Gearbox: totally unnecessary.

Dee

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So the Taycan has a 2-speed gearbox.
As we all know, a gearbox is to overcome the shortcomings of an engine/motor.
So why did Porsche make a gearbox as electric motors really don't need a gearbox after all due to their power and torquecurve.
I guess it was to defeat Tesla but in the end it isn't that quick after all, still ridiculously quick though...

So, my conclusion is that it only added extra weight and that has killed the extra performance (and efficiency) which I think was the whole concept of adding a gearbox: to improve performance.

What Porsche should've done is raise the ratio more cuz only then it would benefit the performance (if you wear proper shoes that is).
I'm talking 0-60 times here.
Ok, you'll loose some topspeed but still it would make much more sense.

What are your thoughts about the advantage of a gearbox in the Taycan?
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Let's see what Porsche says.

From the Jalopnik article.

Porsche says it used two gears “in order to improve efficiency, and also to help optimize both low-speed acceleration and top-end speed”

The article says “at about 100 km/h, or 62 mph, first gear runs out of steam, and the motor isn’t able to send much torque to the rear wheels (and at 81 mph, the motor hits its 16,000 RPM max speed), which hurts vehicle acceleration.”

“It’s at the point around 62 mph vehicle speed that the Taycan upshifts, yielding the solid green curve you see below, allowing for more torque at the wheels, and thus more acceleration to a higher top speed.”
(The torque curves have appeared in other threads).

Then goes on to say “Range and Normal mode, Porsche told us, prioritize second gear to optimize efficiency. “

I guess the question is, is there a single gear ratio that will outperform this?

And that takes you to the Plaid, one gear, a motor generating 1020 hp, with rotational speeds up to 20,000 rpm. (but you have to jump through some hoops to get there.)

So could a Taycan with just one gear beat this? I don't think so. It just a way more powerful motor spinning at way higher RPM's.
 

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I tend to believe the gear box is mostly un-necessary complexity for a very narrow use case - acceleration at high speed - speeds that for the most part are not legal on most roads (excepting germany of course) - but Porsche is a performance brand - EV's do tend to lag once you're at 70-80 mph or higher…

and a top speed of 163 mph makes Taycan one of the slower vehicles in Porsche's portfolio - so for a performance brand the limitations of EV torque curves must be a hard pill to swallow without a gear box

I think the long term proof will be "in the pudding" so to say…

will future Porsche EV's continue to have a gear box - or will a different solution emerge - or will the requirement for a gear box fade away due to changing expectations…time will tell.

so far after owning a Taycan since July 2020 - I have no love for the gear box, and it simply seems un-necessary complexity - and potential future maintenance both of which don't thrill me.
 

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It does makes sense in the context of driving in Germany. Given Porsche's sports car branding and more frequently encountered high speeds in Germany, the 2 speed gearbox does help with high speed acceleration, and probably efficiency at higher sustained speeds. It probably also helps explain why the Taycan on a mi/kwh basis outperforms most non-Tesla (and Lucid) peers in efficiency at 70mph per insideevs testing

That said, I agree with others that it likely will become obsolete in future generations. Tesla has proven that there are other ways to overcome efficiency and power drop-off issues at higher speeds with a single speed
 
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Dee

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I guess the question is, is there a single gear ratio that will outperform this?

And that takes you to the Plaid, one gear, a motor generating 1020 hp, with rotational speeds up to 20,000 rpm. (but you have to jump through some hoops to get there.)

So could a Taycan with just one gear beat this? I don't think so. It just a way more powerful motor spinning at way higher RPM's.
Well, my point is, with a higher gear ratio Porsche could have beaten the Plaid but building a gearbox that can withstand 25.000+Nm is a completely different thing (Taycan does around 15.000Nm at the wheels in 1st gear, gear ratio 15:1).
I can remember Tesla tried this with the Roadster but was unable to achieve this for a production vehicle.
Still, Porsche proves you can use just a single motor for fast acceleration and high topspeed by using a gearbox instead of one big motor (or two on each wheel).
Unfortunately the gear ratio is just too conservative to really mean something and now it's just a heavy weight which add even more complexity and parts that can break down.
In this configuration I don't see the bigger advantage of a gearbox in a Taycan, it's more like a disadvantage if you get my point.
But then again, Porsche does some very good engineering so I think these gearboxes are pretty much bulletproof.
Anyway, thx for replying.
 
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So the Taycan has a 2-speed gearbox.
As we all know, a gearbox is to overcome the shortcomings of an engine/motor.
So why did Porsche make a gearbox as electric motors really don't need a gearbox after all due to their power and torquecurve.
I guess it was to defeat Tesla but in the end it isn't that quick after all, still ridiculously quick though...

So, my conclusion is that it only added extra weight and that has killed the extra performance (and efficiency) which I think was the whole concept of adding a gearbox: to improve performance.

What Porsche should've done is raise the ratio more cuz only then it would benefit the performance (if you wear proper shoes that is).
I'm talking 0-60 times here.
Ok, you'll loose some topspeed but still it would make much more sense.

What are your thoughts about the advantage of a gearbox in the Taycan?
I think the next generation of the Taycan will NOT have a two speed gearbox. If you look at Rimac, they introduced the two speed gear box at first, but with the development of the motors, their cars have now settled for a single speed gearbox. A lot of complexity and weight svaings.
 
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Dee

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I think the next generation of the Taycan will NOT have a two speed gearbox. If you look at Rimac, they introduced the two speed gear box at first, but with the development of the motors, their cars have now settled for a single speed gearbox. A lot of complexity and weight svaings.
Exactly.
Funny thing is Porsche has a substantial share in Rimac.
 

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After driving a base taycan i drove a tesla model y long range. Despite having more HP i was disappointed from the tesla in regard of sprint between 60-120kmh. Maybe that was due to gearbox. Also in television i saw a drag race between tesla and taycan and the taycan was overtaking the tesla within the 1/4, mile despite tesla was quicker in the beginning.
 


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EV's can solve the problem of having torque at both low and high speed by using two different kind of motors in an all-wheel-drive setup.
Typically a motor at the rear optimised for low speeds and a motor at the front for high speed torque. I understood this is also what Tesla is doing.
ICE cars can't do this because they only have one motor.

The reason is not to have better performance in the RWD version, because they reduced that in software.

Maybe Porsche did it because the engineers still wanted to have some work for the gearbox departement. :)
I assume it is conservatism and lowering risk in a domain they were not yet familiar with.
 

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Exactly.
Funny thing is Porsche has a substantial share in Rimac.
Agree and that was probably one reason Porsche opted for the two speed at the initial stage. That was the thinking then, but now technology has further developed the motors etc.

will be interesting to watch
 
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Agree and that was probably one reason Porsche opted for the two speed at the initial stage. That was the thinking then, but now technology has further developed the motors etc.

will be interesting to watch
Indeed.

Still it's such a great sound to hear the gearbox shifts up and down.
I love it (still). 🤗
 

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I hit 90+ almost every time out, so the gearbox is a plus. I also find the car to be smoother off the bottom in second than in first, so I like the option of each.
 

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I think most people are familiar with this:

Porsche Taycan Gearbox: totally unnecessary. 1657749420936


Notice how the 1st gear wheel torque follows the 2nd gear wheel torque in the constant HP region (around the upshift).

We can extend this further to arbitrary gear ratios.

The below graph shows a constant HP torque curve in red.
The X axis is mph.
I've marked the Y axis in gear ratio.

From there. You can draw a straight line out to the constant HP curve and that will be the motor torque curve (the straight line until the constant HP torque curve, and it follows the constant HP torque curve from there).

I've put two lines on here. One for 1st gear (purple) and one for 2nd gear (orange).
But you could put a line on there at any gear ratio and see the expected torque curve.

Porsche Taycan Gearbox: totally unnecessary. 1657750586286


So, the actual torque curves are like this:
Porsche Taycan Gearbox: totally unnecessary. 1657755090123

Porsche Taycan Gearbox: totally unnecessary. 1657755124529


Now, the other thing to consider though is the maximum motor speed.
I've added another green, dashed line here for that.

Wherever the straight line from the gear ratio intersects the green line, that's the maximum speed for that gear ratio.

Porsche Taycan Gearbox: totally unnecessary. 1657750542131


So, our torque curves will actually stop at those maximum speeds here:
Porsche Taycan Gearbox: totally unnecessary. 1657755741410


And we're left with the following two final torque curves within the motor's speed range for each gear:
Porsche Taycan Gearbox: totally unnecessary. 1657755813243


Porsche Taycan Gearbox: totally unnecessary. 1657755857905


So, it is as @JimBob quoted from Jalopnik.
First gear for for low end acceleration.
Second gear is for top end speed.

Neither gear can do the other anywhere near as well.
And anything in-between will be a compromise of both.

So.......

Does the two-speed gearbox improve performance?
For a given motor power and within the limits of traction, YES.
Inarguably.
There's no debate to be had on that point.

Could they have done as well or better with a single speed gearbox?
Changing nothing else, no. There is no way a single speed gearbox would have been better. You are either sacrificing significant top end speed, significant acceleration, or both.

But what about the weight reduction of a single speed gearbox?
The weight for the whole gearbox is quoted at 70kg. Assume half that goes away with changing to a single speed gearbox. The weight difference is honestly negligible.

It’s less than the difference between me or my wife driving.
It's 1.5% of the mass of the Turbo S.

And acceleration equals force / mass, so you are not going to see big gains here.

So, the two speed gearbox is required then?
No. The alternative is more HP*. But that's basically it. You can maybe sacrifice some top end speed if you don't feel ~150-160mph is necessary, but not nearly enough. Not unless all you want is the first gear top speed which is lower than the speed limits of some US highways.

*or significantly less weight, but I don't see that happening anytime soon.


-------------
note: I just plugged in approximate values for the curves, so exact points maybe slightly off, but the relationships stand. I don't need any messages about how a top speed in the graph is 3 mph off or something.
-------------
 
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@Jhenson29 , great explanation of the gearbox and how it is done just now. I agree with you that at the time there were not many options, and without a redesign of a lot of components, motor, inverters, motor gearbox etc etc, it would have been a bad design.

However I think the development has moved on significantly. Higher torque, higher revs, better electronics etc so the need for a gearbox is not as crucial going forward.

See the article below. And remember Porsche have a stake in that company and learn a lot from them.

https://insideevs.com/features/436049/rimac-two-speed-gearbox-stupid-video/

So time will tell with next generation Taycan. And I would not think 70 kgis something to sneeze at.
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