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Discussion in 'Roadster' started by jordanthompson, Oct 30, 2016.
Tesla Roadster - In Depth - Gas 2
A few points not quite right...
That article reads like someone did some web research, compiled a bunch of stuff they found online about the Roadster and strung it together. There is no real analysis, no driving experience report, no new insight. And yes, some errors for sure.
I'd like to hear TEG's evaluation.
Well, a lot of that is sort of true. The most glaring inaccuracy I see at first glance is the statement that there is another upgrade that is available beyond the battery. While Musk claimed there would be improved range through lower resistance tires, new ball bearing, a few more aerodynamic body modifications, to this day, the only upgrade is the battery itself...
I'm kind of curious why they published the article in the first place. Where's the news?
I think the author must have just learned about the Roadster or just started looking deeper into the car as well as the history from what I take. If you read the comments you can pull that from him, he's also fascinated it seems. If there's any errors feel free to comment or what's better email him with what you may feel needs to be changed to be more accurate. Looks like others were giving him suggestions which he thanked them and made the appropriate edits.
The internet is full of "articles" that are just filler, content that is easy to pull together and hopes to attract clicks but contains no new information or useful analysis. That "article" is one them.
Well, I will forgive him for any inaccuracies as he put in this line: “wins the Coolest Car I’ve Ever Driven award!"
Clearly he tried to dig up some real details and put a lot of them down in that article. It doesn't seem too far off even though it wasn't perfect.
I wouldn't be suprised to learn that some of the dates he may have pulled from research we did here in the TMC Roadster forum.
He probably spent time going through what people have put in Wikipedia as well:
Tesla Roadster - Wikipedia
It looks like he already updated it some from the comments he got after the original version.
Here are some comments as I read through the updated version:
This leaves out some details of the 1.0 -> 1.5 transition.
The 1.0 drivetrain was only in the first batch of Roadsters temporarily until they got the promised 1.5 retrofit ready.
The 1.0 drivetrain had an analog PEM, and (apart from maybe Elon's and some test cars) the customers had the gearbox locked in 2nd gear.
Between the lower torque analog PEM, and the gearbox locked in the higher gear, 0-60 acceleration was no where near what was promised.
The 1.5 drivetrain introduced the digital PEM with such a low end torque bump that they no longer needed the lower gear.
To get the promised 0-60 I think they had to reduce the new top gear a bit so top speed dropped from something like ~135 to ~125...
So the mention above of 200 lb-ft of torque was short lived. All of those Roadsters came back in to the shop to have the 1.5 drivetrain digital PEM retrofit with ~277 lb-ft torque.
As a commenter has pointed out, it should be 0.2 sec or 2 tenths. Not 0.2 tenths ( 0.02 )... Sloppy number work.
Um, err... That isn't really what I saw happening (from a distance). Far be it for me to try to paint a more complete picture, but I would use phrases more like "due to problems working through production issues", "clashes of egos", "desperate measures", "pushed out", etc.
I think Tesla claimed they lost many orders over faith lost due to the TopGear "stunt" which TopGear claimed to have done for "entertainment value".
Who concluded that this sort of "publicity" helped Tesla? The "any publicity is good publicity" mantra is perhaps overused.
I think the specific details of what it actually was able to provide were conspicuously unpublished.
I suppose if one were to validate the SF to LA claim, there would probably be a lot of asterisks... Things along the lines of "at a fixed speed of 30mph the whole way", or "drafting behind a truck", etc.
It is certainly a big improvement, and a relief to Roadster owners that a more modern replacement option with a serious range bump is now available... But the SF to LA on one charge boast might be a tad overstated.
As was mentioned before, that was pre-announced, but never seemed to materialize.
Wasn't it supposed to be based on Model 3 chassis, not Model S ?
And I think the time-table for any possible next generation Roadster has been a moving target.
More than "a tad". Tesla's own blog post at Roadster Road Trip Update: San Jose to Los Angeles on a Single Charge states "drive non-stop from San Jose to Los Angeles on a single charge in a prototype of the Roadster 3.0 upgrade." They did it with just 20 miles or range remaining and the ended in Santa Monica, not downtown LA which is farther. Obviously the trip was driven in Range Mode. It was done at the speed limit or a bit less. It was likely done with all or most of the 3.0 upgrades, not just with the higher capacity battery.
It certainly has and what that article stated is basically just made up speculation.
That was my understanding as well. For a long time now, my "Roadster lust" has been tamped down by mumbling to myself "must wait for Model 3 deliveries".
And isn't that just an unfounded rumor?
Maybe I am off topic here. But I still believe that range could be extended with a simple 2 or 3 speed Planetary Gearbox. I do not now what kind of Gearbox was used (and failed) in the earlier Roadsters.
Take a look at German Autobahn speeds (in left line) where guys run at 120+ MPH. this is way off the ideal torqure figure of the current e-motor. If an optimised gear ratio could be PRE-selected BEFORE a planned long range trip, I am sure it would compensate for a bigger thus heavier Battery pack. And if it is only a Range increase of lets say 10 - 15 % the argument for a lighter car (smaller Battery) is there.
Yes, I can hear them scream PLEASE NOT AGAIN!
Now since TESLA has enough Data and experience, I am sure it crossed someones mind at TMC.
Tesla Motor Torque curve - Google-Suche
Unlike infernal combustion engines, electric motors have pretty good efficiency across the rev range.
Adding a multi-speed gearbox reduces efficiency of power delivery, although I suppose you might be able to get to a slightly more efficient motor RPM to make up for the losses of a multi-ratio gearbox.
Roadster Efficiency and Range
EVs tend to have very modest energy storage (compared to gasoline tanks), but do OK with it because they are so much more efficient than a fuel burning engine.
But when you get up to high speeds (100mph+) things like wind resistance just start to make the overall efficiency per mile poor (no matter what you drive), and the limited energy storage in the battery pack starts to run down annoyingly quickly.
Right, as I see in the last graph, the max efficiency is about 93% which is a rather small area. Yes, it is true, in this graph the areas of 92, 93% are much larger.
But has the increased range of dual motor MS not something to do with optimized drive gear ratios? Otherwise I can not explain the better efficiency as compared to RWD models? Is it soley because of vectoring between front and rear drive units. It is not logical that a 200+ kg heavier vehicle goes further. Maybe it is much more complex than I think and the power/energy sharing between front and rear DU is a secret of our cars.
Friends of mine who ask me how many miles I have to "sacrifice" for having AWD. And when I tell them that I actually have an even better range than with only one DU and less weight. They dont believe me. Has it also something to do with Battery SW? Charge levels max / min?
It is fascinating anyhow!
The model S AWD comes with different gear ratio between rear & front(& different motor sizes also for PxxD)
This allows programming the car to distribute the power where it is most efficient depending on each motor's optimum torque/speed curve...
Back to your regularly scheduled roadster topic...
Wow, that actually confirms my theory / assumtion.. thanks for clarification!
PS: of course I meant to say in my earlier posting "Areas 91& 92" are much larger than 93%
When I picked up Roadster #33 on Halloween, 2008, I was told that my car was the first or second one delivered with the 1.5 drive train already installed. My friend who has #2 (not Founders #2, that's Martin) had to wait many months before Tesla got around to replacing the 1.0 drivetrain with 1.5.
Are you sure about the analog PEM? That's not how I understood the development sequence. I believe all the production cars had the digital PEM. What I remember JB saying at the first "town hall" was that higher-current IGBTs had just become available and that was what allowed them to squeeze more torque out of the motor so that it could achieve the desired acceleration with a gear ratio between the 1.0 drivetrain's first and second gears. As you say, the top speed, which was limited by the 14000 RPM limit on the motor, was reduced as a result. As I recall, the discussion of top speed was kind of finessed.
It is possible that 1.0 had a first gen digital PEM, and it was only the EPs with analog PEM.
In any case, the article quoted 200 lb-ft, and I saw that published for 1.0, and then it jumped up to > 270 with 1.5
I was guessing that it was due to the switch to digital, but I suppose it could have been an IGBT upgrade.
I also recall hearing that the need to switch to a single gear "forced" them to re-engineer to a digital solution.
That efficiency pic I posted earlier I think was just some random AC motor chart, not specific to any Tesla motor, so take it with a grain of salt, and "your mileage may vary".
The efficiency improvements for AWD model S could possibly be explained by other things like:
#1: 4 wheel regen opporunity?
#2: New front motor being a different design that is overall more efficient?
So, I wouldn't just assume that AWD model S being more efficient is all about having different gearing available.