Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Porsche Taycan's Two-Speed Gearbox

wired.com

Post reply on HN
Print view View original

191–200 of 219 posts

Re: The Porsche Taycan's Two-Speed Gearbox

#191

Post by fluffything »

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…

I drive from Ingolstadt to Bonn regularly and on average I am able to get ~170km/h average speed for the trip. If I'm lucky (e.g. at night) I surpass ~180km/h. That requires a lot of cruising at 250km/h. Starting with a full tank I still end up with gas to spare. I had a Ford Focus 10 years ago and I remember managing ~150km/h average speed for the trip without refuelling...

If I need to charge an EV once for 20 min to be able to complete the trip then the car probably does not make sense for this use case. An Opel Corsa would finish the trip faster, for a fraction of the price.

Now if you give me an EV that can do 500km at >180km/h avg speed without recharging under normal german traffic conditions (lots of 250km/h mixed with lots of 130km/h) and is still left with some power for a bit of city driving then that would be an improvement.

Re: The Porsche Taycan's Two-Speed Gearbox

#192

Post by chasd00 »

solotronics wrote: post #153
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.

I drive a supercharged sports car that does 0-60 in 2.9 and do it every couple of days on a rural road near me, adrenaline is great! This is definitely an outlier though.. I get the impression from reading the forum for my car that most people don't push it near its limit regularly.

the car, tell me.

Re: The Porsche Taycan's Two-Speed Gearbox

#193

Post by AgloeDreams »

nraynaud wrote: post #67
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?

It's about efficiency at various speeds, plus having to intake more air to cool more things increases drag, the best way to improve cooling performance is to improve power use in the first place.

Re: The Porsche Taycan's Two-Speed Gearbox

#194

Post by mcot2 »

simonsquiff wrote: post #171
jm1234567890 wrote: post #169

Earlier quoted context omitted.

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

It does not. Raven altered the motor and suspension, battery is same as it ever was for MS (18650) M3 uses 27100, which is taller so can’t just be dropped into the current MS

Not 100% accurate. It is a new battery pack but still based on the 18650 cells. Tesla battery packs have a numerical code which was incremented for the packs in the raven models.

The most pronounced new feature is the ability to charge at up to 200kW on the new V3 superchargers. M3 can do up to 250kW and non-raven S/X can only do in the low 100s.

Re: The Porsche Taycan's Two-Speed Gearbox

#195

Post by mcot2 »

coribuci wrote: post #182
eigenloss wrote: post #159

Earlier quoted context omitted.

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

Higher voltage means less current for the same power. Since the power dissipated on the battery is proportional with the current you want to draw less current. What a lot of people do not understand is that the lack of a gearbox in an electric car is a big problem. When the motor is running suboptimally the excess energy taken from the battery will be transformed in heat.

It depends what speeds make the motor run sub-optimally for a particular vehicle. The range 0-80 MPH is sufficient for almost all normal driving. If you want to make an efficient track car that can operate at high speeds optimally by all means introduce a gearbox. Its going to add more weight, complexity and maintenance though. I don’t think thats the target for any of Tesla’s cars besides the 2020 roadster though.

Re: The Porsche Taycan's Two-Speed Gearbox

#196

Post by gwbas1c »

compiler-guy wrote: post #109

The level of hubris here is pretty high. "No reason"? "No performance benefit"? Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out. I'm sure the transmission is a giant set of engineering tradeoffs (what project isn't), and maybe it won't work out and wil…

> Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out.

I honestly don't understand this. Almost all of us drive at safe speeds on public roads and sit in traffic.

Focusing so much on racing just comes across as a distraction. I love my Model 3, But my older Leaf was fast enough for me.

Re: The Porsche Taycan's Two-Speed Gearbox

#197

Post by enragedcacti »

gwbas1c wrote: post #196
compiler-guy wrote: post #109

The level of hubris here is pretty high. "No reason"? "No performance benefit"? Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out. I'm sure the transmission is a giant set of engineering tradeoffs (what project isn't), and maybe it won't work out and wil…

> Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out. I honestly don't understand this. Almost all of us drive at safe speeds on public roads and sit in traffic. Focusing so much on racing just comes across as a distraction. I love my Model 3, But my olde…

Then you are absolutely not the target market for any Porsche, let alone this one. Not a dig, I'm not the target market either.

Re: The Porsche Taycan's Two-Speed Gearbox

#198

Post by NullPrefix »

compiler-guy wrote: post #109

The level of hubris here is pretty high. "No reason"? "No performance benefit"? Porsche is spending billions of dollars to bring a very high performance track-focused sports-sedan to the market. Hundreds of extremely good engineers are getting paid millions of dollars to figure this problem out. I'm sure the transmission is a giant set of engineering tradeoffs (what project isn't), and maybe it won't work out and wil…

> But it can't be so obvious that random Joe-and-Jane HackerNews know the answer off the top of their heads and Porsche doesn't after all the resources it has spent to figure out the problem.

Does this same discussion-closer apply when we talk about software? Plenty of software companies with the same hundred engineers millions of dollars thing. Yet we are allowed to talk about their fuckups. What makes you think cars are different?

Re: The Porsche Taycan's Two-Speed Gearbox

#199

Post by maigret »

ztjio wrote: post #177
reitzensteinm wrote: post #168

Earlier quoted context omitted.

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.

Once around the ring is not an issue. It's a day at the track that's a problem, not one lap. And not an issue at all if you're fine with waiting periodically while the battery temp comes back to optimal.

Do you have data for a Tesla completing a single Nurburgring lap at full speed? AFAIK they failed each time so far https://insideevs.com/news/323053/tesla-model-s-fails-to-lap...

Re: The Porsche Taycan's Two-Speed Gearbox

#200

Post by kwhitefoot »

robotresearcher wrote: post #95
adrianmonk wrote: post #74

Earlier quoted context omitted.

I wonder if this is part of why their dual-motor models get better range. I could see it being better for regenerative braking, too.

Double the regenerative braking is why they get better range, I bet, despite being heavier.

The two motors in a Model S are different ratings. It seems that at cruising speed the car can choose the most efficient one to use and let the other one 'freewheel'.

Two motors probably gives better control over regen and certainly over braking but the regen rate seems to be determined by the battery, inverter, and design decisions. In my 2014 Model S 70D the maximum regen is about 50 kW, at least that's what the display shows, but the motors can develop at least 250 kW.

I suspect it is also limited for safety reasons, 250 kW of braking would give deceleration of about the same magnitude as the maximum acceleration. At 100 kph (27.8 m/s) the car has an energy of about 1.62 MJ so at 250 kW it would come to a stop in 6.5 seconds.

Actually my car does 0 to 100 kph in about 5.6 seconds so it clearly produces more than 250 kW.

Sorry for rambling on, your comment set me thinking and then I just had to check my working.

Post reply on HN