Two Speed EV transmission a good idea?

Mr.Smith

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Porsche has engineering roots in transmissions for performance and reliability/longevity, but is the two speed transmission a good idea for EVs?

Some have been complaining about the shifting, not being in the right gear etc... Is this something that can be fixed with software updates or will the J1 platform be the last to have this technology?
I would find it odd if Porsche spent the time & R&D budget for this this technology to not be used in lowest cost, next gen MEB platform.

Consider reliability/longevity/warranty before comparing to other OEMs with 20,000 RPM EV motors
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Miwa

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For cars that need to be quick off the line and be able to drive on the autobahn, yes, a few gears is a good idea. If the Taycan had a 3rd gear for like 120mph+, it's have a much higher V-Max.
 

fullmetalbaal

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It makes sense to have a 2-speed transmission on an EV with a very high top speed to allow the good performance to continue to that higher speed.
An electric motor has a massively better characteristic for traction than an IC engine but it still will run out of steam at high speed or be struggling at low speed when there is the speed range of a Taycan.
At least it doesn't need 8 gears (or the 12 we calculated and IC engine would need to be as good as a CVT!)
Not sure this is true ("transmissions make sense for very high top speed"). The electric motors in the Model S Plaid, Rimac and apparently the Mission R all hit high speeds and have crazy acceleration at the same time. Arguably, the Model 3 Performance already does the same thing.

A transmission weighs quite a bit and takes space, costs ~5% efficiency loss , represents an additional failure point, and hurts in day-to-day driving performance (chance of being in the wrong gear).

I view the 2 gear transmission as an oddity that will go away with J2 at the latest.

To me this strikes me as a solution brought about by an engineering team used to using transmissions in this way, and swinging that hammer no matter whether this really was a nail or not. Either that, or the VP of Transmissions Engineering needed to make sure his org had its pound of flesh in the new strategic direction. The only other answer would be that Porsche wasn't able to source the right motors - and that seems really really unlikely.
 
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kreshi

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Not sure this is true ("transmissions make sense for very high top speed"). The electric motors in the Model S Plaid, Rimac and apparently the Mission R all hit high speeds and have crazy acceleration at the same time. Arguably, the Model 3 Performance already does the same thing.

A transmission weighs quite a bit and takes space, costs ~5% efficiency loss , represents an additional failure point, and hurts in day-to-day driving performance (chance of being in the wrong gear).

I view the 2 gear transmission as an oddity that will go away with J2 at the latest.

To me this strikes me as a solution brought about by an engineering team used to using transmissions in this way, and swinging that hammer no matter whether this really was a nail or not. Either that, or the VP of Transmissions Engineering needed to make sure his org had its pound of flesh in the new strategic direction. The only other answer would be that Porsche wasn't able to source the right motors - and that seems really really unlikely.
I see a lot of wrong in this. The wrong gear thing barely happens. Only if you insist on driving in normal only and still wanting to drive it sporty. Other than that in Sport/Sport plus the car is always in the right gear.

When the Taycan was compared to the latest P100D, the Tesla had no chance at all against the Taycan at higher speeds. The 4S at a certain speed flies away from the M3P.

This is their first modern EV and the first EV transmission. I think they will just improve this and make it better and better. I bet Rimac did not use one due to lack of dev team for transmissions and space to put it.
 
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I see a lot of wrong in this. The wrong gear thing barely happens. Only if you insist on driving in normal only and still wanting to drive it sporty. Other than that in Sport/Sport plus the car is always in the right gear.

When the Taycan was compared to the latest P100D, the Tesla had no chance at all against the Taycan at higher speeds. The 4S at a certain speed flies away from the M3P.

This is their first modern EV and the first EV transmission. I think they will just improve this and make it better and better. I bet Rimac did not use one due to lack of dev team for transmissions and space to put it.
Agree with everything you said. Also that other company tried to do the 2 speed transmission, failed and gave up on its development.
I believe ZF is still trying to develop its 2 speed transmission, some other suppliers are as well, so we know there is value in it. From top high speeds, improved efficiency, less stress on the motor.

Playing devils advocate, but why didn't Porsche use it for the Mission R concept?
 

fullmetalbaal

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I see a lot of wrong in this. The wrong gear thing barely happens. Only if you insist on driving in normal only and still wanting to drive it sporty. Other than that in Sport/Sport plus the car is always in the right gear.

When the Taycan was compared to the latest P100D, the Tesla had no chance at all against the Taycan at higher speeds. The 4S at a certain speed flies away from the M3P.

This is their first modern EV and the first EV transmission. I think they will just improve this and make it better and better. I bet Rimac did not use one due to lack of dev team for transmissions and space to put it.
The wrong gear happens when driving around in town and for example wanting a quick jump from 20mph to 50mph. I'm not talking about tracking the car or driving it in the mountains. I'm also not completely flooring it. I'm asking for a 6/10 decent but not crazy acceleration. Happy to take a video. There's reviews that talk about this as well - I'm not making this up.

As a side note: I've been playing with it a bit. The threshold of when it kicks down vs. not seems arbitrary to me. Of course, fully pushing down on the accelerator causes the downshift, and feathering the accelerator does not. But if you shove it halfway down, it seems dependent on a whole bunch of other variables too. And when it shifts, it leaves you in a lurch for subjectively felt 0.5s. I'm going to try and measure it more objectively.

Why are you trying to compare the Taycan to the previous Model S? The current model is the Model S refresh and Plaid. Taycan has not chance at all at high speeds.

I'm not saying Taycan won't get better. It will. I'm saying one way it gets better is by ditching the transmission.
 

kreshi

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The wrong gear happens when driving around in town and for example wanting a quick jump from 20mph to 50mph. I'm not talking about tracking the car or driving it in the mountains.
Happy to take a video. There's reviews that talk about this as well - I'm not making this up.

Why are you trying to compare the Taycan to the previous Model S? The current model is the Model S refresh and Plaid. Taycan has not chance at all at high speeds.

I'm not saying Taycan won't get better. It will. I'm saying one way it gets better is by ditching the transmission.
Just increasing horsepower to make up the issue at high speeds is no solution. The Turbo S has been out for a while now too and I am comparing cars with similar performance stats. I don’t even know why I even have to explain this. With Tesla now only the Plaid exists and the rest is gone I guess. The over 800hp Model S after 200kph accelerated like a Golf GTI, so yes the transmission makes a lot of sense.
 

Miwa

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The wrong gear happens when driving around in town and for example wanting a quick jump from 20mph to 50mph. I'm not talking about tracking the car or driving it in the mountains. I'm also not completely flooring it. I'm asking for a 6/10 decent but not crazy acceleration. Happy to take a video. There's reviews that talk about this as well - I'm not making this up.
If you're in Normal mode, and you didn't floor it, the transmission was in 2nd the whole time anyway?

Playing devils advocate, but why didn't Porsche use it for the Mission R concept?
Race cars don't have to live through a warranty program. Less weight, but lower expected lifetime is easily a tradeoff a race car would take.
 

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Just increasing horsepower to make up the issue at high speeds is no solution. The Turbo S has been out for a while now too and I am comparing cars with similar performance stats. I don’t even know why I even have to explain this. With Tesla now only the Plaid exists and the rest is gone I guess. The over 800hp Model S after 200kph accelerated like a Golf GTI, so yes the transmission makes a lot of sense.
Whether 1 e-motor with 1200 hp or 1 e-motor with 700hp and a transmission is the right answer is what we are arguing about. I'm making a bet that the former will dominate.
 
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Race cars don't have to live through a warranty program. Less weight, but lower expected lifetime is easily a tradeoff a race car would take.
Very good point. I do think the oil cooling and the high capacity battery of the Mission R will be the next technology to trickle down to the road cars
 

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I’m not sure everyone here understands power. If you have a flat power curve, the transmission is irrelevant and serves no purpose, as its only purpose is to keep you in your peak power range, assuming you’re past the traction limit in your peak torque range. Power IS what accelerates you at high speed. You can ignore the transmission entirely and only look at power vs wheel speed (which is effectively just torque vs wheel speed).

The model S plaid definitely sets the bar on flat power curve, even vs the taycan in high gear and to me demonstrates that transmissions are not necessary in EVs. I’d rather put the gearbox mass toward a more powerful motor all things being equal.
 

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I’m fine with the 2 speed. Can get caught in normal if you suddenly need to step on it but no more than an ICE car. I like the different character sport and sport+ have holding onto 1st much longer. I suspect the 2 speed may be replaced in time as Porsche develop their tech.
 

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If you have a flat power curve, the transmission is irrelevant and serves no purpose, as its only purpose is to keep you in your peak power range, assuming you’re past the traction limit in your peak torque range.
Agreed on the gear changes having no affect on wheel torque within the constant power range, but…

I would assume they optimized first gear for the traction limit and this put them past the limit they were either capable or comfortable with for max motor speed, thus the second gear.

And, all other things equal, they’re better running the motor as slow as possible, which is probably why the gear change speeds are the way they are.

Only other way to get more torque is more HP.

Which way is right/better? 🤷‍♂️

I’ll tell you what I will place a bet on…Porsche is dedicating more resources to this than this forum has available…😁

I’ll trust their judgement. 👍
 
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