Tesla serves that market very well. But that isn't Porsche's market. Porsche's target market cares a lot about handling, and performance in track-like conditions.

> Are saying that Porsche--which is spending billions of dollars on the Taycan and its transmission--is doing this for no good reason? Yes, they are. They are saying that "better on a track" is a bad reason, and "it makes more money" is a bad reason. That is not a claim that Porsche is incorrectly engineering to reach their goal, or doing anything unprofitable. It's an opinion.

In what way is "better on track" a bad reason? Lots of cars have features which are only really useful on a track, are all of these cars needlessly complex?

Re: The Porsche Taycan's Two-Speed Gearbox

#163

Post by GhostVII »

kazinator wrote: post #73

> Multispeed transmissions must be robust to deal with the massive amounts of torque that electric motors can generate in a very short period of time, says Shashank Sripad, a mechanical engineer also from Carnegie Mellon. Put a manual clutch on it; problem solved. Manual boxes can be built strong. Then make it at least a 3 speed so there is a decent H pattern there from the stick user's perspective, and so that the r…

If you put a manual gearbox in it, I bet a single bad shift would tear it apart with all that torque at low RPM. Also would probably kill the clutch unless you are a really good driver, and it is hard to shift when you can't hear the engine RPM.

And I don't think manual gearboxes are any stronger than a well built automatic but I have nothing to back that up except intuition.

Re: The Porsche Taycan's Two-Speed Gearbox

#164

Post by adrianN »

eigenloss wrote: post #159
solotronics wrote: post #150

Earlier quoted context omitted.

Another reason the Taycan can output near maximum power for a much extended time period is it operates at 800v vs 650v as compared to the Tesla.

Higher voltage alone does not magically give you longer sustained maximum power.

It's also unclear to me why a gearbox alone would give you longer sustained maximum power.

Re: The Porsche Taycan's Two-Speed Gearbox

#165

Post by kazinator »

GhostVII wrote: post #163
kazinator wrote: post #73

> Multispeed transmissions must be robust to deal with the massive amounts of torque that electric motors can generate in a very short period of time, says Shashank Sripad, a mechanical engineer also from Carnegie Mellon. Put a manual clutch on it; problem solved. Manual boxes can be built strong. Then make it at least a 3 speed so there is a decent H pattern there from the stick user's perspective, and so that the r…

If you put a manual gearbox in it, I bet a single bad shift would tear it apart with all that torque at low RPM. Also would probably kill the clutch unless you are a really good driver, and it is hard to shift when you can't hear the engine RPM. And I don't think manual gearboxes are any stronger than a well built automatic but I have nothing to back that up except intuition.

> it is hard to shift when you can't hear the engine RPM.

A third-rate hardware tinkerer could come up with a circuit that makes a motorboating sound from a speaker at the engine RPM. That could be heard just during shifting activity, like when the clutch is out.

> Also would probably kill the clutch.

It would require a special clutch design. The clutch is not needed when starting, of course, because since the motor can generate torque right from zero RPM, the transmission can be engaged. A clutch mechanism needed when changing gears due to the mismatch in speeds that needs to be bridged. The existing two-speeder must have something serving as a clutch, just not a manually operated one.

Speaking at torque at zero RPM; can't that be modulated down somehow? Surely there must be some way of managing the motor to bring in torque gently. This must be happening already, right? I mean, electric cars don't burn rubber each time they get moving.

> I don't think manual gearboxes are any stronger than a well built automatic

That's easy; just define the requirements for "well built" so that it is so, and don't care about weight, size, and other things. The automatic transmission from a bus is probably stronger than the manual in an econobox car.

Re: The Porsche Taycan's Two-Speed Gearbox

#166

Post by threeseed »

mtw wrote: post #60
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.

Porsche is joining Formula E next season so I imagine they will get up to speed pretty quickly.

Re: The Porsche Taycan's Two-Speed Gearbox

#167

Post by 9935c101ab17a66 »

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.

I'd wager the vast majority of driver's have never really floored it, and especially from standstill. People care about getting from point A to point B safely and conveniently, and flooring it to get from 0-60 as fast as possible is ridiculously unsafe, has no utility (except very rarely when merging), and is terrible for both your car, your tires, and your fuel economy.

This is not a car for the general public, it is an incredibly niche, specially designed machine should conform to the public's driving patterns. On top of that, it STILL has an insanely fast 0-60 time.

Granted, I could be missing the point you're making. Apologies if that's the case.

Re: The Porsche Taycan's Two-Speed Gearbox

#168

Post by reitzensteinm »

zaroth wrote: post #160
ztjio wrote: post #136

Earlier quoted context omitted.

So, I'll just hop in here and lay out the spoiler. There is a major performance difference in the Taycan, it's endurance, and it's highly likely this transmission is a key element to achieving it. For those that don't know, Tesla's cars can not keep their maximum performance up for a very long time. The battery gets hot and lowers power output until it cools back down. The Taycan, while not having as impressive max s…

This is more of a function of battery chemistry on the S/X - the Model 3 does not have the same power restriction under load.

Which makes Elon's promise of sending the Model S round the ring a bit confusing.

Presumably it would be a suicide run to match the Taycan, which to my understanding would involve modifications and not be eligible for the same category.

Either it was an idle boast, or we're about to see the launch of the 21700 Model S.

Re: The Porsche Taycan's Two-Speed Gearbox

#169

Post by jm1234567890 »

reitzensteinm wrote: post #168
zaroth wrote: post #160

Earlier quoted context omitted.

This is more of a function of battery chemistry on the S/X - the Model 3 does not have the same power restriction under load.

Which makes Elon's promise of sending the Model S round the ring a bit confusing. Presumably it would be a suicide run to match the Taycan, which to my understanding would involve modifications and not be eligible for the same category. Either it was an idle boast, or we're about to see the launch of the 21700 Model S.

The new raven model S has the same battery chemistry as model 3

Re: The Porsche Taycan's Two-Speed Gearbox

#170

Post by rasz »

gburdell3 wrote: post #31
elonismycopilot wrote: post #22

Earlier quoted context omitted.

>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. There isn't a single published metric in which the Performance Model S doesn't trounce the Taycan.

Does the Taycan overheat and go into limp mode if you take it to the track?

Does it pop glued coolant lines making you pay for track cleaning like the rest of track oriented Porsches? https://rennlist.com/forums/997-gt2-gt3-forum/592328-catastr...
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